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pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

[HVAC] Goodman 2 Stage HP Defrost

Now that heating season his here, I turned on my heatpump to keep the place warm.

The unit is 2 stage 24/36Kbtu rating with a timed defrost. A few weeks ago there was a service man in to do a fall tuneup and he recommended that I set the defrost timer to 120 minutes form the existing 60 minutes. I made this change that day.

Fast forward to today. I noticed that the unit seemed to be running almost continuously on low when the outside temperature was around 30*. I did not recall it behaving like this last year so I investigated. First thing I saw was that the warn air discharge air was about 4* cooler than normal. The next thing I saw was a good heavy coating of frost on the top half of the outdoor unit but nothing on the lower half.

It looks like there are 4 lines coming out of the TXV valve that feed the outdoor coil so I would assume the R410A would be equally distributed to all 4 segments of the outdoor coil. There was frost on the large line from the compressor, through the accumulator to the TXV.

So the question: should I have seen equal frost on a 4 coil sections. It seems very strange that only the top was heavily frosted.
--
The difference between genius and stupidity is that genius has its limits.


Tex
Dave's not here
Premium
join:2012-10-20
kudos:2
If I had to guess, I'd say the system is undercharged. Charging R-410A systems is critical and they need to be charged according to the manufacturer's charging procedures. There needs to be a solid column of liquid refrigerant to the TXV for it to feed properly.

What do you mean by "4* cooler than normal"? Normal compared to what? Also, how do you, the homeowner, control the timed defrost? I've never heard of a service technician suggesting that the homeowner make these types of adjustments, especially since it involves getting into the outside unit controls.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
Hi Tex,
I had hoped you would be here today to comment. Thanks!

The tech I had to do the fall service was kind of green a 19 year old tech school graduate who was in love with texting on his iPhone. I specifically asked him to check the charge in this unit but he had more excuses than I could count: 1. Its raining ( rain had stopped by this point ) 2. It's too cold out to get an accurate reading ( it was 60* at the time ). 3. It sounds like it is OK. He did not do much, lets leave it at that.

By 4* cooler, I meant the discharge air at the register was 4* cooler than normal. I have a digital temperature monitor in the supply duct in one of the spare bedrooms. Normally with an OAT of 30* I see about 93*, when the icing was on the top 1/2 of the outdoor unit, the discharge was 87* ( the thermometers read in C* so I did not realize the temperature was actually 6* cooler until I just converted it).

This is a communicating thermostat system and the timed defrost can be set from the User Preferences menu, so I did not have to open any covers.

Later tonight when it cools off outside again I will try to get a temperature reading of the coil sections using my IR gun. If that does not work, my Fluke has a thermocouple probe that I may be able to get in contact with the fins and get an accurate reading.
--
The difference between genius and stupidity is that genius has its limits.

guppy_fish
Premium
join:2003-12-09
Lakeland, FL
kudos:3
Put it back to every 60 minutes, two hours is to long to run without running a defrost cycle


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
good advice. I already did reset defrost timer to 60 min, (:>)


Tex
Dave's not here
Premium
join:2012-10-20
kudos:2

1 edit
reply to pende_tim
The outdoor temperature should be at least 60*F to check subcooling, so your greenhorn knew that much. The warmer, the better. They can be checked in the heating mode, but checking them in the cooling mode in warm ambient conditions is best. I still don't understand why Goodman would want the homeowner jacking with the defrost times, but, then again, I've never worked on or installed a communicating Goodman 2-stage heat pump.

Anyway, unless there is an airflow issue, about all I can see from here is a refrigerant charge issue. Keep in mind, the indoor return air temperature will affect the discharge air temperature as will the outdoor air temperature affect the BTU heating capacity of the system. At best, with 30*F outdoor temperatures, my guess is you're getting only 2416K-3018K BTUs of heat in low speed. But, I still think you have a refrigerant charge issue.

Edit - BTU capacity on low speed @ 30*F ambient


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to guppy_fish
Why? The defrost cycle only needs to operate if it is needed by frost/low temp on the coils. A temperature sensor on the coil controls it. The timer will put the unit in defrost only if the temperature sensor is calling for a defrost.

My unit runs for days sometimes and never goes into defrost. It is in no way a timed function. The humidity of the air really is the determining factor. When it's snowing or freezing rain around the freezing point is when the coil frosting really shows up. The unit might go into defrost every timed cycle.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
On the Goodman there is a time/temperature measurement that call for defrost. It appears that the defrost board counts down xx minutes and then polls the OCT sensor. If it is below freezing, a defrost cycle occurs.

This is a cut/paste from the Goodman Service Manual:

DEFROST CYCLE - COMFORTNET TM MODELS
The defrosting of the outdoor coil is jointly controlled by the
UC PCB and the outdoor coil temperature (OCT) sensor.
The OCT sensor is clamped to a feeder tube entering the
outdoor coil. Defrost timing periods of 30, 60, 90 or 120
minutes may be selected via the dipswitch settings on the UC
PCB. In a communicating system, the defrost timing periods
can also be selected in the communicating thermostat user
menu. During operation the microprocessor on the UC checks
coil temperature via the OCT sensor every 30, 60, 90, or 120
minutes when there is a call for heating. If by the time the
microprocessor checks the coil temperature, and it's low
enough (approximately 31°F), and if there is a call for heat
from the thermostat, the PCB will initiate a defrost. When the
microprocessor detects the coil temperature to be high
enough (approximately 75 F), or 10 minutes of maximum
defrost cycle time has elapsed, whichever occurs first, the
defrost cycle is terminated and the timing period is reset. The
field service personnel can also advance a heat pump to the
defrost cycle by simultaneously pressing the "TEST" button
and the "RECALL" button on the UC board.
--
The difference between genius and stupidity is that genius has its limits.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
What I said. The unit will never go into defrost regardless of the time unless the coil sensor calls for it. Excessive coil frosting will necessitate excessive defrost cycles.

From the original description of the problem it appears that the unit may need a charge adjustment.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
It is forecast to get in the mid 60s here mid week so I am planning to get someone in with gauges (and experience).
--
The difference between genius and stupidity is that genius has its limits.


tp0d
yabbazooie
Premium
join:2001-02-13
Carnegie, PA
kudos:6
reply to pende_tim
said by pende_tim:

The tech I had to do the fall service was kind of green a 19 year old tech school graduate who was in love with texting on his iPhone. I specifically asked him to check the charge in this unit but he had more excuses than I could count: 1. Its raining ( rain had stopped by this point ) 2. It's too cold out to get an accurate reading ( it was 60* at the time ). 3. It sounds like it is OK. He did not do much, lets leave it at that.

If this was really the case, it sure sounds like yer guy doesnt know or doesnt care to do his job well. I would call the company back and ask for someone that -does- know his job. You're paying for it, correct?

Ive never seen the draw for a heatpump in a freezing climate. They only work well to 35-40°, anything less is a frost issue. Guess you have good electric rates..

-j
--
if it aint broke, tweak it!!
currently on FiOS (kick aZZ!)


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

1 edit
The company is coming back on Thursday with a different tech. It seems the last one was in the "maintenance" section, Thursday's person is from the service side.

We will see how it turns out. I know the company has excellent qualified people as they have worked here before and done an excellent job.

I did the math very carefully and conservatively before getting the HP. Compared to Propane, operating the Heat Pump costs about 50%-60% less. This calculation was verified last winter when I compared my actual electric bill, backing out the base load for the house, to what I would have paid for Propane based on degree days.

And yes, we only pay $0.102/KW for power including all fees and stuff.

--
The difference between genius and stupidity is that genius has its limits.

Spensergig
Past my Prime
Premium,MVM
join:2000-03-26
Bradenton, FL
reply to pende_tim
Placeholder to "reopen" the thread.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
?

Pende_tim never gave any update from his post on 2013-Oct-28 5:06 pm.

»Re: [HVAC] Goodman 2 Stage HP Defrost

Spensergig
Past my Prime
Premium,MVM
join:2000-03-26
Bradenton, FL
This "reopen" was for another poster trying to add new information.
»14-Day "Petition a Moderator" Account Restrictions

nma851
Premium
join:2013-10-13
USA
Reviews:
·AT&T U-Verse
reply to pende_tim
Hey pende_tim See Profile

I do not have the "rights" yet to reply/add to your post but the Mods got this re-opened for me to pose the following. I still cannot reply and/or quote as I need to, so alot of this is being done manually. I do apologize in advance but I can ONLY post to the "Original" or the Mods who re-opened it through their post (guess it gives another "14 days" with their posts only).

Since I have the same equipment, more/less the same circumstances, with the exception of having Natural Gas as the AUX/E heat versus strips (or propane as I didn't see which you have), I'm asking for some of your time for comparison/contrast discussion. It is unclear though if you have a Hybrid (Dual-Fuel) like myself since there is mention of Propane being considered, but no mention of Propane being used as the Supplemental specifically. I'll assume you have the "traditional" setup of HP/elec strips as your Supplemental (AUX/E-heat). Whenever you mentioned the propane costs & the 50-60% savings you're experiencing via the HP in our climates, I am VERY glad to have a "real-life" savings comparison now. I'm curious on some other items that may be helpful to you as well. Granted, this isn't the same as natural gas rates/propane rates, but our similarity is our climates, HP's, comfort/temp-swings, and most importantly, savings.

First & foremost, would you mind posting your Model # of that HP and the AHU (or furnace if you DO have an LP as your Supplemental)? I do not want to error by using the wrong model's specs. Next, were you able to get the charge verified and/or resolved as previously indicated?

I'm in the Midwest & installed a Hybrid system (Dual-Fuel) myself a couple years back after doing the same as you did - comparing bills, doing the math, and for that I want to say KUDOS right off the bat too! Since I am disabled now, all I can be is an "Educating Mechanical Engineer" versus a "Real-World-Working" one. Life can be cruel at times I suppose.

Further, I as well concur with Jack_in_VA See Profile to where the defrost should *only* be controlled by the coil temp; having some timer kick-in a defrost, every hour, is unnecessary.
said by Jack_in_VA:

Why? The defrost cycle only needs to operate if it is needed by frost/low temp on the coils. A temperature sensor on the coil controls it. The timer will put the unit in defrost only if the temperature sensor is calling for a defrost.

Now I understand you changed that back and I guess I'm still wondering "why" this is a changeable option to begin with whenever a defrost is based on need, not by time. It can poll it every minute (in theory) for all I care; however, the only rationale for a defrost is to ensure optimum heat xfer, and I suppose I fail to see the point of why the Manf. would even offer a "user-configurable timer" to initiate the defrost based on "time" versus "temperature". Guess this is a topic for another day about this particular aspect. Learn something new each day!!

Nonetheless, my decision was based on all the same/similar costs of electric/gas/previous gas-only & over-sized furnace. More info on the entire system and a Hybrid is at my thread here if you're interested: »[HVAC] Premature Low-Ambient AUX concurrent kick-in/HP SP lockout .

My bills have been cut in half as well, despite having the size & type of home I have. My only drawback, regardless of the system being used, is that I have a split-level home (quad to be exact), my lower floors tend to stay cooler anyways, and once the outdoor ambient gets to 30d or less, the ONLY way to overcome the 60-65 temps downstairs was by placing my lockout SP (lockout setpoint - making the HP stop & switch over to Natural Gas) at 30d. While this is not essentially "ideal" on traditional HP systems, in the case of a Hybrid (using the natural gas once below 30d, using the HP above 30d), my actual bill comparisons DO prove there are still significant savings while also achieving the comfort desired on the lower levels. If I'm losing you, just let me know. I'll take all the time needed to clarify.

Since it is unknown as to what your Supplemental heat is (assuming strips unless you advise you're using a Hybrid as I am - yours being propane, mine being natural gas, if that IS the case), do you know what that lockout SP is? Reason I'm asking is to basically confirm you're as "optimized" as possible given we are in MUCH colder climates than the "traditional" HP users are & as equally curious about your comfort levels on each floor/room/etc.

Back to comparisons, my Goodman HP system (GSH13048, TXV Cased Indoor Coil, & Supplemental is GMH950904C 2-stage natural gas) is not the one controlling the SP's/Lockouts - my Stat is. This is due to having an outdoor ambient sensor which allows me to control all aspects of the system from the Stat. Otherwise, I would have to have a fossil-fuel kit if the Stat wasn't controlling). Auto changeover from HP to AUX occurs at 30d, if the HP is struggling (such as during AM recovery), it will kick-out the HP and kick-on the Gas to get the temps up, and the Stat does all of this for me. Defrost is controlled by the HP coil temp, not by time as previously discussed, and for the first time this year I actually hit a defrost cycle before going into full Natural Gas at 10PM or so last night - the time of this post. We're not getting above 25 or so today, likely will be no HP today/tonight either.

Since the nat gas is my supplemental, it not only runs ALOT less than the HP, but it also maintains a far better comfort level in the lower living room. The upstairs bedrooms are slightly dampered to avoid huge temp swings upstairs, however I'll take THAT drawback over the 60-63 degrees downstairs any day.

I certainly apologize for the lengthy post . All being said, since you're located in an area that has lower outdoor ambients during the winter months, how is your system fairing as to the aforementioned "System Summary/History" I've posted? It would be nice to finally be able to compare/contrast to someone who is utilizing an HP in primarily colder climates and the impacts on our fuel costs.

If you're still having issues as well, please let us know. The rest, if you're up to it, would be nice to just have some discussion about.

Thank you for your time & hope you have a good one as well as ALL issues resolved!!


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1

scooper

join:2000-07-11
Youngsville, NC
kudos:2
reply to pende_tim
Having grew up on the great plains of Kansas (but we live in NC now) - when our heatpump died in 1997 we also went for a heatpump / propane furnace system. Since then - experiance has shown that approximately 80-90% (or more) of our heating needs can be taken care of with the heatpump alone. Our heatpump will keep the house warm down to the lower 20's, and it's significantly cheaper to do so over propane.

I have no idea if our system has a SP set, and our thermostat is a Honeywell RTH7600 that I installed (specifically for its ability to control our system and also for the programmability). It mostly switches when the heatpump is no longer keeping up with the heating demand, or we can now set the thermostat on emergency for furnace only if necessary/ desired.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

1 edit
reply to nma851
Sorry for not following up on the original post.

The tech came out and checked the charge and the superheat and subcooling were all in spec, however the subcooling was at 7* which is the low end or the 7-9* range, I asked about adding a bit a 410a to bring it up a degree and he said he did not recommend this as overcharging can be a real problem. Since it was technically in range, no problem. He ran a manual defrost cycle and it seemed to work as designed.

He then said that 120 minutes was way to long of a defrost timer and suggested a 90 minute setting.

We have not been there recently to monitor the performance but should be back later this week. It will be cold so I will be able to give it a good test.

The system I have is a ASZC180361 2 stags heat pump and a AVPTC313714 Air handler with 10Kw resistance supplemental strips. It is installed in Southern Delaware near Ocean City, MD.

With my system I have the strips locked out above 25* and the Communicating thermostat takes care of managing the 2 stages and the strips. For the most part, the strips are seldom used even when the OAT gets down to 20*. The key is to avoid radical manual changes in room temperature. If I have a scheduled temperature change, the 'stat anticipates the upcoming change and starts the heatpump early so it has time to make the adjustment. I have this system on the main floor and the floor plan is fairly open, so temperature variations are not a real issue for me.

My defrost is a time/temperature sequence. If the sensor is below 28* and a heating call is active, the timer will start a count down. If the temperature goes above 28*, it is my understanding the timer will reset.

I made my cost savings calculation by looking at the ft^3 of propane used per heating degree day from the past 2 years. I read my meters every day when I am there so I have a pretty good handle on use.

Last year I did a pro-forma calculation of the propane use each day and compared it to the use I estimated my heat pump added to the base load of the house. Even if this estimate was way off, at the end of the heating season, my total electric bill ( which included a second 18,000 btu heat pump in the " upstairs bonus room/ 4th bedroom" was much less than just the propane bill would have been.

Hope this helps.
--
The difference between genius and stupidity is that genius has its limits.


Tex
Dave's not here
Premium
join:2012-10-20
kudos:2
According to the product specifications, superheat at the suction service valve is 7-9°F. Subcooling is 8-10°F. I would have liked to see 10°F subcooling, but that's just me.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
Thanks, Tex.
Sure is hard to find a good tech, that is why I usually end up doing a lot of stuff myself. However when it comes to HVAC, I do not have the experience or tools. Maybe since I am retired, this could be an excuse to go back to school? ( Just kidding ).

Since the measurement was done when the unit was on high speed, it looks like we were 3* too low on the subcooling to reach your 10* target.

Now to get into a little theory: how much of an impact does this 3* make on Heating performance as far as efficiency and Delta T? How much of an impact will this make on Cooling performance?

....And to get a feel for how "short" the charge may be, the unit shipped with 188oz of R410a for 15' of line set? Any ideal how many oz are required per foot of additionaal line set? If I recall correctly the installer did not add any R410a to the system when it was installed. I have not measured the line set length, but it is pretty close to 15'.

Thanks Tim
--
The difference between genius and stupidity is that genius has its limits.

pandora
Premium
join:2001-06-01
Outland
kudos:2
Reviews:
·ooma
·Google Voice
·Comcast
·Future Nine Corp..

1 edit
reply to pende_tim
I bought 2 Goodman 4 ton heat pumps last year. IIRC the defrost cycle starts every half hour when heat is on and operating, but if there is no frost, it doesn't continue. I don't think 2 hours is a good idea if you are in an area that regularly gets cold.
--
Congress could mess up a one piece jigsaw puzzle.


F100

join:2013-01-15
Durham, NC
reply to nma851
nma851, thanks for your post about the duel fuel units. Is yours a package unit or split system?

We have a Natural Gas package unit with AC and just had to replace the combustion blower and collector box. Box had rust and fan wouldn't spin. Our unit was made in 1995 and so is on the verge of getting ready to be replaced. Glad I didn't have to do it yesterday. I'm looking at replacing it with a system like yours that uses heat pump most of the time but can use NG for the Aux heat since I have NG. Since a package unit has all the parts for AC, really all they have to do is add the reversing components to make the heat pump. Then just add the extra controls like yours. I believe the stat you have requires a 7 wire setup. It sounds like the best way to go. The stat does all the controlling.

I was reading about the Goodmans yesterday so just wondering how you like yours. I'm trying to find a system that I like. We have about 1800sf but 2 story. The one unit serves both floors but we have to close downstairs vents to get enough flow upstairs. The 2.5 ton unit we have now works pretty well for us.


F100

join:2013-01-15
Durham, NC
reply to pende_tim
pende_tim, I didn't see this mentioned in this post but from what I understand R410a isn't as easy to recharge. It is a blend of refrigerants not a compound like R22. So if it is low, or leaking, the mix in the blend of the R410a that is left is not the same since the refrigerants that make up the mix bleed off at different rates which changes the composition of what is left in the system. That makes it hard to just top off like the old R22 that I have. You have to pull all the puron (brand name) and replace with new to do it correctly. You can't fix the blend by adding more puron.

When R22 leaks, it is still R22 in the system. You can add more R22 and the mix is the same. The R22 freon acts more like water. You can change it's state but it is always water, event when it evaporates or escapes the system. R410a is like a mixed drink, some parts settle out at different places. Some float on top, some sink to the bottom, some in between. If it's sealed inside the system , the mix is fine. Let some out and one part of the mix escapes while the rest stays.

Tex and others seem to know better than I but R410a seems to be more sensitive to the amount of charge in the system to operate best. I don't know if it's the higher pressures or what.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
I suspect the system was never fully charged from the get go, no leaks AFAIK.

Yes I do appreciate that R410a needs to be charged as a liquid, not vapor to make sure the blend is proper.
--
The difference between genius and stupidity is that genius has its limits.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
reply to pandora
I am set for 90 minutes now. I will see how it goes when I get back there, probably tomorrow.
--
The difference between genius and stupidity is that genius has its limits.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
My unit has not been in defrost in weeks now. Regardless of timer settings the coil temperature has not required it.

nma851
Premium
join:2013-10-13
USA
Reviews:
·AT&T U-Verse
reply to pende_tim
No apology needed at all. This scenario got my attention when I saw a few things, especially the climate and the SP's for the OAT's. This gives ME a good "comparison point" and you certainly exhibit quite a bit of vigilance, not to mention knowledge, by doing the right things according to Manf. Specs. Further glad to know you're within a good range at this stage of the game. It is difficult to get a good charge/read during colder temps. Ideally, I'm sure you're going to recheck again once warmer since you know what you're doing/up against/using your brain. I'd love to be retired vs disabled, but we're NEVER too "old" to learn!

I don't want to be too repetitive/redundant here either so I apologize in advance if I do.

Also, happened to notice the HP model # appears to be an Amana; could be some Goodman/Amana" joint effort of some sort but all I'm pulling are Amana specs. The "Communicating Stat" and "Comfort Net" portion kinda made me think a bit more on that, & whenever I use that model# you've provided, it's bringing up Amana instead of Goodman. Don't worry about it - just FYI for ya. Amana-Goodman, Goodman-Amana - they all seem to be commingled when searching; story of our lives LOL. That manual Tex See Profile provided is the same one I found for the model#.

I'll try to not irritate much this time & keep it to the "bare bones" :)

Tex See Profile is one heck of a good knowledge base as well. I've read MANY of his posts since joining and I look up to him whether he realizes it or not . His "outside the box" thinking makes ME think/explore when I otherwise would not have.

OK -
said by pende_tim:

My defrost is a time/temperature sequence. If the sensor is below 28* and a heating call is active, the timer will start a count down. If the temperature goes above 28*, it is my understanding the timer will reset.

Since we're similar in all aspects except our Supplemental heat (you having 10k strips, me having natural gas), I looked up that timer just to get a better idea of what I'm dealing with before speaking about it. This OT18-60A (Outdoor Temp), which I found in the Amana accessories from your model's spec manual, I see where I misinterpreted. That timer only "tolls" during a call, and from what I was seeing in the post(s), I believe I merely misunderstood that it was "tolling" irrespective of what temperature the coil was at. Specs clearly define the operation as: "...clamped to a feeder tube entering the outdoor coil. Defrost timing periods of 30, 60, or 90 minutes may be selected by connecting the circuit board jumper to 30, 60, or 90 respectively. Accumulation of time for the timing period selected starts when the sensor closes (approximately 34° F), and when the room thermostat calls for heat. At the end of the timing period, the unit’s defrost cycle will be initiated provided the sensor remains closed. When the sensor opens (approximately 60° F), the defrost cycle is terminated and the timing period is reset. If the defrost cycle is not terminated due to the sensor temperature, a ten minute override interrupts the unit’s defrost period." It has a fail-safe as well, so once the 10min mark is reached, the defrost cycle terminates & HP operation resumes & the entire process repeats itself.

Strip SP of 25, IMO, is a good SP for our climates & given the Stat/System is calculating the best use for you, even at the 20d you mentioned, not bad in the least!!!

This is a prime example of GOOD use of staging on an all-electric ("Traditional") HP system in a primarily COLDER climate.

Again, my apologies for the mis-read and believing that REGARDLESS of run-time, you're getting a defrost whether you want one or not! Lesson learned on MY part!

said by pende_tim:

The key is to avoid radical manual changes in room temperature. If I have a scheduled temperature change, the 'stat anticipates the upcoming change and starts the heatpump early so it has time to make the adjustment.

Right on the money again; good use of the Stat's function to gradually bring up the temp upon a change in occupancy. Amazing what the recovery function will do - such as today, when we were in the teens, this gave me the first "true" ability to assess the Stat & System's ability to recover without under/overshooting while also ensuring the HP wasn't kicking in. Since you do not have the "Multi-Level Syndrome" as I call it, not feeling the variations is certainly a plus.

said by pende_tim:

Now to get into a little theory: how much of an impact does this 3* make on Heating performance as far as efficiency and Delta T? How much of an impact will this make on Cooling performance?

Ughhh... Well - while we want to be as optimum as possible, getting that 10d sub in these OAT's is gonna be a challenge. You're on 410A as well, that "kinda" changes things a bit but the concept remains the same. Of course, having the specs Tex found helps and using that, while using these "general rules of thumb" so to speak, about all we'd be doing is "Guesstimating" of which I DETEST . I'll probably be crucified by my colleagues over this but I'll post it anyway for REFERENCE (there - hopefully this disclaimer saves me LOL).

Subcooling at 7d and ?? on superheat (from your post) would generally indicate your under a bit, but I agree with the Tech who did not want to do that as over would cause problems as well. Once you're in good OAT's, then you'll be *truly* optimized, no guessing, no speculating.

Low subcooling & high superheat= Under;
Low superheat & high subcooling= Over;
Low subcooling & low superheat= (Not your problem here - you would be getting what you are if the case) is a backwards orifice, and yeah I've seen it before unfortunately, no orifice at all, or refrigerant is free-flowing due to an open (or missing) orifice.
Very high superheat & slightly high sub: Usually indicative of a blockage anywhere from the coil/dryers/orifice/TXV/list goes on. Also not the case in your situation
Could have blockage in coil, TXV strainer screen - settings, etc., orifice, filter dryers etc.

Hopefully, the tech took his readings properly to get your current charge proper. 410A's, depending on how much you've read/learned/etc., require multiple measurements of temperatures using a dry & wet bulb readings as well as 410A temp/pressure conversion chart for saturation temps (unless you're gauge set does this for you). The "simplified" version of getting the accurate reads is by following a precise method - there is no way around it. FYI, this aspect can go on forever in a day, as sat temps change with the refrigerant being used, and I don't want to inundate .

As reference for ya as it relates to 410A charging for your subcooling:
Measure OAT;
Measure the dry bulb temperature @ the return duct;
Measure wet bulb temperature the same way as the dry bulb @ return; the difference between the wet/dry bulb gives the "load" on the evap;
Measure the liquid-line temperature (has to be attached WELL & a few inches from the service valve) to determine sub-cooling;
Attach gauges & measure liquid and suction pressures. Now we use the conversion chart to change the high side pressure to the saturation temp;
Now we subtract the liquid-line temp from the sat temp giving us the subcooling.
Then we look at the Manf Spec sheet, find the applicable pressures for the OAT as well as the subcooling level needed based on those specs;
If the subcooling is too low, additional refrigerant is needed; if too high, too much refrigerant is in the system & will need to be recovered PROPERLY, not just vented.
Subcooling can have a "double-check" by also measuring the temp @ the TXV to see if there's any differences in the read as you shouldn't have a difference.

On the gauge set I have, it's an expensive one I got before my "demise" & inability to walk again, all this gets all the reads & sats through the age of digital technology. Some of the older gauges/temp sets would as well & if all else fails, we look at the old-faithful paper charts.

Superheat is performed in the same fashion, but obviously through different reads from the opposite side of the system (Suction side). Superhead temp checked at the end of the evap, at or as close to the TXV expansion bulb, that is in turn converted into saturation temp per the 410A chart, & comparing that read to the read of the ambient at the bulb & the load (WB/DB difference). We get our suction read, convert to saturation the same way, and compare to the ambient temp close to that suction line read.

Obviously, I didn't go totally in-depth as I'm just trying to give the overview.

Delta T: (TD), temp difference across the coil, if you do not know how to take these measurements::
Measure temp @ supply near the coil;
measure temp @ return near the AHU;
Difference between the two is your TD;
Should be around 15-20 degrees. This can also help confirm your subcooling/superheat are up to par. YOUR specs call for 7-9SH & 8-10SC, but - again - risking the overcharge did not outweigh the benefit of throwing in a bit more refrigerant to hit that 10d mark on your subcooling. I would say it's fairly negligible, for now, as long as you are still getting that TD range. If you are NOT, then I would worry about it. Come summertime, you'll be able to get the best charge under the most ideal conditions.

Again, not to get anyone irritated or the equivalent, this was all for FYI or Reference-type purposes only, not for "Have at it" purposes.

nma851
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reply to F100
said by F100:

thanks for your post about the duel fuel units. Is yours a package unit or split system?

Hey there - glad to hear from another Hybrid owner for once!!

Mine is a split system. As far as I am concerned, the system I chose and put in with my wonderful two hands has served me VERY well. Switching over from an 80% AFUE gas-only that was located at one end of the house to a Hybrid (and moving it to the center of the house) really made the world of difference on the bills. I actually anticipated LESS but got a heck of alot more. I am actually saving about 50-60% as compared to the old system. Moving my Stat to the "main" level as well made the world of difference. Why they put the thing on the LOWER level to begin with was beyond me. Maybe that was their "cure" to get it warmer - while being able to sunbathe upstairs. In the summer, it would be the same - hang meat downstairs & sunbathe upstairs. Initially after getting this place, I moved the stat to the main level which made a huge impact on both heating & cooling, but I still had to damper off rooms (in the basement, not at the supply vents to not lose static pressure), respective to whether cooling was operating or heating was operating. It was a never-ending hassle! :)

My only drawback is I STILL cannot overcome the "Multi-Level Syndrome" as I call it - due to the age of the house, insulation, etc. etc. The lower level (large family room, bathroom) is still cooler than the rest of the place in the winter. Despite moving the location of the furnace to the center of the house, since I was able to do that now (direct vent - no chimney needed on a 93% efficient furnace), "sort of" made a little dent in the problem. We still have to damper the upper/lower floors in winter/summer, but without utilizing TWO independent Split-Systems, it's unlikely to ever overcome the major temp differences between the 3 levels (4 if I include the basement/laundry/mechanical 'level').

said by F100:

Then just add the extra controls like yours. I believe the stat you have requires a 7 wire setup. It sounds like the best way to go. The stat does all the controlling.

You are correct that I opted to utilize the Stat to do all my controlling. Instead of getting a fossil fuel kit, which would be required to ensure that the Gas Furnace does NOT EVER operate with the HP, I went with the Outdoor Temp Sensor that I could get with the Stat. Mine is the Honeywell VisionPro (well, now its the Honeywell RTH9590WF wifi-voice Stat) and that handles the functions of HP lockout SP's, fossil-fuel kit, you name it. I'm STILL learning new features I knew nothing about. Word of caution - DO NOT EVER SAY 'THERMOSTAT' FOLLOWED BY SOMETHING TEMPERATURE RELATED! It WILL respond & end up reacting to that voice command LOLOLOLOL! I think I said something about "see if the thermostat says 62 or 70", so I could see if the iPhone app was showing the same as the Stat, and I ended up lowering my temp to the nighttime setting of 62 degrees at 7:00 at night. Was totally comical after-the-fact but prior to, I thought the dang system went out on me! Technology has come a long way, but there are a few 'quirks' :).

said by F100:

We have about 1800sf but 2 story. The one unit serves both floors but we have to close downstairs vents to get enough flow upstairs. The 2.5 ton unit we have now works pretty well for us.

Any multi-level, IMO, is going to have it's bit of differences up/down stairs. Depending if the ductwork is sized properly now, enough returns/supplys, and locations, it will impact your airflow by restricting it. I had to replace several going to the upper level as they were too small (4") but I wasn't about to tear into walls to make the ENTIRE run to those 3 rooms 100% "right". This would have cost WAY too much money for me & getting 75% of it "up to standards" was acceptable to me. I do NOT recommend that, as that was my own personal decision based on funds/conditions however if they are accessible and/or not costing an arm, leg, and some remaining fingers/toes from the other arm/leg, it would be in your best interests to get the ductwork 100% correct for your home throughout. Ideally, it would need to be throughout but since the additions were done prior to me buying it, I wasn't going to pay all that additional money to tear into walls, ceilings, and attics just to have 2 systems to "zone" the upper from the lower floors.

I'm surprised, however, that 2.5 tons of cooling is sufficient and is likely the 'main' problem with having to close the downstairs supply vents. At 1800SQFT, you should really have a 3 ton, especially with a 2-story home. That is just a "guesstimate" of course, but I would definitely get a 3-ton for your cooling (if you don't go with a heat pump). Again, there is NO way anyone could accurately give that 'magic number' as to the tonnage/BTU's for you online without doing a proper load calculation, but IMO, I would seriously consider going up a notch. Further, oversizing will cause just as many issues as undersizing. In the summer, if oversized, you'll cool too quickly without removing enough humidity. Undersized, that A/C will never stop running. Since you're in NC, that's even a warmer zone (trying to do a load calc example here), and at 3 tons you're still at the "pushing it" end to where you might need a 3.5 ton. Before you DO decide on any of this, ensure the house has a full & proper load calculation done otherwise you will never get the benefits of that new system, even if you decide to go with an HP or not.

Where I am in the Midwest, it's primarily cooler, which is one of the main reasons why I went with the natural gas as the Supplemental (or "Auxiliary" "AUX") heat. If my HP cannot keep up on a given day, which given my house conditions and everything else, is give/take 25-30 degrees. Chances are, it will automatically switch over to the Aux and the HP stops. Same with the morning recovery from the night time temp to the day time temp. The system stages which is the most efficient and the most comfortable means to heat/cool. These systems & controls have come a LONG way but will be virtually useless and of no benefit unless properly sized for the home & without proper airflow through the home.

I'm not really a residential person either - before becoming disabled I was a commercial/industrial mechanical engineer but the concepts for residential were not difficult for me to figure out. There are MANY others on here that are far more familiar and experienced than I am as it relates to residential applications. Before moving forward, I suggest to open a new thread with this question, link these posts to the NEW thread, so that way others will see the subject & be able to add to the conversation. This way, you'll be getting far more responses than you would through this post being "hidden" within a different/unrelated post. Hopefully that will help you all out further before moving forward. If your main question was more/less about the Hybrid HP setup & was answered, no biggie either & hopefully my own personal experience with my setup helps with your decisions.

Either way you go, before getting that replaced, please ensure you have the contractor perform a PROPER load calculation for your home. I wouldn't keep repeating it if it wasn't of the utmost importance! :)

Feel free to ask anything else if you have any more questions, if I missed something, etc. & I'll do my best to answer (or let someone else that has better knowledge answer). Take it easy & take care

pandora
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reply to Jack_in_VA
said by Jack_in_VA:

My unit has not been in defrost in weeks now. Regardless of timer settings the coil temperature has not required it.

I think my unit tests for frosting every half hour, but only starts a defrost cycle if frosting has occurred.
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