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pandora
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join:2001-06-01
Outland
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2 edits

The addition saga continues

Well ... today the electrical rough in is scheduled (any time now). After that, a framing inspection is required, the insulation and an insulation inspection, finally drywall. Then paint, trim, doors, floor, socket covers, fans and what not. I'm guessing another month to a month and a half.

The project came in at the highest estimate I made. (I took the architects high estimate, added 20% then added 20% to that). We are right in line with the highest financial cost.

My only disappointment at the moment is the pre-finished cement siding will likely require some touch up work, as the 10.5" exposure required a 2nd set of nails which are exposed and will need to be painted.

The interior work looks like art to me. All copper to the bathroom / kitchen / laundry. Overall I'm very pleased with the result.

Oak stairs arrived. Oak flooring is on order. If anyone is interested, I'll be taking pictures after the electrical passes. Then all the trades work will be approved.

We have had 2 power failures, and the generator worked well and was fully automatic both times.

There was discussion about heat pumps. Our lowest exterior temperature was 15F so far on heat pump (it was the lowest temperature night we had during the period we have had the heat pump working). Temp in house was kept to 74, I set it to 76, and it took about 20 minutes to reach that in a 1,600 sq foot area. Temp out of the vents was 91-92F, which is the same as when it's 50F outside.

The heat pumps do not use additional current when defrosting. They turn the fan off, and defrost for up to 10 minutes, then run for half an hour before defrosting again. A frost sensor will terminate defrost in about 10 seconds if there is no frost or not a lot of frost (no impairment to function).

I can post some pictures of the work if anyone is interested. In an abundance of caution, I had the plumber run a 2nd steel propane pipe to the attic from the outside where the underground high pressure propane comes to a "stub". It's sized to handle up to 160,000 BTU.

The garage has a 45,000 BTU propane heater, with a garage thermostat that is analog and runs from 35 to 85 degrees.

The biggest problem with the heat pumps has been the MERV 13 filters, which seemed to get clogged after a month in the existing home (there was sheetrock cutting and some work going on, so it may have shortened the life of the filter a bit).

The house with major appliances all on, draws about 215 amps per leg. The upgrade from 200 to 400 amp was probably justified. The air handlers use 83 amps per leg in emergency heat (and there are 2, so that's 166 amps just for the air handlers when both are in emergency heat and on). The electric oven, convection heat microwave, electric hot water heater and 40 amp spa help to push amperage over 200 per leg.

Overall it's impressive imo. I like copper pipes, and feel the Ethernet will be useful over time. We will be testing each Ethernet cable with a tester my electrician is borrowing for Ghz operation. He says it can also test for 500 Mhz. Any line that can't handle high speed will be re-run.

I will never again attempt to manage a project like this, it is beyond my comfort level and my understanding is too limited. The costs, and various delays could potentially have been better managed. However, the changes to the home look great.

In the upper floor of the existing home about 1,200 sq ft of the legacy space will have all wall drywall removed, the exterior walls will have 2" strips added to the existing 2x4's and R21 insulation will be installed. Each room will get the same Ethernet (4 sockets with 7 Cat 6 runs and 2 or 3 RG 6 runs). Plus 2 runs of just electric sockets (quad). Each room is on it's own 20 amp breaker for sockets, 15 amp for lighting.

A final 800 sq ft area of the legacy home is scheduled for a remodeling after CO, and will be remodeled similar to the new standard.

My circa 1970 house with late 1960's design, has been mostly refurbished to more modern standards. All sheetrock with the exception of some ceiling sheetrock will have been replaced in the past few years. The lowest exterior insulation will be R15, but most walls will be R21. Ceiling insulation will be R38, insulation under the floor in the area over the garage will be R30, a 4' deep by 26' wide supported overhung floor that goes behind the garage will be insulated with R30 then 2" of foam board which is supposedly R10. I'm uncertain if one adds the R value of the foam and the insulation.

I'm happier with the result than I expected. The tradesmen really created a work of art imo. It's a bit sad that it'll all be covered. At the same time, I'll know what went into it.
--
"If you put the federal government in charge of the Sahara Desert, in 5 years there'd be a shortage of sand." - Milton Friedman"


garys_2k
Premium
join:2004-05-07
Farmington, MI

Oh, yes, put up plenty of pics, PLEASE! I'm sure I'm not the only one that would like to see this as it goes up.



nunya
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reply to pandora

As explained before, this is incorrect unless you have some new magical heatpump:



The heat pumps do not use additional current when defrosting. They turn the fan off, and defrost for up to 10 minutes, then run for half an hour before defrosting again. A frost sensor will terminate defrost in about 10 seconds if there is no frost or not a lot of frost (no impairment to function).



While in "defrost" mode, the Heatump is actually running as an air conditioner - dumping cold air into the house through the A-coil. The heat strips in the air handler come on to counteract the effects of cooling.
--
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pandora
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said by nunya:

While in "defrost" mode, the Heatump is actually running as an air conditioner - dumping cold air into the house through the A-coil. The heat strips in the air handler come on to counteract the effects of cooling.

NO.

Turns out that is a misconception on this board (or at least the belief that running of cold refrigerant to air handlers when defrosting the compressor is ubiquitous for all heat pumps is in error).

The heat pump doesn't circulate cold refrigerant to the air handler when defrosting. The heat pump fan also stops blowing. The coils get hot. I have seen this, as we had a glass viewer on the refrigerant line to the air handler when looking for air bubbles. No refrigerant moves out of the compressor during defrost.

In addition I have spoken with both the HVAC installer and the manufacturer tech support rep (the one for HVAC installers not normal residential customer support). No running of cold refrigerant the air handler.

This may not be the case for all heat pumps. I can only speak to what I have seen and been told by the people installing and building my units.

My current units are 18 SEER Goodman, I believe the case was identical for my older 14 (maybe it was 13?) SEER Ruud. I do not recall the old unit ever causing cold air to blow.

Even if cold refrigerant were to come to the air handler when in heat mode, it wouldn't blow it to the home. The air handler in heat mode has a minimum temperature for the refrigerant before it will blow air through the coils, similarly there is a maximum temperature for the coils when running air conditioning.

I have come to learn that my system is called an engineered system, and that the system has a fairly smart controller which seems to affect the behavior of the air handler. How much the controller affects the behavior of the air handler with respect to these conditions is beyond my current understanding.

The complexity of all the systems, HVAC, electric, and plumbing is greater than I imagined. My respect for quality tradesmen and their value has improved.
--
"If you put the federal government in charge of the Sahara Desert, in 5 years there'd be a shortage of sand." - Milton Friedman"


cdru
Go Colts
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join:2003-05-14
Fort Wayne, IN
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said by pandora:

The heat pump doesn't circulate cold refrigerant to the air handler when defrosting. The heat pump fan also stops blowing. The coils get hot. I have seen this, as we had a glass viewer on the refrigerant line to the air handler when looking for air bubbles. No refrigerant moves out of the compressor during defrost.

This would seem to magically work differently then every other heat pump out there. The current 18 SEER unit on Goodman's website also doesn't seem to have any type of heater in it's schematic (page 23) aside from the crankcase heater which is usually under 100 watts.

If it doesn't have a heater.. and doesn't run in cooling mode pulling heat from inside... where's the heat coming from?


nunya
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reply to pandora

YES! You are wrong. The refrigerant can't do work without a pressure change. It can't change pressure without using energy.

Where does this magical heat for the defrost mode come from if it's not pulling it from inside?

You keep insinuating you have something special, and you don't.

»www.achrnews.com/articles/unders···peration
--
If someone refers to herself / himself as a "guru", they probably aren't.


pandora
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First, I claim nothing special. My claim is for the units I have had experience with as this isn't my vocation. I don't have a lot of experience with a diverse number of heat pumps.

Second, the coils heat and defrost the unit. In defrost mode the coils become very hot fairly quickly. I don't understand why the fan turns off in defrost mode, but it does.

The compressor can heat or cool the coils based on the direction of the refrigerant through the system. I assume if a unit is frozen (in need of defrosting) the frost will cool the vapor without any need to visit the air handler.

I'll hazard a pure guess here, the defrost sensor may determine if the refrigerant is being cooled when in defrost mode (indicating a need for defrosting). I have seen the units enter defrost mode and exit within seconds. Why run refrigerant to "cool" the air handler, when frozen coils are sufficient?
--
"If you put the federal government in charge of the Sahara Desert, in 5 years there'd be a shortage of sand." - Milton Friedman"



PSWired

join:2006-03-26
Annapolis, MD
reply to nunya

Maybe the heat contained in the refrigerant loop, along with the heat generated by the compressor itself during normal operation, is enough to defrost the coils in his unit? The mitsubishi ductless units I have at work don't even have heat strips and they run through a defrost cycle just fine. The indoor air blower is off during defrost.


harald

join:2010-10-22
Columbus, OH
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reply to pandora

well, I do claim to be an expert. I was the engineer who handled the reversing valve product for Ranco, who manufactured over 90% of the reversing vales in the world.

There is one loop in a heat pump, and all the refrigerant passes through it. There is no capability to prevent the refrigerant from passing through the inside coil.


pandora
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said by harald:

well, I do claim to be an expert. I was the engineer who handled the reversing valve product for Ranco, who manufactured over 90% of the reversing vales in the world.

There is one loop in a heat pump, and all the refrigerant passes through it. There is no capability to prevent the refrigerant from passing through the inside coil.

Noting your past tense, and accepting your implicit assumption technology never changes, I'll defer to your expertise.
--
"If you put the federal government in charge of the Sahara Desert, in 5 years there'd be a shortage of sand." - Milton Friedman"


cdru
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Fort Wayne, IN
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reply to pandora

said by pandora:

Second, the coils heat and defrost the unit. In defrost mode the coils become very hot fairly quickly. I don't understand why the fan turns off in defrost mode, but it does.

The coils become hot the same way your indoor coils heat the house. When in defrost mode though, you want the coils to heat up to melt the frost/ice, instead of heating up the outside air in general. The outdoor fan turns off so that the coils heat faster and the heat isn't wasted warming the surrounding air.

The indoor fan may turn off initially in defrost mode in an attempt to defrost the coils without having to use previously conditioned air, emergency heat strips, and/or other fuel as a heat source. If there isn't a call for heat, but a call for defrost, it may run until the indoor coil reaches a temperature cutoff and the blower turns on. This is when some report that they feel cold air from their vents, as the air isn't heated as hot as when in heating mode. If there isn't an auxiliary source of heat like heat strips, there may be no choice but to blow cold air during the defrost period.

I assume if a unit is frozen (in need of defrosting) the frost will cool the vapor without any need to visit the air handler.

Yes the frost would cool the vapor, if the unit was in cooling mode. However in heating mode, refrigerant returning from the air handler is in a cooled, condensed form. It needs to be EXPANDED back into a relatively warm gas absorbing more heat. The outdoor coil acts as a heat sponge of sorts. If the coils are frosty or iced up, it act like an insulator preventing air from circulating around and the coils absorbing heat from the air.

I'll hazard a pure guess here, the defrost sensor may determine if the refrigerant is being cooled when in defrost mode (indicating a need for defrosting). I have seen the units enter defrost mode and exit within seconds. Why run refrigerant to "cool" the air handler, when frozen coils are sufficient?

You're last statement is backwards. It's the outside coils that are "cooled" when in heating mode.

If the unit enters and exits defrost mode in a few seconds, something is wrong. You're units for instance has a "SmartShift" feature where the compressor shuts off for a short period before and after mode changes, as well as a short cycle protection which is hard on the compressor shortening it's life.

robbin
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Leander, TX
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reply to PSWired

said by PSWired:

Maybe the heat contained in the refrigerant loop, along with the heat generated by the compressor itself during normal operation, is enough to defrost the coils in his unit? The mitsubishi ductless units I have at work don't even have heat strips and they run through a defrost cycle just fine. The indoor air blower is off during defrost.

As a result of your post I found an interesting study on a Fujitsu running in defrost cycle. Fujitsu behavior is as you described for your Mitsubishi.

"During the reverse cycle itself, power usage is modest since the system is taking heat from a mild source and dumping it to a very cold sink (the iced-up coil in the outdoor unit). Since there is no electric resistance backup heat (as would be found in a standard residential heat pump), the overall effect of the reverse cycle is negligible. Also, there are no times where the supply air temperature dips below the return air temperature."

www.bpa.gov/.../BPA-Report_DHP-FujitsuBenchTest-July2009.pdf


Hagar

join:2004-10-31
Sunnyvale, CA
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reply to pandora

Pandora,

You have some nice heatpumps COP 1.22 at -10 Fahrenheit, very nice.
Your heatpump does not blow cold air during a defrost cycle and does not have heat strip in the indoor air handler. Both are good things and what is expected of a modern heat pump.
I personally hate electric heat strips in the indoor air handler, never the optimal solution IMHO.

Now where does the heat needed for the defrost come from? There are only two sources available, the compressor and the warm house. A good heatpump would use both because you want the defrost time to as short as possible. All the time you are in defrost mode the pump cannot heat your house which is the purpose of the heatpump in the first place.
Language like ‘The heat pumps do not use additional current when defrosting’ is not as clear as no heat strips in the indoor air handle. ‘No running of cold refrigerant the air handler’ sounds like marketing speak and is at best misleading, technically speaking it is incorrect. Much better to say not blowing cold air indoors during a defrost cycle.

Most people who have not seen a modern heatpump in action will be surprised how well they work in cold weather.
Laws of thermodynamics have not changed and defrost cycles still reverse the refrigerant flow and take heat from the house.


ncbill
Premium
join:2007-01-23
Winston Salem, NC
reply to pandora

Still don't understand why you didn't off-load more heating needs to propane.

e.g., water heating, space heating, cooking - one can still buy gas oven/range units that require _no_ electrical power.

90F feels pretty cool vs. a gas-fired furnace.