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laserfan

join:2005-01-14
Texas

Better way to switch HVAC to heat strips?

We have two heat pump systems, with auxiliary heating strips, and the compressors are unfortunately located close to our bedroom. When cooling in the summer, the compressors are acceptably quiet, but in the winter they can be quite noisy particularly when they go thru their defrost cycle.

So in the wintertime, when temps here in TX are likely to approach freezing or below overnight, I change the System setting on our t-stats to EM HEAT and towards morning when the house gets cold and heat is needed, only the fans w/heat strips come-on; no compressors.

I would like to be able to automate this behavior, but two things stand in my way:

1. First, while the t-stat has Sleep, Wake, Leave, and Return automation, this is for temps only and can not change the System setting

2. The t-stats (Honeywell TH8321U) have an Outdoor Air sensor capability, which would automate the process ("lock-out the compressors below x degrees e.g. 35deg outside") but their location in the house would be very difficult for me to run sensor wires to their locations

So I'm wondering if anyone knows another way to do this. I'm thinking maybe a local control outside at the compressors that would keep them from coming-On below 40deg or some such, and then the inside thermostats would automatically bring-on the heat strips ("Aux Heat On") because the compressors aren't carrying the load.

Anyone here familiar with this dilemma? When we built this house, we'd just moved down here and weren't familiar at all with heat pumps thus didn't know some of the issues. And the nature of the home site was such that placement of the outdoor compressors was very limited--even today I wouldn't know a better location for these than near the MBR where they are presently.


pike
Premium,MVM
join:2001-02-01
Washington, DC
kudos:3
I'm fairly certain the Ecobee thermostat would allow you to do #2. It can be set up to pull the outside temperature from NOAA based on your ZIP code instead of using on an outdoor temp sensor.

scooper

join:2000-07-11
Youngsville, NC
kudos:2
reply to laserfan
You do realize that using the heat strips is about the most expensive way to heat your house ?


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
reply to laserfan
How old are the heat pumps?


R4M0N
Brazilian Soccer Ownz Joo

join:2000-10-04
Glen Allen, VA
reply to scooper
said by scooper:

You do realize that using the heat strips is about the most expensive way to heat your house ?

+1

I actually try to AVOID turning the heat strips on... Those things can suck up like 15kw


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to laserfan
Heating with the strips at "freezing" temperature still costs about 2.5-3 times more than with the HP.
While the units do sometimes go in defrost, that shouldn't be such a frequent event (but of course it depends on the temperature and humidity). In fact the noise should be comparable to the cooling cycle, minus the fan.
I would have the units checked. My units only seldom go in defrost even when it gets in the 10-15F range and the only indication that I have is the furnace starting - no additional noise.


PSWired

join:2006-03-26
Annapolis, MD
Most of the older heat pumps I have seen make a bunch of noise when the reversing valve switches positions and the refrigerant changes pressure quickly. Sounds like a big whooshing/hissing noise and is often pretty loud. I wouldn't want it happening by my bedroom window.

At any rate, I think this thing will do exactly what the OP wants:

»www.acwholesalers.com/ProductDet···odazAAYg

Installation instructions:

»www.acwholesalers.com/v/vspfiles···ions.pdf

It's just an outdoor thermostat with SPDT contacts. Use it to interrupt the heating signal to the outside unit.

laserfan

join:2005-01-14
Texas
Thanks PSWired--you're exactly right about the noise my 10yr old Carrier heat pumps make. I'd talked my builder into installing two of these on our main house and it turns-out that the Goodman unit in our previously-built Guest house is a lot quieter FWIW.

I've just glanced at the link but it looks spot-on to what I need to do.

Yes folks, I am very well aware that heat strips are expensive to run. Some things in life are worth paying for, like night time peace & quiet...



nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
10 years is still young, but have you considered replacing the the HP units or relocating them?
--
If someone refers to herself / himself as a "guru", they probably aren't.


AVD
Respice, Adspice, Prospice
Premium
join:2003-02-06
Onion, NJ
kudos:1
said by nunya:

have you considered replacing the the HP units or relocating them?

It might be cheaper in the long run to relocate the units away from your bedroom.
--
* seek help if having trouble coping
--Standard disclaimers apply.--

laserfan

join:2005-01-14
Texas
reply to PSWired
said by PSWired:

It's just an outdoor thermostat with SPDT contacts. Use it to interrupt the heating signal to the outside unit.

Seems odd to me that the Goodman doc says nothing about using it to lock-out the compressor. I'm thinking I simply insert the Goodman unit to the Y (compressor) terminal thereby opening the circuit below X degrees?

If this is right, then I'm wondering at what point the heat strips turn-on:

1. Immediately because the outdoor unit compressor doesn't come-on, and thus *it* closes the W2 contact to the heat strips, or

2. After some delay when the t-stat realizes it ain't gettin' warmer thus the compressor must not be running, then the t-stat makes the W2 connection to the heat strips

Do you know, or can you guess, PSWired for my 38EYG Carrier heat pumps?

@nunya as I said already there's no better alternate location for these units...I will consider newer, quieter units when one of these craps-out I suppose, but for now a few extra bucks during extreme cold temps is easiest for me to accept.


PSWired

join:2006-03-26
Annapolis, MD
#2. I can't say for sure, but if it's a conventional controls setup the thermostat will have to wait till it realizes the heat pump isn't working to switch in the resistance heating.


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting
reply to laserfan
I can think of a way to do it with a simple timer and contactor. It's not kosher though. You would be "tricking" the t-stat into thinking it's running the HP when it's actually running the strips.
--
If someone refers to herself / himself as a "guru", they probably aren't.


PSWired

join:2006-03-26
Annapolis, MD
But he only wants the strips to run at night if there's a risk of a defrost cycle. Warmer nights are OK to run the heat pump.

If he could get a cable from the thermostat to an outdoor location, he could use that thermostat I linked to do what you're talking about--it's got SPDT contacts on it.


PSWired

join:2006-03-26
Annapolis, MD
Oh, and laserfan:

Yes, just run the Y line through the normally closed contacts of that thermostat.


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting
reply to PSWired
Heatpumps are always going to be "at risk" of running the defrost cycle. Some run on a timer, fancier ones have an ice sensor. Even in warmer (above freezing) weather, they can go through a defrost cycle.

I had a Bryant (Carrier) HP that we called the "tornado siren", although it sounded more like someone getting the electric chair while a tornado siren was running.

Anyway, the installer came out and putzed around for a while but never made any difference. Called a different company out of frustration and they narrowed it down to 2 things: 1) it was overcharged 2) it had a reversing valve which was notoriously noisy.
They replaced the reversing valve, and "viola", no more elephant. Of course Carrier would not honor the warranty and it ended up costing me about $600.
Glad I have gas heat now.
--
If someone refers to herself / himself as a "guru", they probably aren't.


PSWired

join:2006-03-26
Annapolis, MD
Hey, I was looking to see if that compressor had a temperature-based defrost control, and came across this:

»www.docs.hvacpartners.com/idc/gr···-3pd.pdf

Defrost Control Board

Incorporates a defrost relay, defrost
timer, and low-voltage terminations.
The defrost control is a time and
temperature initiation/termination
control which includes 4 fieldselectable
(DIP switch) time periods
of 30, 60, 90, and 120 minutes. The
control includes built-in 5-minute
compressor delay for units equipped
with single-phase scroll compressors.
This control also includes a fieldselectable
(DIP switch) Quiet Shift
mode, which if selected, maintains
quiet operation during defrost.

Might be worth checking to see if that "quiet shift" mode is turned on!


PSWired

join:2006-03-26
Annapolis, MD
Also, here's a thread on the quiet shift mode:

»hvac-talk.com/vbb/showthread.php···st-Noise


Tex
Premium
join:2012-10-20
kudos:2
reply to laserfan
said by laserfan:

said by PSWired:

It's just an outdoor thermostat with SPDT contacts. Use it to interrupt the heating signal to the outside unit.

Seems odd to me that the Goodman doc says nothing about using it to lock-out the compressor. I'm thinking I simply insert the Goodman unit to the Y (compressor) terminal thereby opening the circuit below X degrees?

If this is right, then I'm wondering at what point the heat strips turn-on:

1. Immediately because the outdoor unit compressor doesn't come-on, and thus *it* closes the W2 contact to the heat strips, or

2. After some delay when the t-stat realizes it ain't gettin' warmer thus the compressor must not be running, then the t-stat makes the W2 connection to the heat strips

When the outdoor temperature is above the temperature setting of the control, the heat pump will operate normally. When the outdoor temperature is below the temperature setting of the control, the normally closed set of contacts open ("Y" compressor) and the normally open set of contacts close ("W2" indoor heat strips). This is shown in Figure 9 of the Installation and Operation Instructions.

laserfan

join:2005-01-14
Texas
Thanks Tex, I had DL'ed a newer version of the OT18 instructions and that schematic escaped me. I think that's exactly what I want. The thing I wonder about is whether my tstat will know the heat strips are on, i.e. in EM HEAT (system mode) there's a red LED to indicate "on heat strips" and in normal system mode, when the heat strips are on (as for when the HP can't keep-up) then it says "Aux Heat On" in the display. A minor thing to be sure...

@PSWired I'd seen the "Quiet Shift" in my 38EYG docs but haven't checked yet to see if that DIP switch actually exists iin my unit. I'd not investigated cuz I'd assumed there was a downside to using it (without knowing what that was--the docs don't tell of course) and that thread says "more compressor starts" so I dunno. But I have to try it to see what diff it might make to the bizarre sounds these units now make in any case. Great thread BTW; confirms I'm not alone in my unhappiness with my Carriers.

@nunya congrats on your gas heat! When we moved to So. TX from MN we'd had zero experience/knowledge of heat pumps, and have learned to hate them. I should have done propane heat but retrofitting that-in would be a bear. BTW both my units started life being under-charged; later I had them properly charged and they work (cool, heat) a LOT better since, but under BOTH circumstances they are noisy in heating mode and when defrosting.

Guys these responses are why I love the Internet; thanks so much for helping me with this!