Does your thermostat keep the reversing valve energized when system is off?


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MichaelSK

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Honeywell RTH7560 thermostat keeps the reversing valve energized even when “mode” is set to “off”. There is no need to keep a nominal 26vac on the (orange) lead, the reversing valve solenoid remains very hot when the system is not being used. I spoke with the Honeywell consumer help rep who stated that the thermostat should de-energize the valve when the mode is set to “off”.

My concerns are: 1) this is the third thermostat (same model), 2) I called the technical guys at Honeywell and asked if there was a recall - he responded “no there is no a recall on that thermostat,” 3) my valve gets very hot 168 f after 10 minutes, 4) seems that this behavior would shorten the reversing valve life-span, 5) could be a fire hazard, 6) this thermostat is widely used, few consumers would be aware that the device is energizing their reversing valve when the system is off. Indeed, how many repairs and shortened system lifespans are r/t to this behavior?

One last question, the consumer, i.e. nontechnical rep, stated that the thermostat should not be energizing the reversing valve - what’s your experience? IMHO, the reversing valve should only be energized in most heat pumps when the system is actually RUNNING in COOL; the thermostat should not be keeping the valve energized when the system is idle - perhaps for months at a time.
 

hj

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I had a friend who had a problem like that, except it reversed ALL THE TIME, so his heating cycle used the auxiliary heat strips to overcome the cooling load, at an extremely costly, and nonrefundable, expense to him.
 

WorthFlorida

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What brand of unit you have? Do you have AUX heat strips (two stage heat)? One stage cooling? You could have it miss programed it for the third time but I don't know what would keep the voltage connected to the O terminal 100% of the time. It is why a miss wire would be my first concern, then programming.

Is this new thermostat & new install or did this problem just started The reversing valve de-energized places the system in heat pump mode, energized it is in cooling mode. There could be three things going on, miss wired, a short (chew wire, etc) or the thermostat is bad or programmed wrong.

Remove the wire on the "O" terminal and check for any voltage on the wire, there should be no voltage. If there is, something is miss wired at the compressor or a shorted wire. Also check the O wire inside the air handler that it is free and clear of any other wire. If it goes to a terminal to connect to the wire going to the compressor, be sure no other wires are on it.

If the thermostat has power on the "O" terminal in heat mode or off, it's a thermostat problem. Do check that the wire from the AUX terminal is not touching the O terminal. LOOK for SHORTS.

Another thing you can try is reprogram the thermostat for a single stage cool only system and there will be no voltage on the O terminal since a cool only system has no reversing valve.
 
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Echevy350

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Hi, I’ve been searching for answers for this exact problem I’m having too so I signed up for an account. Was a solution ever found? I’m getting constant power to the reversing valve solenoid even when the heat pump is switched off. I have a new Goodman Packaged heat pump, wiring, and digital Honeywell thermostat, and walked by the unit a few days ago and heard the humming solenoid.
I’ve tried two different Digital thermostats and same result. I disconnected the orange wire at the heat pump and it does have power coming from the thermostat so it is definitely a thermostat issue. I noticed the only time the solenoid de-energizes and stays off is if I switch it to heat mode, and then turn it off.
I hooked up my old manual thermostat and it will de-energize when switched to off. Any suggestions?
 

WorthFlorida

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Be sure that you have the thermostat programmed as two stage heat pump (assuming you have electric heat strips), one stage cool. The reversing valve is energized for cool mode, de energized during heat pump mode operation. Voltages is ~24v ac.

1) At the thermostat, remove the wire at the O/B terminal. There should be no voltage at the O/B terminal with No Call for heat or cool. Also, with the thermostat in "system off", no voltages except on the R and RH terminals.

2)Turn the thermostat to heat mode and raise the temp to call for heat, there will be no voltage on the O/B terminal.

3) Lower the temp setting to turn on cooling, voltage should be on the O/B terminal.

If any of these do not pan out then check the program. Under the System menu go through each page. This is a Honeywell TH9320 WIFI. I have a one stage cool, two stage heat (heat pump, electric strips as "AUX" heat).

I'm suspecting the first pic is the problem. Type of change over valve. Most systems are the top option as shown, but there are some systems that do it in reverse. Goodman should be standard or the most common.

If the program looks good and the and the thermostat checks out good, check the wiring in the air handler. Thermostat wiring goes to the air handler then connected to go to the compressor unit. someone may have confused an orange wire for a red. Red always have 24v ac on it.

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Stuff

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Maybe this is a "feature" of a digital thermostat so that the reversing valve doesn't flip when you turn it on and off. Looking at the wiring diagrams manual thermostats physically disconnect both O and B when in the off position.

If your valve is humming then this might be an indication that it needs to be checked.
 

Gilmour

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Honeywell RTH7560 thermostat keeps the reversing valve energized even when “mode” is set to “off”. There is no need to keep a nominal 26vac on the (orange) lead, the reversing valve solenoid remains very hot when the system is not being used. I spoke with the Honeywell consumer help rep who stated that the thermostat should de-energize the valve when the mode is set to “off”.

My concerns are: 1) this is the third thermostat (same model), 2) I called the technical guys at Honeywell and asked if there was a recall - he responded “no there is no a recall on that thermostat,” 3) my valve gets very hot 168 f after 10 minutes, 4) seems that this behavior would shorten the reversing valve life-span, 5) could be a fire hazard, 6) this thermostat is widely used, few consumers would be aware that the device is energizing their reversing valve when the system is off. Indeed, how many repairs and shortened system lifespans are r/t to this behavior?

One last question, the consumer, i.e. nontechnical rep, stated that the thermostat should not be energizing the reversing valve - what’s your experience? IMHO, the reversing valve should only be energized in most heat pumps when the system is actually RUNNING in COOL; the thermostat should not be keeping the valve energized when the system is idle - perhaps for months at a time.
Sorry I know this is an old post but I'd like to confirm this behavior. I have a Honeywell IAQ thermostat system with the EIM. It's cooling season here and I noticed that the reversing valve was energized and felt hot to the touch. The Bosch Geothermal system it's controlling works fine (reversing valve should be energized to cool). If I switch the stat to heat the valve de energizes. If I switch to off from heat the valve stays off. In cool mode it's always on even when there is no call for AC. If I switch to off from cool the valve stays energized. The Bosch system control board correctly obeys the command from the EIM, the valve de energizes when the 'o' wire is removed from the EIM. I've had the system for over 8 years. This is the first time I've noticed this but it must have been happening all the time.
 

WorthFlorida

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Does it stay energized when the temperature is satisfied and the thermostat turns off the system? I'm sure you went through my post above. If you suspect it's the thermostat, I would do a factory reset and reprogram it. I would do a voltage check on the O terminal to see what the thermostat is doing

A reversing valves are well inside the compressor unit and to get access you need to remove its covers. Was it an add on when using a geothermal system and it's external?

I'm not at all familiar with the IQA let alone a geothermal system. I'll be reading into the IAQ soon, it's the first I've heard of it.
 

Stuff

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Since the two years this thread started I've verified a couple of things.
  1. Mechanical thermostats had their O and B terminals tied to the Cool-Off-Heat switch independent of temperature. With that your reversing valve was on or off the entire season. Exceptions were thermostats that had an Auto setting that switched automatically between cooling and heating.
  2. Some new thermostats (e.g. Nest) have a setting to make the O/B be seasonally or each cycle. They default to seasonally.
One theory is that per cycle puts strain on the reversing valve and the system is more reliable if it only moves a few times a year. (theory disproven below)
 
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Fitter30

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A 24vac solenoid coil draws about 15 - 25 watts of power. 25watts @ 24 vac= 1 amp, at 120vac .21 amps.
The armature ( the piece the coil moves) keeps the coil from burning out. If armature doesn't pull up coil will be toast within a minute. Coil temperature runs from 150° f to 200° f.
 

Fitter30

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Since the two years this thread started I've verified a couple of things.
  1. Mechanical thermostats had their O and B terminals tied to the Cool-Off-Heat switch independent of temperature. With that your reversing valve was on or off the entire season. Exceptions were thermostats that had an Auto setting that switched automatically between cooling and heating.
  2. Some new thermostats (e.g. Nest) have a setting to make the O/B be seasonally or each cycle. They default to seasonally.
One theory is that per cycle puts strain on the reversing valve and the system is more reliable if it only moves a few times a year.
How many times in heating season does a reversing valve cycle in defrost ? And what about units that rv is powered for heat?
 

Stuff

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Good point about defrost cycle which blows that theory. Maybe in Arizona the reversing valve doesn't move. Many are timer based so quite a few times during the day no matter what.
 

Stuff

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A 24vac solenoid coil draws about 15 - 25 watts of power. 25watts @ 24 vac= 1 amp, at 120vac .21 amps.
The armature ( the piece the coil moves) keeps the coil from burning out. If armature doesn't pull up coil will be toast within a minute. Coil temperature runs from 150° f to 200° f.
Your wattages are bit high. Even the link you posted lists 6 - 16 watts nominal.
 
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