OWB with heat pump backup.

[i'mstihlaguy]

I searched and couldn't find anything so I am asking if anyone has had any experience setting up thermostats / controls for an OWB with heat pump backup. I have a water to air hx in my plennum all ready to go when I get the OWB in a couple weeks. I have already spoken with my HVAC installer who tells me the air handler blower is controlled by a PCB. He said he's not sure how to break into the blower circuit without disrupting the heat pump's ability to control the blower when / if needed for backup. He said he would get a wiring diagram and try to figure something out. The heat pump is an Amana 13 SEER model with Goodman branded air handler. The air handler also has electric resistance coils to back up the heat pump when it can't keep up. Any help would be appreciated.

 

[Scrapiron]

I wish...

I could help. I've got the same setup- OWB with a heat pump downstairs and upstairs (though technically not a heat pump upstairs since it's just electric strips).

The heat pump and OWB have separate thermostats and then are wired together at the air exchange. I wish I had a wiring diagram, but both units are a RATs nest. Nothing fancy and I turn off the heat pumps when running the OWB, however, I guess I could keep the heat pumps set at say, 60 to kick on if the OWB dies down. My new HVAC guy (not responsible for said rats nest of wiring) and I agree it's not wired properly for that and would probably explode.

When my unit(s) die (and they will since they're both about 25 yrs old) we'll rewire to meet code and set it up so it works that way. We'll also replace all the duct work to improve the air flow. It's worse than a crazy roller coaster ride now. We were both scratching our heads why someone would route ducts that way. He also wasn't a big fan of the OWB water in the attic but it sure does get toasty warm upstairs.

Long post to say I want to do the same thing. I'd be more than happy to share the contact info of my HVAC guy, he knew what needed to be done both inside and how to improve the wiring configuration at my Taylor stove. Not sure if he can help over the phone, but maybe he can fax wiring diagrams if you let him know make/model of heat pump.

-Skot

 

[oneoldbanjo]

I have a OWB with a new Carrier Infinity Series pump. The Heat Pump has a SEER of around 15/16 and it is very efficient. It has a computer and a variable speed fan and when you need heat it first tries a very low setting and the blower runs real slow - it tries that for about 20 minutes and if the heat is not sufficient it ramps up to a higher speed and the computer tries to use as little energy as possible to heat the house.

The fellow that sells and installs the OWB used to work for the company that installed my Heat Pump and they have a very good relationship - all the employees knew each other and they worked together to make this system work.

In most older systems the Heat Pump thermostat is just turned down a few degrees and the second OWB thermostat is wired into a fan center that can turn on the furnace blower when heat is needed. The OWB runs hot water through the heat exchanger installed in the furnace continually and simply turning on the blower will put heat into the house. My Carrier Furnace has a computer as part of the system and it monitors the indoor temperature, outside temperature and humidity and calculates what it should do to save energy - and it is impossible to just tap in a fan center and run the furnace blower.

What we had to to was install a Zone Valve on the heat exchanger in the furnace and just set the furnace blower to run on the low setting 24/7. When my OWB thermostat calls for heat the Zone Valve routes the hot water through the heat exchanger installed in the furnace - when we don't need heat the Zone Valve routes the OWB water through a bypass loop. The water from the OWB goes through the Hot Plate for the water heater and then to the Zone Valve for the exchanger in the furnace. This system works very well and heats our house nicely as the furnace blower is running very slow and hardly makes any noise at all. It has never failed to keep us very warm - and if we need more heat in a hurry we can just change the setting on the Heat Pump Thermostat to run the fan at the Medium or High speed. Having air circulation 24/7 eliminates any hot or cold rooms in our house and it allows the elecronic air cleaner to remove dust from the air continually. I don't believe this requires much electricity - as our utility bills are about $ 70 a month and that includes running our electric clothes drier.

 

[i'mstihlaguy]

I could help. I've got the same setup- OWB with a heat pump downstairs and upstairs (though technically not a heat pump upstairs since it's just electric strips).

The heat pump and OWB have separate thermostats and then are wired together at the air exchange. I wish I had a wiring diagram, but both units are a RATs nest. Nothing fancy and I turn off the heat pumps when running the OWB, however, I guess I could keep the heat pumps set at say, 60 to kick on if the OWB dies down. My new HVAC guy (not responsible for said rats nest of wiring) and I agree it's not wired properly for that and would probably explode.

When my unit(s) die (and they will since they're both about 25 yrs old) we'll rewire to meet code and set it up so it works that way. We'll also replace all the duct work to improve the air flow. It's worse than a crazy roller coaster ride now. We were both scratching our heads why someone would route ducts that way. He also wasn't a big fan of the OWB water in the attic but it sure does get toasty warm upstairs.

Long post to say I want to do the same thing. I'd be more than happy to share the contact info of my HVAC guy, he knew what needed to be done both inside and how to improve the wiring configuration at my Taylor stove. Not sure if he can help over the phone, but maybe he can fax wiring diagrams if you let him know make/model of heat pump.

-Skot

Thanks Scrapiron. I had a similar conversation with my HVAC guy about frying the heat pump's contol circuit if both thermostats called for heat at the same time. Please send PM with contact info for your HVAC guy.

 

[barnyardman]

I had a Heatmor installed last week. We have a oil furnace. The OWB guy installed a seperate thermostat for the OWB. He did the zone valve with a by pass for when OWB thermostat calls for heat. He installed a relay in furnace (not sure how its wired) & it will let the fan work for which ever unit calls for heat.

 

[i'mstihlaguy]

I have a OWB with a new Carrier Infinity Series pump. The Heat Pump has a SEER of around 15/16 and it is very efficient. It has a computer and a variable speed fan and when you need heat it first tries a very low setting and the blower runs real slow - it tries that for about 20 minutes and if the heat is not sufficient it ramps up to a higher speed and the computer tries to use as little energy as possible to heat the house.

The fellow that sells and installs the OWB used to work for the company that installed my Heat Pump and they have a very good relationship - all the employees knew each other and they worked together to make this system work.

In most older systems the Heat Pump thermostat is just turned down a few degrees and the second OWB thermostat is wired into a fan center that can turn on the furnace blower when heat is needed. The OWB runs hot water through the heat exchanger installed in the furnace continually and simply turning on the blower will put heat into the house. My Carrier Furnace has a computer as part of the system and it monitors the indoor temperature, outside temperature and humidity and calculates what it should do to save energy - and it is impossible to just tap in a fan center and run the furnace blower.

What we had to to was install a Zone Valve on the heat exchanger in the furnace and just set the furnace blower to run on the low setting 24/7. When my OWB thermostat calls for heat the Zone Valve routes the hot water through the heat exchanger installed in the furnace - when we don't need heat the Zone Valve routes the OWB water through a bypass loop. The water from the OWB goes through the Hot Plate for the water heater and then to the Zone Valve for the exchanger in the furnace. This system works very well and heats our house nicely as the furnace blower is running very slow and hardly makes any noise at all. It has never failed to keep us very warm - and if we need more heat in a hurry we can just change the setting on the Heat Pump Thermostat to run the fan at the Medium or High speed. Having air circulation 24/7 eliminates any hot or cold rooms in our house and it allows the elecronic air cleaner to remove dust from the air continually. I don't believe this requires much electricity - as our utility bills are about $ 70 a month and that includes running our electric clothes drier.

Thanks Oneoldbanjo. Sounds like your setup does the trick. The only downside I see is when / if your fire goes out. Your heat pump t-stat will call for heat and the air will be passing through the cold hx drawing off some of the heat. Unless you turn the OWB t-stat down below the heat pump t-stat setting, the zone valve will let the cold water continue to circulate through the hx. This isn't necessarily a bad thing though because that keeps your OWB water from freezing over an extended period of time. And this would be a rare occurrence anyway.

 

[mtfallsmikey]

Things have really changed in the last 10 years or so in regard to heat pump control schemes, which is better since every mfr. had their own way of controlling the blower, 2nd stage heat, reversing valve, defrost timer, etc. Things are more standardized now. Only bad thing is if you smoke a PCB control, price to replace it is downright salty. On an older heat pump, the OWB could be wired in to eiether 1st or 2nd stage on the t-stat, which the older stats for heat pumps were 2 stats in one; 1st stage ran the condenser until heat output decreased to a point where the electric heat (2nd stage) was required, you could adjust the 2nd stage to come in earlier or later as required. My advice in any case is to keep the OWB controls separated as much as possible, except for blower and possibly secondary circ. pumps.

 

[oneoldbanjo]

Thanks Oneoldbanjo. Sounds like your setup does the trick. The only downside I see is when / if your fire goes out. Your heat pump t-stat will call for heat and the air will be passing through the cold hx drawing off some of the heat. Unless you turn the OWB t-stat down below the heat pump t-stat setting, the zone valve will let the cold water continue to circulate through the hx. This isn't necessarily a bad thing though because that keeps your OWB water from freezing over an extended period of time. And this would be a rare occurrence anyway.

Yes I agree that if the fire goes out.....the Heat Pump will come on. For normal daily operation this is not a problem as we keep our OWB thermostat set at 68 and our Heat Pump Thermostat at 66 - and we never have a situation where the fire goes out enough to drop the OWB temperature below a point that it won't heat the house. I build small fires in the morning before I leave for work and at night before I go to bed - I always add just a couple of armloads of wood and that keeps the fire going. If we go away for an extended period we warm the house and garage higher than normal just prior to leaving. We then turn the thermostat in the garage off, lower the thermostat in the house to 55 and then fill the OWB up as full as we can get it. Last Thanksgiving we left on Thursday morning and when we returned on Sunday night there was still a fire going in the OWB. If the fire were to go out the air flowing through the heat exchanger will keep the OWB from freezing, and then when the temperature in the house drops below 55 the Heat Pump will come on to heat both the house and the OWB. Our house is very well insulated however as it is made out of styrofoam panels that are 6" thick in the walls and 8" thick in the roof.....and we only lose about 4 degrees a day if the heat is turned off.

For us.....our system works very well.

 

[i'mstihlaguy]

Okay, I couldn’t give up on this just yet. The goal of course is to control the blower from the OWB t-stat as primary and heat pump t-stat as back up without burning up the heat pump’s PCB. My blower is multi-speed but you have to manually set it on the speed you want. My loop to the water to air hx in the plenum will circulate continuously. Why couldn’t I plumb an aquastat in the supply to the water to air hx with a set point of 20 to 30 degrees below normal operating temp? The aquastat would control a relay or some other device that would determine where the input voltage for the blower motor comes from. This would isolate the heat pump circuit. Under normal operation, where the OWB is supplying water in the normal operating range, power to the blower motor would come from a separate circuit controlled by the OWB room t-stat. If the water temp. falls, say 20 to 30 degrees, then the aquastat would operate the relay letting the system revert to the normal heat pump operation controlled by the heat pump room t-stat. Any comments?

I created the attached diagram to help explain this. I am not an EE so please forgive my rudimentary diagram.

 

[KRB64]

OK, what's a PCB?

oneoldbanjo, you probably aren't too far from me (Frankfort). What brand is your OWB? I envy your insulation. I'm dealing with a 100+ YO house and upgrading the insulation is on the list when funds allow.

 

[projectsho89]

OK, what's a PCB?

oneoldbanjo, you probably aren't too far from me (Frankfort). What brand is your OWB? I envy your insulation. I'm dealing with a 100+ YO house and upgrading the insulation is on the list when funds allow.

PCB= Printed Circuit Board. It's one of the acronyms electronics guys use to describe almost any circuit board.

In this case, it's the controller for the furnace. It accepts the signal from the wall thermostat and, using these inputs (perhaps more, depending on the complexity of the control system), provides system control of all outputs such as the blower, AC compressor, heat pump, etc.

I do have to ask, what kind of OWB is running +250F. Perhaps identifying your setup in your signature would help, your favorite song/artist doesn't.

I've got my system on propane backup that will kick in when the incoming OWB water drops too low to provide useful heat. Turned out to be pretty simple although I'm still playing with the adjustment. All it took was a simple $13 water heater upper thermostat from Lowes that lies on top of my horizontally-mounted heat exchanger and some wiring. All I do is intercept the call for heat fromt he thermostat and, based on the temperature of the HX, either passes the signal on to the control board unchanged (cool HX) or directs the call for heat to a blower on signal (up-to-temp HX).

This is based on a typical 4-wire thermostat hookup. If you are using something else, it won't work as I implemented it

If you are, indeed, running at such temps, then my solution won't work as WH thermostats are typically only available for temps up to 180F (commercial version).

Steve

 

[cfabe]

Well here is how I would set it up. Install a separate 1-stage heating thermostat to control the OWB next to the heat pump thermostat. Wire R on the new thermostat to R on the old thermostat. Wire W on the new thermostat to G on the old thermostat. This will run the blower only on the air handler when the owb thermostat calls for heat. And the heat pump thermostat will function normally. The owb thermostat is doing the same thing as turning the fan switch to "ON" instead of "AUTO."

The other common method used is the "intercept at furnace" method like projectsho89 mentioned but that gets tricky with a two stage heat system (like your heat pump is).

 

[i'mstihlaguy]

Well here is how I would set it up. Install a separate 1-stage heating thermostat to control the OWB next to the heat pump thermostat. Wire R on the new thermostat to R on the old thermostat. Wire W on the new thermostat to G on the old thermostat. This will run the blower only on the air handler when the owb thermostat calls for heat. And the heat pump thermostat will function normally. The owb thermostat is doing the same thing as turning the fan switch to "ON" instead of "AUTO."

The other common method used is the "intercept at furnace" method like projectsho89 mentioned but that gets tricky with a two stage heat system (like your heat pump is).

That sounds so simple. I can't wait to run it past my HVAC guy. If this works for me then I owe you big time.

 

[projectsho89]

A second simple thermostat adjacent to your primary thermostat is indeed the simplest if all you want to do is control the furnace blower at a single speed. Anything other than that, it gets more complicated.

In my case, I decided to make the switchover transparent for the benefit of my wife who has zero interest in tinkering with anything.

Steve

 

[KRB64]

Well here is how I would set it up. Install a separate 1-stage heating thermostat to control the OWB next to the heat pump thermostat. Wire R on the new thermostat to R on the old thermostat. Wire W on the new thermostat to G on the old thermostat. This will run the blower only on the air handler when the owb thermostat calls for heat. And the heat pump thermostat will function normally. The owb thermostat is doing the same thing as turning the fan switch to "ON" instead of "AUTO."

The other common method used is the "intercept at furnace" method like projectsho89 mentioned but that gets tricky with a two stage heat system (like your heat pump is).

So will this same hookup work for me too, running forced air propane? Assuming my circulator pump is already running 24/7. To operate the [ump on demand would take a different course of action.

 

[oneoldbanjo]

KRB64:

I guess I am a "Kentucky Yankee".....I live about 20 miles south of Cincinnati and about 1.5 hours northeast of you.

My system worked great this weekend while I was away and I will probably post it. I loaded it up with wood Thursday morning, turned the heat off in the garage and lowered the house to 60....and when I got home last night the furnace had a 12" bed of coals and about 1/4th of the wood left.

 

[cfabe]

KRB64 - It should work with any forced air system that uses a "normal" thermostat. My system happens to be configured in the "intercept at furnace" method but it was installed before I bought the house. If my aquastat that controls the intercept ever goes bad I'll just change it to the dual t-stat method.