Dual heating set-up with AA-130 and forced air

I have my AA-130 almost plumbed in completely. It will serve as the primary heat next to a forced air propane system ( i'm using a water to air heat exchanger). I want to wire the AA-130 so that it will run on a call for heat and the blower will turn on in the forced air furnace but not the gas valve. At the same time, I'd like the furnace to take over if the boiler goes out--in which case the blower and gas valve would turn on.

How do I best do this?

A friend of mine has suggested that I wire the thermostat directly to the FA furnace with an in-line aquastat hooked up to a pipe in the boiler primary circuit. On a call for heat, the FA will attempt to operate, turning on the blower...BUT, if the auqastat senses heat in the pipes, it will not allow the gas valve to turn on. If the pipe is cold (i.e.-the boiler is not operating), it will let the valve open and the FA unit will heat the home.

If I am understanding this correctly, he wants me to bypass hooking up the thermostat to the boiler's main aquastat to do this. That would mean that my circulator would run constantly, wouldn't it? Is this good?

It also requires an extra (3rd) auqastat. I would have the main aquastat on the boiler, the highlimit and this in-line stat.

Is this an acceptable way to do this? Is there a better way? I was thinking that I would like my circualtor to run only on a call for heat and if possible do away with the need for a third stat. What is the best way to wire this?

Thoughts?

Mark

Mark,

First, I'll say that my system is air over water, and I have a york heat pump for the living area, and a fan/coil unit for the basement. Seperate coils and ductwork, no fire, no basement heat. I wanted to lock the HP's compressor out, but I wanted the HP to come back on if I lost fire, etc. I also did NOT want a second thermostat controlling the boiler. I called York and asked how to prevent the outdoor unit from running [as you wish to lock out your burner]. I was told which wire to break. Like you plan, an aquastat controls the heat pump's compressor "lock out" temp.

On pumping your water 24/7; If the piping is in a conditioned area, the heat loss from the piping from running the pump 24/7 would not be lost. That's how my system is currently setup. It is simple, and works well in winter. However, I must admit though, with warm outside temps in the spring, the basement get warmer than it needs to be due to the heat loss from the unisulated piping. Not hateful hot, but warmer than I'd like. It's a shop, and I try to keep it 67 ish. It was warm today [mid 60s], no heat load on the boiler, and it was 70 in the basement. I am thinking about setting my system up to cycle the pump as needed.

Your furnace may have an extra 24 v circuit in it to allow running a humidifier, etc. My heatpump has such a circuit. It supplies 24v current whenever the fan runs. If your furnace also has such a circuit, it could be used to control a 24v/115v circulator relay. If you have no such circuit, someone good on controls could figure a way to power another style relay from your fan's circuit to run the circ pump.

The one issue with the "heat pump, or in your case, burner lock out" aquastat is, if you want to cycle your circulator, the aquastat will need to be on the boiler. My 'lock out" aquastat is mounted right at the coil, with short wires to the heat pump's air handler. If I change my setup, I'll need to move that aquastat to the boiler.

Good luck with the install.

Dave

I run a hydro fancoil in my ductwork from the a/c and heat pump. I have 2 thermostats, one for the a/c heat pump, and one for the axeman. The thermostat for the axeman starts and stops the circulator to the fancoil, when the fancoil is warm, their is an aquastat that senses the heat and makes the circut for the fan to start. The 2 systems are NOT electrically tied together, only heat in the fancoil tells the fan to run. I can set the second thermostat a couple degrees lower in case something would not work, and the heat pump will kick in. My thermostat for the a/c has a (I believe green) wire that starts the fan, that is connected to the aquastat . It's the type of thermostat that their is a switch if you want to run the fan by itself. CAN YOU RUN YOUR FAN FROM THE THERMOSTAT WITHOUT A CALL FOR HEAT ?

I would buy a taco hydro air control:

http://www.pexuniverse.com/taco-hydro-air-fan-controls

Wire this control to a thermostat. wire the outputs R, G to the furnace -They are dry. Wire T-T to the boiler aquastat. If you want a strap-on aquastat on the pipe also , you can do it or buy the time delay model to delay start the fan.

Wire a second plain jane thermostat to the R-W of the furnace. This will be in parallel to the hydro air control. Set this thermostat lower than the first. This is your backup stat.

R-G on a furnace will run the blower only. R-W will run the heat with the gas valve.

Just a suggestion.

markleo wrote:I have my AA-130 almost plumbed in completely. It will serve as the primary heat next to a forced air propane system ( i'm using a water to air heat exchanger). I want to wire the AA-130 so that it will run on a call for heat and the blower will turn on in the forced air furnace but not the gas valve. At the same time, I'd like the furnace to take over if the boiler goes out--in which case the blower and gas valve would turn on.

How do I best do this?

A friend of mine has suggested that I wire the thermostat directly to the FA furnace with an in-line aquastat hooked up to a pipe in the boiler primary circuit. On a call for heat, the FA will attempt to operate, turning on the blower...BUT, if the auqastat senses heat in the pipes, it will not allow the gas valve to turn on. If the pipe is cold (i.e.-the boiler is not operating), it will let the valve open and the FA unit will heat the home.

If I am understanding this correctly, he wants me to bypass hooking up the thermostat to the boiler's main aquastat to do this. That would mean that my circulator would run constantly, wouldn't it? Is this good?

It also requires an extra (3rd) auqastat. I would have the main aquastat on the boiler, the highlimit and this in-line stat.

Is this an acceptable way to do this? Is there a better way? I was thinking that I would like my circualtor to run only on a call for heat and if possible do away with the need for a third stat. What is the best way to wire this?



Thoughts?

Mark

Did you get your solution yet?

Depending on what brand and model t'stat is being used there could be different solutions.

I don't believe that the AHS Coal gun takes calls from T-Stats to initiate its fan motor. The way mine is wired it merely monitors its own internal temperature and starts the fan as it sees the need to do so. The only T-Stat it sees is its own.

lsayre wrote:I don't believe that the AHS Coal gun takes calls from T-Stats to initiate its fan motor. The way mine is wired it merely monitors its own internal temperature and starts the fan as it sees the need to do so. The only T-Stat it sees is its own.

Yes, AHS uses a single-acting aquastat to maintain temperature. Axeman Anderson on the other hand provides a triple-acting aquastat with their boilers.

I like steamup's suggestion...simple and functional.

Rob R. wrote:I like steamup's suggestion...simple and functional.

An aquastat on the pipe is simple and effective (simple mechanical switch). If it has the adjustable differential, you can control how long it takes for the fan to stop, run a dump zone without extra wiring on the fan side, and doesn't have an extra pc board to burn out.