How to add boiler to existing thermostat?

[98kx1927]

My house has an ASHP that is a two stage heat pump with a two stage electric backup. It is controlled with a Honeywell TH8000 series thermostat.

I've read a couple threads on here about adding in control for the boiler, by using an SPDT aquastat that would just disable the heater if the water temp at the exchanger is hot enough. Will this kind of a solution work when it is a two stage heat pump?

I talked to the guy that installed my ASHP and he recommended just installing a separate thermostat for the boiler and setting it a couple degrees above the heat pump. I really don't like this idea along with having to keep them in sync with each other and then having to do it twice. Once for upstairs and once for downstairs.

Slowly planning my boiler install,
david

 

[brant2000]

I have a similar setup and decided the only option that would really work is to install a second thermostat. I also was hesitant to do so, but it's worked out well and causes no problems. Both thermostats are pretty much set to a constant temperature all the time during the heating season, so I've had no issues managing them.

The way I have mine set up is that the HX loop generally always has flow (no automatic pump/valve control for this). The thermostat just closes the ASHP's blower relay, on a call for heat. I've found it to work really well because unless the temperatures are pretty low, the convective heat provided from the coil without the fan supplies a fair amount of heat to the house.

 

[NCFord]

The second thermostat is by far the easiest. We heat almost 100 percent on wood so don"t use the heat pump much, but when we do all i have to do is turn the second one off and the primary back to heat. Super easy. Fyi, when my blower kicks on with a call for heat it also activates a relay that turns on my pump from storage to the heat exchanger in thr duct work.

 

[98kx1927]

What I would like to do is use an aquastat and a SPDT relay to control the first stage of the compressor. If the water is hot, don't enable the compressor, if cold then run the heat pump. What I don't know is if I can run the second stage compressor independently of the first stage.

If I were heating off wood, but it wasn't enough for the load for whatever reason, and the second stage kicked on, would that be OK?

david