Best Of

I got so focused on the wiring, that I missed the capped tankless coil and the reason why there was a triple aquastat. They should have changed out the control when they capped the HX and saved a lot of fuel.

I installed the 2-pump control and a simple L6006 aquastat this morning and all is good.

Educated homeowner here who recently completed a whole house remodel from bare studs.

Please keep the cast iron radiators. The quality of heat and comfort from these is hard to beat (I had them in a previous house, and I now have radiant floor heat with a wood stove - also nice heat - I would never choose forced air).

If you are doing extensive renovations, consider improvements to the building envelope (insulation and air sealing) to reduce heat loss. This can reduce the size heating system you need by a lot (and reduce fuel cost).

Consider a hot water heat pump for domestic heating. Your cast iron radiators are likely 2-3x oversized and can run with significantly lower temperature water (120 degrees F on your coldest day) and that makes either a geothermal heat pump (somewhat expensive) or a air-source hot water heat pump (less expensive) a viable option if you are ditching the oil system (I second the recommendations from others to get rid of the oil system(s)).

Radiant floor heat is really, really nice, BUT is a lot of work to install and it is hard to find a capable designer and installer (I did this work myself). There is a lot of opportunity for a bad install with radiant floor heating. Plus, you already have cast iron radiators - if I had those already in the house I renovated I would have just used them with my geothermal heat pump instead of installing the radiant floor heating.

New York State (I think) still has some good incentives on heat pump hot water heaters and geothermal heating systems (and maybe air-source heat pump heating systems as well).

@Alan (California Radiant) Forbes

I got called in to start up an oil boiler once where the plumber installed a boiler for heat but it had an unused tankless coil in it so it was hot all the time.

Instead of replacing an expensive aqustat I installed a relay in front of the aquastat breaking the 120 to the aquastat with a relay pulled in from the thermostat and jumping T & T in the aqustat.

Thanks, I can be a drain at the end of the farthest baseboard and see the pressure. Was think of doing that anyway to try and purge form the 4th floor as a push and pull.

It looks like you have a ~130KBTU/hr boiler, which is probably extremely oversized for your actual heat loss - one advantage of such an oversized system is the rapid recovery from setbacks. Depending on what your control setup is, you could have the heat pump maintain steady-state at either 62F or 68F, but use the boiler to quickly recover from the setback. With programmable thermostats you might be able to do something like:

• Boiler and heat pump are 62F overnight
• At 6AM, boiler jumps to 68F and starts pumping out heat. Heat pump is still at 62F.
• At 8AM, heat pump jumps to 68F (and the house is probably already at 68F), and boiler falls back to 66F so that it only kicks on if heat pump can't maintain heat.

There are two questions here:

First is, does a setback cause a house to lose less heat? The answer is yes. The amount of heat lost to the environment is determined by the difference between the inside temperature and the outside temperature, with a setback the inside temperature is lower some of the time and loses less heat.

The second question is whether the setback will save you energy. With a combustion appliance the answer is yes, a BTU is pretty much a BTU. But with a heat pump it becomes more complicated, because a heat pump uses a variable amount of energy to produce a BTU. First, the colder it is outside, the less efficient a heat pump is. So if you're running the heat pump less when it's warmer and more when it's colder— like you would if you turned the thermostat down when the house was unoccupied during the day — the setback may not save you anything. Some heat pumps have supplemental heat, when the controller detects that the heat pump isn't meeting the heating load it energizes resistance heat to supplement the heat pump. The supplemental heat is much less efficient than the heat pump, typically about half as efficient. Often the way the heat pump detects whether the heat pump is meeting the heating load is by comparing the thermostat set point to the inside temperature. In such a system, a setback will guarantee that the supplemental heat runs regularly, which will increase your energy usage.

Generally the recommendation for heat pumps is not to use the setback.