vanagon
New Member
Hi delta-Ts are hard to maintain at very low boiler output temps. Most low-temp systems run 5-10F delta-Ts on the radiation when the temps are well into the condensing zone. It's all a matter of just how quickly the radiation can emit that heat into the house and the pumping rate- it takes a LOT of radiation to put much heat into a 70F house with 85F water, and you WON'T be seeing a 14F delta-T on the radiation.
I guess my basic question is whether this means that a Delta-T pump on the secondary loop is a bad idea, when using the outdoor reset sensor (since sometimes the boiler temps will be high, and sometimes low.) I want to avoid a scenario where the Delta-T pump slows down so much that the primary loop is recycling water. i guess at these temps I would be in the condensing range anyways, so that everything would be okay?