Indirect Water Heater off a Steam Boiler

Ron R

Having a problem with an Indirect water heater piped to a steam boiler. The current issue is that the boiler is steaming during the call for domestic, and heating up the radiators in the house with no call for heat. It's strange because the water heading into the indirect is around 130 degrees and yet steam is leaving the boiler. We have a 10 degree drop across the indirect supply and return. Does anybody have experience with this sort of problem?

Charlie from wmass

Yes

I have seen it on large boilers with small indirects or blocked coils. What type of pump are you using and How is the piping run for the flow to and from the indirect? Also where is the aquastat located relative to the piping and what is it set at?

Ron R

Inbdirect Water Heater off a Steam Boiler

Thanks for answering Charlie. We are using a stainless steel taco 007 which is connected to the un-used return tap on the boiler with 1" pipe. After the pump we have a strainer, then a tee which is supplying the indirect on the run and a baseboard zone on the bull. After the indirect heat exchanger, we are using a 3/4" zone valve (the baseboard zone also has a zone valve) , then heading back to the boiler where we are connecting to a tee at the base of the sight glass (no other tappings seemed suitable for this Dunkirk boiler). The aquastat is a "strap-on" (again- lack of tappings so we couldnt put it in the boiler) currently on the 1" pipe upstream of the circulator, right off the boiler. We started with a 180 setting and after the hot radiator complaints tried 130. we have a double-pole double throw fan center relay which is energized when the end switches of the zone valve closes. One normally open contact of the relay energizes the circulator, the other normally open is in series with the strap-on and closes "t" and "t" on the boiler. Rh going to the heating thermostat in the house is on the normally closed contact and so it opens when the domestic is calling.

Dennis Foley

Clogged strainer

The strainer is probably clogged, causing the indirect to keep calling for heat, but not activating the reverse aquastat.