Rob R. wrote:Does the boiler drop by 47 degrees or does it drop TO 47 degrees F?
wilder11354 wrote:47*C =117 degrees F, 87*C = 188* F, so your losing about 71Degrees Farenhiet with a larger zone(load) demand. The 47*C thats what it maintains while zone( load) is on, no lower?
lsayre wrote:McGiever offered a very good answer. A bypass.
I installed an aquastat that shuts off my zone circulator when my boilers internal temperature falls to 145 degrees F. (63 C.) and does not permit it to start back up again until the boiler is recovering and has hit or exceeded 155 degrees F. (68 C.).
I also have a "differential pressure bypass valve" installed that functions somewhat as McGiever's solution intends, though not exactly (as that is not its primary function or intent).
steamup wrote:Coal boilers are not sports cars. They are more like freight trains. They take time to speed up and slow down.
It is very common to have the boiler temperature drop on startup of a large zone, especially if that zone is a cold one like a garage.
If your boiler has the typical honeywell aquastat, if the water temperature drops below the low setting, the pump will shut off until the boiler water temperature catches up. This will create even more load on any boiler in series. (depending on piping and pumping).
Better get that tankless set up in parallel with the coal boiler. Manually change it over or add controls for automatic change over.
EDit - Oops, forgot this is in the AHS forum. They do different things with their controls.
chevymatt wrote:Thanks Isayre. That's a good idea. Does the aquastat cause the circ pump to constantly kick on and off? It seems like as soon as the cold return water came in it would kick the zone back off? I'm just trying to figure it all out not questioning your suggestion.
chevymatt wrote:Yes I followed the advice and I've got it turned down to about 116*. It still radiates heat from the slab for hours and I'm not sure what to do next.