On Apr 21, 9:02 am, andy everett wrote:
My brother-inlaw has problems with his hot water supply. The furnace
heats the house OK but the hot water, supplied by the furnace, seems to
work best only when the furnace is also heating the house. It seems like
the furnace has the wrong control, one for a furnace that only
supplies home heat. Assuming that the furnace has the proper control
does it seem that the control has failed in some way such that the
furnace will cool all the way down when there is no demand for home heat
and thereby allowing the heat exchanger coils to no longer heat the
domestic hot water?

Thank you for any ideas,
andy

There should be an aquastat somewhere on the boiler. It's basically a
thermostat for the hot water. There should be a dial on it for you to
adjust, normally hot water is set to about 150. Either it's set to
low, or the aquastat and/or the wiring is not working right. that's
why you only get hot water when the boiler comes on to heat the house.