Passive Hot Water System


Old 08-27-18, 07:45 PM
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Passive Hot Water System

Just bought a house with a relatively new Boilermate passive hot water heating system (Amtrol). Having trouble getting hot water out of the system. It is fired by an oil furnace. From everything I can tell it is functioning properly, the water at the tap just isn't that hot, about 90 F at the tap at most. Can't figure it out. Boiler kicks on when its supposed to when you run hot water for a while and occasionally throughout the day on its own but nothing too frequent......water lines into the tank appear to be circulation water at the right temperature and does show the 20 degree difference between the hot water line in and out.....

I am thinking its just a bad thermostat (has a manual thermostat) and it just thinks the water in the tank is hotter than it really isÖ.if I turn the dial up above the 120 mark it kicks on the boiler and the water at the tap will get a little hotter but again nothing close to 120.

Any suggestions on how to test the manual thermostat on the unit or what else the problem might be?
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Old 08-27-18, 10:07 PM
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Welcome to the forums.

It does appear that the aquastat that controls the water storage tank is defective.
Is that just a basic aquastat ?
A few pictures of your piping and setup there would be real helpful.
Old 08-28-18, 04:26 AM
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When you said that "if I turn the dial up above the 120 mark it kicks on the boiler and the water at the tap will get a little hotter but again nothing close to 120", what dial are you speaking of? Is it the domestic coil thermostat or the thermostat for the boiler? And, what do you mean by the term "passive hot water heating system".
Old 09-01-18, 06:39 PM
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If you feel the domestic hot water outlet pipe from the heater when hot water is running, is it hot? Hot enough to not be able to keep your hand in it for long? If it's hot then your heater is working fine and you have another issue. Possibly a cross connection at a single handle shower valve where the cartridge is shot.
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