Quote:
Originally Posted by Retlaw
Because the domestic supply pressure is usually greater than the boiler will stand, and dometic water pressure is not constant.
During the night the water pressure on fire hydrants is a heck of a lot greater that during the day.
Retlaw.
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The domestic water does not pass through the boiler (heat exchanger with the fire under it, or above it in some weird ones - always seamed odd having the fire burning downhill to me) that section is a closed circuit with expansion vessel to allow for water expansion when heated. The filling loop is supposed to only be fitted while topping up but almost everyone leaves them in place. This is a safe guard to prevent boiler water with chemical additives from entering the domestic cold water if for example you isolate the water into the house to repair a leak which will make the boiler pressure higher that the cold water.
The domestic water only passes through the clean side of the hot water heat exchanger.
I would guess the pressure changes you refer too are due to supply and demand on the system during the day/night.
I am sure Derek will explain that I am a complete idiot and am talking out of my booty when he next pops on
