My baxi combi 80e has an intermittent fault with the demand hot water running cold and the system is also losing pressure. there are no leaks, but the overflow is putting out more water, hot when the central heating is on

Mike, December 2009

hi
strong blast of air from the expansion vessel, pressure decreases whilst heating is on and there is a constant small leak from the overflow. pressure does not increase with time. it sounds like the PRV, the cold water from the hot tap only started after this fault. is the PRV easy to fit?
thanks ste

mike, December 2009

could just be pressure relief faulty if it drips all the time but in my opinion they only fail after theyve opened and why did it open??? usually expansion vessel.

before doing the below mentioned vvv if you had boiler pressure of 1 bar cold does it rise beyond 3 bar on guage when the heating has been on for 20mins or so then release water out????????

if it does rise to 3 bar plus check vessel like mentioned below

sorry for the ar*e over t*t posts.

ste, December 2009

maybe your boiler has a pin holed diaphragm or faulty microswitch on domestic hot water flow switching, usually just fail but can become scaled and a bit hitty missy. get a manual from partsarena.com/baxi and look for water section and microswitch for ideas on location and open hot tap and try making the switch manually with something plastic just in case :-) if it fires when you make the switch try replacing diaphragm.

expansion vessel, big red disc located on back of boiler, if you put your head over the top of boiler and look down next to flue connection to boiler you'll see the red disc has a valve like the ones on your car,
unscrew the cap off and you'll see the pin inside the valve, give it a short press with something thin and observe.

strong blast of air - its fine

weak amount of air - needs recharged

nothing at all - needs recharged

water - its fooked :-)

recharge is- pressure relief valve held open and connect foot pump and pump up to 1 bar, remove foot pump, close pressure relief valve and top up water pressure to 1.5 bar and all should be well.

ste, December 2009

thanks ste, hot water fault is intermittent and when it fails it doesn't run hot at all, when it runs cold, the green light on the boiler doesn't light up and the boiler doesn't fire up. how do i recharge the expansion vessel?

mike, December 2009

expansion vessel fault is the water outside bit and loss of pressure, either need recharged or replaced.

more info on hot water please, cold all time,? boiler fire up? hot cold hot cold? boiler recognise hot demand (tap neon)?????????????

ste, December 2009