DIY Doctor

Central Heating problems

Postby Cavalier » Sat Apr 19, 2008 11:10 am

I have a few problems with my central heating system that may all be connected.

1- low hot water pressure that can result in the shower pump not working. Occasionally have to run the bath to build up the pressure of the hot water to get the pump to turn on. (the shower and pump are located beyond the pipe work for the bath). cold water pressure from the feed tank is not particular high.

2- occasionaly we find we have no hot water due to the 2/3 way valve appearing to be stuck on the central heating. Have to shutdown the system, press in the plastic switch on the side of the valve, occasisonaly give the valve a tap and turn it back on. (sometimes have to repeat) This will usually opening the motorised valve and within 30 mins have hot water.

3- Noisy pipes in the loft caused by very hot water being expelled into the expansion tank. (not the cold water feed tank). Have checked the pipes and one was banging against a joist that i have sorted but the system is still noisey. More concerning is the amount of boiling water and steam being expelled. Seems to be happening excessively which can't be cost effective. I have recently removed a radiator for decorating which could have aggravated the situation but it was doing this beforehand so the problem is not a new one.
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Simply Build It

Postby htg engineer » Sun Apr 20, 2008 8:15 pm

Replace actuator to 3 port valve - problem number 2 resolved.

Low hot water pressure - tank or cylinder ?
always been a problem just occurred ?

Check water level in tank - ball valve operating correctly. Alternatively check for blockage in pipework.

The 3rd problem seems to be that the central heating is pumping over into the expansion tank, any work carried out to system ? pump changed ? Does the central heating or hot water get too hot ? or hotter than normal ? could it be boiling/overheating ?
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Postby Cavalier » Mon Apr 21, 2008 8:52 am


The water pressure has always been fairly low. Had been considering raising the height of the cold water tank to see if it improves things. Could go a further 400mm higher probably. Water level appears OK and as far as I can see the ball valve is functioning correctly. The tank never drains empty. When the bath or shower runs you can hear the tank refilling.

With the 3rd problem I have not noticed the water or heating getting too hot. The temp is set around 60-65 degrees on the hotwater cylinder.
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