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mondial · 6 Mar 2006

My 15 year old boiler makes all the right noises, lights up on cue and produces luke warm water. All thermostats (boiler, water tank and room) are up to maximum but the hot water and the radiators don't get hot. Literally, just luke warm.
I had a new pump fitted a few weeks ago, also a new three way valve last year.
Any help would be greatly appreciated.

ChrisR · 6 Mar 2006

Does the boiler's flow pipe get hot? With boiler stat on max it should be too hot to touch.

mondial · 6 Mar 2006

Only warm. definately not too hot to hold. Could it be the boiler thermostat and, if so, how easy is this to change?

ChrisR · 6 Mar 2006

Could be the thermostat then. Changing that on this particular boiler is a corgi job, because you need special kit to check they don't leak carbon monoxide once the case seals are disturbed.

Could also be the gas valve.

bathjobby · 6 Mar 2006

Eliminate the obvious first; you don't say what setting you have the boiler therm on ! How long does the boiler stay on for when it fires ?

ChrisR · 6 Mar 2006

All thermostats (boiler, water tank and room) are up to maximum

I'm assuming it used to be ok?

mondial · 6 Mar 2006

I confirm the thermostat is on maximum.
All was ok up until a two or three weeks ago, when I turned the boiler thermostat up from 30 to 40 to increase the heat output from the radiators. That was fine initially but it has progressively become cooler and feeds less radiators. The water in the tank is barely tepid whilst one, or at most two, radiators are luke warm. And that is only if the hot water is turned off.
The boiler lights up and runs for perhaps one or two minutes before stopping. There is a low hissing noise from the boiler when it is working which wasn't there before. Might be totally unrelated. How would I know?
HELP - PLEASE.

ChrisR · 6 Mar 2006

Either

the boiler is working OK and the heat isn't getting out due to poor circulation, due to a blockage, lack of water or dud pump. The flow pipe from the boiler would be very hot in this case (and hissing indicating heat!). Or

the boiler isn't working properly, many possible causes, some mentioned.

mondial · 6 Mar 2006

The pipe from the boiler to the pump is very hot, the pump is working fine and the inlet pipe to the three way valve is hot. The hot water is not getting from the three way valve to the tank for some reason, neither is it circulating round the system, although the outlet pipe from the valve to the radiators is hot. I am going to get a man to add a descaling agent tomorrow which I am told will be in there for 6 weeks befor the system is pressure flushed. Just keeping my fingers crossed.

Thanks for all your help.

EliteHeat · 6 Mar 2006

It's very ,very unlikely that you system will be so bad that its circulation will be restored by flushing.

Your problem lies elsewhere. The pump has been changed recently - did your problems start immediately after this event by any chance?

mondial · 7 Mar 2006

No, although it worsened immediately after. Previously, and one of the reasons we changed the noisy pump, was because we could have either the upstair radiators on, or by turning each on of those off individually we could have the downstairs ones on but if the water came on by the timer, then all heat was lost in the radiators.
Now, the water is hot up to the pump but does not seem to go anywhere. could it be the three way valve? This was replaced 18 months ago and the Electric part of it was replaced a couple of weeks ago. Again, in an attempt to get the system working.

bathjobby · 7 Mar 2006

Have you bled the system ? Is the pump fitted the right way round ?

EliteHeat · 7 Mar 2006

Start wih the basics and verify that you have enough water in your system to circulate and dissipate heat.

Tie your F&E valve up and drain a few gallons of water from the system. Check the F&E tank - is it empty?

mondial · 7 Mar 2006

Thank you all for your help and suggestions. I finaly called in an expert who found the system totally blocked in the "H" ? pipe. He cleaned this out, put in some form of solvent and it started up fine. Now he wants to flush the whole system in six weeks time. Expensive but it was bloody cold!
thanks again.

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