2 things about the boiler in my new house that I'd like to check out with our friendly plumber members:

1 Its a worcester bosch combi boiler, 1987 vintage, with two separate controls on the front for hot water and heating temperature. The hot water dial makes no difference to the delivered water temperature, it just comes thru stinking hot. I presume this control must use a thermocouple, correct? If so should it be my first port of call for a fix?

2 The central heating pump seems to run all the time, independent of the timer position and independent of whether the heating temperature has been satisfied. The only way to stop it whirring away is to turn the boiler off at the mains. I've heard this could be a solenoid valve problem, any thoughts? Does running the pump 24/7 pose any particular problem?

Cheers,

Dave

Anyone?

On a combi boiler generally the pump runs all the time the CH is on and temperature is controlled by stats on the radiators

Cant help with the other problem though ....sparks not plumber

On a combi boiler generally the pump runs all the time the CH is on

What i meant was that it runs all of the time that the boiler has electricity to it - even if you set heating and hot water to 'off', the pump is still pumping. The only way to stop it pumping is to turn of the boiler's electricity supply.

I have had a similar problem where one of the solenoid (diverter?) valves had not closed fully and the electrical circuit to the pump was still live. Closing the valve manually provided a temporary cure.

Cheers for the opinion Denis, thats 2 people now suggesting solenoid valves. Mmmm...

Yeah either solenoid valve or faulty temperature sensor. When the system stops the temp of the water in the heat exchenger rises quickly as the pump stops and the water stops moving. To prevent the boiler overheating some boilers run the pump on a bit until the temperature drops. Faulty sensor may make boiler think that the temp is permanently high so pump keeps running.

Hope it helps.

Cheers Johnny, anyway cunning ways to test the parts or is it a case of replacing the cheapest first?

Cheers,

Dave

Cheers Johnny' date=' anyway cunning ways to test the parts or is it a case of replacing the cheapest first?

Cheers,

Dave[/quote']

Not really. It sounds like you have enough problems to justify getting an engineer out to run through a fault finding process. the diverter valve seems like a good bet. It's motorised and if it does bring the pump in/out then you'll hopefully see the auxiliary contact on it for the pump. You should check that the valve is moving to its full extents when operating. There's often a manual overide tab on the side you can move it yourself a little in the direction of travel one the motor has stopped.

The "Diverter Valve" Is actually called a "Zone Valve" It directs hot water between the heating system and hot water system. The Zone valve should have a lever on the side of it which you can move and thus shut one side off (heating or hot water). The pump shouldn't be running all the time and as said before should only be running a few minutes after the boiler has switched off to remove any excess heat from the boiler stopping it from overheating or locking out which is another term used.

Not really to sure how you can test the system but if you are handy with a screw driver and spanner you can usually replace the thermostat yourself, it will be the part with a thick copper wirer coming out IIRC which pushes into the main burner chamber but I am not sure if you need to be CORGI registered to do this by law now.

HTH

Not really to sure how you can test the system but if you are handy with a screw driver and spanner you can usually replace the thermostat yourself' date=' it will be the part with a thick copper wirer coming out IIRC which pushes into the main burner chamber but I am not sure if you need to be CORGI registered to do this by law now.

HTH[/quote']

I thought the thermostat measures the temperature of the water leaving the heat exhanger as opposed to the actual burner temperature. The only copper wires i've seen are for the burner ignitors but i'm sure your right.

You only need to be CORGI registered to reconnect a joint in the gas supply. this includes the supply pipe, meter and gas connections within the boiler. If you read the CORGI regs closely enough you will also see that it isn't illegal for you to work on 'your own' gas system. It's a bit of a loophole (if it still exists) and not recommended.

They don't award CORGI registrations for a laugh.

Cheers fellas, at least you've given me a start. Rest assured I won't be going anywhere near the gas side, the water pipework gives me enough headaches as it is. I'm a chartered engineer by day so as long as its a simple-ish fix then I should be good to have a crack at it.

I thought the thermostat measures the temperature of the water leaving the heat exhanger as opposed to the actual burner temperature. The only copper wires i've seen are for the burner ignitors but i'm sure your right.

Actaully you may be right the only other stat I can think of is on the Cylinder itself them, I can ask my Father who is a Corgi regisitered central heating engineer and he will be able to advise, or maybe not I forgot he is in Kenya at the moment LOL

Actaully you may be right the only other stat I can think of is on the Cylinder itself them, I can ask my Father who is a Corgi regisitered central heating engineer and he will be able to advise, or maybe not I forgot he is in Kenya at the moment LOL

They short of CORGI fitters in Kenya?

They short of CORGI fitters in Kenya?

Aparently

Nah he does alot of charity work for a friend out there about twice a year.