Combi boiler help please, running hot then cold...

danyorks

Hi guys,

Just recently our combi boiler has started outputting hot/cold/hot/cold when running a bath, sometimes it is fine but most of the time you will return to a cold/tepid bath. It doesnt seem as bad through the taps.

Is this a common problem that could be fixed via DIY or at least something I can read up about so I dont get fleeced by a plumber.

Cheers in advance.

Dan

usignuolo

It sounds like a similar problem to mine. Have you noticed if it only occurs when CH is off? What make is boiler?

white_wine_1

Hi

I had the same problem on a worster boiler and it was the diaphragm in the pump I managed to get one for £14.00 and just about managed to fit it myself. Go to a local plumbers shop and give them the name and type of boiler tell them what the problem is and they should give you a better idea plus they may be able to tell you of a plumber that will not rip you off Good Luck

gas4you

Yet again my post giving you the answer has been removed with no explanation. Why?

Aquatronixjenny

Heat exchanger bu$$ered? Thats a guess as I am still getting my hours for my gas course! Gas4you, is that right?

gas4you

No, not unless you mean the plate HE.

The first thing I would do is remove the plate and clean it. But then at present we do not know which boiler/model it is, so may be something completly different if it hasn't a plate HE.

Lets see if this post get removed!

Aquatronixjenny

*giggles*

Are we not supposed to give gas advice?!? :eek:

I still have 25 days left of gas experience before I can go on my course

lindos90

We had exactly the same problem a couple of years ago. ive been trying to search my subscribed thred history to see if I asked about it one here but cant find it.

We tried a couple of things, but in the end it was the temperature sensor, only cost a couple of quid, and was easy to fit. If that hadn't worked we would have called a plumber, but it did!

As I remember there were several reasons why the water can run hot and cold, it might be worth trying the 'diynot' site too.

A quick google found this..

http://www.diynot.com/forums/viewtopic.php?t=239731

And then... https://forums.moneysavingexpert.com/discussion/311417
Depends on how confident you feel about trying things like this really, and knowing when you are getting out of your depth.

gas4you

Aquatronixjenny wrote: »

*giggles*

Are we not supposed to give gas advice?!? :eek:

I still have 25 days left of gas experience before I can go on my course

Anything to do with a plate HE on most combis is nothing to do with the gas side of things. Just water.

So yes I agree in general, but not in this case possibly.

BUT, on a few combis one may need to remove the gas valve to gain access to the plate, so in this case it MUST be carried out by a RGI.

blackshirtuk

The boiler is heating the water, then the water leaving the boiler gets too hot so the boiler shuts down until water leaving the boiler is cool again, and then cycles.

One solution is to turn DOWN the required temperature of the water. This will stop the boiler overheating the water.

gas4you

blackshirtuk wrote: »

The boiler is heating the water, then the water leaving the boiler gets too hot so the boiler shuts down until water leaving the boiler is cool again, and then cycles.

One solution is to turn DOWN the required temperature of the water. This will stop the boiler overheating the water.

This won't stop it, as the plate is blocked on the system side.

The heat from the system water can't transfer across the plate to the domestic cold to be heated quick enough.

The boiler registers the system side is up to temp so shuts off, then comes back on again when it cools.

Because this is a system side fault, then boiler does not think anything is wrong with the temp, hence why it doesn't lock out and display any fault code.

If it was the domestic side scaled up, then this would usually, but not every time, result in an overheat fault code and the boiler locking out.