Temperamental hot water from Combi to shower ONLY!

suisidevw

As above, have a Worcester Bosch combi fitted in 2007 with a thermostatic shower in the room almost directly above.

Now running the shower it'll stay hot for say a minute then go freezing for 15 seconds and keep repeating this.........

Is there anything that should be obvious that I should check/fix or is it a plumbers job?

Many thanks

WestonDave

May sound like a really bizarre suggestion but try descaling the shower head if you are in a hard water area. Our Bosch will go cold like that if the hot water draw from it is too low (the thermostat thinks that the low amount of water is too hot so shuts it off) so if the shower head is blocked so there is too little hot water going through it might be involved.

MX5huggy

I presume the shower has been in some time. If not I had this problem with a shower mixer where the feeds were the wrong way round cold in to Hot and visa versa. Just turned the fitting over.

Other wise I would suspect something wrong with the shower valve do you know its make and model?

suisidevw

Thanks Weston Dave. Will try that.

MX5 H - thanks for that. I will get the make and model of the shower later.

gas4you

Are you sure it is not doing it on other hot taps as well. The shower is the most sensitive to this fault so will always appear worst affected.

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.

Another solution is to increase the flow of water through the boiler, but this expensive and would require at least a pump fitted, at worst a bigger diameter water main from the water main in your road!

gas4you

If the above is the scenario you have, then you need the plate HE removed and cleaned. The system side of it would be blocked.

redlee

We've had this a couple of times over the last 5 years - it was our boiler (not a worcester) one of the sensors was furred up.

Owain_Moneysaver

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....

Another solution is to increase the flow of water through the boiler, but this expensive and would require at least a pump fitted, at worst a bigger diameter water main from the water main in your road!

Running the basin hot tap while showering may make enough difference.