Shower not Triggering Potterton Combi Boiler All aspects of plumbing questions and answers, help, tips and information

[Rugbyjack2005]

Hi,

I bought a new house a couple of months ago and the shower has never worked properly. It is a recessed shower with a main shower head and a secondary handheld shower head. It has 2 levers - the top lever has 3 settings - upright which is off, left which is the handheld shower head and right which is the main shower head. The lower lever sets the temperature. Unfortunately there is no make or model marked on the shower anywhere.

The shower is not a power shower and works directly off the combi boiler (Pottetton) and was always scolding hot with the temperature control not working properly. Given it was getting hot water, I assumed that it was the thermostatic cartridge in the shower at fault and after searching high and low for the correct size (quite difficult when you don’t know the make or model), I ordered a replacement this week and fitted it yesterday. I thought all was well as I tested the handheld shower head and it seemed to work perfectly. It didn’t test the main shower head as I didn’t want to get wet and assumed if the handheld shower head worked, the main shower head would work too.

When I had a shower this morning, using the main shower head, the shower only delivered cold water, regardless of the temperature control lever setting. I checked the combi boiler and the boiler wasn’t lighting. Oddly though, the boiler lights when you select the shower to the handheld shower head but not the main shower head.

The taps around the rest of the house work fine. The kitchen tap has always been a bit temperamental and doesn’t always make the boiler light when selected to hot.

Any idea what is wrong. I am thinking the boiler pressure valve needs adjusting. Thoughts please.

[Rugbyjack2005]

Update: I had a shower this evening and the boiler turned on when I used the main shower head but only at a high temperature setting, it turns off again when I select a slightly colder setting leaving me still only able to take scolding hot showers! It does however lead me to believe that the issue is with the boiler.

How do I adjust the boiler so that it turns on at a lower temperature setting?

[Rugbyjack2005]

I have adjusted the micro switch on the DHW flow valve on the boiler which has allowed me to select a much lower temperature on the shower so no more scolding hot showers. The kitchen tap is still intermittent though - if I wind the micro switch in any further, it resolves the kitchen tap issue and gives me more temperature selection on the shower but the boiler then doesn’t turn off when it should.

I would have thought that I should be able to turn the micro switch a little more than I can before having problems with the boiler not turning off. Any ideas what I can do to resolve this?