Combi boiler - hot on one tap cold on other?

[Jarvo273]

Hi, I'm not a heating engineer but am hoping someone can help with this puzzle....

i had had a brand new combo installed within the last year. It works great but sometimes the mixer shower runs tepid. Not always though. However, if I turn the hot tap in the bathroom on and the shower heats up. This doesn't work if I turn the cold tap on.

more puzzling, the hot tap that I turn on to make the shower hot runs stone cold. But they both come from the same combi boiler. If I turn the her tap on on its own its is hot.

I cant ant work it out. Something is strange and I think it must be the way the pipes are plumbed but hope some one can help.

Thanks
neil

 

[Riley]

Is it a thermostatic shower?? I'd be more inclined to think the temp control valve in the shower is on the fritz and you're helping it to balance by opening the hot tap

 

[Jarvo273]

Is it a thermostatic shower?? I'd be more inclined to think the temp control valve in the shower is on the fritz and you're helping it to balance by opening the hot tap

Hi, thanks for responding. That's an interesting point. It's like a mixer handle that you can twist to mix the hot and cold and I'm pretty sure it has some kind of passive thermostatic aspect to its control of the mixing. Does that make sense? But I'm just trying to work out why the running cold tap would then be stone cold when both feeds are coming from the boiler.

Thanks neil

 

[Riley]

It's really finger in the wind without eyes on mate. I've seen thermostatic cartridges do some weird things when they are slightly clogged is the hot tap you're turning on a stand alone hot tap or is it a mixer?

 

[Jarvo273]

It's really finger in the wind without eyes on mate. I've seen thermostatic cartridges do some weird things when they are slightly clogged is the hot tap you're turning on a stand alone hot tap or is it a mixer?

No, it's stand alone. This morning the shower was fine and piping hot. Very frustrating. Appreciate your thoughts on what it might be anyway. Thanks

 

[Riley]

I'd still be looking at the cartridge in the shower mate

 

[Jarvo273]

I'd still be looking at the cartridge in the shower mate

is the cartridge the big metal bit that does the mixing? Thanks. I will see if I can get it replaced.

 

[Riley]

Yep