Mixer shower goes hot then cold...

[Cobby]

Hi all, I was hoping to get some advice re a problem I'm having with a mixer shower. Recently had a new boiler fitted. We have a bar type mixer shower, problem is it won't stay hot. It will start hot then after a few minutes it will go cold. The boiler fires up when you start the shower, stays hot for a few minutes and then goes cold and the boiler light goes off. Sometimes it will go hot again after a few minutes other times you have to run the hot bath tap to get the hot water going again. Don't have any problems with the hot water in the taps, this stays hot.

Any advice would be much appreciated.

Cheers

 

[rocketmanbkk]

How's the hot flow to the shower?

 

[Cobby]

Thanks for the fast response. What do you mean by hot flow? Sorry I'm very much the amateur!

 

[SimonG]

Clean the showers filters.

 

[JCplumb]

You mentioned that you had your boiler changed.
What type was your old boiler and what type is the new one?

 

[Unregistered]

Sounds like the flow rates are out and the cold is overpowering, these thermostatic showers need the flow rates to be within a certain range to operate properly, maybe your older boiler had a different flow rate

have you noticed the difference at the taps on flow rate in comparison to your old boiler ?

 

[clemda1]

I'd concur with the flow rates answer. Shower mixers are designed to work on balance pressures and flow rates on both the hot and cold. If you changed to a combi more than likely the flow rates of the hot and cold supply out of the calibrated range of the thermostatic mixing valve.

If you know the manufacture of the unit then you can give them a call and ask them to send you some flow restrictor inserts. Its more than likely these were including in the original kit that came with the mixer shower but the plumber that fitted them discarded them. If you still have the original packaging might be worth having a look.

If you can't ID the manufacture then your least expensive option might be to replace the mixer and insure the new one is compatible with combi... good luck

 

[Radioman]

As above, common issue when changing from gravity to Combi. If it's a standard bar shower with pipes at the normal centres then the cheapest option at the moment is to change for an Aqualisa Midas 100, they are on a big discount at showers2u web site.