Combi boiler & shower problem

[ZACCCC]

Three weeks ago I had a Baxi Duo-tec Combi 28 HE A boiler installed in my house. Very soon after installation I discovered that in the course of the installation the cold water supply to the tank in the loft had been cut off, which meant that I couldn't get a bath or a shower.

The company sent two guys out who reconnected the supply to the tank but now I can't use the shower (which is gravity fed and attached to the bath mixer tap) because the water comes out either very hot or completely cold and I haven't been able to achieve a steady flow at a comfortable temperature no matter how delicately I've tried to fine tune the hot and cold bath taps which supply the shower head.

I've recently heard that combi boilers aren't suitable for gravity fed showers! - which the boiler installer never mentioned!

Can anyone advise me on my best course of action now. Is the solution to install an electric shower? Or maybe put a thermostatic valve on the showerhead? I'd welcome any advice.

 

[JPC]

yes...call the plumbing company back...the shower should now be fed from the combi...not the tank...both hot and cold from the mains/combi so u don't get different pressure problems re ur shower

 

[ZACCCC]

Thanks Jamie.

So you're saying that when the guys came back to rectify the problem they should have connected the mains feed directly to the mixer tap rather than connecting it to the header tank in the loft (which then feeds the mixer tap)?

The only thing is that I thought this was illegal (under safety laws) because if, for example, the kitchen cold tap was turned on while someone was getting a shower then suddenly the water from the shower would become red hot.

 

[ianniann]

Illegal? That might be stretching it a bit.

You already have the hot water feed to the shower running at mains pressure so the shower will be affected one way or the other if taps are used. If the cold is fed from a tank at constant pressure and the hot from the mains at varying pressure, then that is an unfortunate situation. Not exactly fatal though since most combis don't create water hot enough to do serious damage. Having the cold water feed also at mains pressure means that there is less change when the mains pressure changes since both hot and cold will change in a similar way.

You would normally also have a pressure-balancing or thermostatic shower to further even out changes in flow rate and temperature from the hot and cold feeds, but this isn't essential unless your kids think it is a good game to play with the taps while you are in the shower

 

[ZACCCC]

Thanks ianniann.

When you say a thermostatic shower do you mean I could buy a thermostatic valve to fit between the mixer tap and the shower head?

 

[rizsher]

Don't really know very much about the permutations of heating system setups, however, one of the main reasons I got a combi boiler installed in my house back in January was due to the fact that these do away with any kind of tanks/cylinders in the house. Everything is mains fed, cold taps directly to the mains, and hot thru the combi.

Was there a particular reason why you retained your tank?

 

[ZACCCC]

Thanks for your reply rizsher.

There was no particular reason that I kept the header tank in the loft. The installer didn't say that it was now redundant and when he came to rectify the fact that he had cut off the CW supply to the bath he remedied it by reconnecting the mains feed to the header tank, which was still connected to the bath CW tap. From what I've picked up on this forum and from a couple of other sources, what he should have done was set things up so that the CW feed to the bath came directly from the mains.