Combi Shower advice required

[HammerAndThaw]

Hi all

I'm new here so please excuse my ignorance n such matters, but I am trying to avoid spending money on the wrong shower controller.

I currently have a combi boiler, a Gloworm Hot Water Express, and a Shower Force shower controller (simple single controller type, back and forward for pressure, left and right for hot/cold). The hot feed for the shower comes from the hot water supply and the cold is from the mains.

The current shower warms up all the way to bl**dy hot and then cools down to freezing cold throught the shower cycle. It is becoming a pain to use, so I need to change the shower unit.

Would a Gainsborough Ambassador do the job, B&Q are selling them at £114 at the moment, or should I be looking at something else? I have seen various controllers such as the Grohe but have no idea whether they are any better/worse.

I am praying that someone out there with experience of these contraptions will be able to point me in the right direction.

Cheers

Rob G

 

[ArtfulBodger]

The current shower warms up all the way to bl**dy hot and then cools down to freezing cold throught the shower cycle. It is becoming a pain to use, so I need to change the shower unit.

Why? do your hot taps exhibit the same symptoms?

 

[PEDANTICVINDICTIVEMAN]

Got a nasty feeling that your Glowworm Exasperate doesn't modulate, this may mean that whatever you get could be a problem, have a word with Glowworm tech, then maybe a thermostic beast may be the answer

 

[Bahco]

Purchase a good thermostatic mixer.
Both will be at mains pressure and you will have a lovely shower.
As AB said if your other hot taps are going cold you will need your boiler looking at

 

[PEDANTICVINDICTIVEMAN]

Got a nasty feeling that your Glowworm Exasperate doesn't modulate, this may mean that whatever you get could be a problem, have a word with Glowworm tech, then maybe a thermostic beast may be the answer

 

[PEDANTICVINDICTIVEMAN]

Seems to be an echo in here tonight

 

[Bahco]

Beat you to it sorry

 

[PEDANTICVINDICTIVEMAN]

I was reffering to my posting being on twice not you mate

 

[Bahco]

Sorry chap

 

[ChrisR]

Get your boiler checked first. No mixer in the world heats cold water! It's common for scaled combis to go hot cold hot cold etc..
Don't fit a thermostatic mixer to that sort of combi - better chance of stability of temperature with a pressure balanced one. Mira do one whose name I've forgotten, sorry.


Been through this before so it's short, sorry!

Thermostatic mixer decides (say) that it need to cool its output, so it reduces the HW flow. Reduced flow means hotter water from the combi, after a delay. So the mixer needs to reduce the hot flow more. Eventually the combi can't sustain safe output temp with reduced flow so it turns off. And you get cold water in the shower. ANd the cycle repeats.
Scaling in the boiler increases the temperature overshoot and the time delay - all worse.

So the best start is often to descale the hot water heat exchanger, if not the main one as well.

 

[PEDANTICVINDICTIVEMAN]

oops, think you had better go through one or two other shower post's,

 

[HammerAndThaw]

Thanks for the info, and yes I had scoured the forum for info on combi showers, and I had read the very useful post re the pressure and the combi flowing so much hot water that it shuts off and sends cold water.

Perhaps I should mention that the hot water is constant downstairs, and it is at a good pressure. Upstairs it is much lower. If I am running a hot tap it does stay hot, but it's the shower that is causing me the frustration. It would take forever to run a bath, so the shower is the only way out.

I will try the folks at Gloworm to see if they have any suggestions, but if anyone has any suggestions re a particular shower controller in the meantime then please let me know.

Many thanks

Rob G

 

[johnbrist]

I think the Mira mentioned by ChrisR is the 415.

Bear in mind that the shower has to have a minimum flow of HW to keep the Combi firing - so if the showerhead is either badly scaled up or not allowing enough water through, that would also cause the problem.