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New Shower Running hot and cold

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chrisfuz

from United Kingdom

Joined: 18 Nov 2004
Posts: 9
Location: United Kingdom

PostPosted: Sun May 08, 2005 4:19 pm Reply with quote

I have a combi boiler and have just installed a new shower. The mixer says it is OK for combi boilers but when I use the shower it runs hot and cold. My water pressure is good. No other appliances or taps were being used while showering. icon_question.gif
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ChrisR

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PostPosted: Sun May 08, 2005 4:39 pm Reply with quote

MOre details please, on combi inc age, and mixer type?
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PEDANTICVINDICTIVEMAN

from Western Sahara

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PostPosted: Mon May 09, 2005 6:10 am Reply with quote

You might end up having to run the hot basin tap to keep the boiler firing while showering during summer months.
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xbond

from United Kingdom

Joined: 03 Sep 2003
Posts: 43
Location: United Kingdom

PostPosted: Mon May 09, 2005 8:53 am Reply with quote

You may be exceeding your boiler's maximum flow rate, try to reduce the flow...
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Moley

from United Kingdom

Joined: 09 May 2005
Posts: 3
Location: Berkshire,
United Kingdom

PostPosted: Mon May 09, 2005 12:20 pm Reply with quote

As you have a combi i'm guessing that you have a thermostatic mixer valve. Have you checked that the hot and cold supplies are connected the right way around? Thermostatic mixers dont like the supplies connected round the wrong way, just a thought... icon_idea.gif
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chrisfuz

from United Kingdom

Joined: 18 Nov 2004
Posts: 9
Location: United Kingdom

PostPosted: Thu May 12, 2005 10:24 pm Reply with quote

The Combi boiler is an Ideal CF65 or 75 I think. Don't know how old it is at least about 4 years

Shower mixer is this one.

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=35889&id=19454

I'm sure its connected the right way round as red goes hot blue goes cold. Hard to check actual pipes as it is now plastered into the wall behind some tiles.
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ChrisR

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PostPosted: Fri May 13, 2005 7:15 am Reply with quote

The combi doesn't sring to mind, but the most likely source of your problem is sludge/scale in the secondary heat exchanger. They all do it eventually.
If you had your supplies reversed you would get only hot water or only coldwater, typically - at least that's what I got when I did it!

Thescale slows the temperature - sensing down so the combi turns off for long periods to get the temp down, WHen they're clean they switch on and off quickly enough that you don't notice the variation.

Not sure which type of 2ndry h/e you'll have, but they're all descalable with more or less difficulty. They have to be taken out though, as a rule.
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PEDANTICVINDICTIVEMAN

from Western Sahara

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PostPosted: Fri May 13, 2005 7:43 pm Reply with quote

Try running the hot tap on the basin and then turn on the shower valve to approx temp position you would normally use it at, then leave it a while to stabilise and see if it solves the problem, a different shower head letting the right amount of water pass throught the boiler may sort the problem, it has on mine.
Of course if your combi is an old one and doesn't modulate, you could be up shiiitte creek without a paddle.
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cobra

from United Kingdom

Joined: 24 Jul 2006
Posts: 4
Location: West Midlands,
United Kingdom

PostPosted: Fri Jul 28, 2006 12:07 am Reply with quote

PEDANTICVINDICTIVEMAN wrote:
Try running the hot tap on the basin and then turn on the shower valve to approx temp position you would normally use it at, then leave it a while to stabilise and see if it solves the problem, a different shower head letting the right amount of water pass throught the boiler may sort the problem, it has on mine.
Of course if your combi is an old one and doesn't modulate, you could be up shiiitte creek without a paddle.
Does the boiler fire when you turn on shower and does it keep cutting out and restarting- if so could be boiler thermostat cutting out due to faulty stat or scale in heat exchanger or it could possibly faulty thermostatic mixer
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Bambi

from United Kingdom

Joined: 27 Jul 2006
Posts: 15
Location: Kent,
United Kingdom

PostPosted: Fri Jul 28, 2006 8:44 am Reply with quote

Does the water run hot and cold elsewhere, such as the bath. I had this problem and it turned out to be the heat exchanger. It was removed, cleaned and then worked OK. It could be sludged up with scale or debris from a new install. The system may need flushing too, to ensure it don't sludge up again.
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ChrisR

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PostPosted: Fri Jul 28, 2006 10:13 am Reply with quote

Forget it guys, this post's over a year old!
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