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New shower off combi boiler - water runs hot then cold


 
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LMN

from United Kingdom

Joined: 21 Jul 2011
Posts: 4
Location: West Midlands,
United Kingdom

PostPosted: Thu Jul 21, 2011 9:03 am Reply with quote

Can any body help? I have had a new shower installed (Grohe) connected to the combi boiler (Heatline) but cannot find a way to have consistant water temperature. It runs hot for 4 -5 minutes, then cold and back up to warm. I have lowered the combi boiler water temperature to the lowest it can be and the same happens. Any suggestions please?
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kevindgas

from United Kingdom

Joined: 28 Mar 2006
Posts: 5691
Location: Southampton,
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PostPosted: Thu Jul 21, 2011 9:52 am Reply with quote

was a pressure Equalizing valve fitted to the shower inlets? i suspect not! as a result there isn't equal pressure on the showers cartridge causing it to move which in turn causes problems to the boilers modulation. an all too common problem caused by untrained plumbers that have done a 6 week course and think they now how to install
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Agile

from United Kingdom

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Location: London,
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PostPosted: Thu Jul 21, 2011 10:05 am Reply with quote

I am often critical of inexperienced people working on boilers and plumbing but in this case I think Kevin may be being a little too critical.

The Grohe are very good products and work well with combi boilers.

In this case I would suspect a possible problem with the boiler temperature control system. Very unfortunately few boiler engineers would have the knowledge or interest to fully check all aspects of the boiler operation.

There are a couple of tests you could do which may help us to assimilate whats going wrong. First identify the hot water outlet pipe from the boiler and feel it while the shower is being used and see what it is doing.

Next run a hot water tap at about 3 litres per minute while the shower is being used and see if that makes any difference.

An important aspect is to have the temperature control on the boiler lowish. You say you have done that but is it actually altering the DHW temperature?

Tony Glazier



PS
May be a stupid question but it should be asked! Has the hot/cold been correctly connected to the shower?
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LMN

from United Kingdom

Joined: 21 Jul 2011
Posts: 4
Location: West Midlands,
United Kingdom

PostPosted: Thu Jul 21, 2011 10:26 am Reply with quote

kevindgas wrote:
was a pressure Equalizing valve fitted to the shower inlets? i suspect not! as a result there isn't equal pressure on the showers cartridge causing it to move which in turn causes problems to the boilers modulation. an all too common problem caused by untrained plumbers that have done a 6 week course and think they now how to install


the shower was fitted by the company installing my new bathroom, including the shower - this is something I can ask them. Thanks
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LMN

from United Kingdom

Joined: 21 Jul 2011
Posts: 4
Location: West Midlands,
United Kingdom

PostPosted: Thu Jul 21, 2011 10:33 am Reply with quote

Agile wrote:
I am often critical of inexperienced people working on boilers and plumbing but in this case I think Kevin may be being a little too critical.

The Grohe are very good products and work well with combi boilers.

In this case I would suspect a possible problem with the boiler temperature control system. Very unfortunately few boiler engineers would have the knowledge or interest to fully check all aspects of the boiler operation.

There are a couple of tests you could do which may help us to assimilate whats going wrong. First identify the hot water outlet pipe from the boiler and feel it while the shower is being used and see what it is doing.

Next run a hot water tap at about 3 litres per minute while the shower is being used and see if that makes any difference.

An important aspect is to have the temperature control on the boiler lowish. You say you have done that but is it actually altering the DHW temperature?

Tony Glazier


thanks Tony
excuse my ignorance but not sure what DHW stands for - the water from the hot tap is only warm since I adjusted the boiler - is that what you mean?
I will try to identify the hot water outlet pipe and follow your checks whilst the shower is running (later when i am at home).



PS
May be a stupid question but it should be asked! Has the hot/cold been correctly connected to the shower?
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Agile

from United Kingdom

Joined: 26 Jun 2004
Posts: 52979
Location: London,
United Kingdom
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PostPosted: Thu Jul 21, 2011 10:43 am Reply with quote

DHW stands for domestic hot water.

People installing bathrooms are usually primarily carpenters/tilers and many have only very basic plumbing knowledge as thats all thats required for that job.

A real experienced plumber able to diagnose and repair shower problems are difficult to find. I usually suggest shower manufacturers service agents.

In this case it seems you might be able to blame the bathroom fitters ( although it could still be the boiler.

Does the shower temperature adjustment seem to operate correctly and in the expected direction?

You have not answered my question about the DHW output temperature at the boiler while the shower is on.

Tony
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LMN (21 Jul 2011)
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LMN

from United Kingdom

Joined: 21 Jul 2011
Posts: 4
Location: West Midlands,
United Kingdom

PostPosted: Thu Jul 21, 2011 10:51 am Reply with quote

Agile wrote:
DHW stands for domestic hot water.

People installing bathrooms are usually primarily carpenters/tilers and many have only very basic plumbing knowledge as thats all thats required for that job.

A real experienced plumber able to diagnose and repair shower problems are difficult to find. I usually suggest shower manufacturers service agents.

In this case it seems you might be able to blame the bathroom fitters ( although it could still be the boiler.

Does the shower temperature adjustment seem to operate correctly and in the expected direction?

You have not answered my question about the DHW output temperature at the boiler while the shower is on.

Tony



thank again - and for the explanation - I will try the DHW output temperature at the boiler while the shower is on when I am back at home.
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