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Vaillant Combi boiler hot water problems



 
 
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  #1  
Old February 16th 09, 04:38 PM posted to uk.d-i-y
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Posts: 311
Default Vaillant Combi boiler hot water problems

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked that
no one else is calling for hot water at the same time and have tried
adjusting the water temperature to no avail. At a guess it runs hot ok
for about 20 seconds then goes cold for 10 seconds. Any ideas please?
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  #2  
Old February 16th 09, 06:06 PM posted to uk.d-i-y
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Posts: 1,235
Default Vaillant Combi boiler hot water problems

Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked that
no one else is calling for hot water at the same time and have tried
adjusting the water temperature to no avail. At a guess it runs hot ok
for about 20 seconds then goes cold for 10 seconds. Any ideas please?


Does it continually go hot then cold then hot etc?
If so, possible hot water heat exchanger blockage - quite common
apparently..
Or, Primary heat exchanger fault, or possible pump failing - both less
likely, but possible..

Or does it run hot for 20 seconds, the stays luke warm?
That would point toward a divertor valve fault.

Alan.
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  #3  
Old February 16th 09, 06:14 PM posted to uk.d-i-y
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Posts: 311
Default Vaillant Combi boiler hot water problems

A.Lee wrote:
Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked that
no one else is calling for hot water at the same time and have tried
adjusting the water temperature to no avail. At a guess it runs hot ok
for about 20 seconds then goes cold for 10 seconds. Any ideas please?


Does it continually go hot then cold then hot etc?
If so, possible hot water heat exchanger blockage - quite common
apparently..
Or, Primary heat exchanger fault, or possible pump failing - both less
likely, but possible..

Or does it run hot for 20 seconds, the stays luke warm?
That would point toward a divertor valve fault.

Alan.

It alternates hot and cold.
  #4  
Old February 16th 09, 06:21 PM posted to uk.d-i-y
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Posts: 1,235
Default Vaillant Combi boiler hot water problems

Broadback wrote:

A.Lee wrote:
Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine ....

Does it continually go hot then cold then hot etc?
If so, possible hot water heat exchanger blockage - quite common
apparently..


It alternates hot and cold.


I had the same thing, starting around this time last year.
DHW Heat Exchanger was cleaned out, then changed after a few months,
still no good, turned out to be either the primary heat exchanger or the
pump.
Power flushing and chemical treatment did not cure the fault.

It was 10 years old, had never been very reliable, so I bit the bullet
and had a new boiler.
It is possible that a flush out of the DHW HE would cure your fault.
On mine, it took 10 minutes or so to get the HE out, so a fairly easy
task, no idea what it would be like on your Valiant.
Alan.
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  #5  
Old February 16th 09, 06:24 PM posted to uk.d-i-y
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Posts: 2,231
Default Vaillant Combi boiler hot water problems

On Mon, 16 Feb 2009 18:14:50 +0000, Broadback wrote:

A.Lee wrote:
Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot
water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked
that no one else is calling for hot water at the same time and have
tried adjusting the water temperature to no avail. At a guess it runs
hot ok for about 20 seconds then goes cold for 10 seconds. Any ideas
please?


Does it continually go hot then cold then hot etc? If so, possible hot
water heat exchanger blockage - quite common apparently..
Or, Primary heat exchanger fault, or possible pump failing - both less
likely, but possible..

Or does it run hot for 20 seconds, the stays luke warm? That would
point toward a divertor valve fault.

Alan.

It alternates hot and cold.


One or both sides of the 2ndary heatX.
Either
Replace with a new unit and then descale "the spare" at your leisure.
Or.
If you can do without heating and HW for a day then descale the existing
unit. You will not get good results trying to descale either side in
situ. You may, if very unlucky spring a leak between the primary and
domestic sides when you descale.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

  #6  
Old February 16th 09, 08:55 PM posted to uk.d-i-y
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Posts: 3,864
Default Vaillant Combi boiler hot water problems

In message , A.Lee
writes
Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked that
no one else is calling for hot water at the same time and have tried
adjusting the water temperature to no avail. At a guess it runs hot ok
for about 20 seconds then goes cold for 10 seconds. Any ideas please?


Does it continually go hot then cold then hot etc?
If so, possible hot water heat exchanger blockage - quite common
apparently..


possibly, but then the flow rate would drop

Or, Primary heat exchanger fault, or possible pump failing - both less
likely, but possible..


possibly, but it would also present itself in the CH mode too


Or does it run hot for 20 seconds, the stays luke warm?
That would point toward a divertor valve fault.


I can't remember, but, if it opens the gas valve and then has a certain
time window for flame sensing to occur, and its not, that would account
for the behaviour he's seeing



Alan.


--
geoff
 




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