Inside my boiler is a Grundfos switch with a dial for numbers 1/2/3.
the boiler works fine when this is on 1 but if i switch it to 2 or 3
(which i assume will make the water hotter) the boiler will not turn
off if i run the central heating. it just constantly stays on
burning. However if i turn off the downstairs radiators it goes back
to it's stop-start usual self. The problem also is that the water
does not get any warmer with the switch at 2 or 3.

Does this dial control the water temperature? or any clues as to how i
would sort it out... many thanks guys

On Thu, 12 Feb 2004 04:45:41 +0000, Shabs wrote:

Inside my boiler is a Grundfos switch with a dial for numbers 1/2/3.
the boiler works fine when this is on 1 but if i switch it to 2 or 3
(which i assume will make the water hotter) the boiler will not turn
off if i run the central heating. it just constantly stays on
burning. However if i turn off the downstairs radiators it goes back
to it's stop-start usual self. The problem also is that the water
does not get any warmer with the switch at 2 or 3.

Does this dial control the water temperature? or any clues as to how i
would sort it out... many thanks guys

Almost always you set a combi boiler's internal pump to 3 (unless the
instruction say otherwise). Sometimes the instructions say that you may
turn it down but will have reduced water heating performance - which on
most installations would not be welcome.

This setting is how hard the the pump works.

To make the radiators hotter try the knob on the outside of the boiler!


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

OK I agree that the pump should be set to 3, but if i move the switch
into position 3 I can hear a sort of different noise, but when I start
the central heating from position 3, the boiler does not turn off,
just runs continuous and the pressure goes sky high. With the pump on
no. 1 the boiler does the stop-start stuff. How would i get the pump
onto no.3 but the boiler doing the usual stop-start routine.

On Fri, 13 Feb 2004 01:13:27 +0000, Shabs wrote:

OK I agree that the pump should be set to 3, but if i move the switch
into position 3 I can hear a sort of different noise, but when I start
the central heating from position 3, the boiler does not turn off,
just runs continuous and the pressure goes sky high. With the pump on
no. 1 the boiler does the stop-start stuff. How would i get the pump
onto no.3 but the boiler doing the usual stop-start routine.

It is very unlikely that setting the pump to the high setting will by
itself cause any problem.
You should now procede to tackle the cause of the high pressure directly.
See the Sealed system FAQ it is likely that as the _average_ water
temperature rises the system pressure is rising too quickly.
The cause for this is likely a failed expansion vessel.

The boiler will likely operate correctly once the water temperature has
stabilised but this may mean the prsssure will go even higher and water is
thrown out of the vent pipe.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

Very very useful FAQ

My sealed system seems to have partially failed, ie I can keep it from going
over 3 bar by limiting the temp to 75C and keeping min pressure at about 0.4
bar.

I presume that the air will have leaked and needs pumping rather than the
diaphram holed - or am I just being hopeful!!

John


"Ed Sirett" wrote in message
news
On Fri, 13 Feb 2004 01:13:27 +0000, Shabs wrote:

OK I agree that the pump should be set to 3, but if i move the switch
into position 3 I can hear a sort of different noise, but when I start
the central heating from position 3, the boiler does not turn off,
just runs continuous and the pressure goes sky high. With the pump on
no. 1 the boiler does the stop-start stuff. How would i get the pump
onto no.3 but the boiler doing the usual stop-start routine.

It is very unlikely that setting the pump to the high setting will by
itself cause any problem.
You should now procede to tackle the cause of the high pressure directly.
See the Sealed system FAQ it is likely that as the _average_ water
temperature rises the system pressure is rising too quickly.
The cause for this is likely a failed expansion vessel.

The boiler will likely operate correctly once the water temperature has
stabilised but this may mean the prsssure will go even higher and water is
thrown out of the vent pipe.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

On Sat, 14 Feb 2004 18:22:06 -0000, "JohnB"
wrote:

Very very useful FAQ

My sealed system seems to have partially failed, ie I can keep it from going
over 3 bar by limiting the temp to 75C and keeping min pressure at about 0.4
bar.

I presume that the air will have leaked and needs pumping rather than the
diaphram holed - or am I just being hopeful!!

John



Try turning off the heating and remove the dust cap from the Schrader
valve on the expansion vessel. Release the pressure carefully as you
would to let a car tyre down.

If water comes out then you know the answer to your question and a new
vessel is needed. Otherwise, release the water pressure on the heating
circuit completely and then precharge the expansion vessel with a
suitable supply of compressed air or a tyre inflator. Finally
pressurise the water side again.

If you do have to replace the vessel, they come precharged with
nitrogen


..andy

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