Hello people,

I've recently encountered a puzzling problem with a Vaillant GB 242 .
Hot water works fine, but on calling for central heating the boiler
appears to be dead. There is no roomstat and on on operating the
external programmer I can hear a relay click inside the boiler control
box. On switching the boiler off at the spur and on again the boiler
will fire up and I then get central heating for about a minute, the
boiler then shuts down again.

I'm inclined to think its an electrical fault maybe the heating
thermistor being out of range, but since I don't know what the correct
resistance of it should be I can't draw any conclusions. I assume the
overheat stat will prevent the boiler firing up in both hot water and
heating modes? so I can't imagine it is that. Any experts around ? I
deserve an easy boiler after my last (successful ) escapade with an
Isar.

Perplexed

Heeley

On Fri, 06 Feb 2009 10:50:32 -0800, heeley wrote:

Hello people,

I've recently encountered a puzzling problem with a Vaillant GB 242 .
Hot water works fine, but on calling for central heating the boiler
appears to be dead. There is no roomstat and on on operating the
external programmer I can hear a relay click inside the boiler control
box. On switching the boiler off at the spur and on again the boiler
will fire up and I then get central heating for about a minute, the
boiler then shuts down again.

I'm inclined to think its an electrical fault maybe the heating
thermistor being out of range, but since I don't know what the correct
resistance of it should be I can't draw any conclusions. I assume the
overheat stat will prevent the boiler firing up in both hot water and
heating modes? so I can't imagine it is that. Any experts around ? I
deserve an easy boiler after my last (successful ) escapade with an
Isar.


I presume this is the Vaillant VCW 242 GB which is a combi with two white
metal doors and a grey metal fascia?

This problem could stem from a number of sources. The fact that the
boiler works for DHW means a lot of stuff must but OK.
So we know the pump, fan, gas valve, ignition, DHW flow detector, DHW
microswitch, diverter servo valve are good. Also the servo valve must be
able to go to the right from neutral to DHW mode.

No CH?
Could be servo valve not returning under spring pressure to the CH
position. That's the triangular valve front mid bottom. Or the diverter
valve (back right bottom) can't go right. Or there is some problem with
the control boards, or maybe even external controls. Possible with the
temperature sensor. Servo pipe blocked.

Good chance of it being the servo valve not being returned to CH, because
of general crud/corrosion in the DHW flow detector.

HTH if the above leaves you bewildered get in a pro who knows VCWs


--
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

On Feb 6, 8:04*pm, Ed Sirett wrote:
On Fri, 06 Feb 2009 10:50:32 -0800, heeley wrote:
Hello people,

I've recently encountered a puzzling problem with a Vaillant GB 242 .
Hot water works fine, but on calling for central heating the boiler
appears to be dead. There is no roomstat and on on operating the
external programmer I can hear a relay click inside the boiler control
box. On switching the boiler off at the spur and on again the boiler
will fire up and I then get central heating for about a minute, the
boiler then shuts down again.

I'm inclined to think its an electrical fault maybe the heating
thermistor being out of range, but since I don't know what the correct
resistance of it should be I can't draw any conclusions. I assume the
overheat stat will prevent the boiler firing up in both hot water and
heating modes? so I can't imagine it is that. Any experts around ? I
deserve an easy boiler after my last (successful ) escapade with an
Isar.

I presume this is the Vaillant VCW 242 GB which is a combi with two white
metal doors and a grey metal fascia?

This problem could stem from a number of sources. The fact that the
boiler works for DHW means a lot of stuff must but OK.
So we know the pump, fan, gas valve, ignition, DHW flow detector, DHW
microswitch, diverter servo valve are good. Also the servo valve must be
able to go to the right from neutral to DHW mode.

No CH?
Could be servo valve not returning under spring pressure to the CH
position. That's the triangular valve front mid bottom. Or the diverter
valve (back right bottom) can't go right. Or there is some problem with
the control boards, or maybe even external controls. Possible with the
temperature sensor. Servo pipe blocked.

Good chance of it being the servo valve not being returned to CH, because
of general crud/corrosion in the DHW flow detector.

HTH if the above leaves you bewildered get in a pro who knows VCWs

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

Hello Ed,

Thank you for your rapid response. I was hoping you'd read my post. I
have always noted how well informed you are boilers and gaswork.

I've actually got another 242 which was replaced though working ,
from which I can cannibalise parts with a view to perhaps discovering
what the issue can be. Can you acquaint me with the sequence of
operation w.r.t the heating operation of a (grey front panel) 242?

I'd really like to be able to sort this one myself.

Regards

Heeley

On Fri, 06 Feb 2009 12:23:44 -0800, heeley wrote:

Hello Ed,

Thank you for your rapid response. I was hoping you'd read my post. I
have always noted how well informed you are boilers and gaswork.

I've actually got another 242 which was replaced though working , from
which I can cannibalise parts with a view to perhaps discovering what
the issue can be. Can you acquaint me with the sequence of operation
w.r.t the heating operation of a (grey front panel) 242?

I'd really like to be able to sort this one myself.

Regards

Heeley

1) There is a demand caused by applying 230V ac at terminal 4 (or by
joining terminals 3 & $ together which is the same difference).
2) The circulation pump starts.
3) The servo valve (the triangular one on top of the DHW flow detector)
is in the CH position (normal position).
4) The pump forces water through those tiny 4mm tubes to the diverter
valve.
5) The DV moves to the left from its normal neutral mid position.
6) One (or more?) micro switches are activated by the DV (in a box on the
RHS of the DV)
7) The boiler begins the ignition sequence. Which should be OK as DHW is
OK.

--
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

On Feb 7, 7:11*pm, Ed Sirett wrote:
On Fri, 06 Feb 2009 12:23:44 -0800, heeley wrote:
Hello Ed,

Thank you for your rapid response. I was hoping you'd read my post. I
have always noted how well informed you are boilers and gaswork.

I've actually got another *242 which was replaced though working , from
which I can cannibalise parts with a view to perhaps discovering what
the issue can be. Can you acquaint me with the sequence of operation
w.r.t the heating operation of a (grey front panel) 242?

I'd really like to be able to sort this one myself.

Regards

Heeley

1) There is a demand caused by applying 230V ac at terminal 4 (or by
joining terminals 3 & $ together which is the same difference).
2) The circulation pump starts.
3) The servo valve (the triangular one on top of the DHW flow detector)
is in the CH position (normal position).
4) The pump forces water through those tiny 4mm tubes to the diverter
valve.
5) The DV moves to the left from its normal neutral mid position.
6) One (or more?) micro switches are activated by the DV (in a box on the
RHS of the DV)
7) The boiler begins the ignition sequence. Which should be OK as DHW is
OK.

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

Thanks for that Ed

Regards

Heeley

replying to Ed Sirett, 100Packets wrote:
COmbi boilers do not have diverter values. Hot water and radiator systems are
completely separate

--
for full context, visit https://www.homeownershub.com/uk-diy...ng-540813-.htm

On Mon, 23 Oct 2017 11:44:02 GMT, 100Packets
m coalesced the
vapors of human experience into a viable and meaningful
comprehension...

replying to Ed Sirett, 100Packets wrote:
COmbi boilers do not have diverter values. Hot water and radiator systems are
completely separate

What Ed Sirett doesn't know about plumbing, is not worth knowing so
**** off.

Why are you responding to a 2009 post anyway?


--

Graham.
%Profound_observation%

On 23/10/2017 12:44, 100Packets wrote:
replying to Ed Sirett, 100Packets wrote:
COmbi boilers do not have diverter values. Hot water and radiator
systems are
completely separate

Some do, especially old ones, some have two pumps for water to either
flow to the radiators or the HW exchanger.

There is a heat exchanger so hot water is not mixed with primary circuit
water.

This might assist you with posting to a newsgroup, albeit through a website:
https://tools.ietf.org/html/rfc1855

- If you are sending a reply to a message or a posting be sure you
summarize the original at the top of the message, or include just
enough text of the original to give a context.

On 23/10/2017 12:44, 100Packets wrote:

replying to Ed Sirett, 100Packets wrote:

Only 8 years late, and you are replying to professional heating systems
expert - so this is likely to be entertaining...

COmbi boilers do not have diverter values.

Strike one!

Erm, yes they do. Almost all of them.

The Domestic Hot Water is heated by a secondary water to water crossflow
heat exchanger. That in turn is heated by a flow of primary system water
that is heated by the main gas fired heat exchanger. That's the same
water that also flows through the rads. The way the boiler gets it to
flow through the DHW heat exchanger is via an internal diversion valve.

Hot water and radiator
systems are completely separate

Strike two!

No they are not. They both depend on the same primary circuit to provide
a pumped source of hot water, which can be use directly in the rads, and
indirectly for heating the DHW.


And you are out.



--
Cheers,

John.

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