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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Boiler air pressure switch



 
 
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  #1  
Old November 10th 08, 11:46 AM posted to uk.d-i-y
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Posts: 357
Default Boiler air pressure switch

Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that effect.
Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if nothing's
obviously damaged.

It seems to me that the switch is not necessarily the culprit - it could
be doing its job perfectly and warning that the pressure is not changing
due to some other fault. So I don't want to just order another switch
and slap it in.

Any suggestions on how to proceed?

Cheers,

Pete
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  #2  
Old November 10th 08, 01:53 PM posted to uk.d-i-y
external usenet poster
 
Posts: 667
Default Boiler air pressure switch


"Pete Verdon" d wrote in
message ...
Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that effect.
Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if nothing's
obviously damaged.

It seems to me that the switch is not necessarily the culprit - it could
be doing its job perfectly and warning that the pressure is not changing
due to some other fault. So I don't want to just order another switch
and slap it in.

Any suggestions on how to proceed?

Cheers,

Pete


This type of thing can be caused by the change in weather, and having wind
blow back into the flue and cause false detection. You say that a power
cycle sometimes clears it, or is it coincidence that your power cycle
coincided with a drop in the wind, or even the direction changed.

For me, it's a difficult one to diagnose unless you are standing in front of
it, I'm afraid. I hope other more knowledgeable souls come along with a few
more suggestions for you to try.



  #3  
Old November 10th 08, 08:58 PM posted to uk.d-i-y
external usenet poster
 
Posts: 1,226
Default Boiler air pressure switch

On Mon, 10 Nov 2008 11:46:12 +0000, Pete Verdon wrote:

Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that effect.
Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if nothing's
obviously damaged.

It seems to me that the switch is not necessarily the culprit - it could
be doing its job perfectly and warning that the pressure is not changing
due to some other fault. So I don't want to just order another switch
and slap it in.

Any suggestions on how to proceed?

Cheers,

Pete


=========================================
Blow through the air switch tubes - might be a bit clogged up with dust.
It might not work but at least it can't do any harm.

Cic.

--
==========================================
Using Ubuntu Linux
Windows shown the door
==========================================

  #4  
Old November 10th 08, 11:07 PM posted to uk.d-i-y
external usenet poster
 
Posts: 3,864
Default Boiler air pressure switch

In message , Pete Verdon
d writes
Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that
effect. Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if
nothing's obviously damaged.

It seems to me that the switch is not necessarily the culprit - it
could be doing its job perfectly and warning that the pressure is not
changing due to some other fault. So I don't want to just order another
switch and slap it in.

Any suggestions on how to proceed?

You could always check the APS

Check the closed and open contact resistance - you want it to be in the
region of an ohm or less, this involves checking your probe resistance
first. You can activate the APS by GENTLY sucking or blowing on one of
the rubber tubes to the APS. Kink the tube and leave it kinked for 30
seconds or so to check that the APS membrane is not ruptured.Also check
for a split or suchlike in the rubber tubes

check the seals, check the flue,

Are you experiencing the high winds we are getting around here ? If your
flue is exposed, you might be getting blowback

--
geoff
  #5  
Old November 11th 08, 12:00 AM posted to uk.d-i-y
external usenet poster
 
Posts: 3,864
Default Boiler air pressure switch

In message , Cicero
writes
On Mon, 10 Nov 2008 11:46:12 +0000, Pete Verdon wrote:

Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that effect.
Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if nothing's
obviously damaged.

It seems to me that the switch is not necessarily the culprit - it could
be doing its job perfectly and warning that the pressure is not changing
due to some other fault. So I don't want to just order another switch
and slap it in.

Any suggestions on how to proceed?

Cheers,

Pete


=========================================
Blow through the air switch tubes - might be a bit clogged up with dust.
It might not work but at least it can't do any harm.

Well yes it can

you can rupture the APS diaphragm

--
geoff
  #6  
Old November 11th 08, 09:05 AM posted to uk.d-i-y
external usenet poster
 
Posts: 1,226
Default Boiler air pressure switch

On Tue, 11 Nov 2008 00:00:22 +0000, geoff wrote:

In message , Cicero
writes
On Mon, 10 Nov 2008 11:46:12 +0000, Pete Verdon wrote:

Morning,

Over the last few days, I've been getting an intermittent fault in my
boiler (a Chaffoteaux Brittony combi). The code it blinks translates to
"fan on but air pressure switch not activated", or words to that effect.
Turning the power off and on again (can you tell I'm a software
engineer? :-) ) clears it for some hours / up to a day.

I have the service manual for it, and can see that the air pressure
switch and venturi (and the fan) is mounted inside the "sealed chamber"
(but not in the combustion chamber itself). I'm satisfied with my
competence to open this up (and in any case it's not actually
gas-carrying) but I'm not sure what I'd do when I get there if nothing's
obviously damaged.

It seems to me that the switch is not necessarily the culprit - it could
be doing its job perfectly and warning that the pressure is not changing
due to some other fault. So I don't want to just order another switch
and slap it in.

Any suggestions on how to proceed?

Cheers,

Pete


=========================================
Blow through the air switch tubes - might be a bit clogged up with dust.
It might not work but at least it can't do any harm.

Well yes it can

you can rupture the APS diaphragm

=========================================
I meant *disconnected* tubes and should have said so because I wouldn't
ever suggest blowing dust *into* any piece of equipment like a switch.
Thanks for pointing out the possibility of damage to the switch and I
should add the possibility of blow-back of dust into the blower's eyes.

Cic.

--
==========================================
Using Ubuntu Linux
Windows shown the door
==========================================

  #7  
Old November 12th 08, 12:27 AM posted to uk.d-i-y
external usenet poster
 
Posts: 357
Default Boiler air pressure switch

Cicero wrote:
On Tue, 11 Nov 2008 00:00:22 +0000, geoff wrote:
Cicero writes


Blow through the air switch tubes - might be a bit clogged up with dust.
It might not work but at least it can't do any harm.


Well yes it can

you can rupture the APS diaphragm


I meant *disconnected* tubes and should have said so because I wouldn't
ever suggest blowing dust *into* any piece of equipment like a switch.


It's a fair point - without the warning I quite likely would have blown
through the valve body. I'd hope that I have sufficient mechanical
sympathy not to rupture anything in the process though, unless these
diaphragms are unusually sensitive.

At the moment, I'm hoping it's just the wind direction as BigWallop and
Geoff suggested :-). It hasn't happened again since I posted.

Pete
 




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