Glow Worm Combi hot water
 

Hi All,
I have a problem with my Glow worm Swiftflow 80, when I turn on the hot
tap the boiler fires up but only for a few seconds then the gas shuts
off, the pilot light stays lit. The central heating works OK, the gas
remains lit when it is turned on, this (in my mind) rules out a problem
with the fan. I initially thought it was the water pressure switch so I
replaced it, then after reading some previous posts I thought it could
be the HW thermistor but neither of these things worked. The water
pressure switch is adjustable where the original had a fixed
sensitivity, I have not tried adjusting the screw, I just installed it
as it came. Any ideas as to what to try next ?
Regards
Alan

Glow Worm Combi hot water
 

On Sat, 12 Aug 2006 13:57:44 -0700, Maymo wrote:


Ed Sirett wrote:


Have you monitored the water flow switch?
Does the pump operate OK?


The pump seems to be fine, I have just tried the CH for 10 minutes and
it is all working great. While the CH was on I tried the hot tap and
the water heated up, then went cold then hot again and carried on like
this switching every 30 seconds or so. Why would the pump make any
difference to the DHW, surely the DHW would work even if the CH pump
didn't?
How do I monitor the water flow switch, I have a multimeter.
Now that the CH is off the DHW is still cycling hot and cold, the
system is still warm.
Alan

When you run a HW tap without switching the CH on does the water run
cold-hot-cold-hot?
Or does the boiler fire for 10 seconds and never again?

I'm beginning to think you have a problem with a scaled up secondary
heat exchanger.

--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Glow Worm Combi hot water
 

Ed Sirett wrote:

When you run a HW tap without switching the CH on does the water run
cold-hot-cold-hot?
Or does the boiler fire for 10 seconds and never again?

I'm beginning to think you have a problem with a scaled up secondary
heat exchanger.

On closer inspection I now think that the gas is not firing up at all,
the CH has been off all day, I open the hot tap and cold water comes
out shortly followed by tepid water for 10 seconds then cold water
continuously. The boiler makes a noise when the tap is open which I
thought was the gas but now I have doubts, perhaps its just the sound
of the water flowing through the system.

I have a manual for the boiler and I can't find a secondary heat
exchanger, does it have one?

Do I check the voltage of the flow switch with the multimeter in
series? what voltage should I expect when the tap is shut and open?

Thanks for your help.
Alan

Glow Worm Combi hot water
 

In message . com, Maymo
writes


Do I check the voltage of the flow switch with the multimeter in
series? what voltage should I expect when the tap is shut and open?

I don't know this boiler, but current glowworm flow switches tend to
have a pulsed output from a paddle


--
geoff

Glow Worm Combi hot water
 

I disconnected the flow switch, turned the hot tap on and shorted the
flow switch terminals, the boiler fired up, then went out after 10
seconds or so. The water then does the hot - cold hot cycle. When I
turn on the hot tap with the flow switch connected the boiler doesn't
fire. Does this prove that the flow switch is faulty? if so why does
the gas trip after 10 seconds and then relight?
Alan

raden wrote:


Do I check the voltage of the flow switch with the multimeter in
series? what voltage should I expect when the tap is shut and open?

I don't know this boiler, but current glowworm flow switches tend to
have a pulsed output from a paddle


--
geoff

Glow Worm Combi hot water
 

As I said earlier I have replaced the DHW thermister, there is also a
DHW high limit control, what is this, does it do a similar job to the
thermister?
Maymo wrote:

I disconnected the flow switch, turned the hot tap on and shorted the
flow switch terminals, the boiler fired up, then went out after 10
seconds or so. The water then does the hot - cold hot cycle. When I
turn on the hot tap with the flow switch connected the boiler doesn't
fire. Does this prove that the flow switch is faulty? if so why does
the gas trip after 10 seconds and then relight?
Alan

raden wrote:


Do I check the voltage of the flow switch with the multimeter in
series? what voltage should I expect when the tap is shut and open?

I don't know this boiler, but current glowworm flow switches tend to
have a pulsed output from a paddle


--
geoff

Glow Worm Combi hot water
 

In message .com,
Maymo writes
As I said earlier I have replaced the DHW thermister, there is also a
DHW high limit control, what is this, does it do a similar job to the
thermister?
Maymo wrote:

I disconnected the flow switch, turned the hot tap on and shorted the
flow switch terminals, the boiler fired up, then went out after 10
seconds or so. The water then does the hot - cold hot cycle. When I
turn on the hot tap with the flow switch connected the boiler doesn't
fire. Does this prove that the flow switch is faulty? if so why does
the gas trip after 10 seconds and then relight?
Alan


Sorry ...

top posting !


raden wrote:


Do I check the voltage of the flow switch with the multimeter in
series? what voltage should I expect when the tap is shut and open?

I don't know this boiler, but current glowworm flow switches tend to
have a pulsed output from a paddle


--
geoff


--
geoff

Glow Worm Combi hot water
 

On Mon, 14 Aug 2006 05:19:12 -0700, Maymo wrote:

I disconnected the flow switch, turned the hot tap on and shorted the
flow switch terminals, the boiler fired up, then went out after 10
seconds or so. The water then does the hot - cold hot cycle. When I
turn on the hot tap with the flow switch connected the boiler doesn't
fire. Does this prove that the flow switch is faulty? if so why does
the gas trip after 10 seconds and then relight?
Alan

I'm beginning to think you have two problems.

The first problem is that you have something wrong with the water flow
detector. If you care to give the exact model number and the GC number I
might have a manual and I might be able to suggest the type of fault it
has, how difficult the replacement might be and likely costs.

The second problem I suspect is that the secondary heat exchanger is
scaled up (or some other more exotic problem) and this limits the heat
transfer to the DHW. The boiler can't maintain the minimum gas
rate without getting to hot, it then cuts the gas from time to time and
the water goes hot/cold/hot.

The lastest GW are similar to Vaillants but I think you have an earlier
model using different technology for the DHW flow switch.


--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Glow Worm Combi hot water
 

The GC number is 47 313 14 the is Glow worm swiftflow 80 and it
is about 8 years old. The heat exchanger is a twin pass, one pass for
CH and one for DHW. I replaced this heat exchanger last year due to a
leaking tube.
Alan

Ed Sirett wrote:

I'm beginning to think you have two problems.

The first problem is that you have something wrong with the water flow
detector. If you care to give the exact number and the GC number I
might have a manual and I might be able to suggest the type of fault it
has, how difficult the replacement might be and likely costs.

The second problem I suspect is that the secondary heat exchanger is
scaled up (or some other more exotic problem) and this limits the heat
transfer to the DHW. The boiler can't maintain the minimum gas
rate without getting to hot, it then cuts the gas from time to time and
the water goes hot/cold/hot.

The lastest GW are similar to Vaillants but I think you have an earlier
using different technology for the DHW flow switch.

Glow Worm Combi hot water
 

On Tue, 15 Aug 2006 08:34:06 -0700, Maymo wrote:

The GC number is 47 313 14 the is Glow worm swiftflow 80 and it
is about 8 years old. The heat exchanger is a twin pass, one pass for
CH and one for DHW. I replaced this heat exchanger last year due to a
leaking tube.
Alan

Ed Sirett wrote:

I'm beginning to think you have two problems.

The first problem is that you have something wrong with the water flow
detector. If you care to give the exact number and the GC number I
might have a manual and I might be able to suggest the type of fault it
has, how difficult the replacement might be and likely costs.

The second problem I suspect is that the secondary heat exchanger is
scaled up (or some other more exotic problem) and this limits the heat
transfer to the DHW. The boiler can't maintain the minimum gas
rate without getting to hot, it then cuts the gas from time to time and
the water goes hot/cold/hot.

The lastest GW are similar to Vaillants but I think you have an earlier
using different technology for the DHW flow switch.

Sorry, I don't have that manual to hand.
You are continuing to top post replies - please adjust your newsreader.


--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Glow Worm Combi hot water
 

I have now replaced the DHW flow switch and the DHW limit control. The
boiler now lights for 30 seconds then goes out then relights etc. AFAIK
I have replaced all the temp sensors on the DHW. This boiler has a
crossflow heat exchanger so doesn't have a diverter valve or a
secondary exchanger. There is a good flow of water to and from the
boiler. The CH works fine. Do you think the problem could be the PCB?
Is there any way to test the PCB apart from replace it and see if it
works?
By the way I gave the G.C. number on the manual, the one on the boiler
is G.C. 47-313-09
Regards
Alan