saunier duval lockout problem

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29 Aug 2006
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Middlesex
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My combi boiler goes to lockout everytime I draw hot water or use the heating,although once the heating is running it will run for ages if the thermostat is set low .The problem started when new switches were fitted after draining down,many whooshes and gurglings were heard but have disappeared after a few months .Two heating and hot water switches have been changed,the heat exchanger has been cleaned ,spark gap been reset.The problem, when using the heating is only on startup ,if the thermostat is set too high it will cut out but if set low it will run for ages if it does,nt have to stop and restart.This has been going on for about a year now.I am confused about the reference to "flow switch" is this the same as the dhw switch? After the second restart,after cut out it will run fine until it switxches aff after not being used and then the problem reoccurs.
 
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It would help us to help you if you could identify the S-D boiler model you have!

I dont know what you mean by "new switches" !

Tony
 
Hello
Thank you for your reply.The model is S D 30e Fanned flue combi boiler.The "switches" are the dhw switch and ch switch ,small plug on type that have two wires coming from them.They are described in the manual as Water pressure micro switch and pressure differential micro switch.I forgot to mention in my post that the diaphragm on the part that is next to the D H W Micros switch was also changed.
 
I think there is a filter beneath the pump this could be causing the boiler to over heat if it is blocked.Try the pressure diff pin see if is moving in and out freely, this can cause lock out. Oyher possibilities are o/heat stat faulty plus the c/h and dhw thermisters,ign. rate, pump sticking. From memory the lay-out is that of a glow-worm compact 100e.Some of the mentioned tests are corgi territory would suggest a engineer to run some checks possibly phone glow-worm for a parts all in call out.
 
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If the filter is blocked then the SH flow switch will not operate. I prefer to call this the system flow switch because its required to be activated on both CH and DHW.

The filter or anywhere else could be partially blocked and reducing the flow to the point that the boiler is actually overheating because the reduced flow is not removing the heat adequately.

That filter is the first think to look at! I have a feeling it may be very inaccessible towards the bottom back ???

I must totally rely on GG that it exists because I try to avoid going to S-D boilers and I am only well experienced in the earlier models, although have one to do today!

Tony
 
If you have worked on a glow-worm compact 100e then you have worked on a sd 30e same boiler different badge. The pump maybe opposite side if the filter is in situ it will be under pump and can be tricky to get at depending how much working space is available. tHE MODERN sauniers are okay to work on like many i do not like the older sauniers the words leak and sieve spring to mind.
 
gasgeezer said:
I think there is a filter beneath the pump this could be causing the boiler to over heat if it is blocked.Try the pressure diff pin see if is moving in and out freely, this can cause lock out. Oyher possibilities are o/heat stat faulty plus the c/h and dhw thermisters,ign. rate, pump sticking. From memory the lay-out is that of a glow-worm compact 100e.Some of the mentioned tests are corgi territory would suggest a engineer to run some checks possibly phone glow-worm for a parts all in call out.

Where abouts is the pressure diff pin? Just a thought but the boiler locks out before any heat has a chance to build up susually within 10 or 20 seconds,does throw new light on anything?Ignition rate how do I check that?
 

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