Sime Friendly Format cuts out then re-lights

13 Apr 2015
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United Kingdom
I'm from Australia where we don't have central heating, so I'm new to how these systems work. I've done a fair bit of reading, unfortunately none of which has helped me understand the symptoms my boiler is showing.

I filmed a short video of it "running":

In the video you can see and hear (turn the sound up) that the main burner ignites, stays running for a few seconds, then extinguishes. A few seconds later the ignition is activated again and the boiler relights, only for the cycle to continue. This doesn't fit with what I would expect to happen if there was a problem detecting ignition, or if a thermostat/thermocouple was reading incorrectly. The cycle begins immediately there is demand, even from cold.

The same cycle occurs with either DHW or CH demand, and the pump and fan can be heard operating also.

I don't intend to fix this myself, but there doesn't seem to be many boiler service people in my area (South Northants) that advertise their familiarity with Sime boilers: the first person we had investigate watched it cycle, checked the gas pressure (fine) and shrugged his shoulders.

Any suggestions on what the cause may be are welcome!
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To a proper boiler engineer these should be no problem diagnosing the fault.

But for safety reasons we don't give advice on gas/combustion issues like that.

We gather that there are very strict restrictions of engineers working in OZ and have to be employed for five years before they can work on their own as so many do here.

I would therefore expect strict restrictions on gas work by anyone who is unqualified too.

Best advice is to find a better engineer. There is little difference between different boiler makes and that one is very typical of its age.

Age is such that replacement should have been done by now in many people's eyes.

Hi there,

If you would like to give us a call on 0845 901 1114, we will gladly put you in touch with a recommended heating engineer in your area who will be able to rectify the fault on your boiler.


Sime ltd.

Gas appliances should only be worked on by qualified Gas Safe registered engineers.

Always check your heating engineer is registered with Gas Safe.
Do you really have Sime service engineers in Australia as well?

Or has Terry retired over there?

Engineers don't like 0845 numbers because they are so expensive to call from mobiles. Better to quote the mobile friendly 01/02/03 equivalent number.

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Hi Tony,

Yes Terry has retired now, but still in the UK.

Our technical line is 0845 901 1114 option 3.

I was presuming South Northants was Northampton?


Sime Ltd
Yes, you are quite right. Speed reading I had thought that he was still living in OZ. Easy mistake to make when trying to only spend a few seconds to read it!

In that case then any competent boiler engineer should be able to fault find and fix it.

But don't expect many engineers to specifically mention Sime as they are only one of many boiler manufacturers.

But a landline style number would still be far better!

Hi Tony,

Yes Terry has retired now, but still in the UK.

Our technical line is 0845 901 1114 option 3.

I was presuming South Northants was Northampton?


Sime Ltd

Quite correct SimeltdUK, I moved to Northamptonshire about 2 years ago, didn't mean to throw anyone off with the mention of OZ, just providing a reason for my own ignorance!

These systems don't seem all that complex to me with regards their operation (I am an industrial control systems engineer) but they are out of my league when it comes to gas safety which I will readily admit, and hence I didn't want to go poking around too much on my own.

I have had the impression from the boiler technicians I have spoken too that they are only comfortable working on the big-name brands that are much more common even though the operation of these boilers must be fairly similar whoever the manufacturer is.

I'll give the Sime service line a call as suggested. Thanks for the advice both of you.
You have not spoken to the right engineers.

Any engineer who really understands boilers will manage with any make even if he has never seen one before!

That Sime is very simple and typical of boiler designs from that time.

I would go to repair any make of boiler even if I had never seen one before!

Was asked to go to an installation of four ( oil ) boilers and had no problem getting three going and identifying the fault of the third which needed a part.

That's even though I go to perhaps only one oil boiler every five years as there are very few in London and so I am not OFTEC registered ( although that's not a legal requirement ) and so would not often be asked.

Good luck with your Sime.

If you are close to the A425 then I could help if you have any problems as I regularly drive from M1 to Warwick.


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