Noisy ignition Potterton 28

[timbach]

Hi Folks, Any chance of some advice? I have called out a gsr engineer and neither he nor Potterton have been able to help.
The boiler is 8 years old and has worked well. Recently with CH on and the boiler is cycling it gives a loud Whooshing bang. It also does this when the HW tap is turned off when the CH is running. It does not do it with just the HW turned on and off.
Runs on propane, gas pressure upstream of modulator valve 38.8 and downstream of valve 34/35 when firing but drops to zero for a few seconds when HW turned off while CH running and then rises over several seconds as whooshing noise happens. Burner never goes out but drops to minimum briefly before whoosh occurs.
CH and HW OK otherwise, water pressure OK, soft water, professional installation.
Thanks
timbach

 

[Agile]

We are not allowed to give DIY advice on gas matters. But I should be able to ask you to give clarification of what you have said.

But if the burner pressure is zero then the flame is expected to go out!

Is a burner pressure of 34/35 really correct for your boiler? We don't know your model!

Is the gas valve depowered when the pressure drops to zero?

You are using non standard terminology so are perhaps not explaining correctly.

This wooshing noise, where is it coming from? Does it follow flame size?

Is the gas valve correct for the boiler model? They sometimes have a soft start device built in.

Tony

 

[timbach]

Thanks for reply Tony,
Gas measurements considered normal apart from momentary drop to zero although Potterton engineer not bothered by this. The gas flame does not extinguish at all during this phenomenon, just drops to a low level then gradual increases accompanied by a whoosh and a bang. I do not know the standard terminology for a whoosh (or a bang) and explosive ignition sounds too strong a description. How about unsmooth ignition with non-uniform sound wave? As stated earlier this a Performa 28 combi installed new and only the DHW flow sensor has been changed over the 8 years since installation. The gsr engineer did not check for power at the gas valve and in reality this would have been impossible as pressure only dropped for a second or so.
Regards
timbach

 

[timbach]

Addendum: The gsr engineer did suggest changing the gas modulating valve "on spec" at £180 plus vat excluding fitting. I am reluctant to go down this route without a firm diagnosis........

 

[AGAS]

Addendum: The gsr engineer did suggest changing the gas modulating valve "on spec" at £180 plus vat excluding fitting. I am reluctant to go down this route without a firm diagnosis........

so how are you going to get this firm diagnoses from ? from here ?
you've paid a potter ton engineer for his advice and not taking it and then asking people on the internet for diagnoses when their sat behind a computer

 

[Stadan20]

I agree with agas, , without sounding rude , are you stupid ? ? , you have had a recommendation from the pott engineer and yet you seek free advice on here , when we haven't even seen the boiler ? I would of gave you the answer but I have lost my crystal ball

 

[Agile]

You never originally said that it was a Performa model.

As far as I am aware, Baxi/Potterton still do a fixed price repair for about £300 including parts and labour.

It is very difficult for me to even feel inclined to make any guesses ( for myself ) on what your problem is based on what you have said.

Seems easy enough for me to test if the voltage supplied to the gas valve is interrupted or not.

Tony

 

[timbach]

The engineer was very doubtful that the gas valve was the problem, hence my use of the phrase "on spec". It seemed reasonable to seek advice of others as to whether this was a reasonable course of action.
A few years ago a woman was admitted to our local hospital with carbon monoxide poisoning, the baby she was carrying was already dead (foetal haemoglobin has a greater affinity for CO than adult Hb). Her husband and dog were also dead. Needless to say their boiler had been serviced a week or so before by, you guessed it, a qualified gas "engineer". So excuse me if I do not take the word of people who call themselves "engineers" (an engineer is someone with a degree in engineering not a person who has been on a gas safety course) as gospel, let alone the bigoted fitters here with an inflated opinion of their skills.
I tried to be polite and provide as much information as possible when asked so did not expect insults and abuse from what I hoped would be a friendly and helpful forum.

 

[dilalio]

And now you have managed to insult every single Gas Safe 'engineer' on here - the only people here, qualified to at least ponder your problem and consider the causes, even if not entirely free to share their "at distance" diagnoses with you.

You have three options...
1. Go with the current engineer's suggestion "on spec"
2. Seek 2nd, 3rd, 4th opinions from other gsr's you pay to attend.
3. Replace your boiler with new, knowing that 8 years is now considered "getting on a bit", within the industry!

Oh, and for your own piece of mind, with such a negative opinion of gsr's, buy a pallet-full of CO alarms to place around your home.

 

[Agile]

Better he gets a fixed price repair from Baxi and then he will get it fixed at a known price.

Not perhaps the cheapest but at least a capped price.

I would never expect a customer to pay for a part on spec. It is my job to diagnose the fault and that is what I do.

 

[dilalio]

But he's had correspondence with Potterton already and a Potterton engineer out, from what he's said!
So, 2nd opinion is the way to go, for op.

 

[Agile]

As I interpret him, he had a GSR engineer attend.

Any reference to a Potterton engineer seems to be related to their help line, who may or may not be engineers. A local advert for staff for tech help lines said "no experience necessary".

 

[plumbskull]

In fairness you are unsure of the engineers diagnosis and it sounds like the engineer is unsure. Not unreasonable to ask for advice in my opinion. Sounds like engineer is out of his depth and wants to throw parts at problem at your expense. I would search for propane installer. Hope this is of use.