Potterton Promax 15 HE problems, getting desperate now.

[Mr P]

copied from plumbing forum

Hi everyone
I have joined this forum in the hope that someone has an idea of what is causing my boiler problems. We have had no reliable hot water since Christmas now!! Please help

Background
During the really cold weather in December the condensate line froze causing water to back up into the boiler. The boiler cut out and would not restart even when the water was drained out. A plumber was called who managed to get it going again (I was at work then so not sure what he did). The condensate is now running into a bucket.

A week later the boiler would not fire up. It would try 5 times and then lock out. After many goes at this it would eventually fire up, on some days it would even fire up first time. As soon as the room thermostat temperature was reached the boiler would cut out and we would have to go through this reset procedure until it finally relit.

A plumber was called again and he noticed the flame was more orange than it should be. He replaced the case seals which were damaged and ordered a new sparker.

He came back today with his gas analyser and found the CO figure was varying from 50 to 140ppm, changing as the flame colour altered (spec 50 to 90)
He measured the output of the boiler which was spot on, as was the gas pressure. He cleaned out the bolier, fan connecting pipes and burner. He took out the flue and checked the seals and that it was fitted correctly.

He replaced the sparker but the boiler would still not fire up easily. He placed his hand across the opening of the fan to check it was sucking air and this caused the boiler to fire up instantly! After this the boiler fired up first time every time, but we could now hear a soft hiss as the gas was being released which could not be heard before. Cleaning out a breather pipe (which was not blocked) caused it to go back to not lighting and no gas hiss again. A hand over the fan inlet and it is now back to lighting again.

The flame is still changing colour, shape and size over a period of time. A few times the flame becomes intense blue and the boiler makes a huming sound like someone reving a car gently, then it settles back to an orangy blue colour.

So what is happening! we think it may be the gas valve but don't want to fork out £120 if it is something else. So has anyone else had this? any ideas?

Thanks

 

[Blake]

Difficult to say without seeing it. Condensate backing up into the heat exchanger causes all sorts of problems and often messes up the spark electrode and can cause damage to the heat exchanger itself.

If you are worried about rising costs, and considering what you have already spent on it, I personally would look at doing a fixed price repair with someone like BG. I don't like them much personally, but it may save you money in the long run.

Just a thought.

 

[Mr P]

The plumber just popped back round - glad he is not charging me by the hour!

Measured the flue gas again at 11ppm CO and 8.5% CO2. The flame pattern is now stable but still a bit orange.
At least it lights every time now.......

 

[Blake]

Well is does sound like you have a decent gas engineer there and he is checking everything he should. Sometimes it is hard to diagnose some faults, and it's as annoying for us engineers as it is the customer. Glad you seem to have made progress with it.

 

[PuraTherm]

I agree bronzino. Some engineers would get the money and not call back when the problem persists. If the problem dose hapen again, have him check the gas valve. Water in the valve could cause the problem you are describing.

 

[John Green]

Promax HE Problems.
Have joined this forum to give members the benefit of my experience.
This boiler was installed about seven years ago and was trouble free untol Nov. 2010.
Boiler failed to light up every two days or so.
When it was reset it always took two ignition attempts from cold. (Lit first time but went out after a few seconds then lit at second attempt.)
Plumber cleaned the condensate trap and swapped the mid position valve. (Cost about £150 for work)
Still failed so plumber swapped igniter elecrodes and flame sensor. (Cost about £70).
Not complaining, as you can't expect the guy to sit on the boiler for two days waiting to see the fault occur.
By this time I'd resurrected the manual and contacted Potteron who suggested I needed new seals.
New seals (about £30 inc. VAT/Packing/Despatch - looked like draught excluder tape) fitted. No improvement.
Fitted new flow thermostat and flow temperatures sensor (another £30). No improvement.
Removed ignition PCB and inspected for charred track/component/relay contacts.
Everything in pristine condition including pin conecting to fuse, which was as new and had never seen solder.
This was soldered on assumption that contact had been intermittent and caused the fault.
Everything works fine apart from two ignition attemps needed from cold, which I suspect as always been a feature from new.

 

[Ho5972]

i presume by the promax 15 he its pretty much the same as a baxi solo 15 he right?

 

[Billy Bob Bob]

i presume by the promax 15 he its pretty much the same as a baxi solo 15 he right?

yep same mare different badge

 

[Ho5972]

thought so!!

i kind of lost my way with the fault description halfway through, but i have worked on many of the solo 15 he's.

common issues i have encountered are the electrode rail, either they start to warp and where out, they are easily replaced, 3 screws and the spades on the front, this usualy cures most ignition problems.

Also with regard the electrodes, during the ignition sequence if you watch them closely, you can see them arking out agaisnt the OUTSIDE of the combustion chamber, rather than above the burner, this causes exsplosive ignition!! as it doesnt ignite the gas first time as it should.

This is usualy rectified by replaceing the ignition harness, (ignition lead in brown sheath and earth lead), take care not to split the sheath.

With regard to the nosie, it sounds like the fan may be fluctuating, causeing over gassing, making the car sound or humming. i have had this problem, after water damage due to a blocked and backed up condense also.

i hope my woffle is of some help!!

 

[Billy Bob Bob]

also not forgetting swarf in the plastic air intake on the fan and occasionally its a bad casting on the heat exchanger