Powermax 155x advice please - Vent and Pump Relay faults?

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Hi all,

I've got a problem(s?) with a Powermax 155x Open Vent that I'm in the process of working through. I have enlisted the help of a central heating installer on this, but he's not that familiar with the Powermax boilers (as so many seem not to be), so we're both kinda learning a bit here! If possible, then I'd like some advice / guidance from some of you experts that we're on the right line please!.... :D

PROBLEM: I turned the boiler on Monday night and after working for maybe 30 mins, it then started making a buzzing sound like a quick-switching relay - It did this on and off for about 10 mins, following which silence from the relay, never to be heard again. The boiler still ran and heated, only now after a short period some very deep rumblings started up from inside it, so I turned it off. Having tried again maybe an hour later I got the same issue - deep rumblings after a while, so I turned it off. I tried once more on Tuesday night, and this time the burner light came on, but then after maybe 10s went out and stayed off. Fan still runs, display is present etc etc - only problem seems to be rumbles and burner either cutting out or not coming on in the first place.


WHAT WE'VE DISCOVERED SO FAR: The cut out / trip-switch top left on the unit (high temp cut-out?) had triggered, so we reset that, however, still rumblings during operation. Next thought was that the boiler was low on water, so we checked that both the vent tank water feed in to the boiler was clear (broke in to the line and it's spotless), and also checked the air vent to the vent tank was clear (blew though it from boiler end - again fine). After a bit of google-ing I found a comment that you must blow DOWN the vent line INTO the boiler to clear some sort of air lock which then allows the boiler to re-fill from the vent tank. We did this (several times) and sure enough, the boiler refilled somewhat - (a funny quirk?!). However, upon firing up the boiler, it started rumbling again! :confused:

Now, since then we've done a fair bit of fault checking, and fault finding and satisfied ourselves that everything has power where everything should, and that both pumps operate etc etc. However all this has now prompted another theory... :idea: A dodgy pump relay on the tank circulation pump??

I understand that one of the 2 pumps is simply there to circulate water within the store cylinder itself to prevent hot-spots... so our current theory is that the relay that powers this pump is not always operating when it should, thus causing the re-circ pump to not operate, thus causing hot-spots and local boiling in the cylinder (the rumbles), followed by the thermal cut-out operation as the top of the tank overheats.

Does this sound like a fair suggestion??!

Whilst I'm getting more convinced this could be the case (plus it ties in with the buzzing relay noise in the first place), we've had that many failed-theories with this boiler that I was looking to pick some brains on here and see if anyone had any experience of such problems??

Can anyone provide suggestions as to what may be up, what else we could check, prior to starting to spend money on spares?

My one other question is that I have seen a couple of threads suggesting the need to blow down the vent line to clear it and allow filling with water again in the event of rumbles / over heats. Is this a rare occurence with these boilers, or are they actually incapable of refilling if water levels get low? Hence is it something I need to monitor? Tank head is probably about 1-1.2m to the top of the store cylinder.

All help appreciated - thanks!! :D

As a final comment, I'll say that I do actually like the boiler when it's working and that this in the only problem I've ever had with it touch-wood - there's an awful lot of comments around with people saying how bad they are, but I'll stick-up for it (for now at least!). Cheers all.
 
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Sounds like a blockage or your pump is gone. The overheat is kicking in because of no flow. I would test the pumps again and also check for flow
 
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Hi guys, thanks for the comments...

Re Pumps:
You mention checking the pumps - are there any other tests to do other than check that they are both capable of pumping when power is applied? Only we've done that, and both are operational and can be made to run when powered. The problem we are having seems to be in commanding them to run in the first place. Do you know if the pump is a "dumb" unit, or does it have some electronic drive unit on it that could be acting up?

Re Blockage:
That was what the CH engineer looking at this first suspected. However, so far no fault found - we've looked inside the vent line, the vent tank water feed line near the bottom of the cylinder, and also removed the CH pump assembly to inspect it - all spotless, no evidence of corrosion / sludge or anything else. Also the blockage theory doesn't seem to fit with the "step-change" failure I've seen here does it?? - i.e. system working fine for last few years without fault, then relay noises monday night and boiler doesn't work properly again. Can you suggest any specific areas we should be looking for blockages?

Are there any specific tests you could recmommend in trying to fault find further?

Also thanks for the Heateam recommendation - I didn't know they existed - what's the difference between Heateam and Baxi then? My current engineer whos working this came about because I tried the baxi website for engineers and all the chaps local to Preston we're booked up for the next 2-3 weeks, or didn't want to travel too far. My current engineer came recommended, but he's not official Baxi / Heateam.

Cheers.
 
Heateam is the official service/repair arm for baxi/potterton. They do fixed price repairs but i do know they are busy up your way currently....but not 2-3 weeks worth! You might have to wait a 2-4 days is my expectation but i don't work in planning so thats a guess.....estimate250-300 quid for the fixed price repair.....unscrew the big nut at the front of the pumps......is the inside spinning? does water come out?
 
He doesn't need phoning! His minions are monitoring every word :evil:
 
only met the guy once but he made an impression.

I have a mixed bag of tricks with commercial and being bonus direct but i often recomend your fixed price repair as it can work out alot cheaper in the long run sometimes.
 
Problem now sorted - figured I'd post a response for anyone else with similar problems following the thread....

I called Heateam on the recommendation of the guys here. Heateam came out within a couple of days of calling and for a fixed price of £289 inc VAT AND parts / labour will fix any faults with the boiler, plus provide a 12 month warranty on the complete boiler itself not just the repaired parts. The guy was friendly and professional.

And the problem: A faulty relay on the PCB (interpart P769) which was preventing the CH pump from firing when the tank was warm. Hence I had hot water in the tank, but couldn't distribute it to the rads.

He also noted the fan was getting quite noisy so replaced that too (interpart P504). A quick google for part prices suggests this was about £250 worth of spares (inc VAT), all diagnosed, replaced and working in about an hour for £289 all-in!!! Can't say fairer than that.

Cheers Heateam, and cheers to the guys here for the recommendation to use them :D
 
Well thats nice. From all the Heateam boys and girls, thankyou. It's nice to get some positive feedback.
 

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