Potterton Promax HE30 FSB - overheating

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*** disclaimer - I'm not doing any work on my boiler myself, I have gas safe heating engineers doing it ***

Hello Forum,

I'm having problems with my Potterton boiler.

A heating engineer replaced the CH/HW motor on our simple CH+HW system, but afterwards the 3-way valve started making a lot of noise whenever the HW was turned on. Not sure whether the noise/vibration was just the inside of the valve mechanism sticking and then releasing rapidly, or a water hammer effect being caused in the pipes.

Unfortunately, after this started (but before the heating engineer returned to fixed the valve - I'm assuming some minor problem arising from the work on the motor beforehand) the boiler has started tripping out with overheat error about 5-6 minutes after firing up. This is not intermittent, it is every time.

The heating engineer has returned and replaced the flow thermostat but this hasn't solved the problem, so their boss is now going to come out and look at the boiler. The overheat occurs irrespective of whether it is CH, HW or both being turned on.

Any ideas on why my boiler might have started having overheat problems shortly after work on the CH motor was completed, but where the 3-port valve was making an awful clunking sound when moving? Could water hammer have damaged something physically in the boiler, or something else?

Thanks in advance,
J
 
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Just had the same with a Valliant boiler, that turned out to be the pump was not functioning correctly. Make sure your pump is set to max then try again, if the flow isnt being pumped it is likely to be a problem and poss cause. It could however be many things (what makes you sure its overheating). Boilers have a starting procedure through to running and any part with a fault could prevent it from firing or running, even if the fan is running slow or a partially blocked flu. Potterton are supposed to be excellent boilers, the new condensing boilers off all manufacturers are pretty poor quality compared to old ones. Keep it as long as you can would be my advice.

Probably need to give more info on what is or isn't happening with the boiler
 
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The boiler is firing up fine, and the code on the outside is definitely overheat. A heating engineer yesterday looked at it, and his infrared camera showed the combustion chamber door seal was faulty. Fortunately I have already bought the part ahead of their visit, so they replaced it. They then got the boiler up and running again, as before, and found the fan we getting too hot and they have found a hole in the sump at the back under the heat exchanger. Apparently it would cost nearly as much to repair as to do a new boiler. But it looks liken the sump part would be c.£65 and I need a second opinion on the cost to put it in. The boiler is a Potterton Promax HE30 FSB. There is only access to the boiler from the front and from the right side as you look at its front.

So definitely overheating issue, and we've fixed one of two problems. Just a question as to whether it is economical to repair now. In the meantime, it is out of commission :(
 
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Why did the motor (Pump?) need replacing?
Has the engineer (?) opened up the pump valves properly when he replaced it?

Has he used the correct pump, has he commissioned it properly and is it set the correct speed?
Replacing a flow thermostat without finding out what is wrong is just parts chasing and would have me doubtful of this engineers ability.
 
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