Powermax 155 not firing up

23 Aug 2005
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United Kingdom

Recently we had to drain the radiator system after it sprung a leak. Since then the Powermax 155 boiler we have just will not fire up. The water system has been filled again, and there's no lockout but the boiler will not work.

Any ideas? Is there a reset somewhere or some airlock that might need bleeding ?
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These boilers feature disproportionatly here.

They are not popular with installers presumably because they are very slightly more complicated although I never have any problem with the few I visit.

I fix boilers by looking at them and seeing how they work, others look at the books.

You should have turned off the boiler before draining the system. If you forgot then an overheat device has probably tripped. It may have a maroon colour one under the top cover but do not open this if you are not competent !!!

If you did turn it off then there might be a low water pressure switch which has not reset. It might reset in time or you might provoke it by turning up the pressure to say 2.4 Bar or yo may have to drain again and clean out the pipework leading to it ( if there is one ).

You did not say who had sorted out the radiator, if it was a professional he should have dealt with the boiler too.

There are a couple of Potty engineers who may have some other suggestions.

Tony Glazier
There is an auto air vent near the pressure relief valve, make sure this is not closed down. Just to check though when you say you have refilled you do mean you have refilled the main cylinder don't you? as this is the heating water which is used to heat the hot water as it passes through the coil, you need to refill the heating and hot water sections for it to work at all.
The emptying of the water system was done as an emergency because it happened at 10pm on a friday night and we where due to leave for a weekend away at 5am the next morning!

The radiator has been replaced by my dad (luckily a builder/plumber, unfortunately not a boiler engineer).

To drain the water system I shut off the valve in the tank in the loft and drained the water out of the valve on the radiator. Unfortunately I didnt turn the boiler off and it *did* turn on halfway through the draining process (having the front door open caused it to kick in) (Bloomin amateurs eh?)

How do I refill the main cylinder? (I have just turned back on the valve in the loft so far). (I would call in a proper engineer but I literally cant afford it till the end of the month at least).
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I thought these were usually installed as a sealed system.

Is it permissible to fit them in an open vented system?

yes there is an open vented version, in this case the powermax OV155X, are there any indicator lights on, and does it do anything?. There is an overheat stat which has probably popped out on yours, but I can't recall where it is...I think its by the fan somewhere
ollski said:
There is an overheat stat which has probably popped out on yours, but I can't recall where it is...

I think its somewhere towards the front when you lift the lid! Should only be opened by a competent person !!!

Well I'm not a competent person but I opened up the top and pushed the overheat stat back (thanks kevplum and everyone) and now we have hot water again.

Thanks for your help!
if your 155 has been dry fired, there is a good chance the heat exchanger may be cracked..........keep an ear out for strange washing machine sounds from it.....

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