'Fraid so......... yet ANOTHER combi problem

gatita

PLEASE could someone help detect what the possible problem is with my central heating combi. The make is PROTHERM 80E (wall hung combination boiler) is approximately 2 years old.

The hot water will heat up as it should some times, then suddenly it refuses to heat up...... most annoying if you are there in the alltogethers and its freezing grh!
When this happens, and the tap is turned on for hot water, the light on the boiler does not change over from heating, TO hot water. As I mentioned before this does NOT happen all the time, also it does not make any difference if the central heating is on or off. I have bled all the radiators.......... made sure the bar pressure is correct......... I called a gas engineer out on Thursday....... he ummed and ahhed and finally said it was the thermostat. He got another one, and for a short time it seemed to work, but now I am back to square one again, so it obviously wasn't the thermostat.
I would be very grateful if someone can throw any light onto what MAY be the problem, as if the engineer is going to come agin and again each time telling me that something needs changing.......... the cost will be horrendous:eek:
Thank you.

moneysavingplumber

Just a hunch based on experience suggests to me it could be the air pressure switch or muck in the venturi tube attached to the flue, or in the air tubes.

It could also be a worn diaphragm. You can check this when it goes cold by seeing if the central spindle on the divertor assembly is pushing out onto the microswitch whilst it is running cold. If it isn't then it is the diaphragm, if it is pushing the switch then it could be the hot water thermistor, all this assuming you have a separate plate heat exchanger for domestic hot water on this boiler, and not an old bi-thermal heat exchanger.

I'd be surprised if it were the PCB as it would be a more consistent fault usually.

ducati996

A friendly piece of advice is to get one of the British Gas service plans.

Normally I wouldn't touch or advise for one of the plans but with a combi boiler you will recoup your monthly "service" costs very quickly.

https://www.house.co.uk (British Gas) have Homecare 100 which covers your boiler & controls for £12 per month (£144 pa).

It may seem a bit but one call out & spare part is going to cost more than than.

caveat_emptor

gatita wrote:

PLEASE could someone help detect what the possible problem is with my central heating combi. The make is PROTHERM 80E (wall hung combination boiler) is approximately 2 years old.
the cost will be horrendous:eek:
Thank you.

Take a look at 'another boiler problem' on page 2 of this MB for solution to a similar problem.

catkins

A friend tried to get a service plan from BG. Engineer came round week before christmas and switched off a perfectly good boiler and told them they needed to spend £5,000! My OH got a CORGI engineer from work to check it and guess what no problem with original system other than sayinf a extra vent would be a good idea. BG not interested in explaining why their engineer was so wrong. So moral is great if they accept you but be careful on any work they say you need befor signig up. Also they will not accept you if you have a pre existing fault.

gatita

Just thought I would let you know what happened. Thank you all for the advice:beer: .......... the gas man came and changed the thermostat which seemed to work fine for a while but it went back to not igniting. I called him out again and he altered the water flow.......... and for the past few days all is well thank goodness. He did say if it was not right this time he would change the diaphram??????? I have my fingers crossed.

gatita

I spoke too soon grrrrrrrrh last night I stepped into a freezing shower! it is really annoying me as I cannot understand why it works for three days, then all of a sudden doesn't................. I did notice that one of the radiators wasn't getting as hot as it should? Oh dear how I hate the winter........

hk_chick

I have a combi boiler too (different brand) you're describing what mine was doing in december (wasn't bad to start off with, gradually got worse). Heating seemed fine, but hot water kept cutting out, so having a shower meant stepping in and out of the stream according to how warm it was!

turns out it was a worn circuit board, giving wrong messages to the thermostat. Nothing to do with thermostats, pressure or anything like that. the heating was actually doing it, too, but as radiators take longer to cool down, I wasn't noticing it.

cost to replace circuit board plus fitting (including original callout) was £199. (same guy who does my servicing, local chap)

have had no problems since

Jazzking

Hi,

We had a Protherm too (model 100e) until last weekend and have had no end of problems with it. Sounds kinda like what you were having problems with but ours just wouldn't ignite, for hot water or central heating. Changed the ignition PCB and it worked for a couple of days, then broke again; tried a new gas valve and that didn't make any difference; replaced the main PCB and that worked for a day but then went back to not working at all.... In the end we had to get a brand new boiler as nobody could figure out what was wrong it and we're been without hour CH for nearly a month

If you end up having to replace it, make sure you go for a well know reliable brand such as Vaillant, Worcestor-Bosch or Glow-Worm. Glow-worm actually produced the Protherms many years ago as a very very budget model, but the glow worm we have now is absolutely fantastic! Hope you get it sorted anyway, I know how frustrating it can be not knowing when it's goin to work or not