Problem on a Baxi Combi 105 HE - hot water

missimaxo

I am wondering of anyone can help - after trying to run a bath and getting a nice lukewarm one instead of the piping hot I prefer - I ventured into our boiler cupboard. At the moment the heating is off and only the hot water was turned on. The pressure on the dial was down to 0, so I topped it up to 2 (as the boiler states it should be between 1.5 and 2.5).

I then tested the bath again and still seem to have a problem - cycling hot water where it starts cold - gets up to temperature and then goes lukewarm, then heats up again in a continuing cycle.

I pulled out our manual and went through the step by step Fault Finding. There are no fault warning lights flashing, and from the very brief test I did on the heating that seems to work fine.

I think from reading the manual the first thing to try is to "clean the DHW temperature sensor" and "DHW heat exchanger". Now I am guessing this is something I cannot do myself. I am pretty DIY savvy but have never worked on a boiler. Is there an easy DIY solution? I am guessing from googlng the heat exchanger could be full of limescale - we live in a very hard water area.

If not - is it an expensive fix and how much would we be looking at? If we were to sign up to a boiler care cover, would this kind of fault be picked up on an initial boiler check or could we get the check out of the way and then claim (I know this is not the most honest thing to do).

I am trying to find the cheapest way to sort this out as we just do not have the money for this at the moment. We can manage without hot water for a while (electric shower and cold fill dishwasher/ washing machine) while we save up but I need to know what would be best.

Thanks

Myser

Could be faulty DHW sensor or scaled up heat exchanger as you mentioned, diverter valve, overheat stat etc. Not something you would want to attempt to repair yourself.

I'm not sure what checks the care cover companies carry out before covering your boiler etc. I do know that there is an initial period where you cannot claim.

Either way, you will need someone Gas Safe Registered to repair it.

Did you re-pressurise the boiler to 2 bar?

southcoastrgi

you should have pressurised the boiler to 1.0 bar when it's not working not 2.0 bar, although thats not your problem at the moment but it will be when you put the heating on

missimaxo

Thank you for your help so far - could you explain why I should have repressurised to 1 bar and not 2. Sorry for sounding a duffer but this is the level it has always been set at before and the suggested range is 1.5 to 2.5 on the actual boiler itself. What will happen when we do turn the boiler on for heating and should I be looking at reducing the pressure?

powerflush

I have found the DHW temperature sensor on those boilers to failure quite often more than likely I would say it is DHW heat exchanger.

I would change both at the same time any and get a fixed price I would say around £175 depending where you are. If memory serves I would £60-£80 for heat exchanger £12-15 for temperature sensor, £80 - £100 for call out labour etc.

gas4you

Definitely the classic symptoms of a sludged up primary side of the plate heat exchanger.

ROY47

I have the same boiler
I had similar but not exactly the same problem. If I turned on the hot top . I only had cold water run through it even waiting 5 minutes allowing the water to get from boiler to tap made no difference

If I turned the hot tap off and back on I would get hot water , turn the tap off ........ cold water , turn tap on .hot water etc.

I have a warranty / service with it , rang them up , chap came out .

I wasn't home ,wife turned on the tap to show the problem ,took a few attempts but cold water through hot tap ...

Turned out to be a rubber diaphragm of some sort had a pin hole in it and wasn't making contact with a switch ?
Well that's what the wife told me !

Have a read here as well

http://community.screwfix.com/thread/75485?start=0&tstart=0