Baxi Combi 105e - Hot water problem.

Katarzyna · 4 Oct 2006

Hi

As it happens I'm the DIY person in the house and my husband dose the cooking.

Can you help guys?

My Baxi Combi 105e is 3 years old. All was fine until 6 months ago when pressure started to creep up on a gauge
(even to 3.5 bar-I had to use safety valve to release it) and water running hot and cold.

Boiler is always set to CH and HW. CH is run by thermostat located in a front room.

When shower or any other mixer tap is on, boiler fires up and I will get hot water for 20 seconds
then boiler cuts off-water gets cold all in an endless cycle. None of the boiler neons are flashing indicating any faults.

Water pressure in taps and shower has not changed since I had this problem.

Last time CH system was flashed was 18 months ago and some inhibiter added. Apparently we do have hard water down here.
Which parts of the boiler can be affected and possibly need replacing?
As far as I know boiler has been installed by an engineer however not corgi registered. How can I have this boiler certified ?
I want to be save but don't want to get to any trouble. I will call the plumber promise.

Thank you very much for any good ideas.

Kasia

Agile · 4 Oct 2006

Sounds as if the secondary heat exchanger is blocked because the installer did not power flush the system.

Once installer by a non CORGi you cannot get it properly Certified.

Tony

Baxmax · 5 Oct 2006

Yes blocked plate heat x.What does dose the cooking mean

bster · 5 Oct 2006

i know that a powerflush is needed to remove all the crap from the system but why does not doing a p-flush lead to a scaled secondaryHE?

cheers again.

kevplumb · 5 Oct 2006

cos all the cr*p bungs up the waterways which are a lot finer

bster · 5 Oct 2006

i see, blocked (with dirt) and scaled (with scaly stuff).

cheers

(Kat - sorry for the minor hi-jack)

ChrisR · 5 Oct 2006

I can do cooking, You have to remember to stab the food before you put it in the microwave. All there is to it really.

Katarzyna · 6 Oct 2006

I'm going to drain the CH system tomorrow and refill to see if it helps.
I know its not a powerflush but I need to see if it will help for now.

Which discaler or inhibitor or both should I use when refilling and at what point?

chrishutt · 6 Oct 2006

Katarzyna said:
I'm going to drain the CH system tomorrow and refill to see if it helps.

You can do better than that. Check out the guidance on mains flushing in the Wiki (or the FAQ topic). Then you can be a Polish plumber.

But it won't clear out the heat exchanger. That will need to be taken off to clean.

Katarzyna · 6 Oct 2006

What about discaler etc? Which should I use?
And is it legal to clean your heat exchanger?

Katarzyna · 6 Oct 2006

Baxmax said:
Yes blocked plate heat x.What does dose the cooking mean

Just wanted to put you in the picture, you know sharing domestic responsibilities.

chrishutt · 6 Oct 2006

Katarzyna said:
What about discaler etc? Which should I use?
And is it legal to clean your heat exchanger?

You need what is called a system cleaner, not a descaler. Prices vary from £4 to £14 for a litre (similar price range for inhibitor too). But you need to read up on the procedures involves - did you check the links I mentioned. You will achieve more with the physical flushing process than with the chemicals, although best results will employ both.

fitz1 · 6 Oct 2006

dead easy to remove hx.isolate boiler(mains power) isolate flow and return and cold inlet using black tap levers under boiler. drain boiler via drain off on left of pump. undo two philips screws on left and right of hx. lift out and clean.it takes about 5 mins to remove.if not completly confident i suggest you get an engineer.

Katarzyna · 9 Oct 2006

Agile said:
Sounds as if the secondary heat exchanger is blocked because the installer did not power flush the system.

Once installer by a non CORGi you cannot get it properly Certified.

Tony

I didn't mention that HW temperature control is not set to full but only to 3/4
however when boiler comes on it will heat to a maximum 80C and then cuts out and on again.
Also after draining the system, refilling and bleeding radiators hot water became much hotter then previously.

Dose this still mean that heat exchanger is at fault or maybe something else?

Agile · 9 Oct 2006

Sounds as if the secondary heat exchanger is blocked because the installer did not power flush the system.

Once installed by a non CORGi you cannot get it properly Certified.

It sounds as if you lucky and dislodged some of the dirt in the sec HE

Tony

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Baxi Combi 105e - Hot water problem.

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