Combiboiler-Shower- Intermittent cold wake Call!

Snowboarder747

:oSorry this is a long one!

Dilemma, please could someone spread a glimmer of light on to my problem?
I have a Brisbane Art deco external mounted shower feeding directly from a Baxi 105e Combi-boiler.

The problem
Water coming out of the shower runs cold for about 20 seconds then returns to its original temperature. Over a six months period this has progressively got worse (more frequent intervals of cold water coming through) to the extent that the mrs has made me do something about it!  >:(

I rang Brisbane they immediately sent out a new thermal valve, I fitted the new valve and cleaned the two hot water filters, which are situated in the elbow joint of the hot inlet pipe at the same time. This didn’t make a scrap of difference.

On to the boiler.
Serviced the boiler as per instruction manual also cleaned both filters in the boiler.
This has helped; the problem is still there just not as frequent. The shower now runs for about 4-5mins, then the boiler cuts out for about 7seconds and then comes back on again causing the water within the shower to become cold.

I have exhausted all common sense avenues from a DIY point of view, whilst I am okay at plumbing I am not a Plummer, but will try anything.

The major dilemma for me is not knowing where the problem stems from. The boiler or the shower? On the face of it you’d assume it’s the boiler however as mentioned the shower is connected to a Combi boiler and as such must have a thermal shut off which will cut the supple of hot water if the water passing through it becomes too hot.

Any help will really be appreciated!
A thread, a pm, even a carrier pigeon!
I don't care just as long as I can stop these cold water wake up calls! :-[

divadee

I know you have probably checked this, but do you have any other appliances on or taps running when you have a shower. eg. washing machine dishawasher etc....

As this could be the cause if you do.

Sorry couldnt be more of a help

Rex_Mundi

I don't know if this will help. When my combi was playing up, a plumber friend told me to check the colour of the flames. They should be burnng with a clean blue flame. He told me that if there was lots of yellow flame, the combi would need a service. I booked a service and the guy used a hoover to clean out the insides of the burners. This immediately solved our problem.

chalky_bertie

We had the exact same problem and after several visits from BG rectified it. On our boiler a Vokera there ire 3 dials, 1 for water temp, 1 for reset/water/water and rads and 1 for radiator temp. The radiator temp dial is on full, the reset dial is turned to water and radiators and the water temp dial was turned to full. However when the gas man checked this while the shower was running after a few minutes it cut out and the shower went cold. He turned the water temp dial down several knotches and hey presto it worked. It was a bit of trail and error while the shower was running but now works fine. Having a shower noe we have to turn the shower dial to very hot but is ok.

chalky_bertie

Just looked on BAXI website and looks like there is 2 dials on the right hand side of the boiler "interface". Turn the one for hot water down a bit until it stops doing it. Hope that is more understandable than the above post.

Mike_Gas

This problem on this model is usually caused by a build up of lime scale in the hot water heat exchanger.
Hope This Helps

Snowboarder747

Thanks everyone for you help! ;D
Mike-gas you have a pm

beefster

Mike - gas may know this............ should the burner modulate to keep the water temp constant despite the amount of flow?? I have the same boiler and without looking in the manual I am sure that is the case...... there is a guide in the manual on how to check these probs. The modulating valve may be stuck......... Or its scaled up!

Snowboarder747

Beefster you've gone a little above my head there
'burner modulate'.  :-[
To be honest I can't recall anything about that but I'll get the manual out and do some bedtime reading.

How would I know and how would I release the modulating value if it is stuck?

thanks for the info