Baxi 105e.

[Spooked]

Hi all.
I have a Baxi 105e combi. (4 years old)
All was fine until I had two radiators added to a sun lounge.
Now, when I run the hot water upstairs, it gets warm then goes cold and so on.
The downstairs is hot.
I have checked what is happening with the boiler by leaving the tap running and watching the flame, and, as soon as the water reaches 80deg it shuts off until the temp has dropped, then fires again and so on.
Could adding these rads have affected anything as I thought the central heating and hot water were completely seperate?

I have watched the three way valve.
When I switch the heating on, the top valve opens triggering the micro switch and firing the boiler, leaving the dhw shut.
When I open the hot water tap, both the heating and hot water valves open?
This doesn't make sense to me. Is the heating valve meant to close on demand of hot water??? Surely two valves shouldn't open at the same time.
I thought dhw took priority over the central heating.
If this is so, should the heating valve shut when a hot water tap is opened??
Does this sound like a pcb problem and a coincidence that we have just added two boilers??
Cheers.
Oh yeah, I have swapped the two micro switches around but the same thing happens so that rules that out.

 

[gstens baxi]

I would say that the dhw heat exchanger is blocked with sludge (dirt) from the heating system , these can be cleaned but it is easier to exchange them. Also get the return filter checked as these can also get blocked.

 

[scatmanjohn]

hi..what you are refering to as the ch valve operating a switch is in fact the pump proving switch or also known as the boiler flow sitch. It operates everytime the boiler runs (in dhw or ch).

Agree with gstens baxi on this one.

 

[Spooked]

Thanks both for the replies.
I hope you are right as this is doing my swede in.
I've been told that no way should both valves open, yet the boiler shows no warning lights, I guess thats cause they are supposed to open together when you draw hot water if scatmanjohn is right.

One problem is, how come the central heating pipes get hot, it doesn't reach the rads, when I turn the hot tap on, is this normal, does a certain amount of heat reach the pipes?

Can this sludge blockage cause all this over heating?
When I draw hot water the temp neons fly up to 80*, the boiler cuts, the neons drop to 60* and the boiler fires up again.
I know these questions might sound a bit thick to those in the know but even if cleaning it out fixes it it is still interesting to learn.
Cheers for the help.

 

[Spooked]

Bit of an update and confirmation please.
It was bugging us that two rads had been added and then the boiler started going wrong, so, last night we disconected said rads.
Of course, this didn't help.
We reconected them.
Now, the ch goes up to 60* even when turned up full, then the boiler cuts out and nothing else happens.
There are no fault indicators showing, the boiler will not reset, it just cools down.
Can blockages cause all this cr*p to happen??
These things are more sensetive than I thought.
Oh yeah, it hasn't been serviced for two years

I await some boll***ings

 

[Spooked]

gstens baxi.
I'm having a go at cleaning this thing tomorrow.
Do I need anythign on standby?
Ie, washers etc.
Cheers.

 

[Spooked]

Boiler is working fine so far!!
Did all that was suggested, thanks both.
Also, for future reference for anyone, I think air lock was my main problem.
The auto air vent was clogged to hell and back.
Thanks again.

 

[gstens baxi]

The blocked air vent is a product of the real problem which is the sludge in the system that if installed as per the installation instruction & been flushed.