Procombi 85HE - DHW hot-cold-hot-cold

[Pallatrax]

Hi guys,

A common topic it seems - hot water runs hot, cold, hot cold...

General advise seems to be sludged up heat exchanger or faulty diverter valve...

Turning the DHW down has stopped the cutting out, chuntering and pressure bouncing, but I'd like the issue fixed on a more permanent basis.

Should I treat the system with Fernox F3 (or F5?) or replace (or descale/clean) the HE?

Many thanks!

Tom

 

[Pallatrax]

I've now got a much better understanding on the HE (why I didn't look on YouTube!?) , so just now after advise please, on whether i;

-remove/have removed and cleaned
-Buy new, or
-Try flushing system and cleaners

Thanks

 

[ianmcd]

yes a partially blocked heat exchanger could cause the problems that you are having but other things can cause the same symptoms, with the system cold turn on a HW tap and when the boiler fires feel the flow and return pipes for your heating and see if one is heating up with just the HW demanded.

 

[Pallatrax]

yes a partially blocked heat exchanger could cause the problems that you are having but other things can cause the same symptoms, with the system cold turn on a HW tap and when the boiler fires feel the flow and return pipes for your heating and see if one is heating up with just the HW demanded.

Hi, and that's for your reply. Sorry for the delay.

The flow does indeed heat up when only asking for DHW. What does that mean, a dodgy diverter valve?

If it helps , before the boiler cuts out the pressure bounces and it 'chunters'..

TIA

 

[ianmcd]

the diverter valve on these uses a service kit, not expensive and easily fitted , I would start there, it could be the plate is partially blocked but I would start with the diverter service kit

 

[Pallatrax]

the diverter valve on these uses a service kit, not expensive and easily fitted , I would start there, it could be the plate is partially blocked but I would start with the diverter service kit

Thank you very much for your help - I'll try that.
Cheers

 

[ianmcd]

Here is the part you need , its a complete cartridge , just when you remove the old one be sure you have got everything out as they tend to break up, then just put the replacement in, a very easy job.

https://www.ebay.co.uk/itm/PRO-COMB...h=item3d82ba1b58:g:1DQAAOSwAE9cXULx:rk:7:pf:0

 

[Pallatrax]

Here is the part you need , its a complete cartridge , just when you remove the old one be sure you have got everything out as they tend to break up, then just put the replacement in, a very easy job.

https://www.ebay.co.uk/itm/PRO-COMB...h=item3d82ba1b58:g:1DQAAOSwAE9cXULx:rk:7:pf:0

Thank you.

I'm a bathroom fitter and tiler by trade (so do plenty of plumbing - and not just speedfit) - so something I should tackle myself do you think?
Cheers

 

[ianmcd]

Thank you.

I'm a bathroom fitter and tiler by trade (so do plenty of plumbing - and not just speedfit) - so something I should tackle myself do you think?
Cheers

yes its easy to do just make sure you cover the PCB housing while doing it to protect from damage incase a bit of water splashes on it

 

[Pallatrax]

yes its easy to do just make sure you cover the PCB housing while doing it to protect from damage incase a bit of water splashes on it

Great. Thanks again

 

[Pallatrax]

yes its easy to do just make sure you cover the PCB housing while doing it to protect from damage incase a bit of water splashes on it

Can I just check..

I've just got off the phone to my old man, who's always been good with these things, but he's no plumber.

The flame goes out and the boiler turns off when we lose supply of dhw. Would a faulty valve cause this?
I know I confirmed the Flow gets hot, which is does, but with my limited access through boxing in, could I have mislead you, and heat from other sources be simply conducted when a demand there?

 

[ianmcd]

yes your boiler is getting too hot because the DHW sensor is sensing cooler water and the safety hi limit thermostat is over riding it and shutting the boiler off

 

[Pallatrax]

yes your boiler is getting too hot because the DHW sensor is sensing cooler water and the safety hi limit thermostat is over riding it and shutting the boiler off

Ok, so no change with diagnosis I presume?

Thanks again