Problem with hot water on logic combi 35

[Rotor]

hi Gents

We are having issues with constant hot water flow with the above boiler. The boiler was serviced over a year ago and had the same issues , at that time the plumber thought the issue was the thermistors and they were changed. This seemed to help the problem but did not cure it and it is now worse.

Here is the senario : when using the mixer shower, the water most of the time goes from hot to cold and will stay cold. if you open up the hot water tap in the bathroom or in the kitchen ,sometimes the boiler fires back up and hot water will come on again and sometimes It won’t. It doesn’t come up any faults on the lcd screen just goes back to winter mode : timer or stat off

I have noticed it mainly happens when only using the shower. Sometimes I notice a stutter in the water supply coming from the shower head then I know it will be getting cold soon. Sometimes I notice a slight drop in pressure also and know that it will soon go cold

Does any one know what could cause the issue.

In the summer I will be installing an extension and extra shower room so will be looking to get a system boiler and water tank installed. So I’m hoping I won’t need to replace the combi just now

Many thanks

 

[Gasmk1]

possibly the shower mixer is at fault

 

[ShaunCorbs]

If it doesn't happen with the kitchen hot then shower cartridge at fault maybe

 

[Rotor]

Thanks for the input guys. Sometimes it happens on the kitchen tap but much less often. Could it be something to do with the flow rate though?
Mixer is a Vado PHA-148-C/2-C/P

I have also reset the boiler
Made sure it is at the 1.2bar and the condensate pipe water trap/pump thingy is clear

 

[ShaunCorbs]

Don't remove the boiler case

 

[Rotor]

Don't remove the boiler case

Why would I ?

 

[ShaunCorbs]

Why would I ?

"condensate pipe water trap/pump thingy is clear"

 

[Chalked]

It will be your shower mixer letting the cold mix across to the hot.
It should have non return valves fitted to the inlets to stop the above from happening. They can also stick open, causing the same problem. .if your handy, remov the shower mixer to check. Or get a local plumber to sort it.

 

[Rotor]

Would that cause the combi burner to switch off ?

 

[Chalked]

Would that cause the combi burner to switch off ?

No flow rate through it, as the cold is mixing

 

[Rotor]

Ahh. A mix up mate , I ment an external one like this

Pump House Boiler Condense Pump with Hose, Clip and Adaptor

 

[Rotor]

No flow rate through it, as the cold is mixing

It happens downstairs as well. Just not as frequent

 

[Chalked]

Ahh. A mix up mate , I ment an external one like this

Pump House Boiler Condense Pump with Hose, Clip and Adaptor

Don’t understand?
Your post was about hot water flow from taps?

 

[Rotor]

Don’t understand?
Your post was about hot water flow from taps?

I

Don’t understand?
Your post was about hot water flow from taps?

That reply was ment to be in a quote for Shaun

 

[Allgoode]

Sounds like a water flow sensing issue potentially with the boiler being that it can happen with the taps as well.
Not really a big issue to sort.
A GSR engineer will be able to sort it out easily as long as part is not seized in place which occasionally happens in which case you will end up with replacing the part housing as well.
I would guess the boiler is several years old & these things can cause the above issue,
Thanks.
Andy (Allgoode)

 

[Rotor]

Hi guys.

So I had my boiler sorted. It was the flow turbine. The internal impeller had started to eat itself up. This would explain why it wasn’t working with the shower as the flow of hot water is less . I thought I would share the findings

Thanks

 

[Harvest Fields]

"condensate pipe water trap/pump thingy is clear"

Could just be a condense pump mate.

 

[Allgoode]

Cheers for the update.
Thought it was that as usual symptoms of turbine failure/sticking due to build up,etc.
Didn't want to post my part thoughts as i know to many people "have a go" even though the case front cover forms part of the combustion box seal.
Hope not to expensive for repair,
Cheers,
Andy

 

[townfanjon]

Not read all the comments.
There is a very common problem with logic HW , a very simple check most heat engineers will know .

 

[Rotor]

Thanks

Cheers for the update.
Thought it was that as usual symptoms of turbine failure/sticking due to build up,etc.
Didn't want to post my part thoughts as i know to many people "have a go" even though the case front cover forms part of the combustion box seal.
Hope not to expensive for repair,
Cheers,
Andy

Andy, no mate he was pretty reasonable . He was an older gent turns out he knew my dad , said at the start that he mostly installs boiler systems and shyed away from repairs as it mostly electronic and electrical.He took the details went away and did some research and came back with the right part. Better than the more expensive younger gun who serviced it last year , when at he time we told him it very occasianly stopped producing hot water said it was the thermistors! When I questioned him as to why he could not test them with a low reseistance ohmmeter ( me being a spark ) he said “na they just change them par for the course” and it made no difference . So I have now found the man to do my system boiler , water cylinder and plumbing work for my extension next summer.