Combi boiler hot water keeps cutting out

[0Floz0]

Hi all,

I’ve got a vaillant ecotec plus 831. When I run the shower off it, the hot water seems to come and go. The shower is above the boiler slightly but in the same room so it’s a very small run.

Hot water elsewhere seems to be fine. It’s not got loads of pressure but going freezing cold mid shower is not fun. When I crank it all the way to hot it tends to kick back in but goes very hot. So I don’t think it’s a max temp issue.

Any ideas on what to test?

Thanks

 

[CountryFan]

If other outlets are ok I’d say the issue is with the shower - cartridge/cold pushing hot out of the way

 

[0Floz0]

If other outlets are ok I’d say the issue is with the shower - cartridge/cold pushing hot out of the way

If it’s not fed through a cartridge, ie directly from 2 taps. What else could cause it? Is it just a case of closing the cold feed slightly so that it doesn’t overpower the hot?

 

[CountryFan]

Is it just a case of closing the cold feed slightly so that it doesn’t overpower the hot?

Certainly wouldn’t hurt to try it, failing that, could then be an issue with the boiler.

 

[Johntheo5]

Hi all,

I’ve got a vaillant ecotec plus 831. When I run the shower off it, the hot water seems to come and go. The shower is above the boiler slightly but in the same room so it’s a very small run.

Hot water elsewhere seems to be fine. It’s not got loads of pressure but going freezing cold mid shower is not fun. When I crank it all the way to hot it tends to kick back in but goes very hot. So I don’t think it’s a max temp issue.

Any ideas on what to test?

Thanks

Can you measure the flowrate from the shower when it goes freezing cold and either measure or estimate the temperature before it goes cold.
What is he DHW (boiler) temperature set to?, its adjustable, 35C to 65C).

 

[0Floz0]

Can you measure the flowrate from the shower when it goes freezing cold and either measure or estimate the temperature before it goes cold.
What is he DHW (boiler) temperature set to?, its adjustable, 35C to 65C).

Stupid question possibly. But how do I test the flow rate? I think it’s set to 55 but will check in the morning.

 

[Johntheo5]

Stupid question possibly. But how do I test the flow rate? I think it’s set to 55 but will check in the morning.

Switch on the shower to your normal settings, then get a container like a bucket or dish and hold it under the shower head (let the shower head in its holder) for exactly 30 seconds, measure this with a 1 litre milk bottle or whatever then X 2 to give the flowrate in LPM.

Your milk bottle (if that's what you use) will be in pints so X the (30 sec) pint measurement X 1.137 to get the flowrate in LPM.

 

[0Floz0]

Switch on the shower to your normal settings, then get a container like a bucket or dish and hold it under the shower head (let the shower head in its holder) for exactly 30 seconds, measure this with a 1 litre milk bottle or whatever then X 2 to give the flowrate in LPM.

Your milk bottle (if that's what you use) will be in pints so X the (30 sec) pint measurement X 1.137 to get the flowrate in LPM.

Not had a chance to do this yet but will try when I can. I just had a shower and thought I’d observe the temp reading on the boiler (it’s basically next to the shower). It gets to 60c then cuts out. Drops to 50c then kicks back in. Gets back up to 60 and cuts out again. It repeats like this but every now and then it’ll drop to about 44, not kick back in then drop to about 37 which is when it gets really cold in the shower. Turning the shower off then turning it back on again seems to get the boiler to kick back into gear. But will still fluctuate.

I’ve also noticed when it’s doing this the water has a slight stutter but I’m guessing that’s due to the boiler pump cutting out?

 

[CountryFan]

I would get an engineer in or Vaillant fixed price repair as you could be looking at a few things.

 

[mcmoby69]

Blocked plate hex. First symptom is shower playing up.

 

[0Floz0]

What’s the best way to clean the plate hex? Just stick it in a bowl of descaler?