Combi Boiler Intermittent Hot Water

reservoir · Dec 30, 2020

Hi,

Worcester 28i Junior Combi Boiler

The hot water lasts only probably 2 or 3 minutes and then become cold for about 30 seconds then warm/ hot again... thought it's the limescale blocks the secondary heat exchanger.

Now the plate heat exchanger has been replaced but the problem still exist!

Could be the diverter valve scaled too? Or any idea?

Thanks

Scott_D · Dec 30, 2020

Is it the same at all hot taps?
Did you replace the plate yourself?

reservoir · Dec 30, 2020

scott_d said:
Is it the same at all hot taps?
Did you replace the plate yourself?

Ummm, I don't know about the kitchen tap... (haven't tried that long) but only notice the shower one.
No, I didn't do it myself.

Scott_D · Dec 30, 2020

It could be a boiler fault or it could be a tap or shower passing and mixing hot and cold water

reservoir · Dec 30, 2020

scott_d said:
It could be a boiler fault or it could be a tap or shower passing and mixing hot and cold water

Thankyou. I will check / keep the hot water tap in kitchen running for a while tomorrow...
Could be the diverter valve within the boiler, do you think?

Diyer171 · Mar 6, 2021

Hi, I’m having the same problem with my boiler, changing heat exchanger didn’t do anything. Did you manage to fix the problem? If so what did you do?

reservoir · Mar 6, 2021

Diyer171 said:
Hi, I’m having the same problem with my boiler, changing heat exchanger didn’t do anything. Did you manage to fix the problem? If so what did you do?

No, not really!
The engineer came for the third time and turned the hot water temperature control knob from 4 to 6. After it, the boiler seems fine.
Is yours the same boiler, and how old is it? Have you tried to turn the temperature to its maximum?

Diyer171 · Mar 6, 2021

reservoir said:
No, not really!
The engineer came for the third time and turned the hot water temperature control knob from 4 to 6. After it, the boiler seems fine.
Is yours the same boiler, and how old is it? Have you tried to turn the temperature to its maximum?

Ours is a Vaillant ecomax and it’s 17 years old so I very much expect to purchase a new boiler but we will be moving house so I really don’t want to be spending 4-5k on a new boiler that we won’t use for long. I have just put the hot water temp up to max now. I think that the plumber who replaced the heat exchanger turned it up and it didn’t make much difference.

reservoir said:
No, not really!
The engineer came for the third time and turned the hot water temperature control knob from 4 to 6. After it, the boiler seems fine.
Is yours the same boiler, and how old is it? Have you tried to turn the temperature to its maximum?

reservoir said:
No, not really!
The engineer came for the third time and turned the hot water temperature control knob from 4 to 6. After it, the boiler seems fine.
Is yours the same boiler, and how old is it? Have you tried to turn the tempOurs is a Vaillant ecomax and it’s 17 years old so I very much expect to purchase a new boiler but we will be moving house so I really don’t want to be spending 4-5k on a new boiler that we won’t use for long. I have just put the hot water temp up to max now. I think that the plumber who replaced the heat exchanger turned it up and it didn’t make much difference.

reservoir said:
No, not really!
The engineer came for the third time and turned the hot water temperature control knob from 4 to 6. After it, the boiler seems fine.
Is yours the same boiler, and how old is it? Have you tried to turn the temperature to its maximum?

Ours is a Vaillant ecomax and it’s 17 years old so I very much expect to purchase a new boiler but we will be moving house so I really don’t want to be spending 4-5k on a new boiler that we won’t use for long. I put the hot water temp up to max about 40 mins ago and just tested, it only lasted 3 minutes before dropping, perhaps I need to give it a day on the max setting. We had a plumber replace the thermal mixer in the shower, but that made no difference. Can’t say I was surprised I had touched the HW copper inlet to the shower when the temperature dropped in the shower and could feel that it was cold, so I was fairly certain that wasn’t the problem. So now I’m stumped.