Boiler Problem !

[Monkey Wrench]

I have a problem with our boiler which is a Vaillant Ecomax 28 Pro system boiler. The system is S-Plan and when hot water only is on the boiler gets up to temperature the dialed-in temperature of 76C within about 8 minutes and then turns off (locks out). Turning the heating circuit on at the same time resolves the problem initially but, considering there are 10 radiators to heat, the boiler soon gets back up to about 74/75C within about 12 minutes.

I have drained down and refilled the system and can confirm that it is definitely not an airlock and all the radiators are getting hot so I have ruled out the pump. The flow and return pipes on both the hot water and heating circuits also all getting up to temperature. I know it must be a circulation problem so I'm wondering weather the boiler heat exchanger could have a partial blockage or it could be something else in the boiler casing the problem !

Any advice would be appreciated. Thank you.

 

[diamondgas]

Easiest way to check circulation is with pipe stats monkey wrench .... Checking the difference between your flow and return pipess at the boiler will give you an idea of how well the water is circulating .. Idealy looking for 2o[SUP]o[/SUP]C diff therabouts ... The higher the difference the greater the flow restriction 🙂

 

[Monkey Wrench]

Easiest way to check circulation is with pipe stats monkey wrench .... Checking the difference between your flow and return pipess at the boiler will give you an idea of how well the water is circulating .. Idealy looking for 2o[SUP]o[/SUP]C diff therabouts ... The higher the difference the greater the flow restriction 🙂

Thanks for the prompt response diamondgas.

Unfortunately I don't have access to pipe stats, are they expensive to buy ?

Additionally, would pipe stats help to indicate weather the restriction was in the boiler or system ?

 

[diamondgas]

The stats wouldn't indicate where the issue could be but can be used to determine the size of the problem ... you could use your hands ... If the flow heats up rapidly to OOOUCHYAFUCSHIA!!! then its a big restriction or pump problem! The difference in how rapidly it heats on hot water or heating will guide you in the direction of potentially what circuit the restriction is on! I wouldn't personally go to the expense of buying pipe stats because my hands tell me a lot 🙂

I wouldn't rule out the pump, by the way, it may be working but could have slowed down!

 

[Monkey Wrench]

I've just had the system running on heating only and again its getting up to temperature far too quickly, 70C within 5 minutes.

The problem is obviously with something common to both circuits which, despite my previous comment, could indicate the pump so no, I'm now not ruling it out. The pumps a Grundfos Aplha+ and is only 7 years old so I'd be a bit peeved if that was the problem as I'd expect it to last longer than that.

I'm going to let the system cool down and then conduct the "OOOUCHYAFUCSHIA!!!" test to see how quickly the flow heats-up.

Thanks again diamondgas.

 

[M.Joshi]

The pumps a Grundfos Aplha+ and is only 7 years old so I'd be a bit peeved if that was the problem as I'd expect it to last longer than that.

You'll be surprised. We've had a pump head fail after a couple of years due to the system not being flushed through before installing the new boiler! Imminent failure is indicative of loud whirring sounds like a jet engine!

 

[Monkey Wrench]

You'll be surprised. We've had a pump head fail after a couple of years due to the system not being flushed through before installing the new boiler! Failure is usually indicative of loud whirring sounds like a jet engine!

Thanks for that M.Joshi. The pump is as quiet as it's ever been, no whirring noises, bangs, crashes or anything !

 

[diamondgas]

If you can, from cold, grab both flow and return, that way you'll feel the difference. On heating, with all rads on full it should take a while to reach max temp!

Common to both is your primary circuit boiler and pump.. There may well be a filter you can check for blockage on the boiler, I'd have to check mi's unless someone here knows?

 

[Monkey Wrench]

If you can, from cold, grab both flow and return, that way you'll feel the difference. On heating, with all rads on full it should take a while to reach max temp!

Common to both is your primary circuit boiler and pump.. There may well be a filter you can check for blockage on the boiler, I'd have to check mi's unless someone here knows?

I have just fired the system up from cold with just the hot water circuit open. I had to take my hand off the primary flow pipe to the pump after about 40 seconds as it became too hot to touch but could quite happily keep my hand on the primary return even though it was getting hot but not nearly as hot as the flow.

I then opened the heating circuit and the flow pipe stayed the same temperature but the return obviously became much cooler.

 

[diamondgas]

Sounds like you've just proven for yourself that you've got a circulation issue and it sounds like its in the primaries. How dirty was the system water when you drained it? Could it be down to muck or is it more likely the pump?