Heat Exchanger Problem? on Combi Boiler

[Peterpann]

Hi

I seem to be having a bit of a problem with our Combi Boiler on the CH side, which I am thinking, after doing some research on the internet, could be the heat exchanger, some help would be appreciated

Problem

Heating comes on as normal, radiators warm up, but the room temperature doesn't reach the cutoff temperature this has become more and more apparent over the past few days as the outside temperature has dropped

After watching the gauges on the boiler (combined water temp and pressure gauge) I noticed that sometimes the temperature gauge shows the water temperature rising then holds at a steady temp for 60 - 120 seconds whilst the boiler is on then it suddenly shoots up and the boiler cuts out, the temp drops very quickly and after a few minutes the process starts again.

Other times (becoming the more frequent) the water temp gauge shows the water temp rising until it reaches the cutout temp (no holding at a lower temp), again cutting out the burner, again the water temp drops rapidly and again after a few minutes the process starts again.

If I adjust the water temp knob to a lower temp it cuts out quicker, it is now on high just to get some heat in to the house

Water pressure is at 2.5bar

Tap hot water works without a problem

Boiler is an Ideal Mini HE (either C24 or C28)

My questions are

1. Am I right it's a heat exchanger issue? and if so could the problem be rectified by flushing the system? or is it a replacement heat exchanger?

2. Am I wrong and the problem is being caused by something different? if so any ideas on what?

Any help appreciated

 

[keego]

Check the pump is running when CH is on.
If I remember right the Ideal Mini hasn't been out that long, is your boiler still under warranty?

 

[Peterpann]

Thanks for the reply

The boiler was installed in 2006 so out of warranty

As for the pump how would I check?

Also I would of thought that with the internal water temp dropping rapidly after it cuts out that the pump was working, if the pump wasn't working I would of thought the temp would of dropped slowly

Also all the radiators are warm and sometimes even get hot suggesting that the pump is circulating the water

I may be wrong this isn't exactly my subject

 

[ServiceNumpty]

Could be a blocked filter.

 

[Peterpann]

Could be a blocked filter

I have noticed that the higher the water pressure the longer it works, i.e. 2.5 bar the boiler fires up and the temperature quickly rises over the 85 deg mark and cuts out however if the water pressure is at 2.9 bar or over the temperature rises and steadies around the 83 deg mark and we get some warmth

This suggests some form of blockage the increase in pressure managing to force the water through the heat exchanger or filter (although I cannot see any mention of a filter in the manual)

Any suggestions?

 

[D_Hailsham]

2.5 bar is on the high side. What is the pressure when the system is cold?

What water temperature do you normally have the CH set to?

 

[Agile]

Something seem to be very wrong with your CH system!

For a properly designed system the CH temperature should give adequate heat with a flow temperature of about 70 C.

It sounds as if your rads are undersized or possibly sludged up.

Do you ever have your boiler serviced and the system checked every year?

If not then what do you expect?

I suspect its sludged up because you are running the system pressure way too high. It should be set at 1.5 Bar when cold. It may rise to about 1.8 Bar when hot.

The advice would be to engage a professional to diagnose the problems and offer a solution.

Tony Glazier

 

[Peterpann]

Hi Tony

It was serviced every year except this year, for some reason he didn't turn up

Normally the pressure was low at about 1 - 1.5 bar it's only since it started "playing up" that I noticed the increased pressure, and not happy at running it that high

However I recently got a quote from the installers of this system for a repair on another boiler in a property I own and was quoted £1500 to replace the 7yr old boiler and flush the system.

I eventually got that problem fixed for £200, unfortunately the guy who fixed it fell off a roof and is off work and I don't want to get "reamed" so I was looking for an answer that pointed to a repair that would sort it out and I didn't get a load of bull about an expensive un-neccessary fix

Hope that made sense

 

[Peterpann]

Forgot to add when the boiler was installed in 2006 the system was supposedly flushed with SM4 and an SM1 inhibitor was used

 

[Agile]

Hi Tony

However I recently got a quote from the installers of this system for a repair on another boiler in a property I own and was quoted £1500 to replace the 7yr old boiler and flush the system.

Hope that made sense

Most installers are not very ( or any ) good at doing repairs. So instead they try to take the opportunity to get you to have a new boiler as they can do that and its a much bigger job for them.

You need to get someone who specialises in repairs!

I doubt there is anything wrong with your boiler apart from perhaps having some sludge in it. More likely a system problem instead.

It needs a competent engineer to diagnose the problem!

Tony

 

[Peterpann]

Cheers Tony

I think I will offer the guy who fixed the last one a free lift, crutches and all to come and have a look at it I'll even do the labour if it will stop the missus moaning about being cold (doesn't bother me I work from home in a room full of computers so it's lovely and toasty )

 

[Valliantcombi18]

Cheers Tony

I think I will offer the guy who fixed the last one a free lift, crutches and all to come and have a look at it I'll even do the labour if it will stop the missus moaning about being cold (doesn't bother me I work from home in a room full of computers so it's lovely and toasty )

Hi Peterpann,

I know that this has been a while since you have posted this, but i was hoping you would be able to tell me how you fixed the problem as i have hear the exact same problem all the repairers that visited me said that it is something to do with the pipes being blocked, i flushed the pipes still the same problem, i am also suspecting it could be the heat exchanger, so wanted to see how you solved your problem before looking into that.

Cheers