Modulating boiler problem

[cully]

Hello forum, could you please advise on the following,
I have a Micromat HS 31kw condensing boiler((bought from eco hometec Doncaster, (who have gone into demise)about 10 years ago when I installed underfloor heating in my house))
and it is cycling between hot / cold every approx 2/3 mins.(It gets up to set temp 60* then falls back to 50*)
The boiler has a modulating fan, burner and pump and I suspect one or more of these are not functioning properly but how do I check this out?
I have a grunfos 15/60 pump external to the boiler but controlled by the boiler operation and there is also a further 15/60 pump at the underfloor manifold that is controlled by the honeywell heating control box and I have adjusted the speed of these but with no change to the cycle time
If anybody can point me in the Direction of finding the source of this problem I would appreciate that
Thanks
Paul C

 

[dcawkwell]

You'll struggle never even heard of this boiler.
I see the manual for it online but that isn't a lot of help and with no illustrations of what is inside.

If it has a gas valve pull off one of the modulating wires and it should jump to low burner.

After that it is identifying the cause of either the gas valve stuck at full burner or the pcb thinking it isn't getting hot, Thermistor.

 

[Dan Robinson]

Not in my office so don't have full access to my files
But, you might get some joy calling MHG on 0845 644 8802.

Ecohometec were a bunch of charlatans.

 

[Agile]

If it has a gas valve pull off one of the modulating wires and it should jump to low burner.

After that it is identifying the cause of either the gas valve stuck at full burner or the pcb thinking it isn't getting hot, Thermistor.

I think that he would be better calling a competent engineer rather than attempting DIY gas/combustion related repairs!

In any case with a modulating fan its not likely to have a gas valve with a mod coil!

 

[cully]

Thanks for the response,
This boiler "Micromat" is a German made boiler also sold under the name Strata, but is now superseded by the ProCon 77 according to the MHG web site.
With regards to modulation the fan, burner and water pump modulate
I am a Mechanical Engineer by profession and I am capable of dealing with the water side and some of the electrical, I do not get involved with the gas side of the boiler. (I know my limitations)
The demise of Eco hometec means there are two ex eco service engineers now that look after the boilers around the country and one will be visiting on the next scheduled service date March 2013 in between services I do whatever I can to keep the heating on and the cost down.
The boiler is 10 years old and in that time has required
A new heat ex changer (leaked six months out of its warranty period, £600)
Control panel (£600) I found the problem, "relay" and it is now a proved spare.
Water pump (£110, repaired old one for spare)
Temp sensor (*2 £20 paid for one)
Three way valve actuator (Approx £70 I think,) cannot repair it as I cannot find a replacement motor)
There's an insight to my involvement with this boiler to date
Thanks again
Paul C

 

[Agile]

Obviously at any of the £600 spend times it would have been better to have bought a new boiler!

I wish that I could be one of only two engineers repairing particular boilers and travelling all over the country.

When I worked for the BBC my work needed extensive travelling but the BBC paid good subsistance allowances which would be up to about £100 per day and provided a nice company car!

Tony

 

[Agile]

The boiler has a modulating fan, burner and pump and I suspect one or more of these are not functioning properly but how do I check this out?

Thanks
Paul C

You say you will not do any gas work! But the fan and burner are both part of the gas/combustion process!

We are not allowed to advise DIYers on gas work and the obvious solution is for you to check the pump and control system as far as you can and then get a competent engineer to come and diagnose the problem.

Many will not touch a model they are not familiar with but I will always repair any boiler regardless of the maker.
Tony

 

[cully]

I agree with you that when the repair cost starts to escalate then it's time to replace .
I did look into a Bosch alternative which, if I have bought it would have required an external three way diverter valve installing to give me what I required, according to Bosch technical.
My boiler has two separate water systems htg. and DHW but I was unsure as to the Bosch boiler efficiency compared to my boiler when it modulates down to 55* supplying the underfloor heating system.
I am aware that the fan is part of the burning process and when the service is next carried out we will establish what is happening whilst we are linked up to the computer
The two service engineers I mentioned in the above thread are now self employed, they were given one days notice when eco hometec went into liquidation
Thanks again Tony for your advice and help
Paul

 

[dcawkwell]

Thanks for the response,
This boiler "Micromat" is a German made boiler also sold under the name Strata, but is now superseded by the ProCon 77 according to the MHG web site.
With regards to modulation the fan, burner and water pump modulate
I am a Mechanical Engineer by profession and I am capable of dealing with the water side and some of the electrical, I do not get involved with the gas side of the boiler. (I know my limitations)
The demise of Eco hometec means there are two ex eco service engineers now that look after the boilers around the country and one will be visiting on the next scheduled service date March 2013 in between services I do whatever I can to keep the heating on and the cost down.
The boiler is 10 years old and in that time has required
A new heat ex changer (leaked six months out of its warranty period, £600)
Control panel (£600) I found the problem, "relay" and it is now a proved spare.
Water pump (£110, repaired old one for spare)
Temp sensor (*2 £20 paid for one)
Three way valve actuator (Approx £70 I think,) cannot repair it as I cannot find a replacement motor)
There's an insight to my involvement with this boiler to date
Thanks again
Paul C

Get it ripped out. I would have pulled it straight off the wall when the heat exchanger went. I could virtually put a new boiler on the wall for that.

 

[BungyStrap]

Cully
Interesting to read your experiences about the Micromat as they aren't too dissimilar to mine, an EC38/45 combi also bought from EcoHometech about 10 years ago.
It was a bit worrying when I received a letter after a few years from MHS boilers (who I think were the UK distributors) informing me that it had just been discontinued and inviting me to buy something else (at an attractive price....not). And in the last month I have received another letter stating that spare parts will no longer be supplied from 2015, and agin inviting me to buy something else!
I've experienced the 3 way valve fail during the warranty period, and a mysterious leak which was eventually traced to the plastic condensate syphon tank tucked round the back.
But most annoying and painful was the control board. The first sign was one day the boiler wouldn't fire up and was found to have locked out. After a reset it was OK for a couple of months, but then did it again, and slowly more frequently, until after a year or so it might fail once or twice a week, and sometimes it would require multiple resets to get it going. The service people couldn't track it down (whenever they called it worked OK). I was reluctant to spend the £600, and was sure I had traced the fault to a dry joint on the ignitor transformer, but still no luck. Eventually I found a reconditioned board from a German company, Heiz24.de. But 3 problems - the display was in German without an option to change it to English, the radiators have never been as hot since ( I suspect that it might be set up for a less powerful boiler version), and finally it has failed to strike up a couple of times in the last month, so I think it too might be on the way out.
I've still got my old control panel and I would be very interested to hear what were your symptoms and what you found to be the cause, and how you fixed it.
I'm very reluctant to replace an expensive state-of-the art boiler which is only 12 years old, but on the other hand if it going to cost £600 every few years.......
Hoping you can share what you found.
Benjy

 

[dcawkwell]

Cully
Interesting to read your experiences about the Micromat as they aren't too dissimilar to mine, an EC38/45 combi also bought from EcoHometech about 10 years ago.
It was a bit worrying when I received a letter after a few years from MHS boilers (who I think were the UK distributors) informing me that it had just been discontinued and inviting me to buy something else (at an attractive price....not). And in the last month I have received another letter stating that spare parts will no longer be supplied from 2015, and agin inviting me to buy something else!
I've experienced the 3 way valve fail during the warranty period, and a mysterious leak which was eventually traced to the plastic condensate syphon tank tucked round the back.
But most annoying and painful was the control board. The first sign was one day the boiler wouldn't fire up and was found to have locked out. After a reset it was OK for a couple of months, but then did it again, and slowly more frequently, until after a year or so it might fail once or twice a week, and sometimes it would require multiple resets to get it going. The service people couldn't track it down (whenever they called it worked OK). I was reluctant to spend the £600, and was sure I had traced the fault to a dry joint on the ignitor transformer, but still no luck. Eventually I found a reconditioned board from a German company, Heiz24.de. But 3 problems - the display was in German without an option to change it to English, the radiators have never been as hot since ( I suspect that it might be set up for a less powerful boiler version), and finally it has failed to strike up a couple of times in the last month, so I think it too might be on the way out.
I've still got my old control panel and I would be very interested to hear what were your symptoms and what you found to be the cause, and how you fixed it.
I'm very reluctant to replace an expensive state-of-the art boiler which is only 12 years old, but on the other hand if it going to cost £600 every few years.......
Hoping you can share what you found.
Benjy

If you were driving around in a 12 year old car. Or using a 12 year old washing machine. I wouldn't think twice about chucking them and getting a new one. I don't know why people persist with degrepid old boilers that don't do the job. When taking one off the wall and putting a new one in it's place is an easy job. Even some of the cheap boilers today will do the job and come with a 5 year warranty.

 

[Agile]

I get some kind of pleasure from keeping some of the older boilers working like the Sine 18, Trisave or Gem.

But the owners of those boilers above are in a situation where the spares are either very expensive or unavailable.

In those cases with a 12 year old boiler the obvious solution is to replace the boiler with a modern unit.

Tony

 

[Dan Robinson]

Micromat boilers can be dealt with by anyone, btu MHG Heating also sold them and still have service engineers and spares.

0845 6448802

www.mhgheating.co.uk