Baxi Combi 80 Eco

[Agile]

This boiler when starting to heat up a stone cold system comes on full power and just as the flow gets hot it turns itself off. It cycles on/off every 10 secs or so.

This continues for a few minutes until the return starts to warm up and then modulates down and runs continuously.

Is this a common problem and any particular cause?

Tony

 

[gazthepottertonengineer]

it sounds to me like your low gas rate setting on the gas valve isnt set correctly job for corgi engineer though as specialist tools are required

 

[Agile]

Thats all very well but there is no accessable low gas rate setting, only the high setting which was set according to the data plate. ( VK4105G 1005 )

Since original posting I have learnt that the gas valve had been changed before and initially exhibited the same problem and the fellow had to come back and presumably reduced the max setting.

Any ideas?

tony

 

[ChrisR]

It cycles on/off every 10 secs or so.

Can't see a mis-set gas valve causing that!

Tried your pot in place of the flow temp sensor?

 

[Slugbabydotcom]

Very thermistery to me or even some crud in the DV.
If anyone happens to need any of those VK4105G 1005 valves I have got about 25 spare here and will sell for cheap.
Apparently a lot were also fitted to bahamas and re-called due to a fault.

 

[gstens baxi]

Try the return filter or that the return filter is not fitted on the flow pipe. this ia common installation fault.

 

[Agile]

Thats an interesting point, the "return" filter is indeed fitted on the flow pipe but its clean and I dont see that it would, on its own cause this problem.

Just to recap, the flow heats up very quickly, perhaps due to a reduced flow for some reason, but the modulation cannot respond quickly enough so the boiler shuts down completely.

Previous "cure" seems to have been to reduce the max gas rate but ignore the underlying cause of the problem. Any suggestions? Dirt in the pump vanes caused by the the return filter being on the flow???

Tony

 

[Agile]

Thats an interesting point, the "return" filter is indeed fitted on the flow pipe but its clean and I dont see that it would, on its own cause this problem.

Just to recap, the flow heats up very quickly, perhaps due to a reduced flow for some reason, but the modulation cannot respond quickly enough so the boiler shuts down completely.

Previous "cure" seems to have been to reduce the max gas rate but ignore the underlying cause of the problem. Any suggestions? Dirt in the pump vanes caused by the the return filter being on the flow???

Tony

 

[Agile]

Thats an interesting point, the "return" filter is indeed fitted on the flow pipe but its clean and I dont see that it would, on its own cause this problem.

Just to recap, the flow heats up very quickly, perhaps due to a reduced flow for some reason, but the modulation cannot respond quickly enough so the boiler shuts down completely.

Previous "cure" seems to have been to reduce the max gas rate but ignore the underlying cause of the problem. Any suggestions? Dirt in the pump vanes caused by the the return filter being on the flow???

Tony

 

[stevieb5]

I had this problem last year, the problem was with the thermostat / thermistor (can't remember what it was called). Got a new one fitted and it works fine now.

 

[gazthepottertonengineer]

Thermistor part Nos 5108265

 

[Agile]

No, the NTC is fine!

I went back and found that there is a max Ch and a min gas rate pots on the PCB although they are not mentioned in the MI.

Reducing the max Ch has stopped the problem as I expected.

The "min gas rate" seemed to have no obvious effect ???

Does the 80Eco work in the 80E version ( which has neither of these pots) ?

Tony