hi, i have a biasi combi condensing boiler and the problem is it fires up ok but after a few minutes the temp on the temp gauge goes straight up to 95 and then shuts off into lockout mode and shows the lit code on the display as safety thermostat lock out? im thinking it could be the primary flow thermistor, which biasi call the ch temperature probe! any suggestions please guys?
biasi combi condensing boiler problem?
- Thread starter bazgas
- Start date
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Do the pipes get hot? It is possible that there is a problem with the circulation and the safety devices are working as they should.
yes pipes get hot and rads start to heat up. it does not happen when running the d.h.w !
If, as I expect, this is on hot water only, then its a blocked plate heat exchanger!
If its on both heating and hot water then its likely somebody has been fiddling with the gas valve who did not know what he was doing! This needs a competent CORGI if thats the problem.
If its on heating only then it COULD be a faulty thermistor but thats extremely rare and most unlikely in your case.
You could measure both thermistor resistances when the boiler is completely cold.
Tony
If its on both heating and hot water then its likely somebody has been fiddling with the gas valve who did not know what he was doing! This needs a competent CORGI if thats the problem.
If its on heating only then it COULD be a faulty thermistor but thats extremely rare and most unlikely in your case.
You could measure both thermistor resistances when the boiler is completely cold.
Tony
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if i was to check the resistance on both thermistors cold, what should i expect to find if the thermistors are working ok? also what should i set my multimeter too?
Resistance about 10K to 13K when at room temperature and the boiler COMPLETELY cold.
You have to select a meter range appropriate to measuring that range or resistances. They should both be about the same!
You have to remove the plug before measuring!
Tony
You have to select a meter range appropriate to measuring that range or resistances. They should both be about the same!
You have to remove the plug before measuring!
Tony
is the blocked heat exchanger a common problem as the boiler is only a few months old? and what would sort that problem out? a power flush maybe! thanks
which model is this?
Its an M96 !
Until he has checked the resistance of the sensors we cannot go any further.
Now he has confirmed that its only recently installed and in senarios like this that usually means its a non CORGI installation otherwise the installer would have been called back.
All gas boilers should be installed by a competent CORGI who will commission the boiler and complete the paperwork. The system should be power flushed BEFORE a new boiler is installed!
After the sensors, the next step would be for the CORGI installer to check the gas valve settings. That will be difficult in this case!
Tony
Until he has checked the resistance of the sensors we cannot go any further.
Now he has confirmed that its only recently installed and in senarios like this that usually means its a non CORGI installation otherwise the installer would have been called back.
All gas boilers should be installed by a competent CORGI who will commission the boiler and complete the paperwork. The system should be power flushed BEFORE a new boiler is installed!
After the sensors, the next step would be for the CORGI installer to check the gas valve settings. That will be difficult in this case!
Tony
Apart from the check of sensors asked you.
As it works on dhw it isn't the heat exchanger or the pump.
As the radiators get a lttle warm it may not be this but first thought is the old dhw flow switch held open by instillation debris. without taking case off to see if red light indicating flow is illuminated one would feel the return pipe is it hot enough to boil an egg? think it's the left hand 22mm pipe, can't put hand on it? stuck in dhw mode!
Other than that are flow and return iso valves open? Has installer been paid? He might have nobbled the system with isolators hidden.
As it works on dhw it isn't the heat exchanger or the pump.
As the radiators get a lttle warm it may not be this but first thought is the old dhw flow switch held open by instillation debris. without taking case off to see if red light indicating flow is illuminated one would feel the return pipe is it hot enough to boil an egg? think it's the left hand 22mm pipe, can't put hand on it? stuck in dhw mode!
Other than that are flow and return iso valves open? Has installer been paid? He might have nobbled the system with isolators hidden.
If its a recent boiler it will not have a red light on the DHW flow switch.
Nor does it sound as if its on all the time.
In any case the temp controls manage the boiler very effectively at a flow temperature of about 65°-70° if the DHW flow switch is jammed on. These later types dont normally jam on anyway.
Tony
Nor does it sound as if its on all the time.
In any case the temp controls manage the boiler very effectively at a flow temperature of about 65°-70° if the DHW flow switch is jammed on. These later types dont normally jam on anyway.
Tony
what is the heating load?
have seen a new m96 do this, the boiler what fitted in new build one bedroom bungalow. it had a rad in the front room/kitchen and a rad in the bedroom and a towel rad in the bathroom. the two rads had tvrs and all the rads where fed in 10mm speedfit...
anyway check burner pressures then range rate down to match heating load. check that the by-pass is not opening and if you want fire in a new ntc if you feel like it. a ntc is cheap enough, so i would fire it in for good measure anyway.
have seen a new m96 do this, the boiler what fitted in new build one bedroom bungalow. it had a rad in the front room/kitchen and a rad in the bedroom and a towel rad in the bathroom. the two rads had tvrs and all the rads where fed in 10mm speedfit...
anyway check burner pressures then range rate down to match heating load. check that the by-pass is not opening and if you want fire in a new ntc if you feel like it. a ntc is cheap enough, so i would fire it in for good measure anyway.
thanks for the replys guys it has helped me out alot. replaced the flow thermistor or as might be nown the c.h probe and that has done the trick. and tony you are a real character, not everybody is a non corgi registered cowboy! there are many out there but i am not one, i am recently qualified and newly registered and find this forum a great help when needing some advice 
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