ok guys, please bear with me as i have not posted here before, and if i have missed any information needed please let me know.
Problem - basic
Boiler seems to have gained a mind of it's own, running central heating when nothing is calling for heat.
setup
NF80 Combi Boiler performing HW and CH duties
Honeywell independent Frost Themostat - disconnected at the moment
1x Honeywell CM67 digital programable room thermostat, connected to the NF80 as a "clock control of heating only" - i know the CM67 is a thermostat, but as far as the boiler is concerned it sees only a on/off command from the CM67 via the switching relay, so should perform as per with a timer clock.
HW is for one bathroom only with low usage
Boiler is usually set to HW+CH operations, 24hr D.H.W Pre-heat mode
Pressure gauge reads 1bar stone cold and 2bar when up to temp and in use.
Problem - more detail
system has been running fine for a number of years now, no major issues other than sticking rad thermostats (now removed) and one timer clock that died (replaced with CM67 room stat)
a few days ago, i caught it heating the rads when the thermostat was not calling for heat, so here's what i tried:
1. initially kept my eye on it turning the required temp down on the CM67 to ensure it was not going to be calling for heat, rads still came on sporadicaly
2. removed the honeywell frost stat, as it's not technically required with the CM67 fitted - problem persisted
3. turned CM67 into manual mode and set to 13 degrees - problem persisted
4 turned off the CM67 (it defaults to 5 degrees frost protection mode in this stting) - problem persisted
5. pulled the battery pack out of the CM67 - problem persisted
Basically, with both of the external heat requesting sources removed or disabled the boiler was still pushing heat (pumping) around the CH system, this was not a constant thing, it does at times switch itself off and on, but i am not sure at what temperatures.
So i switched it from HW+CH operation to HW only, yet the problem still persisted.
the only logical explanation i can think of (as the makers say there is no control in the boiler that should call for heat on the CH circuit independent of an external switch) is that somehow, the HW Pre-Heat circuit is actually firing up the pump for the CH circuit as well, making the boiler seem to have a mind of it's own controlling the CH.
I can not see any way of running the boiler in CH mode only to test this theory
Anyone got any thoughts ? or maybe seen this behaviour before ?
TIA
Problem - basic
Boiler seems to have gained a mind of it's own, running central heating when nothing is calling for heat.
setup
NF80 Combi Boiler performing HW and CH duties
Honeywell independent Frost Themostat - disconnected at the moment
1x Honeywell CM67 digital programable room thermostat, connected to the NF80 as a "clock control of heating only" - i know the CM67 is a thermostat, but as far as the boiler is concerned it sees only a on/off command from the CM67 via the switching relay, so should perform as per with a timer clock.
HW is for one bathroom only with low usage
Boiler is usually set to HW+CH operations, 24hr D.H.W Pre-heat mode
Pressure gauge reads 1bar stone cold and 2bar when up to temp and in use.
Problem - more detail
system has been running fine for a number of years now, no major issues other than sticking rad thermostats (now removed) and one timer clock that died (replaced with CM67 room stat)
a few days ago, i caught it heating the rads when the thermostat was not calling for heat, so here's what i tried:
1. initially kept my eye on it turning the required temp down on the CM67 to ensure it was not going to be calling for heat, rads still came on sporadicaly
2. removed the honeywell frost stat, as it's not technically required with the CM67 fitted - problem persisted
3. turned CM67 into manual mode and set to 13 degrees - problem persisted
4 turned off the CM67 (it defaults to 5 degrees frost protection mode in this stting) - problem persisted
5. pulled the battery pack out of the CM67 - problem persisted
Basically, with both of the external heat requesting sources removed or disabled the boiler was still pushing heat (pumping) around the CH system, this was not a constant thing, it does at times switch itself off and on, but i am not sure at what temperatures.
So i switched it from HW+CH operation to HW only, yet the problem still persisted.
the only logical explanation i can think of (as the makers say there is no control in the boiler that should call for heat on the CH circuit independent of an external switch) is that somehow, the HW Pre-Heat circuit is actually firing up the pump for the CH circuit as well, making the boiler seem to have a mind of it's own controlling the CH.
I can not see any way of running the boiler in CH mode only to test this theory
Anyone got any thoughts ? or maybe seen this behaviour before ?
TIA