Central heating - logic check
Posted: December 1st, 2016, 8:40 am
I have a large central heating system, split into two zones, controlled by two thermostats, one for each zone.
Yesterday, when Zone A was calling for heat, the rads in Zone A weren't getting warm, even though the motorised valve for that zone appeared to be open. I then forced Zone B to call for heat, and which point the boilers* fired up, and rads in both zones warmed up.
* there are 2 boilers, but they are not dedicated to zones; they work in tandem and their output goes through a mixing column, where it interfaces with the circulating water. However, given both boilers behaved the same, it allows me to rule out the boilers as a cause of the fault.
I am therefore tentatively concluding that it must be a signalling failure from the Zone A valve - it appears to be getting the signal from the stat (hence it was open, and allowed the water to circulate once the boilers fired up on command from Zone B) but isn't passing on that call for heat signal to the boilers. However, on thinking about it when I turned off the call for heat from Zone A, I don't think the valve closed again. So maybe it is stuck in the open position (lever was floppy)??
Any help with finalising the diagnosis, please?
And, is that likely to be a replacement motorised head required, or full valve replacement?
Yesterday, when Zone A was calling for heat, the rads in Zone A weren't getting warm, even though the motorised valve for that zone appeared to be open. I then forced Zone B to call for heat, and which point the boilers* fired up, and rads in both zones warmed up.
* there are 2 boilers, but they are not dedicated to zones; they work in tandem and their output goes through a mixing column, where it interfaces with the circulating water. However, given both boilers behaved the same, it allows me to rule out the boilers as a cause of the fault.
I am therefore tentatively concluding that it must be a signalling failure from the Zone A valve - it appears to be getting the signal from the stat (hence it was open, and allowed the water to circulate once the boilers fired up on command from Zone B) but isn't passing on that call for heat signal to the boilers. However, on thinking about it when I turned off the call for heat from Zone A, I don't think the valve closed again. So maybe it is stuck in the open position (lever was floppy)??
Any help with finalising the diagnosis, please?
And, is that likely to be a replacement motorised head required, or full valve replacement?