Boiler is a Grant Vortex Pro 21, installed around 6 years ago.
When Central Heating is demanded from the thermostat the CH pump will come on for a couple of minutes say and then the CH pump is switched off and the DHW pumps starts, the flow light is not lit, this cycle continues varyingly. As a result the CH pump is off more that it is on and the radiators do not get hot at the bottom. This issue has existed for quite some time, say since last winter.
The boiler had its annual service last week but the engineer could not figure out a solution to this problem and said he would speak to Grant directly. It was suggested by Grant that the problem was either one of the thermistors (store and flow) or the control PCB as a last resort. It made sense to purchase all 3 as a package from a cost perspective. The new parts were fitted by myself and the same problem persists. The removed thermistors didn't look in great condition, the wires where they were inserted had hardened, maybe that is normal?
I got a new Hive for Christmas that could control hot water and CH as I want to turn off the Hot water at night and most of the day to save burning oil unnecessarily. I fitted the new hive and have now discovered that if the hot water is switched off then the central heating works as the CH pump stays on continuously when demand is there and the rads all got hot at the bottom as they should.
So it seems that demand is being created by the DHW side and turning off the CH pump. My house has solid walls and floors and all pipework for the heating is 95% exposed so I'm pretty sure there are no water leaks creating the demand, neither are any taps or showers dripping.
I don't have an issue having the engineer back again but it seems to me he'll just be scratching his head once more.
Hot water always works fine.
I'm at a loss so any input greatly appreciated. Thank you.
When Central Heating is demanded from the thermostat the CH pump will come on for a couple of minutes say and then the CH pump is switched off and the DHW pumps starts, the flow light is not lit, this cycle continues varyingly. As a result the CH pump is off more that it is on and the radiators do not get hot at the bottom. This issue has existed for quite some time, say since last winter.
The boiler had its annual service last week but the engineer could not figure out a solution to this problem and said he would speak to Grant directly. It was suggested by Grant that the problem was either one of the thermistors (store and flow) or the control PCB as a last resort. It made sense to purchase all 3 as a package from a cost perspective. The new parts were fitted by myself and the same problem persists. The removed thermistors didn't look in great condition, the wires where they were inserted had hardened, maybe that is normal?
I got a new Hive for Christmas that could control hot water and CH as I want to turn off the Hot water at night and most of the day to save burning oil unnecessarily. I fitted the new hive and have now discovered that if the hot water is switched off then the central heating works as the CH pump stays on continuously when demand is there and the rads all got hot at the bottom as they should.
So it seems that demand is being created by the DHW side and turning off the CH pump. My house has solid walls and floors and all pipework for the heating is 95% exposed so I'm pretty sure there are no water leaks creating the demand, neither are any taps or showers dripping.
I don't have an issue having the engineer back again but it seems to me he'll just be scratching his head once more.
Hot water always works fine.
I'm at a loss so any input greatly appreciated. Thank you.
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