If I'm reading the electrical schematic correctly then it should be possible to put the CH on normally without the boiler heating the heatslave (DHW) tank first as long as the DHW is switched off at the programmer as the DHW Thermostat Live is fed through the DHW programmer. This also seems the logical way of operation. It also then maybe looks that if a HW tap is opened (DHW still programmed Off) that only lukewarm then cold DHW is available, the boiler should still not fire?.
Greenstar Heatslave Oil Boiler Overheating and Pump Running 24/7
- Thread starter scottwhittaker
- Start date
The programmer on the boiler was removed before we moved in. I presumed it was a simple timer/programmer that the room stat replaced. We have a nest smart thermostat but that only works the heating on off and from what I've read online it's not possible to have the boiler not heat the heatslave tank by default.
Even if we call for heat the diverter valve will stay on water until the heatslave tank is up to temp.
Even if we call for heat the diverter valve will stay on water until the heatslave tank is up to temp.
Well, if turning the DHW stat down switched off the boiler before your problem and even though it's clicking when you do so, it's possible that the stat has failed on, if you remove one of the wires from the stats terminals then that should tell you something?. OR when when the stat is apparently off check for NO 230V on one of it's terminals with power on.
Ok will try and check but it's the exact same on CH so I was leaning away for the individual stats. I feel like everything is ok but the burner isn't going off when it should
Yes, but you had to force the diverter to CH?, if you remove the apparent continuous call for DHW then the system might change over to CH when requested and behave normally at least and cut out when the room temp reaches the roomstat target temp or the boiler might stop firing if you turn down the roomstat setting?.
You have checked the flow switch is closed when no hot water demand?
I think on a Grant combi if the DHW temp is satisfied and you then open a hot tap that the boiler will not refire until the stat is again calling. This boiler seems to keep firing even with the stat at minimum but a very hot DHW temperature.
The Grant combi's use a pcb with thermistors to heat store.
On dhw demand the dhw pump will start as soon as heatstore temperature drops burner will fire .
On the older Worcester combi's first thing we would look at in if burner not stopping 1. flow switch 2. heat store thermostat faulty and never satisfied.
If your competent with a multimeter easily checked.
Flow switch always the first suspect .
On dhw demand the dhw pump will start as soon as heatstore temperature drops burner will fire .
On the older Worcester combi's first thing we would look at in if burner not stopping 1. flow switch 2. heat store thermostat faulty and never satisfied.
If your competent with a multimeter easily checked.
Flow switch always the first suspect .
Yes I moved the diverter valve over otherwise I wouldn't have been able to test the heating stat. The boiler would have tripped on the hot water side trying to heat its tank and wouldnt have flicked over to central heating. I suppose that is the only way to bypass the continuous call for DHW.
That's what I was testing, to see if the CH side behaved normally but the controls didn't switch the boiler off when I turned the CH dial down. The dial/relay just clicks, whereas normally it would shut the boiler off as you are lowering the flow temperature of the CH water.
Yes I'm pretty sure this boiler fires every time a hot tap is opened
Can't you check the flow switch and DHW thermostat as suggested above, If you remove one terminal wire from the stat then IMO the boiler should stop firing, removing one wire from the flowswitch (if closed) might allow the boiler to revert to CH when requested normally, you'll have to start somewhere.
Ok Iv disconnected the flow switch at the PCB, turned the DHW dial to 1 and turned the boiler on at the spur.
It fired up and ran, heating the heatslave water tank and then the boiler switched off after about 5 minutes as normal!
So does that suggest the flow switch is telling the boiler its open and therefore the boiler is running on and on.
When disconnected I expect the boiler would presume there was no hot water demand?
It fired up and ran, heating the heatslave water tank and then the boiler switched off after about 5 minutes as normal!
So does that suggest the flow switch is telling the boiler its open and therefore the boiler is running on and on.
When disconnected I expect the boiler would presume there was no hot water demand?
Hmmm I was just about to say no its not firing at all for central heating now (as normally it fires straight up in response to the thermostat) but after about a minute it has fired up. Iv got the CH dial to 1 so I will see if it turns off.
If I turn the water control temp up the diverter is moving etc so all seems good IF it turns off before the high limit stat tells it to!
If I turn the water control temp up the diverter is moving etc so all seems good IF it turns off before the high limit stat tells it to!
Yeah it's gone off. If I turn the CH temp dial up it fires back in!
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