Hi We have just bought a house with a Megaflo (installed about 5 years ago). The Grundfoss pump attached to it runs constantly even if the system isn't calling for HW or CH. The pump only stops when isolated at the circuit board. The pressure in the system seems ok, the port valves for HW and CH seen to be working OK. Any other ideas? Cheers Mark
Cheers I think it is a new problem. i.e. only just started so that rules out the wiring. I've tested the powerheads by turning off the CH and HW and manually opening them; they close OK. They are loose (therefore open?) when the respective CH or HW is being called for. Does this sound like they are OK or is there another test I can do?
As you say, JJ, since it's a fairly recent issue, it's unlikely to be a wiring mistake. Really, to test the motorised valves, you need access to the wiring centre (a box where all the wires descend...), a knowledge of what you are looking for, and a test meter. Or, I guess you could remove the 'head' (the part that holds the motor, switch and wiring) from each one and examine it for a stuck or faulty microswitch (can you post a photo of the valves?) Mind you, wouldn't a stuck valve switch also turn the boiler on? Although a motorised valve is the most likely candidate, I wonder if there's a pump over-run 'stat on the boiler that keeps the pump running to disperse hot water when the boiler has chust turned off? Perhaps that's faulty.
What colour is it, or more importantly, what colour is the base of the pump? If it is bronze, then it is a DHW circulation pump designed to provide 'instant' hot water to taps. If the head has been changed at some stage, you may find it is the red colour. As long as the body is bronze, then that is O.K. It is usual for these to be separately controlled by a timer that switches off only at night. If, however, it is on the same pipework as the motorised valves, then the previous comments will apply.
Thanks for the replies - it is much appreciated. Pic attached for reference. The body of the pump is silver and the base is black.
The pic is with the power turned off and as you can see the pressure is low. When the system is calling for CH and HW the pressure rises to around where the red indicator is. Should I top it up? I.e. when do you check the pressure against the red indicator?
Can't make out from your picture where the pipework goes, it is too dark. Is the pump base (black) metal or plastic? If plastic, it could be a DHW circulator, but without seeing the pipework clearly, I can't tell. If it is a primary circulator, then a stuck end switch is favourite, but that would also fire the boiler.
Your new picture shows it is the main circulating pump on what appears to be a 'S' plan. It may be a faulty motorised valve, but that would also fire the boiler. What boiler do you have and is there a pump overrun thermostat fitted to it?
It is oil fired as pic below. Not sure about the pump overrun thermostat as the boiler is fitted under a utility room worktop so can't see behind - if it would be mounted in full view then no i'm guessing not?
There is no pump overrun thermostat, but the boiler comes with a link in the control panel that goes from terminal 1 to 4, that probably should have been removed when the programmer was fitted. This will put a permanent feed to the pump whilst there is a permanent live feed to the boiler. If you are not confident in checking this yourself, then call in a heating engineer to check and sort.
That's a pre plumbed cylinder, Simple answer is turn off all controls that can switch demand, check switch lives that have power, change the faulty one
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