Ground Source Heat Pumps

JHen1

Hi! Any thoughts on why the level in my expansion tank is dropping? When my P3 pump was replaced in Jan 2025 the engineer topped up the expansion tank with glycol to approx 3/4 full - some time after this the level had dropped quite a bit so I topped it up - say 1L approx . I had the unit serviced a few days ago and the engineer mentioned the drop could be caused when the P3 was replaced - air in the system or something - since then I noticed it a dropped a little more. So since I've topped it up after the P3 replaced, its dropped about 1CM - I appreciate this does not help you. It's not a great amount but it does drop - but it doesn't drop daily or even weekly - but it does drop. The engineer said it could be a leak. I have checked the manifold outside and there no obvious leaks. If there was a leak I would expect the level to drop constantly - no ? Should the level in the expansion tank be constant?

beardymarrow

If it's not dropping consistently, I'd guess it's air making its way out of the system and into the tank. As you say if there was a leak you'd expect it to drop all the time that the pump was running, so fairly consistently (weather dependant). Might be worth printing a tape measure and sticking it on to keep track accurately. 

JHen1

I did as you suggested and put some tape and mark on 19/4. Since this it has not dropped, but I know when I last topped it up it did not drop for some time. How would it make its way into the system? The engineer did find the expansion vessel flat and re-pressurised it, but I assume that is not related (the water vessel that is).

lstevensuk

Mine always drops when we have a dry spell, as in last few weeks. I assume it has a leak somewhere and the clay expanding is keeping it closed during wetter times. It maybe looses a whole bottle every year but that's still cheaper currently than replacing whole system.

DeeWestern

Help! I have a Worcester Bosch Greenstore 11kW (which I think is really Greenline HT Plus C) which has decided to stop working.

I've power-cycled it, and it comes on with Info saying hot water will start in 299 seconds. It counts down from somewhere between 5 and 150 seconds, before the screen fades and looks like it reboots - the counter starts again when I press info.

It looks like the sensors are recording whacky values too, and the machine is rebooting before it's trying to do anything with the heat pump.

I'm smart enough to know something is broken, but does anyone know what?

Is there enough info to say if replacing the Main Circuit Board / Senor Board / Control Unit will be enough?

Or do I need to go through the upgrade to the Rego 1000, and if so, is there a firm in northern England who can install it? Is there a way to check if I have 3 phase power (the power switch on the wall is a red knob I have to turn between 3 o'clock and 12 o'clock to turn off / on)

victor2

@DeeWestern, you'd be better off starting a new thread rather than adding to one that was last updated over a year ago...

QrizB

Is there a way to check if I have 3 phase power?

If you look at your electricity cutout (near your meter), it'll be obvious.

If it has one fuse (like this) you have single-phase:

If it has three fuses (like this) you have three phase:

beardymarrow

https://forums.moneysavingexpert.com/discussion/comment/82030821#Comment_82030821

Hi Dee,

Looks like GT4 (Heating water output) and GT5 (internal air temperature) sensors are either faulty or disconnected, but very odd that both have gone at once. Maybe GT5 went a while ago, but you didn't notice, and it's only now GT4 has gone that it's starting to play up?

GT3 you don't have as that's only for an internal hot water tank. Yours uses GT3x, which looks fine.

Whether those sensors being wacky would cause the constant reboots, I don't know, but if it was me I would swap over the wiring for GT4 with GT1 and GT5 with GT2 to see if it's the board or the sensor, before starting on a new board etc. They are just wires into screw terminals on the top of the little green board behind the big black metal cover plate. Just take a photo first so you can swap it back :-)

Regarding 3 phase, I'd say it's unlikely. QrizB is right on how to check for that.

Alto Energy would cover your area, I'm sure.

DeeWestern

https://forums.moneysavingexpert.com/discussion/comment/82030895#Comment_82030895

This thread is the number 1 resource for heat pump advice in the UK, let's not start splitting discussions!

Thank you all for your advice - the issue was indeed a knackered Rego box, with failing capacitors. This manifested itself with dodgy values being reported, fading screen, and reboots.

Some people seem to be upgrading the electronics to the new Rego 1000, but this needs a 3 phase supply.

This resource was the critical piece I needed - step by step instructions on what to do. The only strange thing is that everyone there had 1000uf capacitors in their boxes, but mine had 3300uf 25v installed - but replacing them with 1000uf is working fine.

Some panic after I got it installed - it came back to life but seemed as though the pump wasn't working as the GSHP just got too hot and and no hot water came out the top. I switched using the installer menu to the electric backup only mode, and that too overheated after an hour.

Replaced the capacitors once more in case by dodgy soldering had failed, but had the same issue. Took some time to think what beardymarrow and lstevensuk would say, and went back to first principles - my red expansion vessel was showing a 0 value on its gauge, turned its little tap, and everything immediately gurgled back in to life and the hot water tank started heating up straight away. After a week without hot water I was giddy 😂

Thanks once again - and let me advise IVT / Worcester owners to order in a couple of capacitors for a quid, just in case!

beardymarrow

https://forums.moneysavingexpert.com/discussion/comment/82061170#Comment_82061170

Amazing work! Well done, and that site is really useful. Thanks for the link.

Regarding the 1000uF vs 3300uF, I don't know exactly what function they perform, but at that voltage and capacity likely to be power filtering, rather than timing, so the 3300uF would provide more ability to filter out larger spikes and dips than the 1000uF. So you're probably alright as you are, but I'd be nervous personally and want to replace with what was installed originally if I was you when I could.