Ämne: How to repressurize ground loop

[spenwade1]

Hey all. Hoping someone can us with what feels like it should be an obvious answer - but we can't figure it out!

The ground loop on our IVT Greenline Plus C7 is down to 0.6 bar. We've checked and topped the expansion vessel but can not for the life of us figure out where the supposed mains water fill valve is to repressurise the ground loop? I think it should be near the expansion vessel on top of the heatpump - but there's no flexible hose or valve or anything like that. I've attached a picture of our heatpump - am I missing something obvious?

We've been having issues with a regular alarm about the "High HTF Delta" between GT8 & GT9. It's still running and producing both heat and hot water but we obviously want to get it fixed before winter. We tried a couple of heat pump engineers and after replacing the sensors, they've decided it needs to be completely drained and clear all the pipes of a potential blockage before refilling - quoting this as a 2 man, 2 day job and about £3k.

Tbh, at that cost - we're considering just replacing the whole unit since it's 15 years old now.  But we'd like to try out repressurizing the loop first before going down either the expensive hopeful repair or replacement route. I'm not sure why our heat pump engineer didn't try this first though - am I just being optimistic this might  our issue?

[Carl N]

Hi!
The pressure on the ground loop on 0.6 bar is not any problem.
It can't be pressurized easy, you need special equipment for this, but 0.6 bar is enought, I have acually 0 bar om mine.
It works with 0 pressure on ground loop, as long as it don't get too much air in the loop.

The temperature difference between T8-T9 is a well known issue, there is 2 flexible hoses attached inside the heat pump that usually get klogged with magnetite (from the radiators).
It is a easy job to just switch these flexible hoses, you can also take them down and clean them inside, the magneitie is hard so it take some violence to get it out of the hoses.

[Spencer]

Hi Carl,

Many thanks for responding to this - it's really appreciated! 

Do you think the flexible hoses would still be an issue in a system without radiators (the house is heated entirely via plastic based underfloor heating)?  If so, does the system need to be drained in order to remove and clean (or just replace) the hoses or should this be possible by closing some isolation valves?

Interestingly, the response from Alto Energy to the low flow problem is this... "I would recommend checking the pressure (if its not at 1.5, top it up using the filling loop) and cleaning out the filter. It may be that the hoses inside have collapsed but there will be a restriction of flow somewhere".  As you say, it looks a bit more involved than simply "using the filling loop"...:0)

Thanks again!

Spencer

[Carl N]

Did they understand that the problem with T8-T9 is not related to the ground loop?
T8-T9 measures the temperature difference of the heat flow and this is separate from the ground loop, there is no connection between them.
If you get a low temperature alarm on T10 or T11, it may be related to pressure on the ground loop.

Usually underfloor heating does not cause problems with magnetite in the flexible hoses, that is good information.
But underfloor heating usually has an external circulation pump that also creates a small flow inside the heat pump, even if the internal circulation pump is stuck.

It can be difficult to detect that the internal circulation pump is broken, it can vibrate and then the feeling is that it is okay.
The best way to check the pump is to remove the center screw and see inside that the impeller is rotating.

[Spencer]

Hi Carl,

I suspect that this may simply have been a misplaced assumption on our part - when Alto said "...checking the pressure...", we've assumed they meant the ground loop pressure as engineers who've been out to look at the HP have speculated that the problem was on the ground loop side.  Since Alto's original message, however, they've since asked us to check that manually starting the P2 pump through the menu gets the internal pump going (which it seems to - it immediately whirrs and I can feel it vibrating but I'll have a go at removing the screw as you've suggested to be certain).

At the moment, there's no UFH running as it's so warm here so simply running the hot water alone is enough to trip the alarm.  We often seem to find that the hot water considerably overshoots its target temperature - current target is 39c but after a hot water cycle, the actual temperature often hits 50c (and not just on its Legionella cycle) so perhaps this is indicator of where we should be looking for a problem (although, we've only been looking closely at the temperatures since the problem began so perhaps this isn't unusual behaviour for the HP...).

Thanks for your in pointing us in what feels like a more promising direction (certainly more promising than the ground loop direction it seems!).

All the best!

Spencer