GSHP - I need help with making it as efficient as possible!

Reed_Richards

countryhouse39 said:

... the immersion is switched off, if it was on it would just work continuously until we switch it off and we'd have boiling water in our HW tank 

Or an exploding hot water tank, that would be enormously dangerous - but fortunately it does not happen.  If you remove the immersion heater cover you will see a little dial with a pointer.  The number on the dial that the pointer points to is the temperature that the immersion heater will heat to before it cuts out.  You will also see a little plastic rod sticking out of the unit.  That is the safety cut-out and will be set to about 80 C.  If for some reason the first cut-out fails (or is set too high) then the rod will pop out, triggering a safety cut-out.  So there is minimal danger of ever boiling the water in your cylinder using your "auxilliary heater".       

countryhouse39

Reed_Richards said:

 So there is minimal danger of ever boiling the water in your cylinder using your "auxilliary heater".       

Yes, I agree, the auxillary heater wont overheat from what I can gather, but the separate immersion heater we have attached to the HWT  - which is switched off at the fuse - just stays on as far as I know as the people before us left it on when they left and we got a ridiculous bill the first month we were here (and that was well before crazy price rises!). So thats why that immersion is kept off, plus we dont need it as far as I can tell  - other than the rare occasions we have had a problem with the pump where we have then been able to still get HW when the pump is off, and we have also been able to get more HW fairly quickly if we have people staying and use a lot more than usual (6 showers in the morning for example!). 

Whether we have the auxillary heater that is part of the pump set up correctly I have no idea though. pic attached of the info for that on the heat pump controls. I think we were told a while ago (years ago now) by a valiant engineer that 4 deg was about right for the temp for coming on, but maybe its not right? Also attach image of stats for how often its on ( i think this is since installation, but no idea tbh!)

Magnitio

Is your heat pump the type shown here:

https://www.vaillant.co.uk/downloads/aproducts/renewables-1/geotherm/geotherm-exclusive-operating-manual-261471.pdf

If so, can you see the stats in the example shown below that are in section 5 of the manual?

countryhouse39

@Magnitio - yes, it is a geotherm. 

Attached is that screen…

Reed_Richards

countryhouse39 said:

the separate immersion heater we have attached to the HWT  - which is switched off at the fuse - just stays on as far as I know as the people before us left it on when they left and we got a ridiculous bill the first month we were here (and that was well before crazy price rises!). 

It might be worth removing the cover to see what temperature it is actually set to.  This may expose wires so be sure it really is switched off and don't touch the wires just to be certain.  I don't see that it should be set to anything more than 60 C.

The ridiculous bill and your current issues might suggest that the hot water cylinder is losing heat a lot more rapidly than it should.  Assuming that you do not have a hot tap left on somewhere,  could this be a failure  of or lack of insulation of your hot water system?  

markin

Is it in a heated part of the house and all pipes lagged?

Reed_Richards

countryhouse39 said:

Whether we have the auxillary heater that is part of the pump set up correctly I have no idea though. pic attached of the info for that on the heat pump controls. I think we were told a while ago (years ago now) by a valiant engineer that 4 deg was about right for the temp for coming on, but maybe its not right? Also attach image of stats for how often its on ( i think this is since installation, but no idea tbh!)

Well the compressor hours is equivalent to about 3.25 years.  During those hours the auxiliary heater is on about 8% of the time which should mean that about 8% of the time your heat pump is running it is 4 C or less outside.  That seems a lot to me.  Check that the auxiliary heater hours is not going up, or only going up when the Legionella cycle takes place, as you think it used then.

You should also be able to read the temperature of your hot water cylinder.  You could check that this is not falling too rapidly when the hot water is not being used.  There might also be a setting for how low below the set temperature the cylinder has to get before it is re-heated. 

Magnitio

countryhouse39 said:

@Magnitio - yes, it is a geotherm. 

And does it have an integrated hot water cylinder or a seperate hot water cylinder, or both? If a seperate hot water cylinder, is it located in a different part of the house to the heat pump?

countryhouse39

Magnitio said:

And does it have an integrated hot water cylinder or a seperate hot water cylinder, or both? If a seperate hot water cylinder, is it located in a different part of the house to the heat pump?

See attached pic - L-R: HW tank, buffer tank & heat pump - all housed in the pump room, which is a store area attached to our house, but the room isnt insulated -  accessed from the garden. 

countryhouse39

Reed_Richards said:

Well the compressor hours is equivalent to about 3.25 years.  During those hours the auxiliary heater is on about 8% of the time which should mean that about 8% of the time your heat pump is running it is 4 C or less outside.  That seems a lot to me.  Check that the auxiliary heater hours is not going up, or only going up when the Legionella cycle takes place, as you think it used then.

You should also be able to read the temperature of your hot water cylinder.  You could check that this is not falling too rapidly when the hot water is not being used.  There might also be a setting for how low below the set temperature the cylinder has to get before it is re-heated. 

Hmmm...is 8% high? we are in Scotland... I'm not sure that its beyond the realms of possibility that for 8% of the time the pump is on (so when its cold enough to need heating) that its 4 deg or less outside. I don't really know how to check if that's crazy or not though. 

I'm not keen on fiddling about with things where there are exposed wires etc  - that's beyond my comfort zone, but will ask engineer to check when he's back fitting the new meter.