Saturday, October 9, 2010

Tuning the IVT Greenline C6

9 Oct '10: Mr BoDidly on the Navitron forum asked a question about the IVT Greenline C6 heat pump, which is the same model as mine. 
Bodidly has a shallow ground loop that is in a groundwater condition and after heavy rain, the water rises to the surface, so this is partially a water source heat pump - the earth is in effect, warmed by rainwater. As it has a huge latent heat of freezing, that's quite an efficient source of energy for the HP.

There were some other good replies, and here is mine,
I have done seven things to my IVT:

1. The 'ChargingtheEarth' circuit with solar panels to recharge the earth store.
(This technique cannot be used by BoDidly, because he has active groundwater in the earth around his ground loop. His groundwater is charging the earth in effect, because water has a big latent heat of freezing.)

The following could all be done to any IVT heat pump and all have been done to mine with the approval of Ice Energy:

2. Insulate internally - There are internal system inefficiencies in the IVT that cause the expenditure on Hot Water to be excessive, that can be solved simply by taking as much of the casing off and insulating the tank. I used superthin insulation like Aktis, formed into pads. In Sweden, people tend to put their GSHPs into garages or outhouses, and the air temp falls to -20ºC so the HW tank is deliberately poorly insulated to stop the machine from icing up. My GSHP is in a heated utility room. I have had the casing off and super insulated it, and once it reaches the right temperature it stays above the target temperature for many hours. For example, today, it has not fired up yet because it was at a good temp at 10pm last night, and its is now 12 hours later and still no need to run.
(Take the front panel off your IVT, reach under and tap the bottom of the water tank.... what do you find? completely naked copper bottom!)

3. Insulate externally - Check that most pipes coming into the IVT are insulated, to reduce system losses. Even the Cold water supply pipe gets very hot, as there is a direct metal link from the tank to the exterior.

4. Fake Thermal sensor- A small fix to stop the heating circulating pump from running when the night temperature drops in spring and autumn night times - my wife cannot stand the sound of pipes running at night. We have a small resistor that imitates the signal of the exterior thermistor - my resistor fools the GSHP into assuming that it is 25º outside. A two way light switch can simply change from one to the other, and we turn it off at 10pm, and on again at 9am. The 4.7 kOhm resistor cost 17 pence from Maplins. I have now set up a simple Timeclock to turn this off and on, but it needed an Omron relay to operate the switch.

5 Timeclock - the IVT has an internal timeclock, and you can save night time heating by simply adjusting it with that timeclock to turn water and space heating off during certain hours. The IVT's timeclocks can manage Heating and Hotwater independently, turning off the heating, or turning down the heating at night.

6. Telecommand - if this is activated, you can disable the heatpump , e.g. at night with a method that was designed to enable the GSHP to be managed with a mobile phone or external controller. Again, we have a simple Light switch to turn the compressor off and on remotely, leaving the GSHP running. At the moment it is able to turn the Hot Water on and off, and we leave the Fake Thermostat to manage the heating.

7. Cylinder Thermostat - As the hot water frequently gets too hot - on the IVT it is sometimes reaching pasteurisation temperatures every day - I have fixed a standard cylinder thermostat to the metal surface of the water tank, and this can use the Telecommand to turn the Hot water off if it is overheating. The tricky bit is that the metal surface is not the water tank, it's the jacket around the watertank, and so you need to set it to about 72 degrees to get the water tank heating to stop at about 55 degrees. If your heat pump is of the type that has a pipe coil inside the tank, then adjust the temperature accordingly.

I could do these as a package deal, as a sort of travelling IVT 'vet' and I could turn up and run through the list 2-7.

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