Heat pump / inverter DIY

Cardew

paceinternet wrote: »

well this is what you said:
"It's the indoor unit that is connected to the 240v supply, and this is what I have plugged into a KWh monitor."

Presumably you meant "outdoor unit" ?

Paceinternet,
If you see the video of the installation the Maplin meter and inside units are quite clearly connected to a 13 amp socket.

So the major consumption of each ASHP system - the outside unit with compressor - is not being monitored.

That of course explains everything!

thechippy

I'll try to expand on the wiring....

Most inverter heat pumps these days that are less than around 5kw nominal output, have the power supply directly to the indoor unit. This can be a fused spur, or from a 13a switched outlet. A cable runs from the indoor unit to the outdoor unit. This cable will supply the main live, neutral and earth to the outdoor unit. It will also have the 2 or 3 wire control circuit. In such a case connecting the energy monitor to the socket or spur will give the entire system consumption.
On larger systems, the power supply feeds the outside unit. An interconnecting cable will then feed the L, N & E to the indoor unit, plus the control wires, so you would have to monitor the supply that feeds the outdoor unit. In either event, the law is such that the supply to the outdoor unit is capable of being isolated by a suitable weatherproof switch within 2m of the outdoor unit.
Does this make sense?

stevehead

thechippy wrote: »

I'll try to expand on the wiring....

Does this make sense?

I hope so! My posts just seem tp be making matters worse

anthonykeates

So:

Indoor unit connected to 13a plug.

Power supplied to outdoor unit via cable.

Outdoor unit isolated from the supply from the indoor unit via a switch (weatherproof, outdoors).

Therefore monitoring the power from 13a plug to the indoor unit will monitor the power consumption overall for both indoor and outdoor units.

Is my understanding correct!!??

thechippy

anthonykeates wrote: »

So:

Indoor unit connected to 13a plug.

Power supplied to outdoor unit via cable.

Outdoor unit isolated from the supply from the indoor unit via a switch (weatherproof, outdoors).

Therefore monitoring the power from 13a plug to the indoor unit will monitor the power consumption overall for both indoor and outdoor units.

Is my understanding correct!!??

Yes, quite correct. The power consumption of the indoor units alone is very low!

stevehead

Cardew wrote: »

Stevehead,

How do you explain that the maximum power shown on the Maplins Monitor is 360watts when your unit input is 1,237watts?

That 360W is not the maximum draw, it's the realtime draw. I've often seen the Maplin monitors hit 1300W during the startup cycle.

paceinternet

Thanks to "thechippy". Apologies to "stevehead". I've only ever seen what you describe as the "larger systems" method, but your manual on page 10 does show the power supply going to the indoor unit.

Cardew

thechippy wrote: »

Does this make sense?

That is what I suggested in post # 146 could be the only way that the monitor could work - but Steve's post contradicted that - especially when he said Richard had explained it well.

The wiring Diagram on page 11 does not show it wired as you suggest.

If it is wired as you suggest how is the maximum consumption monitored only 360watts - less than 30% of the maximum input?

Cardew

stevehead wrote: »

That 360W is not the maximum draw, it's the realtime draw. I've often seen the Maplin monitors hit 1300W during the startup cycle.

The maximum power output is 4,600watts and it clearly shows that it will take 1,237 watts to produce this.(at 7C/20C)

anthonykeates

Cardew wrote: »

The maximum power output is 4,600watts and it clearly shows that it will take 1,237 watts to produce this.(at 7C/20C)

Blimey, I dunno what to believe any more!

Max output of 4600w using 1237w to produce it would be a COP of 3.72 wouldn't it (or is the equation more complex than that?).

So if SteveHead's electric usage was 300kwh for Dec, multiply by say 3.72 = 1116kwh, compared to 3-4000kwh the previous year? If his boiler was only 50% efficient (think before it's been said before somewhere that it is old and inefficient) that would be 1500-2000kwh of actual heat. If the house has since been properly insulated it wouldn't be unfeasible to get a 500kwh reduction in the heating requirements would it? Plus his Gas usage included DHW and cooking, so that would further reduce the differential.

I'm no expert, but I can kind of see how the figures might stack up assuming my back-of-a-fag-packet calcs are roughly along the right lines. Also different weather conditions would have to be taken into account between Dec 2007 and 2008.

Any thoughts??