What should the power draw be on this heatpump?

Forums › Home Workshop DIY › What should the power draw be on this heatpump?

E3xtc

773 posts

Ultimate Geek

#242188 15-Oct-2018 13:25

Seems like a real basic question - but wanting to confirm this so I can understand whats happening. We have the Ci17 heatpump (as detailed here http://www.oasisheatpumps.com/pdf/Oasis-Inverter-Swimming-Pool-Heat-Pump-Specifications-2017.pdf) and reading that spec doc, am I correct in thinking that it shouldn't be drawing any more than 2.86kW of power? I could swear when I last looked at it, it was reporting using approx 4kW :\

Aredwood

3885 posts

Uber Geek

#2108172 15-Oct-2018 13:33

How are you measuring that power draw? As lots of devices don't compensate for power factors. Meaning they will often overread power usage on electric motor and electronic device loads.

Try switching off everything in your house except for the heatpump. And see what your electricity meter reports the usage to be.

E3xtc

773 posts

Ultimate Geek

#2108173 15-Oct-2018 13:34

It has a screen/graph on the unit itself reporting the power use and water temps etc

Aredwood

3885 posts

Uber Geek

#2108188 15-Oct-2018 13:50

Maybe the inbuilt measuring device is not power factor aware. Meaning that the numbers it is reporting are actually KVA and not KW.

If the inverter doesn't have active Power Factor Correction. The measurement device will over read by 40% or so.

Check that you don't have a fault. Poor water flow through the heatpump will cause excessive power usage.

Otherwise just add your own external monitoring.

Jaxson

8043 posts

Uber Geek

Trusted

#2108202 15-Oct-2018 14:18

Might be reporting it's heat/cooling output, rather than it's device consumption?

E3xtc

773 posts

Ultimate Geek

#2108203 15-Oct-2018 14:18

Ahh interesting; there are flow restrictor valves installed, as the installer said that they perform better if the flow is restricted...but I wonder if maybe they are restricting things too much...

Interesting also to hear the power factor correction - as that would land exactly on the mark (ie its reading 4kW and the spec sheet shows 2.86kW - ie a 40% diff)

Thanks for your input Aredwood

Aredwood

3885 posts

Uber Geek

#2108543 15-Oct-2018 22:08

Check the temp difference between the water inlet and outlet pipes when the unit is running at max output. Typically with pool heaters, there should be almost no temp difference. As there should be plenty of flow so the heat exchanger can work at max efficiency. Otherwise you get higher than necessary compressor discharge temperature and pressure. Which means lower efficiency and more stress on the compressor.

The installation instructions should give a recommendation on the ideal flow rates.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2109110 16-Oct-2018 20:30

Rated current is 17.2A and that's pretty much exactly 4kW. Definitely sounds like that, though it's a daft mistake for them to make.

As above, check your revenue meter and turn off big loads (cooking, hot water, heating) and you should get a pretty good idea of what it's drawing.

Quic Broadband

Move to New Zealand's best fibre broadband service (affiliate link). Free setup code: R587125ERQ6VE. Note that to use Quic Broadband you must be comfortable with configuring your own router.

Kickinbac

427 posts

Ultimate Geek

#2110623 18-Oct-2018 19:29

Do you have access to a clamp meter? If you can measure the current draw you can work out the power consumption.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2110635 18-Oct-2018 19:30

Kickinbac: Do you have access to a clamp meter? If you can measure the current draw you can work out the power consumption.

Depending on the model, loading etc, power factor may not be good. So you need a clamp meter that can measure power, not just current. A bit rarer.

Kickinbac

427 posts

Ultimate Geek

#2110636 18-Oct-2018 19:36

I may be wrong but I always understood that inverters (which are basically variable frequency drives) corrected the power factor.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2110637 18-Oct-2018 19:38

Kickinbac: I may be wrong but I always understood that inverters (which are basically variable frequency drives) corrected the power factor.

Some do. I believe some can be quite capacitive, and the correction is often calibrated for full load - operation at lower loads isn't such an issue because the current is lower than maximum anyway.

I have planned to do some proper measuring but haven't gotten around to it.