Power monitoring for L14-20P commercial refrigeration unit with data logging

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geyersm
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Hi,

I've got a product development project going and at this stage I need to be able to monitor and record the watts or kw-hours of a commercial refrigeration unit (similar to the open-face refrigerators you would find in your local grocer). Unfortunately, neither myself or the other engineering student in the group have any real electrical experience. The problem that we seem to be running into is finding a power meter with data logging capabilities that can connect to the higher voltage/amperage of the power supply and the physical plug and receptacle that the unit uses. The solution also has to be relatively inexpensive, as our budget is very limited.

The plug out of the fridge is a L14-20P (125/250V, 20A) which connects into a matching L14-20R. The affordable units that do what we need all use three-wire adapters and we have been warned away from trying to wire the 4-wire L14-20 into a 3-wire.

I'm pretty stumped at this point. I need to be able to monitor the unit continuously for several days, while it records watt readings, and then download the data to my laptop for analysis. If anyone has an idea for a solution, or even just some suggestions on what direction to go in, what to read, etc., I would really appreciate it.

Thanks and cheers.
 
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If you are in the UK try contacting Livingstone Hire, I neither work for or own shares in the company.
If you are outside the UK try test equipment rental.
 
""The affordable units that do what we need all use three-wire adapters and we have been warned away from trying to wire the 4-wire L14-20 into a 3-wire.""

if you do it yourself you'll have to figure out how the wattmeters and fridges are wired.

i'd suggest instead contacting a wattmeter supplier's sales office with this question:

"I want to use your (insert model) wattmeter to monitor a refrigeration machine that has L14-20 plug.
Nameplate of the machine says (insert voltage, amperes, and kw if on nameplate).
What adapter do i need to purchase from you? ""

and when it arrives verify with an ohm-meter that it does NOT interrupt the safety Earth wire.
Earth wire will be the longest of the four contacts on the plug - first to make on insertion and last to break on removal.