How to measure cycling time of my reefer compressor?

[jpendoley]

For you refrigeration gurus-I have an AB Cold Machine CU 100 on my boat cooling a 7-8 cu foot spillover box with a 2 cu foot freezer. I think it was purchased in 2003 or so and came with the boat. I reinsulated the box to r30-40. It runs 7 x 24 in New England all summer. I run it off 240 W solar and with occasional help from a wind turbine and when I motor-boat is on a mooring. 400 amp LA Trojan bank. All things considered, I am pleased with the setup, but I don't really know how much energy it draws in a 24 hour period.

I have measured the amp draw with a clamp meter and it seems to be pulling 3 amps. That is the compressor is running and the fan is whirring away. But I don't know how often it cycles on and off when I am gone. How can I get that count to calculate the draw over a 24 hour period? Is there some kind of a counter device that will track the overall runtime per hour? I'm thinking it probably is on 30 mins or more per hour, but I don't really know and I am trying to tune my energy budget. Standing by for the education
Jim

[sailormed]

Buy a cheap clock on 12V and put in parallel to your compressor feed. Check after xx hours/days/weeks and you have your running time figure.

[sailjumanji]

I use a Sensor Push Smart Sensor HT1 that measures and records humidity and temperature. You can put an app on your phone or tablet, and download the data thru bluetooth. It plots up the temp and humidity vs time, and its very easy to see the cycling. Also good to be able to confirm the temperature range of your fridge, without having to open it.

It's probably easiest to pick the compressor starts and stops from the humidity curve. If in the app, you can touch the graph and it places a line on the time, which you can slide back and forth to pinpoint startup/shutdown.

I am using Isotherm Intelligent Temperature Controls (ITC) on both my fridge and freezer. Once calibrated using the SensorPush, you get unit internal temps at a glance. Each comes with its own thermostat wire (shown installed in the freezer). On our Dometic Cruise Classic 130 refrig, we had problems with the thermostat getting enclosed in ice and not sensing internal temp, and not holding the proper temp. Moving the thermostat away from the cold plate - i.e., installing the separate ITC thermostat - solved the icing issue.

Got no clue why the last pic is sideways!

[Richard Kollmann]

If your unit only draws 3 amps and runs less than 30 minutes per hour with that size of your box there is little you can do to reduce daily energy consumed.
There are 12 volt cycle meters and 12 volt hour meters ether on connected to the control module terminals Small + and F will meter only when condenser fan runs on that unit. Yes fan runs when compressor runs. Do not connect it to thermostat as that circuit is less than 5 milliamp. Also do not connect to units power wires if you want cycle times.

[jpendoley]

Thank you everyone for the suggestions. After a little research, I found out there is such a thing as a DC digital hour meter. Simple install, it is even resettable. I think that is what Sailormed was suggesting. $13 on amazon.
Now I know how to measure total run time over a period of time. Cheaper than buying a Link 10 ampmeter. Seems like a handy thing to have.

The Smart Sensor looks useful too-would enable me to graphically see the effect of changes I make-just a little spendy...

[Clivevon]

I was going to suggest wiring in an engine hour meter but you seem to have it sorted?

[jpendoley]

Clivevon-yes, I do, thank you. Simple thing, but never had the need for one. Now that I know, will be installing an engine hour meter for my recently rebuilt Perkins as well. Cllassic case of too soon old too late smart in my case....

[Clivevon]

Classic case of too soon old too late smart in my case....

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