Split System issue? Energy graph interpretation

[Potluck_Crew]

We are still trying to figure out our energy draw. Finally got an energy monitor on the split systems, that are currently turned off at the inside units.

The Blue graph is what I expected with defrost cycling. But the orange one looks out of wack! These are each 2 zone outdoor units.

Any suggestions would be appreciated!

 

[woodgeek]

Huh. Unlike other appliances, the max draw labels on HPs are not a useful as a gauge of actual usage. The compressor draw in use will depend strongly on outdoor air temp (higher draw at higher temps), outdoor dew point (higher draw at higher dew point) and degree of coil icing (time since last defrost cycle).

I assume the spike is a defrost cycle. If your strips are 20 kW and run for 10 minutes, there you go.

This is bc the compressor is compressing gaseous refrigerant such that it evaporates in the outdoor coil and condenses after throttling in the indoor coil. The work it has to do has to do with its volumetric flow rate (which is more or less fixed by the pump displacement and RPM) and the vapor pressure of the refrigerant that is evaporating, which is higher at higher outdoor coil temps. You can look up tables for current draw and BTU output. Goodman posts those, and I found them to be quite accurate for my split system. Other makers are shy about posting their tables.

Here is a goodman table: https://www.goodmanmfg.com/pdfviewe...ee64f0022fa6258827eff0c00754798.pdf?view=true

For your case, look up the goodman model with the same ASEE tonnage, SEER and refrigerant, and it will likely be close...bc the makers all use the same parts and scroll compressors.

OK... just noticed that the units are OFF. LOL. Looks like the units are cycling something like a defrost even when off. No bueno.

Why not flip off the breakers? In that case, I would let them 'warm up' for a few hours after flipping the breakers on before running them.

 

[stoveliker]

There was a thread on that (cycling some heat when not in use, breaker, and the need for letting it heat up a bit before use after switching on the breaker again) a year or so ago.

 

[Brian26]

We are still trying to figure out our energy draw. Finally got an energy monitor on the split systems, that are currently turned off at the inside units.

The Blue graph is what I expected with defrost cycling. But the orange one looks out of wack! These are each 2 zone outdoor units.

Any suggestions would be appreciated!

View attachment 293423View attachment 293424

It looks like the compressor turned on for 3 or 4 minutes between minutes 49-53 at full power. The maximum compressor wattage for your Mitsubishi is listed at 2,620 watts on the submittal. Mitsubishi also has a compressor minimum run time of 3 minutes or 4 minutes.

How is the mini split controlled? With the remote or a wired thermostat? It looks like it called for heat but it short cycled off after the minimum runtime as it probably satisfied the thermostat setting. A defrost would have two spikes back to back. The blue line looks like its the compressor heater running. They come up on electricity graphs wavy like that. I think Mitsubishi uses either 30 or 50 watts on the compressor heaters.