Random experiment with portable AC unit

[copec]

I have a couple of twin hose portable AC/Heat Pump units. I live about 90 minutes East of Vegas. It’s not like this isn’t a common thing with large facilities compounding evaporative cooling towers with refrigeration cycles, but I thought I would experiment a little with the unit in my garage by pointing a portable evaporative cooler into the intake of the portable AC unit and measure power and temperatures.

At 6:30PM today the intake temperature was ~100F, with the outlet being ~145F, and the unit taking ~1.1kw. Indoors the intake temp is ~77F and the outlet is ~42F.

After turning on the evap cooler and waiting about 10 minutes for the temperatures to stabilize, the outdoor intake was ~71F, with the outlet ~135F. Indoors the intake was ~76F with the outlet ~31F, the power usage dropped to ~900W as well. The evap cooler on low takes ~80W.

So hugely beneficial with my 8% relative humidity right now. I don’t know exactly know how much water the evap cooler consumes, although I converted my yard to xeriscape a couples of years ago, so all-in-all I’m consuming a fraction of the water I used to anyways.

 

[acdoctor]

Just keep an eye on the evaporator coil for frost. Frost will impede the air flow and efficiency will reduce.

 

[BradCagle]

You could build a cowling/reducer on the front of the evap cooler that couples directly with your AC condenser inlet hose.

Then maybe disconnect the fan in the evap cooler, and only run the water pump. Let the fan in the AC condenser pull the air through the evap cooler.

 

[copec]

You could build a cowling/reducer on the front of the evap cooler that couples directly with your AC condenser inlet hose.

Then maybe disconnect the fan in the evap cooler, and only run the water pump. Let the fan in the AC condenser pull the air through the evap cooler.

Yeah, I was thinking the same thing, and make a somewhat nice looking box covering for it.

 

[copec]

I put 6 mister nozzles pointed at my 2001 AC condenser and when the intake air is over 110F it pulls 2kw less with about 2/3rds the duty cycle. I checked the capacitors and had an AC tech check the refrigerant levels at the beginning of the season.

I’m going to connect the 24vac signal wire to a SSR to power a sprinkler valve to turn on the misters. I already have two different types of filters on the water, but I think I’m going to dedicate my rainwater collection to it (with a particulate filter).

@acdoctor Do you have recommendations for hvac tools if I want to experiment? I want to convert an old two ton window AC unit in a liquid to liquid heat pump to simultaneously heat and chill storage tanks as a form of energy storage.

 

[BradCagle]

holy shit, 2kw less is significant.

I had an idea for AC condenser unit. Hook up a 220v grid tie micro inverter (with a few panels connected to it) to the compressor side of the contactor. This way you only grid tie when the compressor is on, and using up all the solar power preventing export.

 

[73powerstroke]

We used to spray the back of window units when it was really hot. I have one of those portable ac units. A delongi penguinio or something. Only has a outlet vent. Never has worked well enough to use.

 

[Wet1]

I had an idea for AC condenser unit. Hook up a 220v grid tie micro inverter (with a few panels connected to it) to the compressor side of the contactor. This way you only grid tie when the compressor is on, and using up all the solar power preventing export.

Keep in mind it takes a while for the micro inverters to do their self-tests and kick on once they see the grid. Depending on the MI, there can be a lengthy delay, which becomes problematic if your system cycles on and off frequently.

 

[BradCagle]

Keep in mind it takes a while for the micro inverters to do their self-tests and kick on once they see the grid. Depending on the MI, there can be a lengthy delay, which becomes problematic if your system cycles on and off frequently.

Good info, thanks. Here in Texas our ACs never stop unless they're dead

 

[Wet1]

Being in CT we see a lot more cycling, but I can certainly understand in your case that thing likely runs 24/7 for a good portion of the year!

 

[BradCagle]

Being in CT we see a lot more cycling, but I can certainly understand in your case that thing likely runs 24/7 for a good portion of the year!

Out of curiosity, what do you think the avg startup time is for a micro inverter?
I have not used them, but really thinking about doing one on my pool pump. It run's on a timer 6 hours a day.

 

[Wet1]

Out of curiosity, what do you think the avg startup time is for a micro inverter?
I have not used them, but really thinking about doing one on my pool pump. It run's on a timer 6 hours a day.

I've never timed them, but they are forced to have a startup delay. If I had to guess I'd say it's probably around a couple of minutes. Maybe contact the mfg of the MI you're intending to use to get more accurate numbers.

For a pool pump that's running for 6 hours straight, it's not much of a concern.

 

[stienman]

If possible, can you measure the humidity as well?

I have a couple of twin hose portable AC/Heat Pump units. I live about 90 minutes East of Vegas. It’s not like this isn’t a common thing with large facilities compounding evaporative cooling towers with refrigeration cycles, but I thought I would experiment a little with the unit in my garage by pointing a portable evaporative cooler into the intake of the portable AC unit and measure power and temperatures.

At 6:30PM today the intake temperature was ~100F, with the outlet being ~145F, and the unit taking ~1.1kw. Indoors the intake temp is ~77F and the outlet is ~42F.

After turning on the evap cooler and waiting about 10 minutes for the temperatures to stabilize, the outdoor intake was ~71F, with the outlet ~135F. Indoors the intake was ~76F with the outlet ~31F, the power usage dropped to ~900W as well. The evap cooler on low takes ~80W.

So hugely beneficial with my 8% relative humidity right now. I don’t know exactly know how much water the evap cooler consumes, although I converted my yard to xeriscape a couples of years ago, so all-in-all I’m consuming a fraction of the water I used to anyways.

The only bad things I've heard about this are 1. frost (already pointed out) and 2. Corrosion/accumulation on the grid, and 3. dealing with water going in unexpected directions.

If the water has low pH (acidic) and/or too soft, then it'll eat through the evaporator. If it is high pH and/or hard water, then you'll need to clean the evaporator occasionally as the calcium, metals, and other dissolved materials stick to the evaporator coils.

Also, for others looking at this thread, this has lower performance in humid environments, and works best in arid areas. In humid areas the evaporative unit can't put much more water into the air, so unless you're spraying water over the coils then the best it can do is cool the incoming air to the ambient temperature of the water you're putting through the evaporator.

 

[copec]

I’m going to instrument it and log everything including humidity. We are about as arid as you can get where I live, but this uses a small fraction of the water that my yard used to use before I converted it to xeriscape so I don’t feel bad about it.

I've been using a raw carbon filter to remove most of the minerals, inline with a calcium inhibitor after. I've noticed that a white dusting of minerals appeared after about a week, but they easily brushed off with a scrub brush.

We have highly "minerated" water, as the well that feeds all the potable water is in Snow Canyon State Park that is pretty much all Navajo Sandstone: https://goo.gl/maps/PGtkb9vt8Q3pRBPL8

 

[Wet1]

Out of curiosity, what do you think the avg startup time is for a micro inverter?
I have not used them, but really thinking about doing one on my pool pump. It run's on a timer 6 hours a day.

I've never timed them, but they are forced to have a startup delay. If I had to guess I'd say it's probably around a couple of minutes. Maybe contact the mfg of the MI you're intending to use to get more accurate numbers.

For a pool pump that's running for 6 hours straight, it's not much of a concern.

I timed an Enphase IQ7 series microinverter for you today, it was pretty close to 5 min from when it sensed the grid signal to kicking on. Other mfg might be different though.

 

[ChrisG]

holy shit, 2kw less is significant.

I had an idea for AC condenser unit. Hook up a 220v grid tie micro inverter (with a few panels connected to it) to the compressor side of the contactor. This way you only grid tie when the compressor is on, and using up all the solar power preventing export.

I was thinking something similar to the load side of a Pool pump timer. Run pump from 8am to 8pm it will always consume the microinverter power. Pump uses 1650w (240v) when running.

 

[BradCagle]

I was thinking something similar to the load side of a Pool pump timer. Run pump from 8am to 8pm it will always consume the microinverter power. Pump uses 1650w (240v) when running.

Absolutely! I plan to do this with my pool pump too.
I want to build a pergola with these

But not sure if I can find a micro inverter that will handle the voltage. Might just have to put standard panels on my pool house roof.

 

[copec]

Absolutely! I plan to do this with my pool pump too.
I want to build a pergola with these

But not sure if I can find a micro inverter that will handle the voltage. Might just have to put standard panels on my pool house roof.

There are a few off-grid inexpensive inverters now that have a mode that will use as much PV available in a zero-export mode to cover the load, and if the load is higher than the PV it is essentially just supplementing the grid power the same as a grid-tie microinverter.

 

[bgflyguy]

The growatt 5000es works this way. No battery required.