AC temperature operation range

[Dfarland]

I am going to add some soft starters to my AC units before this season. How warm does it have to be to safely test them post installation? Is it 60 degrees like a home ac unit?

[dutchmensport]

if the temperatures are too low for the thermostat to tell the air conditioner to turn on, you can always take a hair blower and blow it directly on the wall thermostat. The blow dryer will blow hot air against the thermostat and the thermostat will think the ambient temperature is 120 degrees.

Or, turn the furnace on in your camper and warm the inside up to about 80 degrees. Then flip it over to AC and lower the temperature setting as low as it will go. The AC will also kick on. The AC is not dependent or restricted turning on and off based on the outside temperature of the camper. It's the temperature at the thermostat inside the camper that important.

[CedarCreekWoody]

The OP is asking at what Temps it is safe to run the refrigerant, not how to make the thermostat work. Hopefully one of the a/c folks can answer that.

[Brentw]

Not an AC guy, but I know larger units have a high pressure ( occurs when trying to operate at to cold of ambient temperatures) this will not allow the compressors to start up. I can only assume that RV units will be the same.
Don't know the temperature, but I do not believe you can hurt it, the compressor just will not start.

[Bob Landry]

Originally Posted by Brentw

Not an AC guy, but I know larger units have a high pressure ( occurs when trying to operate at to cold of ambient temperatures) this will not allow the compressors to start up. I can only assume that RV units will be the same.
Don't know the temperature, but I do not believe you can hurt it, the compressor just will not start.

None of this is even close to being correct.

[CedarCreekWoody]

Originally Posted by Bob Landry

None of this is even close to being correct.

So post some accurate facts. That is all the OP is asking.

[dutchmensport]

OK folks, I just went out to my Montana. It has a 15,000 BTU AC / Heat Pump. The outside temperature is currently 25 degrees (burr, its cold out there). The inside of the camper? Well, my digital thermometer just said LO and outside 25.

So, I used a hair blower and blew hot air on the thermometer and the AC/heat thermostat and brought the temperature at the thermostat up to 88 degrees. The outside temperature is still 25.

I then flipped changed the temperature on the control to 68 degrees and flipped on the AC.

Both compressor and fan turned on. Hope this helps.

[jasin1]

It’s not a good idea to start a AC unit in the winter for a couple of reasons

Most commercial and residential AC units that are used in temps below 50 deg or more ( like in a tanning salon or computer room) will have low ambient controls that cycle the outdoor condenser fan off and on to maintain a certain head pressure …( (when you disconnect the fan the head or high pressure climbs)that head pressure range is needed to actually produce cold ( remove heat) in the living or work space..they also will have a crankcase ( compressor heater) to keep the oil inside the compressor from turning to molasses and not providing any lubrication..

Most modern heat pumps have crankcase heaters installed and do not need low ambient controls because you are reversing the roles of the indoor and outdoor coils..( some manufacturers have been skimping on these with scroll compressors). They feel the compressor will outlive the warranty I guess and newer scroll compressors are supposedly designed to make damage less likely

The crankcase heater is most important on initial startup of new units…they recommend unit being energized for 24 hours before first start up in cold conditions

Basically if you start your ac in the winter it’s just hard on the compressor and will not actually remove much heat ( provide cooling) because the head pressure ( high pressure ) will be too low to effectively operate the txv which turns the high pressure liquid into a low pressure gas that absorbs the heat in the air passing over the evaporator coil …can also cause liquid refrigerant to migrate back to the compressor during shutdown which again cause the compressor long term damage

[chuckster57]

I do know that RV heat pumps will not provide any wArm air below 40 degrees. That’s why every one that I have seen had furnace assist.

[CedarCreekWoody]

Originally Posted by dutchmensport

OK folks, I just went out to my Montana. It has a 15,000 BTU AC / Heat Pump. The outside temperature is currently 25 degrees (burr, its cold out there). The inside of the camper? Well, my digital thermometer just said LO and outside 25.

So, I used a hair blower and blew hot air on the thermometer and the AC/heat thermostat and brought the temperature at the thermostat up to 88 degrees. The outside temperature is still 25.

I then flipped changed the temperature on the control to 68 degrees and flipped on the AC.

Both compressor and fan turned on. Hope this helps.

I hope you didn't damage your A/C compressor.

[dutchmensport]

No, it's not like I left it running for hours or anything. It was on for probably 30 seconds. And yes, agree, when outside temps reach about 40 degrees my heat pump blows nothing but cold air.

Actually, this was a good quick exercise for the camper as we are planning another trip next week. Because the camper has been sitting since last November, it's good to check things out anyway. Yesterday, I raised all the electric jacks and did the auto level again. Temps were near 60 degrees yesterday. Today 25.

[jasin1]

Originally Posted by CedarCreekWoody

I hope you didn't damage your A/C compressor.

He probably didn’t damage anything ..its a heat pump so it has the same compressor for heat and cool…it probably doesn’t have a crankcase heater and even if it did you wouldn’t be expected to turn it on for 12 -24 hours before you start it because it’s basically a portable unit.

Is it the best practice to turn on a unit with a compressor crankcase heater for the suggested wait time?….. Yes …. But in real world situations it doesn’t happen often

If your installing a brand new heat pump in someone’s house you start it the day it’s installed.

The op asked the temp range and if it’s bad to run in winter…it is but unless you run it for a long time it probably won’t cause any measurable harm

If you did an amp draw on the same unit starting in 30 deg weather vs 70 deg after sitting all night without having any power to the circuit …you would probably see a noticeable difference in amps to start a cold compressor with thicker oil viscosity

Might just knock days off the end of its life

The advent of scroll compressors has changed how refrigeration works…they are ( scroll) designed to be more forgiving

Scroll compressor technology started back in the late 80s and now it’s in most brands of hvac equipment Although Trane Was one of the last converts as they had their own proprietary compressor they manufactured

You can do almost anything to an ac unit and it will still run…but it could be for a day…a week…or 10 years

[jasin1]

Originally Posted by chuckster57

I do know that RV heat pumps will not provide any wArm air below 40 degrees. That’s why every one that I have seen had furnace assist.

Yeah they don’t provide efficient heat…although the new inverter compressors that basically speed up and slow down can extract heat from the outside air at much colder temps…mini-splits are where you see this and higher efficiency residential split systems

The trade off is the btu’s drop significantly the colder it gets but will still heat.

Regular heat pumps do provide “warm” air below 40 deg but that’s subjective…the room temp may be 68…the heat coming out may be 87 deg which is warmer then the room but colder then your body so it feels cool or cold

[Bob Landry]

Originally Posted by chuckster57

I do know that RV heat pumps will not provide any wArm air below 40 degrees. That’s why every one that I have seen had furnace assist.

The reason for the 40 degree parameter is, that is the temperature at which there is not enough heat in the medium being used(air or water) for the unit to extract and transfer to the refrigerant for heating.
I don't know where the crankcase heater thing came from, but residential split systems, window units, RV roof, nor marine AC's have them. I can not speak to the large commercial systems. Those are out of my wheel house.
Also, ambient temp has absolutely no effect on the starting or running of a compressor. In the case of R410A, any change in ambient temperature will affect the head pressure during operation, but unless it rises high enough to trip the high pressure switch, it has no effect on the speed of the compressor or the discharge air temp. Temp is controlled solely by the duty cycle which is determined by temperature sensing at the thermostat. The compressor will maintain a constant speed.

[jasin1]

Originally Posted by Bob Landry

The reason for the 40 degree parameter is, that is the temperature at which there is not enough heat in the medium being used(air or water) for the unit to extract and transfer to the refrigerant for heating.
I don't know where the crankcase heater thing came from, but residential split systems, window units, RV roof, nor marine AC's have them. I can not speak to the large commercial systems. Those are out of my wheel house.
Also, ambient temp has absolutely no effect on the starting or running of a compressor. In the case of R410A, any change in ambient temperature will affect the head pressure during operation, but unless it rises high enough to trip the high pressure switch, it has no effect on the speed of the compressor or the discharge air temp. Temp is controlled solely by the duty cycle which is determined by temperature sensing at the thermostat. The compressor will maintain a constant speed.

Well yes your right and I don’t want this to turn into a long back and forth over who is right but…ALOT of residential systems incorporated compressor crankcase heaters….it’s just a wrap around electric heater for the compressor or in some cases a small element like a block heater…many things are being phased out more for cost savings then anything else ..and the head pressure absolutely effects the temp of the discharge temp…why do you think when you have a dirty condenser you don’t get adequate cooling?

There is a temperature/pressure relationship


And the ambient temp has an effect because of the oil in the compressor

I don’t know much about rv units but I do understand ac systems and that is the business I’m in and have been for more then 38 years and in business for almost 20…I’ve been on many service calls with shorted out crankcase heaters

Not trying to be dismissive of your knowledge or qualifications but please don’t be dismissive of mine either

This is veering into “what does this have to do with rv’ing” lol

[dutchmensport]

Well, this thread has been a rather interesting and lively discussion. But I have to admit, I know nothing about air conditioiners, other than you turn them on and you turn them off, set the temperature and leave it alone.

In this thread there's been discussion about mini-splits, home air conditioners, heat pumps, there's been discussion about the temperature of oil, and crankcases. And everything is really over my head and pay grade.

But, that's OK. As long as you all understand what you are addressing. However, I don't see where anyone actually answered the OP's original question? What is the ambient temperature around the AC to adequately test his soft-start install.

I made an attempt, got shot down, but no one else seems to have an answer either. Lots of discussion side-stepping the real question though? Are there any "takers" who can provide a true temperature. Just that simple.

[jasin1]

Originally Posted by dutchmensport

Well, this thread has been a rather interesting and lively discussion. But I have to admit, I know nothing about air conditioiners, other than you turn them on and you turn them off, set the temperature and leave it alone.

In this thread there's been discussion about mini-splits, home air conditioners, heat pumps, there's been discussion about the temperature of oil, and crankcases. And everything is really over my head and pay grade.

But, that's OK. As long as you all understand what you are addressing. However, I don't see where anyone actually answered the OP's original question? What is the ambient temperature around the AC to adequately test his soft-start install.

I made an attempt, got shot down, but no one else seems to have an answer either. Lots of discussion side-stepping the real question though? Are there any "takers" who can provide a true temperature. Just that simple.

he will be absolutely fine testing at 60 deg…even 50 would be fine

[Captainf2]

Originally Posted by chuckster57

I do know that RV heat pumps will not provide any wArm air below 40 degrees. That’s why every one that I have seen had furnace assist.

What refrigerant is in these ac now, 410a is good to zero abient