Is it too cold outside to run my AC?

HeatingHelp

Is it too cold outside to run my AC?

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Lance

An ac is a heat pump, just pumping heat in one direction. But we who install both learn to properly charge and adjust both in all temperatures and seasons. Ac can run in colder temps as low as 45F but they need more controls that involve what we call low ambient control. (outdoor temp lower than 65F.). All manufactures can give their specification for their magic number. A low ambient control could change the outdoor fan speed to maintain proper refrigerant pressures, or a hot gas bypass might be used or both. But since most residential units don't have it, ( to save money) they say do not operate below say 65F. (Damage can occur) If you need it a fan control could be added. But it seems a second opinion might be needed by another more qualified or willing specialist? Just so you know, if I need to test an ac in cold weather I can do one of two things, load up the heat on the outdoor unit by blocking the airflow through it, or by disconnecting the fan. This could have allowed the tech to than diagnose a problem.
Of course the final inspection is the home owner's satisfaction in maximum temperature conditions. It is the results that count.
All hvac equipment is engineered for a common condition. A certain indoor temp, humidity level, and an outdoor temp and humidity range. Airflow is specified to handle the conditions this is intended to be sized for. They are designed for this. If it is outside those parameters they will not work well if at all. This is what the code addresses as a minimum standard.
Oddly enough the maximum cool load in Chesapeake bay, Maryland is the same as Tampa, Florida. The only difference is one has a longer cooling season. But no matter what the manufacturer does it is only as good as the contractor you hire to know how to size, install, properly connect and adjust before it works as designed.
We as contractors are supposed to know all of this and be the experts. But you have to find us first. Up to 50% of contractors are known to be unlicensed. And those that are licensed can hire under qualified people. Only about 15% of licensed techs score above 90% on tests, only a score of 70% is required to pass. The tech can be wrong 30% of the time and still work for you. Go figure.
I wish the passing score for plumbers, gasfitters, electricians, and hvac techs will be raised to 85% to get licensed. We work with things that can kill and maim lives or destroy property everyday. This regulation would protect the public better. Gov't would need less inspectors or being understaffed be able to keep up. One itty bitty grade level saves everybody money and makes us safer. Sadly I hear your type of AC complaint every week from people looking for good help.

John Mills_5

I couldn't find low limit for your exact unit. Most brands say below 55 they need protection, something to slow or cycle the fan to keep the head pressure up, maybe a compressor oil heater, bypass of the low pressure switch. I don't see the 60s as being too cold to run it. I know I do.

BTW, the 17 SEER manual says below 55, steps must be taken for low ambient.

JUGHNE

OP said the system would cycle; probably pumping down and off on LPS. Brand I use have enough charge for only 15' of line set. It is very easy to overcharge for extra line......(got that T-shirt)....so I wait for almost hot weather to finish charging.

Also OP mentioned company said defective TXV was in unit. I had that also and AC would pump down and cycle. Some issue about comp oil causing TXV screen to plug.

But how cold for safe operation? I always tell people 55 to 65.

njtommy

Some times it's not so much the out side air temp for start ups for AC. It's the indoor air temps. When the house our building is only 60-65 or even 70 degrees it's hard to do a proper start up. Due to lack of load.

I like to bring the space temp up to say 75F and start from there. You can block off a good portion of the condenser coil to get your head pressure up for start up purposes. It will get you very close to your charge, but sometimes you may need to come back for a top off or to check the pressures and temps once we really get into cooling season.

As for any one who's runs there AC down to even 65 or 55 odt I would still highly recommended an ICM fan speed controller and a crank case heater.

Icm fan speed controls can even be used on heat pumps.

ChrisJ

Regarding crank case heaters.
How would anyone know if the heater failed?

njtommy

@ChrisJ you wouldn't know, but it's something that should be checked when servicing the unit.

ChrisJ

njtommy said:

@ChrisJ you wouldn't know, but it's something that should be checked when servicing the unit.

That's not really going to help the dozens, perhaps even hundreds of times the compressor starts ice cold because of a bad heater.

When the CC heater goes bad in my refrigerator it **** and moans when it starts and the frost line drops some, but all of that is easily noticeable. I can't see anyone ever knowing on a split unit.

njtommy

The heater is to keep refrigerant out of the oil.
But if the unit is cycling and running long periods of time. It's not really a problem. Long off periods of time is when it's an issue. The Scroll compressor can handle this way better then a standard hermetic compressor, but the last thing you want to do is pump that oil out of the compressor especially with the crappy micro channel coil.

ChrisJ

njtommy said:

The heater is to keep refrigerant out of the oil.

But if the unit is cycling and running long periods of time. It's not really a problem. Long off periods of time is when it's an issue. The Scroll compressor can handle this way better then a standard hermetic compressor, but the last thing you want to do is pump that oil out of the compressor especially with the crappy micro channel coil.

IMO there should be a lockout that won't allow it to start of the heater stops drawing current or something.

ratio

Does anyone use the Fieldpiece charging jacket? As long as there's an indoor load it'll drive the head pressure right up, & gives you a nice place to warm your hands at the same time!

njtommy

The problem with a lock out is the customer wouldn't have heat or cooling.if you had a heat pump Heat would just go to the aux or emergency heat and could get very costly. In cooling you really don't need to have crank case heater until the 50s or lower out door air temps.

I have never used the charging jacket and have never needed it. I've always just Bocked off part of the condenser coil to drive head pressure up.