any window AC units that can work at lower outside temps, ie: under 50F? auto temperature shutdown?

[markm75]

I'm lookin to get an AC window unit in my 9x12 office.. not sure on the btu i would need, but i have a lot of computer equipment forcing the ambient temp in the room from about 78 to as high as 85 at times (at mid height in the room)..

I've had window units years ago and i remember having trouble when it got colder.. the unit would freeze up.. do they all do this these days.. as i'd need to run this unit in the winter time too..

I'm hoping to find one with thermostat control, so when the room reaches a temp it shuts off too.

We have whole house ac, but this room gets hot, despite this.

Thanks for any advice..

[ransley]

Thats why they make windows that open

[Stormin Mormon]

If it's that cold outside, consider building an air exchanger, to blow cold outdoor air into the computer room.

Or, run the fan on the furnace all the time. The electric heat (computers) is expensive heat in many parts of the world. Would be a shame to discard that heat. Then your furnace could cycle less often.

A good HVAC guy could put a freeze stat on a window unit.

[HeyBub]

I sympathize.

I once worked for a company that had a small (mainframe) computer room. Had two five-ton AC units on the roof.

One of the AC units had a thermal disconnect to disable the unit when the outside ambient temperature reached (I believe) 40°F.

One night the temperature got below freezing and the computer was running. About 3:00 a.m., the thermal interlocks on all the computer equipment popped. This required a service call from IBM to reset and test all the equipment ($).

After much WTFs over several hours, a simple snip with wire cutters solved the problem.*

In your case, an inquiry to the AC manufacturer of the unit you're contemplating seems to be indicated.

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• The operator was queried thusly: "When it started getting hot, why didn't you shut the son-of-a-bitch down?" His reply: "I had to get the work done!"

The unanswerable rejoinder: "Then why didn't you open the freakin' door!"

[Uncle Monster]

I do a lot of commercial HVAC and refrigeration work and when I have to run a piece of equipment under low ambient conditions like the AC at a restaurant which often has to run in the winter, I install whats called a "head pressure" or "low ambient" control. For the large AC unit that you would find at a restaurant, it's a simple matter of controlling the condenser fan. When the fan is turned off by the electric controller, the head pressure rises until reaching a preset limit then the condenser fan comes back on. This keeps things from freezing up and protects the compressor from flooding with liquid freon. The problem with a window unit is that there is only one motor turning both condenser and evaporator fans. To control the head pressure in that situation you need to modify the plumbing and add a head pressure control that controls the flow of freon. This type of control throttles the head pressure by opening and closing a valve to keep the head pressure within a certain range. What I've written here is a bit simplistic in explaining the process but a good refrigeration guy could modify your window unit. Most AC techs don't get into plumbed in controls which is what refrigeration techs tackle all the time. Here are some links to information that may help you grasp the process and explain in more detail than I can here.

I hope this helps you out.

[8~{} Uncle Monster

[Old AC Guy]

More superior advice from the resident dumbass. You obvioulsly don't have a clue when it comes to heating and air.

[Old and Grunpy]

Sorry Uncle that does not stop refrigerant from floading compressor but actually does the oposit however it helps for compressor from cutting out on low pressure switch and saving compressor from pumping oil out of crankcase. However for the health of compressor if unit is going to be use all year round additional items need to be install (depend) on system size, Crankcase heater, suction accumulator, large Recivers also need rap around heater.

The problem with a

[Uncle Monster]

Most of the systems I install have crankcase heaters anyway. When I order a new unit I get all the bells and whistles like high and low pressure cutouts, phase/voltage protection modules, head pressure controls, etc. Some of the units have suction line accumulators like the 4 ton Carrier condensing unit here at the office. Somebody got on the roof last summer and thought it belonged to my neighbor in the next shop, the silly bastard left the service valves loose and all the freon got loose and went off to kill some helpless little ozones. It took 13lbs of R22 to recharge it and until I saw this huge accumulator next to the compressor, I wondered where in the hell the charge was going. In my previous post I said my explanation was "simplistic". Anyway, I posted what I thought would work for the guy in another thread and suggested a portable AC unit which is what I've used to cool small computer server rooms before. The whole unit is in the room and uses a big hose to exhaust hot air. No low ambient problems there.

[8~{} Uncle Monster

[Stormin Mormon]

With the usual wiring, the compressor and fan come on at the same time. This also happens in window units; compressor and condensor fan are wired on the same switch. However, in too cold outdoor weather, this results in too cold refrigerant feeding into the evaporator. Could easily be sub freezing temp refrigerant, which would cause evaporator icing. Can also result in poor liquid to vapor conversion in the evaporator. Leading to liquid return to the compressor. The restaurant units I've serviced used a pressure control to turn on the condensor fan. A thermal control could be used, but I've not seen one.

[Stormin Mormon]

Dear Tony, got to disagree with you.

The headmaster control (switches on and off condensor fan) does stop refrigerant from floading (try spelling it "flooding") the compressor. Since the headmaster control keeps the refrigerant to the evaporator fairly warm, the refrigerant can then turn to vapor. This provides for good cooling, and reduces the odds of evaporator freezing.

Yes, headmaster switch does help compressor from cutting out on low pressure switch. Has very little to do with pumping oil out of crankcase.

Crankcase heater is good in the winter. suction accumulator, can reduce risk of oil slugging the compressor. I don't think that "large Recivers also need rap around heater", the receiver is typically in the air flow from the condensor. As such, it stays plenty warm. Which music group would you get to rap around the heater? Glad it's outdoors, most restaurants don't like rap music. Unless they are in the city. I've had a couple cases where the hot blast of air from the condensor was over heating the receiver, and I've wrapped it in cardboard so the refrigerant would not pick up more heat.

[Uncle Monster]

ICM makes temperature sensing electronic head pressure controls that I use all the time.

[8~{} Uncle Monster