AC for cold weather use?

[pbon]

Our bedroom gets hot in winter, spring and fall. We would like to add a supplemental AC but I have read most AC are not meant to be run in cold weather. Don’t want a window AC sticking out the window and they aren’t supposed to be used in cold weather due to the AC oil. Was thinking of a portable AC ducted through the wall and up to the attic above (might be 6-8’ of duct) and drained down the chimney cavity to a laundry sink in the basement. Alternative might be portable AC that evaporates but I think those are twin duct units and the duct would have to be longer to get fresh air rather than just exhaust into attic. Don’t want to duct right through visible exterior house wall because it does not look any better than a window AC.

Would consider ducted mini split if they don’t have the same problem if not being intended to run in winter due to the thickness of the oil in the outside unit. I can’t find confirmation on that.

Opening a window can allow too much wind in, which blows the shades and is not sufficient in all of the fall or spring. We have central AC but it is not sufficient in that room in summer. We could spend money making it a new zone but that does not help the rest of the year. We have an air exchanger built into the AC ducting but it is not sufficient to cool this room in winter, spring and fall.

 

[racecougar]

1. What climate/area are you in?
2. Have you considered using powered registers to better distribute your HVAC and even out the hot/cold rooms? They work.

Running AC in one part of the house and heat in another just doesn't compute in my energy-conscious brain.

 

[65ranchero]

A cold weather mini split most likely will be your answer

Those portable A/C's are not all that great
and there are mini split cassettes to install on the wall or ceiling

 

[Syberia]

Define "cold weather." Window fan?

 

[pbon]

NH. Yes, I know running AC in winter while heat is also running elsewhere is not efficient but it is a large, old house and we are willing to pay to be comfortable in our bedroom. We actually have the heat turned off on the bedroom but heat rises and the room underneath is the hottest in the house.

My understanding of cold weather mini splits is that they have a heat pump to provide heat in winter. I don’t think they are meant to provide AC in winter but I am not an AC expert so I don’t know that for sure. I’d prefer a mini split to a portable, though, if a mini split would work.

I looked at cassettes but even the compact ones are over 2’ square so that involves cutting rafters. I could do that but if I can just put the indoor part in the attic right above the bedroom and duct into the ceiling that is cleaner.

As inefficient and weak as a portable is, it seems like the best bet. Since it is located entirely inside, there is no concern about thick oil hurting the unit. It just has to help. Any problem with over sizing an AC since portable tend to be weak, like getting one rated for up to 700 SF instead of 500 SF when the actual SF is 500?

We have been running a fan while we sleep at night for 4 years and it is not enough and we would like more. We also have shades that flap around if we put the fan into the window, but need the fan to block outside light — city living.

 

[malibu101]

I don't know much about A/C systems. But I know these key words.
You are looking for a "low ambient" unit.

 

[racecougar]

What is going on with the room below to make it that hot? It really sounds like better distribution is needed to balance out the house. Not only will that drop the temp in the hot rooms and bring up the temp in the cold rooms, it can reduce the cycling of the furnace depending on where your thermostat is located and how you've set it. From what you've described, powered registers in the cold rooms could really make a big difference here.

One example: https://www.amazon.com/dp/B0792R5KJF/?tag=atomicindus08-20

 

[jlv03]

There are some minisplits designed to cool server or computer rooms.

I think the bigger issue is dealing with what is generating so much heat even in winter?

 

[Phuckin' Jim]

You could mount the mini split's outdoor unit in the basement, then you'd be warming up the basement the same time as cooling that room upstairs.

You would likely run the lineset inside the walls for a neater appearance.

 

[Phuckin' Jim]

Like this:

12000 BTU Floor Mounted Mini Split Air Conditioner - Heat Pump - SENA/12HF/IF

The 12000 BTU Mini Split Air Conditioner by Senville, is designed for efficient cooling and heating. ENERGY STAR Certified with 12000 BTU Mini Split Heat Pump.

senville.com

 

[unslow1]

I used to have a house where one room was still hot in the winter even with the duct closed and covered. We just used to crack a window and run a ceiling fan in that room.

 

[Phuckin' Jim]

Like this, except you could run the lineset down the unused chimney or inside the walls.

 

[Yankeefarmer]

*snip*

My understanding of cold weather mini splits is that they have a heat pump to provide heat in winter. I don’t think they are meant to provide AC in winter but I am not an AC expert so I don’t know that for sure. I’d prefer a mini split to a portable, though, if a mini split would work.

*snip*

There is no separate “heat pump” in a cold weather mini split. The compressor in an air conditioner is a heat pump. It moves heat from the inside of the house to the outside during A/C use, and from outside to inside in heating mode. This is done through valves to change the direction of refrigerant flow. A cold weather mini split will likely have a refrigerant heater to maintain the temperature of the refrigerant at a high enough temperature to safely lubricate the compressor during cold weather starts. Once the unit is running, that heater should not be needed, as the heat being removed from the room along with the mechanical losses will maintain safe operating temperatures. You should just check any candidate unit’s minimum outdoor temperature for cooling mode. Maybe give the folks at Ingram’s a call.

For instance, the MRCOOL Olympus Hyper Heat can provide cooling at outside temps down to 5 deg F.

 

[pbon]

Thanks! That is what I needed to understand. Apparently these low ambient ones with heat pump and wind deflector on outdoor unit are used to cool computer server rooms that are hot even in cold winter temps. I think this is better visually than a portable and I can do a ducted version.

 

[racecougar]

I think the bigger issue is dealing with what is generating so much heat even in winter?

Exactly. If it's a distribution/balance issue, and it sounds like it is, pulling that heat to cooler areas of the house can be done less invasively, less costly, and more efficiently, both in the near and long-term. Running AC and heat at the same time just doesn't make any sense.

 

[Yankeefarmer]

I can understand the OP’s viewpoint. Our house started out as a one bed/one bath four room single story Cape, and then was added onto over the next 20+ years. Each addition included an extension of the forced air system. When we bought it, it still had a single zone which sensed temperature in the original core of the house, so in the winter time all the “new“ rooms, some with 3 outside walls, would cool off long before the “old” part of the house. I even blocked off the register feeding the original bedroom, which was located directly above the furnace, because it didn’t need any added heat. Fixing it properly would mean a new heating system, including all ductwork, and, with raising kids and a stay-at-home mom, there were other uses for the money. I threw a patch on the system by adding electric baseboard heat in the cold new bedrooms. Twenty-five years after buying the house, with the kids grown and gone, I designed and installed a 5 zone hydronic system that delivers incredible winter comfort.

 

[pbon]

Exactly. If it's a distribution/balance issue, and it sounds like it is, pulling that heat to cooler areas of the house can be done less invasively, less costly, and more efficiently, both in the near and long-term. Running AC and heat at the same time just doesn't make any sense.

I agree adding cooling in winter to counter too much heat does not seem logical or cost effective but neither our house nor our lifestyle is logical or cost effective. The AC will just be in one room and the heat is turned off in that room. It’s a complicated house.

 

[jpaw]

Have you simply tried turning the furnace fan to on instead of auto to see if it will even out the temps?
You could rewire the fan to run at a lower speed in the on position and run it continuously.

 

[PoorUB]

Most mini splits will cool to around zero degrees. Many will cool to well below zero.
We installed them to cool mini server rooms all the time.

 

[metlmunchr]

My Pioneer minis can operate in cooling mode down to 5°F outside temp.

I wouldn't recommend a portable to my worst enemy. The original purpose of those things was for spot cooling in hot areas of factories where the ambient temp may be well above 100° and some cooling was needed in a small area to keep working conditions tolerable for a worker or two. Then some marketing trash came up with the idea of selling them to the general public as portable air conditioners. They are energy hogs and their efficiency was overstated by the manufacturers for years until the federal govt stepped in a few years ago to require testing and publishing numbers more representative of actual performance. The real numbers demonstrate the actual efficiency is on par with other types of a/c units produced 40 years ago. In a nutshell, the average portable will use about 2.5 times the energy as a mini split of the same output will use.

 

[pbon]

Ok. It will be a mini split. Thanks!

 

[Phuckin' Jim]

And installing the outdoor unit in the basement would give you the added benefit of heat down there, rather than wasting the precious heat outdoors.
If that scenario is doable for you.

 

[American Locomotive]

Like others have said, I would fix the "hot" issue before throwing more air conditioning at it. If the room below yours is the hottest in the house - why are you not turning the heat down (or off) in that room, first?

Secondly, a much cheaper and more efficient option might be to just be to install a decent sized ducted fan in the attic that draws air from outside. Especially since your issue is in the Spring/Fall/Winter. It'd be trivial to hook such a thing to a thermostat, and you'd be using ~50w of power instead of 500.

You might also want to consider having a duct company (who actually really knows what they're doing) check things over and see if things can be rebalanced air-flow wise.

 

[pbon]

It is a 5000SF house from the late 1800s with a radiator steam system converted to water, along with some radiant floor, with a new variable speed 210,000 BTU boiler, and has 6 zones. Also has two central AC but is not sufficient in this room. Does not have a typical whole house fan but does have two air handlers on separate zones operating through the AC ducts.

We have had several experts come in over the past few years. One turned off the heat to the bedroom. Another said a separate AC zone for the bedroom could be added but our system is not for winter so that would not fix the problem. Another suggested a mini split for the bedroom.

I understand there is probably a perfect way to use what we have and we could probably make a mess of the house and spend a lot of money redoing the existing heat and AC, but everything is good except the bedroom so we will just add supplemental year round AC to it. This house is not about efficiency.

 

[moab11]

Definitely look at mini split systems with a cold weather package. I have a Mr Slim at work that cools a server room even at -40 outside temps. The cold weather package is usually an add-on, but the mini split must be bought with it, it can't be added on later.