Jump to content

Rooftop AC in Cold Weather


randynavarro
 Share

Recommended Posts

This situation was a first for me:

Cold day; 40-50 degrees.

I inspected a poochy-fanooli condo on the top floor of a multi-floor building.

In the condo is an air handler with a roof mounted heat pump / ac unit with electric back up heat. There is no access to the roof (for me at least).

The inside temp of the condo was about 72 deg and climbing as the sun continued to hit the building. I could easily see the need to need the a/c later in the day.

So, running the A/C when its chilly outside runs counter to the notion of NOT running them when temps are low.

So, I'm confused. Are there units designed to operate in cold temperatures or is the whole idea of running them in the cold just more inspector folklore?

Link to comment
Share on other sites

Originally posted by randynavarro

. . . So, I'm confused. Are there units designed to operate in cold temperatures or is the whole idea of running them in the cold just more inspector folklore?

1. You don't want to run an AC compressor when it's cold out unless you know it has a crankcase heater. The compressor might be full of liquid refrigerant. If it's a piston-type compressor, you can kill the compressor this way. If it's a scroll compressor, you won't kill the compressor, but it won't be happy either. In either case, the system won't behave properly unless it was designed (or converted) for use in low temperatures.

2. You can run a heat pump in the air conditioning mode during cold weather because it was designed to be able to do this during it's defrost cycles. However, just as with an air conditioner, the system won't behave properly unless it was designed for low temperature use. With a heat pump, there's really no reason to run it in more than one mode. If it works properly in heating, it'll almost certainly work properly in cooling. The only exception would be if there were a problem with the reversing valve -- such a problem is exceedingly rare.

3. High rise buildings often have cooling systems that are designed to be used in the middle of the winter. There's probably no way for you to tell this though. The safest course is to tell the customer that it's too cold out for you to make a safe and meaninful test of the AC system.

- Jim Katen, Oregon

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...