A standard home circuit is 14 gauge wire, which would have a 15 amp breaker and be able to handle 1800 W (about 5000 Btu). If you have the A/C units plugged into different circuits, and there is little else on those circuits (maybe a lamp or two), then you should be fine. If you plug them into the same circuit, it will blow as soon as the two of them are running at the same time. Even if you have larger gauge wire (12 gauge) protected by a 20 amp breaker, it would only be able to handle 2400 watts, so it will still blow if both units are on the same circuit. You can test if the receptacles are on the same circuit by plugging a lamp into each and seeing what happens as you throw one breaker at a time.

I'll do that test. Thank you!

After much trial and error, I found the bedrooms are wired to a circuit labeled "Dining Room." It's a 20-amp breaker. Both rooms are on it, so it's a no go for the second A/C. Thanks for your help, Kudzu.

This is often surprising to home owners, but if you only exceed the maximum wattage by a small amount, the circuit breakers wan't trip immediately. Instead, it can easily take a few minutes before they trip. This is intentional and prevent nuisance trips. But it can also make it harder to accurately tell whether two large loads are compatible, if all you do is run both at the same time. You could be overloading the circuit without noticing for a while.

But if you do run for an extended amount of time, things should become obvious (even if your loads have irregular and unpredictable power needs).

M-

You're correct about the fact that you can overload a breaker slightly without tripping things. However, the OP was considering putting at least a 3000 watt load on a 20 amp circuit (which would be rated at 2400 watts), and that would definitely cause a trip the first time both units were on simultaneously.

Yes, you'll probably notice within a couple of minutes. But that's exactly it. It could take a few minutes. This is particularly true as air conditioning units don't run continuously but tend to cycle on and off.

I have one circuit in the in-law kitchen, that is completely overloaded. Whoever put that kitchen in, didn't run new circuits at all. So, both the microwave and the water kettle are on the same circuit (plus the fridge and a few other appliances). This is obviously not a great idea.

And in fact, both of these are high-powered appliances that nominally max out the 15A circuit that they are on. If I forget, and turn both of them on at the same time and at full power, it takes close to a minute for the breaker to trip. I just looked at the specs. Conservatively, both appliances have a combined draw of 22A, possibly even more. That's 50% higher than what the breaker is rated for. But it still doesn't trip instantaneously.

And if I look at a typical "trip curve" for a residential breaker, then that's actually exactly what they are supposed to do. In fact, for a 50% overload, UL allows the breaker to take anywhere between 1min and up to 6min to trip.

Small, high efficiency 5000 BTU ACs are available which only need 4.1 amps, so you could use two of them on the same circuit.

Mtvhike, your post sent me looking for one of the high-efficiency models, and I found one on Sam's Club's website with decent reviews, including this one:

I am very pleased with this unit, I needed a Low amperage unit and 4.7 Amps gets it done. As I have two rooms upstairs on a 15 amp circuit, both units now only use 12amps between them. The controller takes a little getting used too, but you can always do it manually if need be.

I'll have to confirm the amps, but does this sound as doable as I think it does? Thanks!

PS: I found these specs for the unit on another website:

• Air CFM (Hi/Med/Lo): 129 / 112 / 100
• Indoor Noise Level dBA (Hi/Med/Lo): 55 / 52 / 49
• Outdoor Noise Level dBA (High): 62
• Cooling Amps: 3.9
• Cooling Watts: 446
• Plug Type: NEMA 5-15P
• Cord Length: 6.4
• Uses standard 115-volt electrical outlet
• UL listed
• Includes remote control and window installation kit
• Remote requires (2) AAA batteries (included)

The unit sold by Sam's Club apparently has a dehumidifier-only setting, which appeals to me since dehumidifying the guest room is my main reason for wanting an air-conditioner in there. I put a dehumidifier in the room after it developed a mildew problem last year, but it no longer works. I was going to replace it, but then thought an A/C would do the job and provide cooling if I had guests.

What's the consensus about using an A/C for dehumidifying?

It should definitely work. The way most dehumidifier work is that they make a coil cold to allow water to condense on it. The room doesn't get any cooler (in fact, it gets warmer) because the heat removed from the coil is just dumped into the room.

An Air Conditioner does the same thing but dumps the excess heat out the window. I don't know what the dehum only switch does on this model, but I suspect it operates the cooling at a minimal rate and possibly redirects some of the heat back in the room to avoid it making things colder.

Note that all AC units have to dump this condensed water somewhere usually out the window, don't mount the unit over a walkway. Also make sure you put the unit in properly level (or at least titled outward) in the window lest the water be dumped on the inside.

Excellent. I'll order one--and maybe get another later to replace the old (and loud) one in my bedroom. Thanks very much, everyone!

I know I’m a year late, but hoping the OP will see this and let us know how it worked. And also the brand and model. I need a couple for the same reason!

Hi - I'm here! I bought the unit from Sam's Club described above. Sam's no longer carries it, but it's available on Amazon:

https://www.amazon.com/Keystone-Window-Mounted-Conditioner-Follow-Control/dp/B00IJYGQLQ

I'm very pleased with it. The setup worked, but not in the way I anticipated when I wrote my original post. I found I don't usually need to run that unit and the one in my bedroom at the same time. However, a couple of months later I bought another window unit, this one a Haier, for the third bedroom. I run both of these new units at the same time often.

Hope this helps.

Alisande-

And I presume they are running on two different household circuits?

A 5000 BTU AC unit will only draw 550 Watts a 20 amp circuit can handle 2400 w you should be fine