How do these combined heating/AC units work?

I am moving into a new apartment with “combined air conditioner and heating” units, like the one in the link below. How does the heating work with these? That is, is the heat powered by electricity, or by steam (like in radiators)?

The landlord is responsible for “heat and water”, but I am responsible for electricity and gas. So, I am wondering how this thing works.


i hope fredrik taking good care of you

The heat should be building heat, nothing more than a simple fan in there controling the on/off.

The AC is an electricity hog, and tha’ts all on you

I used to have a combined AC/Heat unit- I believe the whole thing ran off electricity… I mean the thing wasnt hooked up to anything except what seemed like a heavy duty wall outlet. I dont think it was that expensive to run. I actually didnt even know I had heating cabilties for over a year until it was freezing and I was trying to figure out a way to heat my pad.

@OP - you’re in luck. My dad was an hvac technician for most of my life, and I spent many hours helping him. When I get back to a computer with a real keyboard, I’ll tell you what to expect.

Other than my time spent on the California coast, I have never lived anywhere that didn’t have a combined heater and air conditioner. It’s strange to me that people don’t have them.

Air conditioner? What’s that? On days above 40F, I generally throw a few frozen baby seals in the corner of my igloo to keep things chilled out. In all honesty, most folks don’t have AC up where I’m at. Only need it a few days a year. Electric heating sounds awful though, can’t imagine how expensive that would be in a cold climate. Everyone here runs nat gas.

When I read this thread, I said to myself oh it must be another weird NYC thing lol Never realized people used seperate systems

Ok. There are two types of “combined AC/heat” units. There’s a “standard” furnace, and a heat pump. More on that in a minute. Let’s examine how the cooling function works.

When an air conditioner is in “cooling” mode, it uses two different units–a blower and a condenser. The blower goes inside the house, and that’s what you hear running in your hall closet. It’s what blows the cold air out of your vents. The condenser is the “outside” unit. It blows hot air into the ouside world.

If you look at your blower, it has a “coil” (which looks awfully like a radiator on a car). It has copper pipes in the coil that hold freon gas. The pipes in the coil get extremely cold and the air blows across them, which is why the air in your AC is cold. When the hot air blows across the cold pipes, they actually “suck” the heat out of the air. Then it gets transferred to the condenser, where it condenses the gas in pipes, which turns them extremely hot. Then the outside blower blows across the hot pipes, which transfers the heat outside.

The gas then travels back inside the house, where it expands and gets cold again. Then the air blows across the cold pipes, and the cycle repeats itself. This effectively works to take the heat and humidity out of the air and take it outside.

And that’s how an air conditioner in cooling mode works. Heat pumps and standard furnaces both work the same way.

Heat pumps work the exact same way. When you turn them on “heating mode”, they just reverse the flow of the gas in the pipes. The pipes inside get scorching hot and the pipes outside get freezing cold. So you start to take the heat out of the outside and pump into your house.

A standard furnace is easier to understand. It’s virtually the same as the space heater under your desk.

If it’s an electric furnace, then there is a “heating element” in the furnace. These are basically wires that heat up and glow red hot. Then the air blows across them and it heats up your house.

If it’s a gas furnace, then there are pipes that burn gas, and air blows across them and it heats up your house.

Note this–if it’s a heat pump, it will have a setting called “emergency heat” mode. There’s no emergency about it. All that it does, is it turns your heat pump into a standard furnace. So all heat pumps are standard furnaces as well.

Why do I tell you that? Because if the temperature outside drops below 35 or so (Fahrenheit, obviously), then there’s not much heat to transfer inside. So when it’s that cold, you need to turn your heater on “emergency heat” mode.

OTOH, if your unit is a “standard” furnace, then it won’t have emergency heat mode. (It’s always on emergency heat mode.)

Thanks for the explanation. What I am trying to determine though, is whether the heating/air conditioner unit in the apartment is just a heat pump, or if only the air conditioner is a heat pump and the heater connects to a central furnace. This is important because as a tenant, I am responsible for electricity bills and the landlord is responsible for “heat and water”, which would include central heating. I suppose I can figure this out by asking the building superintendant.

Ah. I thought you just wanted to know the mechanics of them. Sorry if I misunderstood you.

I have no idea what kind of setup they have in those building in Zoo York.

Now what I want to know–why is a dude who cleared $500k after just a couple years in the industry so concerned about what will probably amount to $20/month?

660k for that dump? Damn. My house must be worth $20 million in NY money…

$20/month for heat in NY. Now that’s funny.

The place I rent has heat-pumps. It pretty much blows cold air during the dark depths of winter. Jan/feb this year were miserable and my elec bill was north of $500.

Ok. So here is the deal. The building has a central heating and cooling engine, and the unit in my apartment merely blows air at the predetermined temperature, like 70 degrees or whatever. This seems good, as I will not pay electricity bills for the central unit. Finally, you can sleep soundly.

^I’m certainly glad that you won’t have to declare bankruptcy now.

So the whole building only has one AC unit? What if you want it to be 80 degrees and the guy next door wants it at 65?

I have the exact same setup in my building. The AC is great plus I don’t pay directly for it so I basically have it on from June to September. The heat works well but is way too hot with the blowers on plus they don’t don’t shut off when the room reaches a desired temp so if you leave them on the room is boiling in 20+ minutes. The units themselves emit heat so for the first few years I just never turned on the blower and dealt with the cold nights (probably in the low 60’s nothing crazy), but after the baby came along I had to get an electric heating fan which sets me back about 200 per month on it’s own in the winter.

I cannot control the temperature of the air from the blower. However, I can control the volume of air, that is low, medium, high, etc. So, for instance, if it is cold and I want more heat, I can just get the machine to blow more hot air.

This is really no different than any heating and cooling setup, except you are the thermostat instead of the unit having a thermostat to turn itself off when the room reaches the desired temperature.