Plan B Forum

Summer greetings!

It's not very hot here in lovely Silicon Valley, mornings I am still wearing my sports jacket to work; and a fan is all I need at the weld table...

...but the roomies are sweltering all ready So I, as good landlady Loca, am thinking of biting the bullet and finally installing an air conditioner. (Shocking, I know!) Just a window unit, in the front room should be fine; I can't really go central air as the title suggests.

I'd like to go cheapest of course, but a smaller unit can't cool as big a space, right?

My roommate thought we could put an electric fan in front of the AC to pull the cool air into the room, but this will increase the power usage, won't it?

What are the best/cheapest conditioners, and what do you think this will cost me in extra watt$$$$?

Depending on the layout, a window unit could cool all the rooms on one floor. When my parents first got air conditioning, they put a window unit in the front hall, and because there was a doorway that led from there to each of the other three rooms (living room, kitchen, dining room) the entire first floor was cooled. But the effect will be lessened if passage from one room to another zigzags around corners. Fans don't help all that much because the hotter air that is furthest from the air conditioner has no place to go (that is why central air conditioning systems need return air ducts to pull air out of the room so that cooled air can be pushed into it).

The size of the unit you need is determined by the square footage of the space you are trying to cool (wherever you are buying the unit should have charts that show this). Buying a unit that is too large is almost as bad as buying one that is too small; in addition to using more power than necessary, it will not run enough to remove sufficient humidity from the air, which is as important to comfort as bringing down the temperature (unless you're in the desert, in which case it doesn't matter). The power of the unit will be expressed in BTUs; to the base amount of BTUs based on the room size, add an extra 10% for each of: if the room is sunny, if there are electrical appliances such as a CRT TV that give off heat, if it is on an upper floor. Add 600 BTU for each extra person over two using the room.

So as an example, a room of 250-300 sq. ft. requires a 7000 BTU unit. If the room is sunny and has a CRT TV you need to add 10% x 2 = 1400 BTU. If it usually holds three people, add 600 BTU. So you need a 9000 BTU unit.

Ideally, an air conditioner should be on its own 15A circuit. If this is impossible, make sure it is on a circuit that will not be used for high wattage appliances such as irons, toasters, or hair dryers. If your electrical panel uses plug-type fuses rather than switch-type circuit breakers, you need to use a time delay (D) fuse, rather than a regular (P) fuse, to allow for the short power surge that happens whenever the unit kicks into cooling mode. Otherwise, you will continually blow fuses.

Figuring out how much additional electricity it will use is complicated, but whoever is selling them should be able to give you a rough estimate of your additional power consumption.

Scooter wrote:So as an example, a room of 250-300 sq. ft. requires a 7000 BTU unit. If the room is sunny and has a CRT TV you need to add 10% x 2 = 1400 BTU. If it usually holds three people, add 600 BTU. So you need a 9000 BTU unit..

This sounds just about right. The totality of the home is 1,400 sq.ft. but as stated, we are only trying to cool the front living/family room, and there is a TV there. Fortunately, we have a large shade tree that I've cultivated over the years for just such a situation.

So, to move the warm air out, what about these?





...in the opposite window?

1400 sq ft on one level? You will never cool that with a window air conditioner. And you will need to keep the door of the room with the air condiitioner closed or you will waste huge energy in a futile effort to cool the space. And installing exhaust fans would only exacerbate that.

1400 sq ft is the total space of the mobile home but we're only trying to cool the front room, and the bedrooms stay closed during the day anywayZ.

OK, no exhaust fans, that's good as they would only use up more energy.

Wal-Mart has pretty good prices...the new ones are very efficient and many are very quiet.

Mobile homes tend to have odd-size windows...measure carefully before buying.

Ya know, I was just looking at a Wal-mart unit?

We've picked out a window, which has an outlet that's not used for anything, right now.

Even if the outlet isn't used for anything you'd best figure out if anything significant is wired or plugged into the same circuit (fuse/circuit breaker) before plugging in the AC there.

Econoline wrote:Even if the outlet isn't used for anything you'd best figure out if anything significant is wired or plugged into the same circuit (fuse/circuit breaker) before plugging in the AC there.

Good advice from Econoline. Also, if your home / trailer is insulated, the one window unit, if it's a decent one, will probably do all that you expect it to do.

Try it out under warranty. If it doesn't do the job, return it.

Oooooooooooh.... okay, um...

Econoline wrote:Even if the outlet isn't used for anything you'd best figure out if anything significant is wired or plugged into the same circuit (fuse/circuit breaker) before plugging in the AC there.

...uh, how do I do that?

Plug something like a lamp into the outlet you want to use, turn it on, then go to the electrical box and unscrew the fuses or throw the breaker switches one at a time until you find the one that switches it off. With that breaker/fuse still off, go around the house with that same lamp or whatever, and see which other outlets are also switched off. It won't necessarily be ones that are immediately adjacent - in my apartment, a single breaker takes in the outlets on one living room wall, an entire bedroom with its ensuite bathroom, and the lights in the front hall. Be particularly mindful of outlets where you might plug in kitchen appliances, irons, hair dryers or other high wattage appliances. And again, if your box uses fuses, you need to switch the appropriate fuse to a time delay (D) fuse if it is a P fuse. Do NOT, under any circumstances, try to prevent blowing a fuse by replacing it with a higher numbered fuse, you will overheat the wires in your walls and burn your house down.

Really? You have lights and outlets on the same breaker Scoot? I've never known that before.

Must be a Canadian thang...

Or a North American thang? I've never lived in a house or an apartment that didn't have circuits like that. Some old houses have really screwy circuits--like, one 15 amp breaker for all the lights and outlets on the third floor except for the outlets on the south wall of the middle bedroom, plus all the ceiling lights on the second floor except the one in the closet in the master bedroom (this is a real example from Victorian house in which I lived for over 30 years).

BTW, if you're really lucky some previous occupant may have already labeled all the circuits in the box.

new stuff is mostly seperate. there are places whee it just doesn't make sense to do a seperate run for one or two outlets. Waste of time money and copper.

Interesting...

Both in Oz and the UK, a breaker box will have two sets of breakers so that lights and outlets are kept completely separate.

As Econolone said...old buildings can have all sorts of weird wiring, especially a big house that was split into apartments!

Hmmmmmm... let's see here... First off, I see my box uses switches, and not fuses. Also, it looks my Ex has labeled them...
Interestingly, these's not a lot of them; they seem to be linked to the major power users, like the furnance and the bathrooms each have their own.
Now, I recall the outlets having their own breaker[?]; and I discovered that a few years ago, when an outdoor outlet was overloaded at Christmas.
I remember going to that switch box, and not finding anything tripped; which was strange, so what could I do but re-route the Xmas lights?

Later, I was discussing this with my neighbor [ a former Navy EM Electrician's Mate ] and he asked, if I'd reset the breaker? What breaker?

He said my model home had a circuit-breaker, that should be located indoors in the back of the home, probably in the bathroom. Of course, he was right, that had been tripped, and when I reset it, by pushing a red button, that outlet worked once more.

I haven't done the lamp test yet, but this sounds like the appliances have their own switches, and the outlets have a seperate circuit breaker. Does that sound right?

Could be. If there is only one circuit for all the outlets, you'll want to make sure that, like Scooter said, you don't run any other high-wattage appliances like irons, toasters, or hair dryers off any outlet on the same circuit while the AC is running. (Of course, if you do forget, you now know where the breakers are and how to reset them after unplugging the offending equipment.)

So a breaker pops, no biggie.

My son-in-law and daughter live in a house that is almost a hundred years old, you'll get to know the drill right quick.

Come on, just get a 6,000 BTU window unit plug it in and turn it on if it throws a breaker move something.

A ceiling fan would be best to use in conjunction in lieu of that a pedestal fan on oscillate will work just as well.

As dry as it is in SanHo it should keep a 15x15 cool during the hottest part of the day and help cool another in the evening.

Keep the cooking to microwave or stove top at best, the oven would be a killer...