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Air Conditioning

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wasy

Active Member
Joined
Feb 7, 2006
Messages
1,186
Location
Toms River, NJ
I have a fair size home and a undersized AC unit. I make this assumption because in the summer months my system runs basically 24/7. It's typical for my June/July/August electric bill to be $550-$600 a month.

Surely a second unit that could cool the upstairs bedrooms would take the pressure off the current unit or would I be better off just replacing the current undersized unit with a new efficient larger unit? Would either of these options lower the monthly bill?

I'd appreciate the comments.
 
Not an AC man, but I have two units in my two-story home and it is definitely the way to go for me. As an added bonus, if one goes out, you have the other unit to keep the house cool while you are waiting for the repair man. :cool:
 
We have a 5500 sq ft home with three AC units. We only run them in the day during summer except one unit downstairs because the nights are cool in San Diego. My electricity bill jumps by an extra +- $450 during these months.

Would it save you money to install another unit, definately if your current system is not the correct BTU for the area you are cooling. However, the saving will not be substantial as you would now be running two units.

Brian
 
A couple of questions...

Have you had a service man come out and look at the unit?
It could be low on refrigerant.

The coils could be dirty (inside or outside). Just spraying the outside coils with a garden hose won't work if you are anywhere near cottonwood trees, a pressure washer is in order. Be careful though as you can do a lot of damage to the fins if you don't do it right. A LOT of the newer high efficiency units use stacked coils on the outside unit and if they are extremely dirty the only way to get them clean is to partially disassemble the unit and separate the coils. A job better left to someone with experience...

The line set could be damaged, restricting refrigerant flow.

If all of the above check out OK ask him about putting an oversized evaporator coil in. Sometimes you can gain needed capacity by doing that, and it is chaeper than installing a complete unit. This only works if there is physically enough room though.

Another thing to check is your electrical connections. Sometimes the unit will run with a bad connection for a long time, but wastes mucho electricity. If this is the case it will likely be quite obvious because the wires will be burnt.. A bad contactor can cause problems too...
 
wasy said:
I have a fair size home and a undersized AC unit. I make this assumption because in the summer months my system runs basically 24/7. It's typical for my June/July/August electric bill to be $550-$600 a month.

Surely a second unit that could cool the upstairs bedrooms would take the pressure off the current unit or would I be better off just replacing the current undersized unit with a new efficient larger unit? Would either of these options lower the monthly bill?

I'd appreciate the comments.
Click to expand...

I didn't do all that well in thermodynamics, but I think I can visualize what you have. It'd be nice to see a floor plan and to know the rating of your unit and to what level your home is insulated. No air conditioner is designed for a 100% duty cycle, that is to run all the time and are not going to cool much beyond the room they're in. The simple answer is to get another.
 
We have two AC's a 5 ton and a 2.5 ton that are pretty new( I bought them in 2003). I have a service contract so a guy comes out twice a year to do all kinds of preventative maintenence on both units.

I just had my most expensive electril bill last month ,723 and change because I was running the pool heater all month and keeping the pool at 87 degrees. My kids had some out of town friends, birthday parties and other stuff so I heated the pool for them.

In the summer my bill normally runs at 550-600 a month.
 
Damn, some of your electricity bills are as much as I pay in rent! Gandolph seems to know his way around AC repair, I'd take his advice. If you decide to replace your AC unit with an industrial or commercial refrigeration system, then I can help you with your problems!
 
Yea, before I got into building automation I was the HVAC guy at the local hospital. Nothing like being outside on the hottest and coldest days of the year trying to keep people happy.
 
Yes, I've had a service guy look at the unit and everything is fine it's simpy undersized. I'd estimate that it runs continuous from 9am until 9pm and then cycles on and off.

Looks like I'll get some prices for a new appropriately sized unit.

Thanks for the help!
 
Just to let anyone in Delaware that is on Delmarva Power, if you haven't heard, your bills are going up 53% in June, and Maryland people on DPL, were getting hit with a 35% hike. Still not as bad a BGE's 70%, but bad enough!!
 
The advantage of two units is that you can choose to cool different sections of your house independently, like only the bedrooms at night. If you only have one unit right now, it might be pretty tough trying to put a second one in, you would need somewhere to put the new system, including the return air, as well swap around your ducts.

Things you need to check on,
-What size is your current system, and is the compressor sized properly for the coil
-What is the square footage of your house
-What is the outside temp, and what temp do you have the a/c set on
if you set you a/c on a lower temp than it can actually cool, then it will run continuously, and it may freeze up
-How old is your current system
if it is very old, it may just be time to replace the whole thing

It has been a couple years since I did a/c work, and all I did was install it not size it, but that is what I can think of off the top of my head
 
Keep in mind that it should cycle on and off but not be too large of BTU. When it runs more often than it is off it is actually good as it takes out more of the humidity in the air. Too many install an oversized unit that quickly cools the air but doesn't remove the moisture thus making it still feel hotter.

But you don't want it running constant unless it is a couple of the hottest days of the year or something like that. My guy said he shoots for a balance of maybe runnning on 2-3 of the hottest days of the year fairly constant but not every day. That is in Indiana.
 
Do AC units actually freeze up?? I'm not exactly sure how they work (although I think I have a good idea), but I wouldn't think they ever should. In refrigeration systems, the evaps run about 10 degrees cooler than the room. Since a house is usually set around 70, the coils shouldn't freeze up even if the temp is 30 degrees lower than the set point. Why you would ever want air blowing that cold is beyond me. Can any of you HVAC guys shed some light on this?
 
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