Home A/C Questions...

[ScottB]

My wife said after the fixes, the air as measured at 51°
Sounds like it's good now.
I'll have to see when I get home - it was mid-hi 90°s today.

Scott

 

[Razl]

Bravo on not over-reacting and taking the time to gather your facts and access the situation.

I think the premium 3Ms are MERV 10, which can be too restrictive for some applications. What filters (MERV rating) did they have you use in the end?

Don't worry about feeling like a nOOb, it comes with the territory (of homeownership). Good to hear all worked out well in the end.

 

[ScottB]

Thanks, Razi.
Since I'm a computer guy by trade, I wanted to NOT be like my clients that call screaming that "it's all messed up and goofy and I need it fixed now" B-S.

I got the really high MERV's - I think they were labeled "1500" but have to double-check. They put in the green media that looks like a spider-web as opposed to the very restrictive pleated units I bought - and they they had initially put it.

I got home last night and the house was FREEZING!
I was so happy - it had been 95° most of the day, and the house would normally be about 88° or higher inside.

Thanks to all for the help. I can now relax and worry about how to pay the bills...

Scott

[ June 27, 2006, 01:24 PM: Message edited by: ScottB ]

 

[Al]

quote:

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Originally posted by ScottB:
I've learned quite a bit, and I am now going to try and find out more to avoid feeling like such a nOOb down the road.

Scott

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Glad that you got it straightened out. Yea like me and others stated: Filters being too dirty or restrictive are probably 75% of problems. Make sure you change that frequently. There are electrostatic ones available (I think they cost 75 bucks or so). You just take them to the car wash to clean. If you buy two of those you will be good to go.

 

[thooks]

Well, I see you have it straightened out. I sent you a PM Scott, I guess you can disregard.


As far as the 3M's being too restrictive, that is hogwash.

The real deal is that most residential HVAC Contractors won't put in a large enough return grille. Most homes could stand a return grille that has twice the area of what is usually installed.

If the correct filtered return grille is installed, there is no problems using a micronic filter such as a 3M "red" or "purple". I've been using them for 8 years, but I have return grilles "that are waaay too big for my systems", so the contractors say.

But my friends and co-workers wish they had my power bill, too.

 

[Volvohead]

 

[keith]

quote:

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Originally posted by thooks:
The real deal is that most residential HVAC Contractors won't put in a large enough return grille. Most homes could stand a return grille that has twice the area of what is usually installed.

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I agree. Consider the system as just shifting air around. How fast is the air coming out of the outlets? What is the area of all the outlets added together, and what is the area of the inlet? Now you can calculate the velocity of the air at the inlet (assuming no losses). The faster the flow, the less restrictive the air filter has to be.

We had a Lennox central AC installed 12 years ago. Ours looks a lot like this one, but's it's older and styled a little differently:

HSX15

It's very quiet compared to most others I have heard.

Actually, we installed 2 systems because the first and second floors have their own. We didn't want to tear up the house to run ductwork between the floors. If the system isn't installed when the house is built, you have to compromise. So far it's worked perfectly and it's nice to have two zones of cooling.

Good luck with yours. Call me spoiled if you want, but living in a >100F humid house is miserable and the AC is worth every penny.

 

[ScottB]

The return is ~15" diameter, and **** near sucked my cats down!

I have to get hold of the technician, because they may very well have made other changes/adjustments.

We had a fan put in the attic that used an existing vent (through the roof) which they enlarged, put in an all-new external vent and put it on a thermostat. We can adjust it to come on at the temp we choose (now 85°) That is helping a lot too.

I f we had the top finished, and more money, we'd have done two systems as you mentioned.

The system is VERY quiet. The inside units are right below our bedroom, and the fan/exchanger is out behind my office. All quiet - but the exchanger is very big (about 3'x3'x3.5') and makes almost no sounds.
All of our neighbors have such small units comparatively speaking, that I have to think this is better and quieter.
I am going to build a nice wood fence around it to hide the industrial nature of it. I'll just build it to come apart at all four sides for easy access/cleaning.
Here is the unit


Scott

 

[thooks]

If the air is moving that fast through the return duct ("sucking it"), then it is too small. With a 15" round duct, you should be moving no more than 1000 CFM on the return side, and that is at 800 feet per minute.

1000 CFM is equal to about a 2-1/2 ton unit, or about a 30,000 btu cooling capacity.

Just for comparasion, both of my home's units are 2-1/2 tons, and I have 24x36 filtered return grilles. The contractor wanted to put in something like 20x20 or the like.

BTW, both of my units are Lennox brand and I wouldn't have anything else. They are quiet and one is going on 10 years and works like new. I have never had any preventative maintenance or other repairs on it. Most people aren't willing to pay the extra $800 for a Lennox, tho.

Make sure you give the "outside unit" (Condensing unit) atleast 42" clear space on all sides, and more than 6' above it.

This will allow almost as much non-restricted air to be pulled through the coils. Ideally, you want 6' of clear space around them.