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Old 06-23-2006, 06:17 PM   #1
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Decisions, Descisions…


I am seeking advice.

We are going to replace our very broken central air system in our 2200 sq ft. colonial with forced gas heat located in northern Illinois.

The current system is: 1992 Heil 5000 100k btu forced-air gas furnace and a 3-ton Janitrol A/C system.

I am looking for opinions on several fronts:
1. Do I up to a 4 ton?
2. Seer 13 or go higher?
3. R-22 or Puron. I know the Freon laws and am certified. I also have a lot of R-22.
4. The furnace has a heating issue where the gas cycles on and off yet the blower remains running as if the heat exchanger is too hot and cycling the gas. This does not condemn the furnace I know, but the question is would it make any sense to upgrade the furnace as long as I am going to be upgrading the A/C?

Your opinions are appreciated.

Thank you for taking time out of your day to respond.

Maxemily

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Old 06-25-2006, 07:05 PM   #2
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Decisions, Descisions…


If it was me I would stay with a 3 ton unit. You get a greater “feeling” of cooling with less humidity. One of the primary functions of an AC is to remove moisture in the air and in order to do that it needs to be running --- the longer it runs the more moisture it removes. With a unit that’s bigger, it will have the capacity to cool faster, turning off sooner and then not have the time to remove the moisture. Yes there is a point where the trade off doesn’t make sense any more economically, such as if the unit is literally running all day long and your electricity bill goes through the roof. On the flip side, if you get a unit that’s much too big, you’ll be looking and evaporator icing and that’s not good… If the 3 ton unit can hold the temperature with out having to run half the day then you shouldn’t need to go larger.

It’s a bit harder to say about your furnace. You might be able to get a good deal if you buy both. How old is it?

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Old 07-01-2006, 03:00 PM   #3
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Decisions, Descisions…


Hello there. In response to your question regarding size, you cannot simply pick out a rating based on square footage of your house. In fact, any good HVAC contractor will perform a heat loss/gain analysis to truly determine what the system requirements are. Simply replacing you system "in kind" may not be correct especially if the house has undergone improvements since the existing system's installation. For instance, anything that reduces heat loss/gain in the home, i.e. window replacements, upgrading the insulation, etc., could actually make the house more efficient and perhaps warrant a smaller system.

Keep in mind one important fact regarding sizing of an HVAC system. Arbitrarily overdesigning the system will not make it better. In fact, an oversized air conditioning system will perform poorly compared to a properly size system since it will short cycle and typically not run long enough to properly dehumidify the air. Where I live in Chicago, Illinois, I have seen a zillion HVAC systems installed in new condos (we've been experiencing "condo-mainia" for the last 10 years) that were improperly designed, sized and installed.

As far as efficiency is concerned, 13 Seer is the minimum allowed by the US Dept. of Energy as of January 2006. However, you need to be careful. Upgrading to a 15 Seer unit will cost a GREAT deal more and you may not enjoy a terrible increase in performance to warrant the additional cost. I have two new 13 Seer units and I will warn you, they are MUCH bigger than the 10's, however you will enjoy the fact that they are much quieter too.

You're looking at spending a lot of money on your project and I hope that you research contractors to ensure that you find a good one. Good luck!

BigJim
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