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03-10-2009, 10:19 PM #14Regular Guest
- Join Date
- Feb 2009
I know what you mean. I fault the lax building codes. I asked the builder if I could pay for:
1. Upgraded windows
2. Tyvek wrapping on the house
3. The best caulk money can buy
I was told no each time or that the price they would quote would make me say no.
So I have spent time installing v strip and upgraded weather stripping on the windows and doors and went so far as to remove the window casing and add spray foam on the worst windows. All exterior facing outlets have the insulation covers.
One of the contractors thinks they installed an undersized furnace at 64,000 BTU. He claimed he services the same model house up the street and theirs is bigger. It has some credibility, as on cold windy days, the furnace doesn’t shut down. I also don’t set back the temperature at night since it takes 3 hours to warm up again in the morning. I get lots of air flow from the vents though.
The existing condensers were dropped on the ground on pads and were far from level. I built frames of 2x4 pressure treated lumber to level them off.
I could roll the dice and what until the AC fails and replace it during the summer at the going rate with no rebates or tax credits. I would only buy a mid grade replacement in this scenario and keep the 64,000 BTU single speed 80% furnance. It could go this year or last 5 to 8 years more. Who knows? We just seem to get couple more each year fail on the street.
The other option is to replace with a modulating 95% variable speed furnace with a high efficiency two-stage AC unit, intelligent controller and take advantage of rebates and tax credits. This option would cost me about 1.5 times (after rebates and credits) of a mid level replacement AC unit.
I agree that I would only save about $400 to $500 a year on energy. But since I am convinced the AC will fail during my stay here, I am leaning towards spending 1.5 times now and saving the $500 per year and enjoying the improved comfort.
I need to find some experts to look at the duct work and calculate the load properly.
03-11-2009, 08:45 AM #15Regular Guest
- Join Date
- Sep 2006
Correcting poor build quality is always annoying - especially on a new home. I can probably guess who the builder was. Some are notorious.
Unfortunately, the sub used for the HVAC work probably fell into the same quality pool as the rest (low bidder), but they were responsible for the most (or at least one of the most) expensive systems within your home.
As beenthere suggested, get the homeowner version of HVAC-Calc from this site and do your own load calc. You will find out a lot about your home and where the issues probably are. It is good to do some "what if" analysis such as replacing those windows and the impact of the heat gain/loss. You will know where to spend your time and money. It was one of the best steps I took.
Nothing wrong with a unit having long run times - you want that when the conditions are at or a little beyond design conditions. If fact, any modulating equipment will run almost all the time delivering the heat or cooling at the rate the home is losing it. Design conditions will be about 9 - 10* for winter and 92 - 93* summer. This winter we have had at least four times in which we were well below the design conditions and all your heating equipment should have been running almost non-stop during those periods. Systems that are constantly cycling or short cycling are very inefficient.
The point on saving a few hundred dollars per year is that will only happen if the ducting is top notch and and all the air doesn't end up outside the conditioned space of the home just as fast as it is being heated or cooled. And, (this is the real point) if those deficiencies are corrected you will see most of that savings with the equipment you already have.
A top notch HVAC contractor can tell you whether there are issues with your air conditioners and furnaces and the likelihood of a pre-mature failure. This can't be a company whose primary focus is to sell product, but rather, a company that will do an honest evaluation of what you have, explain the results to you in a way you can understand and then you can make a realistic and rational decision.
The only way to do an honest evaluation is to gather data and analyze it. You can not make good decisions with out data and the right company that knows what to do can provide lots of it. But people replace systems all the time just that way - making decisions in a vacuum. Contractor hears you aren't happy with what you have (for whatever reason) and goes into sales mode to sell you something that you think will make you happy. More times than not you won't be. Look around this site and you will find discussion after discussion about people who have spent lots of money and still have the same problems they had before, but now don't have the money to fix the real problems.
When you find someone to check your ducting you should confirm that they will analyze and remediate any duct/air flow issues using Manual D. If they say they have been doing this since you were in diapers and just know how to do it - send them packing. Same with any contractor who will be replacing equipment, if they don't do a load calc using Manual J pass on them (most will make excuses like you have already heard such as it had to be done when the home was built and so the sizes you have now must be correct - wrong!! - most home have over sized equipment). This is even if you have done a load calc yourself. They are the pros, they should be doing a professional job. If nothing else, to confirm you have done it correctly.
If equipment capacity does, if fact, need to be larger than what you currently have then your duct work will have to be addressed for that too. More times than not duct work is undersized (putting your hand in front of a supply vent will not tell you whether there is adequate air flow with the proper static pressure) and installing high capacity equipment on already undersized ducting is only going to make matters worse.