Q. I have two questions concerning heat (or the lack thereof) pumps. First, I think you mentioned this in one of your columns years ago, concerns the air circulation. We have a 2400 square foot rancher with a full unfinished basement. We wanted to close off or at least greatly reduce the air vents in the rooms upstairs that are not used much thereby getting more "heat" to the main rooms. Will that help? We seem to recall that you had said not to do this?
Second, our heat hump is a 13 year old Lennox and I assume nearing the end of its projected life. In anticipation of replacing it what are the better models? I have heard that some models now run part of the resistive heat elements for a short time whe n in the heating cycle thereby getting the temperature up quicker (and warmer air output) while reducing run time. Kind of a trade off in operating cost. I have also heard that some of the newer models have become much more efficient for other reasons u nknown to me. Your opinion is greatly appreciated.
A. Now that we are getting closer to the cooling season-- the weather for which heat pumpís cooling loads are sized and a time during which they work the hardest, itís a good thing to examine what you have critically.
That your 13 year old heat pump is still working is both good news and bad. You are correct in your assumption that age 13 is at or near the end if the unitís working life. Heat pumps have traditionally had a reputation for lasting eight to twelve years on average. Thatís because they provide both heat and cooling.
Itís not uncommon for an air-conditioning system alone to last fifteen to twenty-- and Iíve seen older. I have also seen heat pumps push twenty and their owners are so proud of them. But those old clunkers are like old cars-- they may run OK but have tr ouble passing gas stations for all the fuel they guzzle. The same is true of older heat pump and A/C units-- they eat electricity at prodigious rates. So much so that as of last year the U.S. Department of Energy mandated that all units manufactured after Jan 23 2006 had to be able to achieve a SEER of 13 or greater. SEER means seasonal energy efficiency rating and is a formula in which the amount of cooling Btus produced over the season is divided by the watt hours used to produce it.
That sounds a bit arcane but hereís a little trick you can do. Go out and look at the equipment tag located somewhere on the side of your unit. It will have the manufacturerís name, serial and model numbers on it. Look to see what the maximum overcurrent device-- fuse or breaker-- is listed for that 13 year old unit and Iíll bet it will read in the 40 to 50 amp range. A new unit for the same output is in the 25 watt range. It doesnít take much math to figure out the newer units are designed for much less electricity for the same cooling.
Unfortunately, unlike replacing the unit in the past when all you had to do was pay for a similar sized exterior unit to renew the system, you now will need to replace the outside unit, refrigerant lines and interior coils because to get SEER 13 you will have to use the new refrigerant, R410A (called Puron®), which works at much higher pressures than did the old R22 or Freon®. And it will cost about twice what just the old outside unit did.
As for closing off the excess room space, HVAC manufacturers and wise heating contractors say this practice doesn't really save energy. Your heating and cooling system is designed to heat a specific square footage of living space and will continue working at the same rate. It can't sense whether registers are open or closed. Additionally, the cold air from the unheated rooms will filter back into the rest of the house Ė like leaving a door or window open. Your best bet is to make sure youíre properly weather tight and well insulated.