ROANOKE TIMES
Copyright (c) 1995, Roanoke Times
DATE: Sunday, December 10, 1995 TAG: 9512300002
SECTION: HOMES PAGE: D2 EDITION: METRO
COLUMN: Hints for Homeowners
SOURCE: STEVE ELDER
Despite the lingering doubts of the thermally challenged out there, heat pumps can keep you warm. And when properly installed and working right, with a backup system for exceptionally cold weather, they can function much more economically than straight electric resistance heat.
Unfortunately, for a variety of reasons many of them do not work as well as they should. Usually either poor installation or poor maintenance is the problem, not a flaw in the concept or design.
Heat pumps move heat. In the winter they move heat to the inside of a house from outdoors. In the summer it's the other way: they move the heat from inside a house to the outdoors. In summer operation the heat pump is essentially the same machine as an air conditioner.
Many of the same maintenance rules apply to both. The greatest single problem with heat pumps is that owners frequently don't bother to change the filter regularly. A clogged filter has noticeable consequences. For one, it can add as much as 30 percent to your heating and cooling costs, since the system must run longer to get the desired results. (The inside coils clog up with dirt, causing low air flow and insufficient heat exchange.)
A clogged filter also will shorten the life of the compressor due to the necessarily longer running time, and it can make the condensate drain line clog up, causing water to run out onto the floor or onto the top of the furnace.
Furnace filters cost less than a dollar and should be changed (or cleaned if you have a washable filter) every month, not every lifetime. Also, avoid buying the electrostatic filters. They do a very good job of filtering the air, but in doing so they significantly retard the air flow, leading to the same problems as a dirty filter. They have earned the reputation of "compressor killers'' as a result. (Note: do not confuse an electrostatic filter with an electrostatic air cleaner, which is a hard-wired multi-component device costing up to $700).
Also, give an occasional look at the blower. Its vanes are cupped to make it move more air. If the vanes fill with dirt because of poor filter maintenance, their curves flatten out and they move much less air, resulting in poor system performance. It is also important to keep the outside coils surrounding the compressor clean. This means good yard maintenance in the area: mowing so that grass clippings are not thrown against the unit, taking care with the weed whacker so the vanes don't get damaged, keeping the vines off the unit, trimming back encroaching bushes and not building a deck that blocks top discharge units.
While you're at it, make sure the dryer vent does not come through the wall right behind the compressor. Units fail every year because the coils get clogged with lint.
The other main source of heat pump problems is poor installation, particularly in some town house or condo developments where speed of construction, maximizing use of interior space and marketing may take precedence over mechanical design.
Simply adding more refrigerant to a system to boost performance is a simplistic and potentially harmful practice, yet there is a tendency to do this without analyzing the whole system. Proper problem diagnosis entails checking all operating components of the system, which means all of the above: proper duct, line, and compressor sizing, condition of both inside and outside coils, and correct level of refrigerant. Have your system checked at least once a year, and if your technician doesn't look like he's shaving yet, consider changing companies.
As far as agencies are concerned, your safest bet is probably a Comfort Assured company. This label means that the dealer or service company has taken a high-powered comprehensive course in maintenance and repair from a power company guru and has received a certification. Your local power company can provide you with a list of Comfort Assured dealers.
A properly designed and maintained heat pump system will provide a very satisfactory level of comfort, particularly in a temperate climate.
You may have heard of some new kinds of heat pumps on the market, which have resulted from recent developments in design: ground source heat pumps (don't get one) and scroll compressors (do get one).
A ground source heat pump is a system that extracts or deposits heat to coils buried in the ground or immersed in a body of water instead of being exposed to the air. The big efficiency advantage stems from the stable temperature of the earth. As your local spelunker will attest, earth temperature below the frost line usually remains at 55 to 57 degrees year round compared to the 100-degree seasonal variation in air temperature.
This heat pump operates at the highest point on the efficiency curve and does not require a backup heat source. The downside is the prohibitively expensive installation cost, which usually cannot be recouped under normal conditions. These systems make some sense for new construction in hostile climates; but for the time being they are not generally practical.
The scroll compressor was patented in 1905 but not widely marketed until the past few years. It consists of two parts as opposed to the 15 parts of a standard piston compressor. The engineering is elegant in its simplicity and offers a host of advantages. Scroll compressors are quieter, significantly more efficient, require less supplementary gadgetry, last 50 percent longer and produce 8-to-10-degree warmer air. They have made the piston compressor a thing of the past. Get one and be happy.
(Next time: heat pump controls and dual-fuel heating systems)
Steve Elder is a Roanoke home inspector. Questions and comments may be sent to him in care of The Roanoke Times, P.O. Box 2491, Roanoke, Va. 24010-2491.
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