Lazy tonight, anyone direct me to a good trade study on payback time for the differential cost??
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no.. but a good discussion can always be found in Grainger's catalog.. been using their vcariable speed blowers since 1980
Mike Smith Rhode Island : Design / Build / Repair / Restore
Junkhound, the old single speed blower in my up unit burned 460 watts per hour. If I ran it all year every day,( I didn't) cost would have been $322 per year. The new variable speed blower is rated at 120 watts, so continuous operation at full speed would cost about $84 per year.
The unit when set to "fan on", only operates at 50% speed. When actually cooling or heating, the fan runs at 50% for the first minute, and 80% for the next 7.5 minutes, before going to full speed until thermostat is satisfied. We often run the fan for many days/weeks, just to filter air. So, real world, a lot of the year would be at 50% draw, and a fair amount at 80%, and very little at 100%. Whisper quiet at the low speeds.
From that pattern, I would guess we save about $250 / year compared to full run of the old unit. There are other benefits, such as the increased humidity removal with the first minute of cooling at 50% speed, and the last 3 minutes after cooling or heating at 50% speed getting all the goody out of the coil after the compressor shuts down.I can't remember the cost difference to calculate the payback time.(1999)
Only my take on it, not a scientific study, but hope helpful to you.
Paul
my take from reading on other forums is that the variable speed mtrs are more susceptible to moisture, and especially to power surges (lots of those here in summer - coastal South carolina.
And they cost a lot more to replace ($600 for the motor??) and are harder to diagnose.
what is the cost difference for a season of operation ? not full time operation? . In April May and Oct November my system does not run at all.
So you pays your money and takes your chances.
personally i am in the KISS box and like a motor anyone can fix cheaply and is "on the truck' . In 21 years i have replaced two indoor blower motors in my 3 1/2 ton heat pump, one last week.
i really think HVAC people like to sell them - adds cost - like the $1000 "NAV system" on your new car - been lost much in a car? not me.
Edited 1/16/2004 7:19:21 AM ET by wain
Wain, I like the KISS system, but have loved the economy using variable speed. The spring and fall months, when little A/C or heat needed, just happen to coincide with pollen months here in Virginia, so leaving the fan on at little cost is our real world. Also, house is a lot less dusty all year.
We got a 10 year parts and labor warranty free by buying (luckily) at promotion time of year.
In our down unit(not var speed), now 28 years old, we have the original blower, and it has had oil in the taps every 2 years, and pulled for vane cleaning once or twice. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
I understand.
there could be real benefits to it.
different subject- have you ever heard or seen how energy calc programs handle open houses, that is houses with cathedral ceilings and open upper halls and walkovers?
Wain, no, I have not. The variables must be tough with these houses with great rooms that are 28' high. Just came back from one 10 min ago, and calculating the heat gain/loss is going to be a challenge due to the balconies, high glass, open space down stairs etc. If you have something new, enlighten me. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
the heal loss calc is probably doable. whats got to be an art is assigning capacity to say two heat pump units.
Its an overlooked calculation I think