The $800 Resistor Pack

November 19, 2007

Back in 1999 I had a house built. That wound up being an extremely stressful time in my life, as we’d also just moved to the Nevada City area, and my wife was pregnant. Word on the job site was that several sub-contractors bet the under for our marriage surviving, but that which does not kill us makes us stronger.

Once the house was actually done, life became much better. And we’ve been very, very happy with our house. Other than one thing. As that famous bard once wrote, “The first thing we do, let’s kill all the HVAC companies”.

I’ve got a panel house, built from SIPs – structural insulated panels. Very efficient, and very air-tight. The two kind of go hand-in-hand. Which means we need make-up air, a steady stream of fresh goodness from the outside so our dog’s fart doesn’t stink up the place for two weeks. Plus you can get sick house disease, where carpet chemicals, mold, and diapers can make you physically ill if you don’t get enough fresh air on a regular basis.

But when you bring fresh air in, old air has to go out. And this old air is air that we’ve carefully, painfully heated (or cooled) using natural gas or electricity. So venting air is essentially throwing good money and precious energy out the window – kind of like running the A/C with the front door open.

Enter something call an air-to-air heat exchanger, or heat recovery ventilator (HRV). This forces the air we’re venting to flow next to the air we’re pulling in, so that some of the energy we’ve expended to heat or cool the air inside the house gets transfered to the fresh air being pulled in from the outside.

So far, all good. Sounds like a great idea. And in theory it is. But then there’s reality:

  1. We wanted a 220 CFM (cubit feet/minute) HRV unit with 74% efficiency and a 320 watt power draw. The efficiency tells you how much of the potential energy is extracted from the inside air on its way out. The watts tell you how much power is needed to run the fans that pull and push the air through the system.
  2. What we got was a Carrier HRV model VC5BAB027000. This is a 200 CFM HRV unit with 68% efficiency that draws 500 watts. Unfortunately the general contractor signed off on this change, without talking to me or the engineer who did the energy calcs and drafted the original recommendation.
  3. After calculating the electrical cost of running the unit during the fall/winter, when compared to the cost of using gas to heat the air, we’re breaking even for half the year. And that doesn’t include the cost of the unit. If we were just basing it on energy cost, then you’d still have to factor in the energy required to build the unit, which is huge when it involves metal fabrication.
  4. Oh, and this unit had been discontinued two years before we had it installed. So the spare part situation was already heading downhill (see below) by the time we first switched it on.
  5. When I was trying to do the calculations for energy savings (above), I contacted Carrier to get the full specifications. Nope, can’t do that. I’m not a certified Carrier dealer. Now that just feels wrong. If I bought the unit, why is it OK for a company to refuse to send me information that I need to correctly operate it? This bugged me so much that I worked my way up through Carrier to the office of the president, but then the customer defense system proved too strong, and I was forced to admit defeat.
  6. Then the unit stopped working. About two years after the five year warranty expired. Nice. What failed were two relays on the circuit board. I’ve included the photo below, so you can understand why it makes sense for Carrier to charge $812 for a replacement. I mean, the relays alone are almost $3.

Carrier HRV Board

Now I’m not an electrical engineer, so perhaps my reasoning is off, but it looks to me like this board has got about 12 resistors, 13 diodes, 10 capacitors, three relays, two ICs, and a transformer. Total cost would be in the range of $5 – $10. Heck, I even looked up the price for the relays – $1.29 full retail per.

What’s interesting (as in the Chinese curse of “may you live in interesting times”) is that for parts distributors that have this in stock, it was $280, then $350, but now if you want it from Carrier it’s $812. Seems pretty clear that they’ve got a limited supply of these boards left, and the price heads up as boards get sold. Which, from a pure economic model makes sense, but from a customer loyalty perspective is dead wrong.

I’m in the midst of a startup ( so my free time is virtually non-existent, but I’m still tempted to buy the two relays and try to replace them myself. There’s no way in hell I’m going to pay $812 for that board, so the other option is to throw away this $2400 unit and replace it with something new. The only bright spot is that I can get a more efficient model, with the air flow that I want, for about $1100 plus installation.

Anyway, a friend said that the fundamental problem is that HVAC companies are in the business of selling sheet metal, but they don’t want anybody to figure that out. So they create a closed network of dealers, restrict the flow of information, and pray each night that they don’t get hit with a consumer rights class action lawsuit.