Sunday, November 28, 2010

HRV Problems

The HRV system was finally "completely" installed, by Duke's HVAC. Here's what I discovered on the back of the house one day a couple weeks ago when I got home from work:

The upper hood in the middle is the existing high speed bathroom ventilation. The ones on the lower left and right were meant to be the HRV intake and exhaust. Fantek customer support recommends that, on the same plane, the intake and exhaust vents should be at least 6 feet apart, and that the intake should be at least 6 feet from any other exhaust including attic vents. The maximum distance in this case is 3 feet between the bottom two vents, and 1.5 feet between the bottom two and the middle one.

When I complained to Paul, he asked where I wanted them. I considered what would be the easiest thing to do. There's very little room on the wall in the chase upstairs. The diagonal distance between the lower right hood on the picture and the upper left corner where the wall runs is maybe 5 1/2 feet. So I said why not put the intake on the roof,  thinking perhaps it would have a longer pipe like a chimney.

Here is what we got:

The intake is so short it will draw in fumes from the asphalt shingles when they heat up.

I remeasured everything this morning but there is simply no way we can get 6 feet between the HRV exhaust, bathroom exhaust, an attic vent, and the HRV intake. It seems fairly clear that the bathroom exhaust needs to go out the roof vent, since it will be fairly strong.  I also think the HRV exhaust will need to go through the roof, since I don't see any place where we can put it on the wall.  The attic vent can stay on the right lower side of the back house wall in the picture above. That leaves the HRV intake. We could run a duct into the bedroom and out the bedroom wall, extending the chase we put in for the duct that runs to the hall. The extension would be below the wooden frame in this photo:

The vent would then run out the wall on the right side. Or we could simply put the duct at the upper corner of the attic area even though it is around 6" short. That might not be such a problem, since the attic vent won't be forcing air out like the exhaust. The hood will direct it downward and the intake will be much higher on the wall.

The front HRV is in better condition. There, I asked our good friend Duke to direct the intake through an existing attic vent in order to reduce the number of vents on the front of the house, but Fantek customer support tells me there needs to be a separate 6" hooded vent for the pressure to work. So we can just move the exhaust to the bottom below the attic vent, and put the intake where the exhaust is now. That way, the exhaust will not re-enter the house through the attic vent, and there is at least 8' between these vents and the intake.

One thing is for certain, though. You would have thought our good friend Duke would have given Fantek technical support a call before he started hacking around on the back side of our house. I'm certain at least one and possibly two of the holes need to be patched, either in place or by replacing the siding and cutting new holes.

The other problem is that I have an ominous feeling about the noise the HRV will generate.  On Monday, I was working at home and several times a rumbling noise started up above my head.  I think this was probably our good friend Duke starting up the HRV unit. I tried it again today and it was nowhere near as quiet as the unit Paul showed us at another job he did, when we were trying to decide if we wanted to put in HRV. Paul showed us an HRV installation he had done himself, in which the unit was hung from wires. No vibrations are transferred to the building structure. Running fully on, the HRV was absolutely quiet, and we requested that our unit be mounted similarly. But when I got home from a conference in Washington earlier this month, I found that our good friend Duke had used heavy metal bars to fasten this one down, though there were a couple of shock absorbers and some missing rubber gaskets which supposedly would cut down on the vibrations. He installed the rubber gaskets on Monday but if what I heard on Monday was the HRV, there still might be vibrations transferred to the house frame.

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