Wednesday, December 23, 2009

Solar Hot Water IV: The Installation Experience

Chris and Justin from Sunwater Solar came by and had a look at our house. We decided to put the collectors on the east side since the west side is occupied by the solar PV. The east side gets sun primarily in the morning, but since the solar PV is higher value in the afternoon (about 3x the tariff other times), having it on the west side is a better deal. So it made sense to keep the remaining space on the west side, about enough for another 3 PV panels, for solar PV if we decide to add some in the future.

Then came the question of where to put the tank. We initially considered putting it in a small house next to the sauna, or maybe next to the fireplace pod that sticks out from the house, but ultimately we decided to repurpose the cold air return for the forced air heating. We had the forced air heating taken out a couple years ago and put in hydronic floor heating, so we didn't need the space any more. It is on the second floor in the hallway. The space consisted of a plenium with a large grate on the front, which led into the downstairs furnace room. When we had the hydronic furnace installed in the furnace room, the plenium was blocked off from downstairs. As we discovered when we opened up the space and removed the plenium, the flue from the furnace and the gas fired hot water heater in the downstairs mechanical room ran up the middle. We had a bit of work to do on the space.

Point to note when planning a solar hot water system: be sure to include enough time and money for upgrading the space where you plan to put the tank and the pump station if you are not going to use your existing tank.

Sunwater doesn't do the kind of drywall and carpentry work needed to modify the space, so we asked a friend of ours who is a contractor, Tim Hmelar (check out his new business, Purple Coupon) to do it. Tim is the most reliable contractor I know, his work always comes in on time and at or under budget. Together with Tim's brother Frank, who sometimes helps him on jobs, we decided to put a door in the side of the space and a hatch where the grate for the cold air return was located. The pump station then could be installed in the upper space on the inside of the hatch, with the tank below it. Just under the hatchway, we decided to put a platform on which someone could sit while servicing the pump station.

Because the flue ran up the middle of the space, Tim and Frank had to move it to the back. You can see the new location before the platform was installed:

The black pipe is the vent from the bathroom, which is on the wall immediately to the right of the flue.

Here's a view of the bottom where a plywood floor was installed to support the tank:

One issue we ran up against was what to put on the inside walls. By code, if there was any loose wiring, we needed to have some kind of protection in place to keep someone from accidentally grabbing the wires. But the amount of space in the closet was pretty tight, especially since I wanted to wrap the tanks in additional insulation. The normal thickness of drywall is 1/2" but it turns out you can also get 1/4" drywall, which is what we ended up using. This gave us another 1/2" of space. In addition to that, Tim put 6" of closed cell foam insulation on the roof and at least 3" on the walls of the closet, to reduce the amount of heat transfer into the house in the summer, when the tank can get up to 175F.

The downstairs gas heater tank looks pretty normal as you can see from this picture:

The insulating blanket isn't doing much good since it is not tight against the tank, and, by the way, the outer skin is vinyl, which is quite unhealthy. But we were were going to change all that.

The guy Sunwater sent to do the installation was an older tradesman, quite pleasant to talk with, but I began to have some suspicions about his competence almost immediately. One day I came home from work after the tank had been installed, and found that he had connected the feed lines from the collector to the top heat exchanger instead of the bottom. Now, heat rises, so this configuration would have caused the tank to stratify with the incoming cold water line injecting cold water on the bottom and the hot water on the top, where the water outlet for the domestic hot water is. I called him up and made him change the plumbing.

In the picture below, you can see the bottom of the fully installed Superstor tank, where most of the interesting stuff is happening (there's some on the top too but not as much):

The two lines in the back with the black foam around them are the feed lines from the collector, going through the correct lower heat exchanger. The corrugated line is the pressure overflow from the tank, the line it is connected to is the pressure overflow coming down from the expansion tank and pump station in the upper chamber above the platform. The line entering the tank is the cold water input from the house and ultimately the main. The other line in the elbow on the right side is the hot water running to the gas hot water tank downstairs, you can't see the pipe running down from the top of the tank where the hot water outlet is because it is behind the door frame. There is also another pipe running across behind the cold water input, connected to the pan, that's also an overflow pipe to the drain. In the back is the furnace and gas hot water heater flue.

Below you can see the internals of the pump station in the upper chamber before the cover was put on:

The brass colored cylinder is the pump, three gauges on the front provide information about the temperature (to and from collector) and pressure in the feedlines. The feedlines coming from the collector through the outer wall of the house are on the top. The blue wire is the power cord (110v, 15 amp, we also had Tim install a plug for it). Here's what the pump station looks like when the cover is on:

And here you can see the white expansion tank:

The grey wire in the background is the sensor cable from the collector, the corrugated line is the pressure overflow from the expansion tank to the pipe going to the drain downstairs, and of course the ubiquitous flue.

Since the solar hot water acts as a preheater for the gas heated tank downstairs, it needed to be plumbed into the gas tank. Here's a picture of what that now looks like:

The grey knob you see in the middle is the mixing valve. It is where the hot water from the tank is mixed with cold water to keep the domestic hot water below 120F. Above that temperature, scalding is possible. As for the rest, the grey steel line on the left is the pressure overflow, the horizontal  line with the red lever on the  bottom is the hot line from upstairs, feeding into where the cold line would normally go (for preheating), the horizontal line on the top is the cold going to the tank upstairs. The grey knob is where the domestic hot water comes out of the gas tank. In the back on the right is a feed line for the hydronic boiler, from the cold line, and a cold line that goes into the tank, with the red lever now in the off position. Switching the front red lever to off and the back to on causes the solar tank to be cut out of the loop. Unfortunately, there is no way to switch the gas tank out of the loop (more on this in a later post).

Charging the collector feedlines with the heat transfer fluid requires a very specific pressure adjustment to match the height difference between the collector and the expansion tank, and also any air in the feedlines must be purged or the bubbles will cause a lock and prevent pumping. After the installer charged it up the first time, the tank didn't seem to be getting any heat. It turned out that the pump wasn't on because he had forgotten to turn on the power switch! He came and fixed that, but then the pumps were really loud and there still didn't seem to be any heat getting into the tank. So he came back again: he had forgotten to bleed the air out and so the lines were locked. When I checked the pressure after he finished, it turned out he had way overpressurized the lines, as if there were 10 vertical feet or so between the collector and the expansion tank instead of the 2-3 feet there is. By this time I had had enough of this guy. When I discovered that the unions on the tank and in the pumping station were leaking hot glycol (and copiously at that), I called Justin and told him I wanted somebody who knew what they were doing put on the project.

Justin was very accommodating and worked with me to get the problems fixed (also, I didn't send him his last payment until he did, just to make sure). But it took another month before we could get the unions properly fixed. Justin sent one of his best guys over, and he first re-soldered the unions on the tank. But he couldn't get the pump station unions tight. It turns out they have a kind of pressure coupling which seals when tightened, but when overtightened, leaks. So he had to send his very best guy to come and cut through the pressure couplings. One slip and they would have had to reinstall the entire feedline set from the collector again (or, at least, a substantial part of it)! But thankfully he managed to cut just precisely right and they reinstalled the pressure couplings. Both sets of unions now looked solid.

Despite the fact that we had such problems with the installation, I don't hold it against Justin, and I would still recommend Sunwater. As it turns out, the installer had only been working for Sunwater for a few months, whereas the other two guys had been working with Justin for years. I've been in this situation myself: you hire someone with a great resume and they turn out to be a dud (or, even worse, they falsified the resume and don't know the basics of the job). So I didn't hold it against him. Justin really tried to get the system properly fixed, and ultimately did fix it to my satisfaction. However, this does point up a problem with the whole area of residential green energy and energy efficiency remodeling: many contractors and/or the people working for them don't have a clue. So they often do things, especially when it comes to insulation or weatherizing, that are ineffective or, in this case, downright harmful.

Point to note when planning a solar hot water system:be sure you understand how the system is supposed to work and what is needed in terms of insulation to make it efficient, and make sure the contractor does the work necessary to ensure it works properly.

Note to President Obama: "Cash for Caukers" won't work if the caukers don't know how to wield a cauking gun so they can properly insulate. Most people in construction in the US are in the business because they can't do any other work. Unlike Europe, where trades require a substantial amount of technical training, and where the trades have over the last 10 years upgraded their members' training through in service education to address energy conservation and green energy equipment installation, the assumption in the US seems to be that anybody can do this work without any training. If this kind of attitude goes into "Cash for Caukers" the resulting weatherization is not going to save energy, it will be a colossal waste of money. I'd recommend to the Congress if they want to do "Cash for Caukers" that they should budget enough that any contractor who plans to participate must take a 6 month course in energy efficiency building so they understand what they are doing. And - just to be on the safe side and avoid fraud - have people trained to inspect the job periodically the way building inspectors do, since most inspectors don't have the training to spot improperly installed green energy devices or ineffective insulation either.

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