Tuesday, March 4, 2008

Don’t Get a Water Heater with a Tank

I came home the other week and as I was wandering around the house looking for something and I noticed that the wall was leaking. Now it had rained the day before so I was not particularly surprised that there may be water dripping from certain places on the house. But as I walked back by, I noticed that there was a puddle on the concrete in the carport, and more interestingly, the carport was dry, as it doesn’t rain in the carport because the carport has a roof like most carports do. Upon further investigation, the water was dripping quite profusely and was warm.

Not so long story short, there used to be a water heater in that part of the house. There isn’t now. Moral of the story, don’t get a water heater with a tank.

For a long time, I’ve espoused the wonders of tankless water heaters. Having no (in actuality very little) tank, they don’t need to keep a bunch of water warm all the time on the off chance that you’ll be needing it. Think about it, you use hot water to shower once or so per day, your dish washer (be it you or your wife or that machine under your counter) needs hot water every day or so, and your washing machine may need it every day or so if you lean toward using hot water for washing. Characteristically, your tankie water heater is doing nothing but keeping water warm for about 22 and a half hours per day. There is no such thing as perfect insulation, so that means some of that heat is escaping into your house. My old tanked water heater had only a single inch of insulation, which means it was heating the utility room. Heating with electric resistance is inefficient as is using your air conditioner to remove that extra heat in the summer.

You may read past posts here where I had said I wanted a tankless water heater, I was just waiting for the old one to die, and what a grand exit it was. I’m gonna have to replace a bit of the subfloor in the utility room now. Who knows how much else I’ll have to fix. Anyway, my brand spanking new Seisco RA-28 came in the mail today, yes, you can send a water heater in the mail. It’s about the size of a briefcase, about 16x16x5 or so. The only snafu in installing tankless water heaters is the power requirement. My old 40 gallon electric water heater used at max 4500 watts, but all the time. It heated rather slowly because of the limited power usage. Though it works slightly faster, a gas water heater is the same way. The Seisco uses at max 28,000 watts. Of course it wont need that much all the time, it will only heat the water as much as is necessary at the time it is used. To install a water heater with such requirements means new power hookups for it because the old ones wont work. Herein lies the added cost, I had to buy 75 feet of #1 copper wire, and 50 ft of #8. That totals up to about $150 and add to that the heater itself at $750 and the rest of the wiring and conduit and plumbing and I’m looking at about $1000.

This may seem like a lot at first, but my little EPA sticker on my old water heater said that it would cost me over $500 a year just to operate. A tankless water heater is supposed to shave about 30% off that and I expect a bit more because I no longer have to push hot water 50 feet across the house through the cold crawl space. The water would lose about 20 degrees on the way, that’s a lot of energy wasted for a shower. So I’m expecting to save about $200 off that expected water bill per year, and that means that the tankless water heater will actually pay for itself in five years or so, not a bad investment by any means especially since it is expected to last for better than 20 years. Additionally, its functionality to be able to “top off” pre heated water will make it easy to install a solar water heater later on if I get the chance. Additional savings will come from our low flow faucets and ultra low flow (1 gallon per minute) shower head.

My calculations conclude that this water heater will be able to, during a shower, heat water from well below freezing to well above scalding temperature. I’ve accidently installed a valve on the hot water line to slow it down for running baths in case the heater can’t keep up with something like 6 gallons per minute that the tub faucet uses. It’s one of those ones with only a single valve so you can’t limit the flow if necessary. You see, a tankless water heater has a certain ability to raise a certain amount of water to a certain temperature at a certain speed, and a tub faucet is designed to drain a pre heated tank as quick as possible so I need to make them work together.

For your benefit, I am going to detail some of the install with pictures and descriptions here and of course, I’ll answer questions and give updates on energy usage after a month or so. After February’s power bill, I’m hoping to be able to make some adjustments to our energy usage. It was the highest in KWh’s per day since we’ve lived here. I did adjust the furnace to use less propane because that’s several times as expensive as using the heat pump so we are saving some money there.

Here is the installation, I won't add a whole bunch of useless details, it took about 7 hours to do. If you have any questions, leave them in the comments section, I always answer comments.

Here's what the Seisco looks like right out of the box, I put my RAZR on it for a size comparison. About the size of a really thick square briefcase.

Here's what it looks like right out of it's own box, you can see the four chambers for the heating elements and the big wires that go to those, and you can also see the circuit board and all the sensors with white and yellow wires.

The pictures I have here are the ones taken after everything was done, so you can see that the wiring is finished. One thing I'd do differently is to use black wire instead of white because white is usually recognized as being neutral which is definitely not the case here.

The black oddly shapen little boxes are the relays when themselves run on 24VDC which I assume is made by the transformer to the left. The silver things underneath the wires that are hooked to the intake pipe are called TRIACs. They are kind of like switches for the less electrically enclined, they are bolted to the tube so the incoming water can cool them directly.

I used 3/4" flexible blue conduit with the snap in ends you can buy with it. They snap directly into the water heater side plate. To attach them to the wood wall plate, I used threaded ones, drilled a 1" hole and hand screwed them into the hole, they fit almost perfectly and look professional. When the wall around it is finished with drywall, it will fit in well.

Here is the subpanel I installed to handle the power, it is rated for 125 amps which is what it will handle, make sure you dont get the six space one that is identical but says you can't use the 7th and 8th spaces. I don't know why they are there if you can't use them. There are four 30 amp breakers, one for each heating element. The heater specs call for #1 copper wire to the box which is quite expensive especially since I bought 20 feet too much. I did the same thing here with the blue conduit, one end snaps into the box, the other end screws into the wood at the top of the wall the heater is mounted on. I used standard 1 1/2" gray pvc conduit to carry the thick wires to the main box.

Here you can see the 125 amp main breaker for the subpanel as well as the 200 amp main breaker for the house. Follow the directions, make sure your house can handle the load. For this heater, you need at least 200 amp service. This is no problem for a new house, but some older ones may have a problem.

This is what it looks like with the cover off. I had expected it to fit differently which is why the pipe ends are where they are. This actually works better however because there are no sharp bends in the hoses. I used 18" braided plastic hoses because they are black, very flexible and look good. I thought of using stainless ones but they cost about 50% more, and I thought they'd lose more heat.

Insert drywall around the edge of the wall plate here and it will be finished. This is about the cleanest installation of anything I've ever done. Not that anything else was dirty, I just wanted this to look as professional as possible for the sake of longevity and convincing others to do the same.

Here is the final result. Add drywall and it will be finished. It is very close to the shower which eliminates the vast majority of the heat loss between the utility room and the bathroom where the prime use of the hot water is. The pipes are also insulated and as I discovered yesterday, the pipes will stay warm for quite a while, I don't have to wait and dump a bunch of cold water in the bath when I am topping it off.

The shower works beautifully, though my wife and I have been very careful with it to get used to the new quirks of the system. Actually, the water gets warmer a bit more gradually, instead of just slamming us with the hot stuff.

One thing I did have a problem with last night was when running a bath, it just wasn't getting warm enough even when I turned down the flow. I thought this was very strange considering the shower only uses about 2/3 of a gallon per minute from the heater and it has no problems. I adjusted the temperature up on the control board and it fixed the problem even with a higher flow rate. I am not sure if the problem was the flow rate or the temperature of the incoming water (it snowed last night.) However, the problem was remedied with no issues resulting. I'll just add that to the "getting used to new technology" sheet.

One of the benefits I like especially is the fact that the heater doesn't even keep the water in the chambers very much heated. It maintains a slight temperature gradient between the various sensors, you can barely tell, it is maybe just a few degrees above room temperature. But the less heat there is, the less there is to be lost so this is a very good thing.

At the end of March when we get the power bill, I'll give you an update on how that goes. Until then I'll be enjoying my shower.


1 comment:

Anonymous said...

Look forward to finding out how much your electric bill changed since the install.