Installing a tankless water heater

[Piwoslaw]

Originally Posted by Daox

I'm also not sure if this would be any better than buying a much less expensive boiler with the same efficiency and just having my own ~15 gallon water tank with its own circulator pump on it and super insulate it.

Only ~15gallons? Whip out your welder and make a 200-500 gallon heat buffer tailored to your present and future needs!

[Daox]

Haha, yeah I'm sure that could be done and I might do that when I get the boiler setup. I just used 15 as the number since thats what the boiler I posted about had for capacity of DHW.

[Daox]

Well, apparently the cheaper electric units don't monitor temperatures either (except for scalding protection). I did find one that does though. The unit I'm currently looking at is a Stiebel DHC-E 10-2 which I've found online for about $280. Still cheaper than a new gas tank heater, and reusable after the solar panels get installed.

[AC_Hacker]

Originally Posted by Daox

Well, apparently the cheaper electric units don't monitor temperatures either (except for scalding protection). I did find one that does though. The unit I'm currently looking at is a Stiebel DHC-E 10-2 which I've found online for about $280. Still cheaper than a new gas tank heater, and reusable after the solar panels get installed.

Looks interesting.

Make sure the temp rise specs work for your usage patterns...

Maximum temperature increase above ambient water temp. is 65 /87 @ 0.75 GPM, 49 /65 @ 1.00 GPM, or 33 /44 @ 1.50 GPM.

The positive reviews I have seen so far were based on low flow applications...

With an unlimited supply of hot water, smaller storage space, and reduced energy costs this unit is perfect for sinks and most low-flow applications.

provides hot water ro kitchen sink

-AC_Hacker

[Daox]

I measured my ground temperature this morning, it was just above 49F. The main water draw I'm worried about is the shower. A while back I measured the flow and it draws ~1.25 GPM. At this flow rate, the DHC-E 10 should be able to provide me a 53F increase or just over 100F water. I'm still debating weather to go with this unit or go with the next size up DHC-E 12 unit which would provide ~115F water @ 1.25 GPM. It doesn't cost that much more ($300), but you have to run heavier gauge wire to it too. Once the solar is in, either of these units will be plenty large enough to get me through summer and even winter will not be an issue I don't think.

[Ryland]

One common solution to on tank-less water heaters that can't keep up with demand or give the temp rise that you want is to install a tempering tank, basically a water heater that is set to 70F or 80F to warm the water from the well up to just above room temp, at this lower temp the losses from the tank are so small it would take days for it to cool down enough to cause it to reheat.
I've thought about doing something like this only with a small 5-6 gallon tank water heater that could then be super insulated, so the big tank brings your water from ground temp up to room temp and the small tank boosts the temp up the rest of the way but small enough that a foot of insulation all around it is not going to take up all of your utility room.
I realize that one of the advantage of a tank-less water heater of course is that you save space so adding a tempering tank is going to be a draw back, but if you have the space then the tempering tank should last the rest of your life as it will hardly be working, scale build up should be low because it's not getting as hot and it's not having to come on very often, it would also make your on demand water heater last longer because it would not be working as hard ether, less thermal shock as well.

[Daox]

Thats a great idea! Even if it wasn't heated, but just left to get up to room temperature that would be enough. That would take up a lot of slack and reduce the electric bill. Even with the solar panels in place afterwards it would still help out. The space a tank takes up isn't an issue for me. Any ideas where I could get a cheap tank that could be used for this purpose? Would you think a 55 gallon steel drum work for now? Perhaps coat the inside with something?

[AC_Hacker]

Originally Posted by Daox

Would you think a 55 gallon steel drum work for now? Perhaps coat the inside with something?

In my area, there are more than a few businesses (a teriaki sauce factory comes to mind) that buy product (vinegar) in 55 gal plastic drums, which they re-sell for not much money($8/ea). I bought about 8 of them to hold dirt while I was drilling my back yard.

& & &

You might want to investigate the temperature conditions under which bacterial is able to grow in water... may or may not be an issue.

-AC_Hacker

[Daox]

I have some of those blue plastic barrels. I'm not sure they'd hold up to the pressures used for domestic water though. Mine is set to around 60 PSI.

[Ryland]

Originally Posted by Daox

I have some of those blue plastic barrels. I'm not sure they'd hold up to the pressures used for domestic water though. Mine is set to around 60 PSI.

They do not hold up to the pressure, they start to swell at about 20psi, same with the steel barrels, you can get tanks that will take the pressure but your best best is most likely going to be finding a used water heater that doesn't leak that someone is replacing.