DHW Piping

awaltiii

I have a situation on piping a SuperStor DHW generator to a boiler.

In this situation, the boiler is about 35 FT from the kitchen faucet. I am considering installing the SuperStor under the kitchen sink and insulating the piping to and from the boiler.

My guess is it is more economical to have the SuperStor under the kitchen sink as there would be less water wasted waiting for the HW to get to the kitchen faucet every time the faucet is turned on. I have not seen any information on this subject. Has anyone seen any information on this situation?

Any opinions on this???

Al Gregory

You can put the water heater anywhere and use a bronze circulator and a loop to keep the water near the fixtures hot

awaltiii

Thanks for the idea, but I remember reading an article somewhere (possible in PM Magazine) that indicated the annual costs for such a setup was in the $100 to $200 range for the electricity to run the pump as well as the heat loss.

I figured if I moved the DHW heater away from the boiler, I would be excercising the pump more 70 FT of piping vs 20 FT, and I would have to account for heat loss through the pipe insulation.

I guess the difference is the aded load to the pump + heat loss in an extra 50 FT of insulated pipe vs the slug of water going through 35 FT of pipe each time you turn on the HW faucet in the kitchen.

I had never really thought of this situation until I saw an old electric HW heater at this house (not in service) that was placed directly under the kitchen sink.

hr

But you will

be running 180° boiler water from the boiler to the tank location, possibly 1". Seems the heat loss from this would be greater than the loss from a 1/2" recirc line and supply at 130°?

hot rod

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Uni R

DHW Piping

Where are the other hot fixtures and how would they be impacted? Would you be moving away from them? There doesn't seem to be any correct answers here and there are a ton of variables. You have many options. A small electric tank under the sink that bridges the 35' wait for hot water. You could put in a recirculating system (ideally on a timer). You could place the DHW tank closer to the kitchen fixture as suggested but in that case you'd want it piped with large diameter piping because you'd be increasing the head losses and that would cost you for the piping and insulation. You could put one of those devices that sends cold water in the hot water lines back. You could also better insulate the hot water run and use narrower than 1/2" piping for it (like 3/8") although that impacts flow and increases velocity and will make any traditional plumber scream. The variables are the cost of wasted water, the cost of wasting BTUs, the cost of waiting for water and the cost in materials and time for doing any of these solutions. Personally, I wouldn't move the DHW farther from the boiler unless I lived somewhere that never got above 50 degrees out all year long and then it would be part of the system. If the waiting bothered me, I'd go for type K 3/8" (unless I had low water pressure) because it holds about half as much water as 1/2" L and almost a third as much as 3/4" L.

Todd_9

hot water recirc

I have done this succesfully with no pump. If you use a swing check on the "return line" from the fixture and tee into the bottom of the heater it should work. Basically you are just using the differance in the weight of hot and cold water to displace each other in the lines.

Uni R

hot water recirc

Todd, this typically requires a basement, more vertical distance than horizontal distance and the return path cannot have any upward turns or it'll have a thermal trap. You also have to leave off some insulation near the return, but they are excellent when you can take advantage of them in a building.

Todd_9

recirc

It sounds like he does have a basement - or a really high kitchen cabinet.

Thanks for pointing out those other things though. I forgot about pitch in the return pipe, it does make sense that the trap would stop flow.

ScottMP

You'd be supprised

in the thermal energy in a 40 gallon hot water heater.

I installed a re-circ line about 80 feet away with no rise except about eight feet. I installed a pump and went back after it was wired. It worked perfectly. Only problem ... the electrician forgot to wire the pump. It did it all from gravity in the tank.

Scott

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Doug Wagoner

Location of the DHW tank

I would be hesitant to use the valuable space under the kitchen cabinet for the DHW tank. First, I would have an angry wife. Second, you may be creating greater losses with two lines from the boiler than the one from the tank near the boiler. Third, there is a better way to get hot water quickly rather than relocating the tank in valuable cabinet space. Consider the mess when it leaks and the difficult change out. No way, if there is room near the boiler.

Uni R

Oh man...

Scott, just don't tell that to people who have tried and failed to set in up in small 2 storey houses... ;-)

awaltiii

I actually would be installing the DHW tank in the basement under the kitchen sink.

I have gotten feedback with a few ideas I did not think of (including yours). I guess I will have to digest all of the information to come to a decision.

Thanks for your input