DHW Coil Piping

Mark (PA) · Post by **Mark (PA)** » Tue. Sep. 23, 2008 11:05 am

I hope this question doesn't sound too stupid but here goes. Generally I understand how to pipe the DHW coil in the EFM 520.

But I am wondering how to do it in this situation...

I have an electric hot water heater. I would love to turn the break OFF during winter while I am using the Coal boiler to do DHW but I need the ability to turn it ON also in case I have to shut down the coal furnce for any period of time. My oil boiler does not have DHW.

Can someone tell me the easiest way to accomplish the piping with this situation in mind? I know I don't want to pipe the outlet from the DHW into the inlet of the Tank becuase then i'd have to go thru 40 gallons of COLD water to get to the hot.

OR am I thinking of this all wrong? I assume I need to be able to valve off the Coil when needed also?

And not to get off topic but I have a series setup right now so my oil burner will be valved off as long as I don't need it. is this OK? Or will the oil burner rust and fall apart? DO I need to do anything specific there?

Thank you all VERY much!

Sting · Post by **Sting** » Tue. Sep. 23, 2008 11:26 am

Mark

Check your PM

WNY · Post by **WNY** » Tue. Sep. 23, 2008 12:06 pm

Do a search on HOT WATER COIL or DHW COIL, there are numerous ways to pipe it, with and without a pump. But, you can use your existing PRV entry and the drain entry on the tank without having to disconnect the plumbing to it, but you will have to drain it to hook stuff up correctly. I would leave the breaker on, if the stove can supply enough hot water, the heating element can automatically supplement it. If it stays above a certain temp, then the electric wouldn't be used anyway.

LsFarm · Post by **LsFarm** » Tue. Sep. 23, 2008 12:32 pm

Or., with a few valves, you can bypass the electric hot water heater/tank and use just the instant hot water coil in the EFM for your hot water, then when you want to swap back to electic DHW, just turn a few valves and flip on the breaker.

Personally I'd use the electric tank like WNY suggests, as a holding tank for hot water,, Electric tanks typically are well insulated, so if you use hot water at least twice a day, once in the morning, and also at night, the coil in the EFM will 'recharge' the hot water tank with very hot water, and it will stay hot for 12+ hours till the next hot water use.

This is pretty close to what I do with my Propane hot water heater, I have a water/water heat exchanger , which does pretty much what your EFM's coil does, this heat exchanger preheats the well water as it enters the Propane DHW heater, raising the water to 150* or more,, my propane use for hot water in the heating season is zero. Your electric use for hot water heating should be zero with a similar setup.

Greg L

Tommc_2 · Post by **Tommc_2** » Tue. Sep. 23, 2008 2:59 pm

Greg, do you have any pics of your DHW setup?

Freddy · Post by **Freddy** » Tue. Sep. 23, 2008 4:40 pm

WNY wrote: you will have to drain it to hook stuff up correctly. I would leave the breaker on, .

Just thought I'd grab this out of context and remind you to make sure the electricity is off before you drain the tank, and that the tank is verified full before you turn the electricity back on. If you turn on the power to an empty tank the elements last exactly 1/3 of a second.

U235a4 · Post by **U235a4** » Tue. Sep. 23, 2008 6:35 pm

here are a few pics of my water heater / direct hot water. take note the boiler is missing from the picture since it needed a minor repair after 50 years of service and while Axeman-Anderson are doing that they are also doing a few updates to it. Also I have a cold water line that goes thru my basement from the well to the boiler room and a Hot water line that starts at the water heater and end in the boiler room.

First picture is of my hotwater heater that has a shut off on the cold side and hot side along with unions to make repair easy.
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Second picture show the cold water line and hot water line coming into the boiler room with two shut off there also.
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Third picture shows the mixing valve and shut offs for doing repair.(note that the mixing valve is two close to the boiler and will be moved to somewhere in the second picture because of heat soak into the cold water line and sometime water is H.A.H.
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and for HAHA's here are the expansion tanks I went with two half size units for a fail safe instead of one big unit. Both have shutoffs/drains (for checking pressure or removel)/unions for removel they are special BG fittings
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