electric water heater as a storage tank

Steve Paul

A while back on the "WALL" there was a discussion about using an electric water heater as a storage tank, connected to a submerged coil in a boiler.I really like this idea. I plan on using a 40-50 Gal. water heater and a bronze circulator. The circulation path will be from the hot side of the heater, through the circulator, to the bottom of the coil, to a "T" on the drain nipple. The water heater will be fed cold water through the regular cold inlet and dip tube. I am thinking that the lower thermostat should be used to control the circulator because this is the area of the cold water entering the tank. I will set the water heater thermostat at 120-140*F, and the boiler low limit at 160-170*F. Does any one have any corrections, suggestions or better thoughts?

Steve Paul

keith

aqua booster

conversion. By the time you buy the misc. parts to make your electric hot water heater function like a aqua booster you are just about at the same price.

Bob Gagnon plumbing and heating

elec heater storage

that is the way i have been doing it fot a few years. less than half price for the same tank, and it has a built in thermostat. i use them when the boiler has a tankless coil already. you will also need a check valve so it dosen't overheat. bob

steve gates

have done lots

of these. use 50gal(not much price diff) bronze circ sized for the hx,from the bottom of the tank to cold side of hx, hot side of hx to cold inlet on tank, tee incoming cold behind circ(allows water to go both ways for small draws ect.), unhook the elements and the upper tstat, lower tstat operates the circ, low limit operates the boiler. wire nuts allow you to use top of tank junction box for wiring a neat look. because of our hard water this has eliminated the need for tempering valves(and having to replace them as often as every 1-2 years). AND no one has ever complained of not having enough hot water.

Patchogue Phil

Dip tube length

Steve

Do you cut the dip tube on the tanks COLD inlet, to the half way mark? I read this somewhere - the explanation is that the circulated HOT water being put into the tanks COLD inlet and dip tube will put the heated water right back near the bottom of the tank where the circulator pump will draw it again from the drain valve. Even tho heat rises, the pump will draw off mostly just heated water. It SOUNDS likely on paper. What is your thoughts and/or experience?

P.S. Is my sketch correct?

Thanks
Phil

PJO

Circulator Needed?

Do you have to have the circ? I put a very similar set-up in my house without one, and it's great...50 gallon electric hwh after the coil. My water pressure (off my well pump) simply pushes things along...am I missing something here?

I piped it so I can use each individually if needed as well. Nearly all the time, the tankless feeds the cold side of the "tank" and I have never ran out of hot water...although my three kids aren't teenagers yet :-)

Take Care, PJO

Bob Gagnon plumbing and heating

patrick

are you using the elec. heater- with the tankless as a pre heat? i am using it just for storage. without a pump to shut off when its satisified, the water tank will reach the same temp. of the boiler, too hot. bob

steve gates

no @ yes

I don't cut the tube,anymore. never noticed a diff when I did. And yes your drawing is correct. I suppose if you use a higher flow circ it may happen though. I usually use a 003 which is fairly slow. The boiler I use with this setup is a Larrs Endurance.

PJO

No, but...

I can "control" the temp. of the water entering the tank (after the coil) using the tempering valve. I normally keep it at about 135F or a bit higher (checked with a low-tech thermo) - jump in PAH to give everyone the reason! I suppose the electric is technically a storage tank most of the time.

If I didn't have that valve, I guess that would be a problem...at what point does the elctric hwh not like an incoming temperature? 160F? It's been four + years and it's doing pretty good so far (that's the sound of knocking wood you hear).

The only times I have really cranked the temp. up coming out of the coil was when my kids had croop...bolting into the boiler room, switching the valves, turning "up" the tempering valve and feeding the (coil) hot water direct to the shower for a quick "steam room"...I did not have time to check the temps. though :-)

Patchogue Phil

circulator choice

How does the TACO 003 compare with the 006 for use in this application? When do you use one over the other?

TIA
Phil

Unknown

Does it make a difference where

the cold from the house is piped in ? We usually tee it between the circulator and the inlet of the coil. Doesnt seem like it would make a difference though.

Dave Yates (PAH)

You KNOW the reason!

135 eh? I keep my system at 145! Here's what's needed to ensure safe reliable storage, transport in the distribution system and delivery of potable hot water. It's a three step process & very simple.

1 - Maintain storage at or above 140 degrees F.

2 - Install a thermostatic ASSE 1017 certified mixing valve at the water heater outlet that will maintain 140 degree F + or - 3 degree F delivery to the distribution system. Add recirc so D-system is held to 140.

3 - Within 18" of the use, be it a kitchen sink, lav or bathing module, install an ASSE 1016 pressure balance or 1017 thermostatic / pressure balance device, which can be the faucet itself in many cases. Set to deliver a max of 110 degree F hot water.

No chemicals; no bugs; stable steady state temperatures = safe reliable potable hot water. FYI, the Z21.10.1 regulation governing domestic hot water heaters states "The outlet water temperature shall not increase more than 30 degrees F above its maximum initial temperature, nor exceed 190 degrees F."



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Big Ed

Aquabooster

As Bob has mentioned add a check valve or a heat trap to prevent a gravity flow which would over heat the storage tank. Some use the cold inlet for the coil return which would act like a trap. But beware because some electric heater dip tubes have a small hole drilled near the top that would brake the trap and over heat the tank . Don't know the reason of the hole in the tube? Maybe to break up stacking?

There must be a dozen way to hook up a booster , all with pro and cons . Some also add checks to force the incomming cold water through the coil. This would preheat the incomming water and also flush the coil at the same time . I use to set them up to back flush the coil as well . But the draw back of a direction check is that it would drop the hot water pressure with the coils resistance. With out a direction check the hot water would have better pressure , but I would add valves so I could flush out the coil manually now and then. Without the forced water running through they would plug up in a hard water area.....

I also like to place the circulator pushing on the incomming coil side. The plastic impellers don't seem to last on the hot side of the coil return sitting on top of the tank. They turn to dust in a few years.......

Me myself I like a directed fired heater... Size the boiler for the heat load and the water heater for hot water load. Always made more sence to me if you can.......

steve gates

that's the way I

was taught. Now, it's be the water! ?Will the circ spin if the inlet is before the circ and the pressure is ____ ? Will it turn backward or deadhead? Now that I think about it I replaced a two year old circ that was piped in after the circ...hmmm I don't think I charged him either. ?What if it's spinnin backward and the juice comes on? Oh, now I gotta be the juice...

steve gates

go to the chart

003 shows 6gpm@5ft. 006 shows10gpm@9ft. If I remember the Endurance produces 2gpm forever. More flow than that it begins to dropoff. Forget the rate...Joannie?

Bob Gagnon plumbing and heating

cold water piping

i pipe the cold in at the top of the tank in the cold water inlet. that way there is no pressure loss going through the tankless. the older ones are restricted with lime. bob