Using Electric Water Heater to Feed Indirect

Joe107

I saw a post like this one from a couple years ago so I think this is doable but wanted to get some opinions about my specific situation. I currently have a cracked oil boiler with a 50 gallon indirect. I'm able to run the boiler once or twice a day for hot water. I'm thinking of switching to propane for a few reasons. It will be 6 weeks at least before I can get a propane tank buried on my property and a new boiler installed. I'm concerned that if the boiler leak gets worse we'll have no hot water.

I thought of getting a 40 gallon (because now it's 2 of us in the house most of the year) electric WH to solve my current problem and also give me a backup source of hot water down the road for when the new boiler eventually breaks down at some point. I'm thinking that during winter I will turn off power to the electric WH and use the indirect. During summer I may use the electric WH depending on cost of electricity vs cost of propane.

I am not a plumber but have been doing my own plumbing work for almost 30 years. How should I plumb this? Do I go from the outlet of the electric to the inlet of the indirect (less work) or tee into both the hot and cold lines and install shut off valves so they can be used independently? If I use the second method should I drain and refill whichever tank has been sitting unused (likely for months) before using it? Or do I drain it when I shut down one water heater and switch to the other?

I was thinking of going with a Rheem Marathon WH because Rheem says it should last a lifetime and it's less than twice the cost of the standard models from the professional brands.

Please let me know your thoughts.

Thanks,
Joe

Jamie Hall

Whole bunch of different ways to set that up -- and they accomplish slightly different things. I think, off hand, that I'd probably pipe the electric and the indirect in series -- one after the other -- but I think I'd go from the hot outlet of the indirect to the cold inlet of the electric, and then to the house. That way you always get flow through both, and while you don't get the volume storage of the hot indirect, with just two of you the 40 gallons in the electric should be ample when the indirect isn't in use. The advantage is that you don't have a seasonal change over -- in the summer with the boiler off, the electric just does its thing. In the winter, if you have the thermostats set right, the electric just sits there as additional storage, but would kick on if the indirect started to run out (or the boiler failed!)/

Derheatmeister

Or you could install one tank that has both a coil and a element.
Edit: https://cdn.shopify.com/s/files/1/0616/4096/6343/files/HX_SOLAR_STORAGE_TANK_SPECIFICATION_SHEET.pdf?v=9067423782942692121

random12345

I'm surprised you've decided to switch to propane. What made you go that direction?

hot_rod

It depends on how complicated of a piping arrangement you want. If you want to valve off either one, it will take a handful of ball valves or 3 way ball valves

Joe107

@random12345 When I gave my wife all of our options I mentioned that it was good this didn't happen during winter, we would have had to move out due to the 6-8 week wait to get a new oil DV boiler, she said get propane! There's a local company that will bury a 1,000 tank for me on a lease for only $250 and unless they're lying, their per gallon price for lease customers is very reasonable (and that's not just for the first fill). But now you got me thinking again, we could get the oil DV boiler and in a few years replace our air conditioner with a heat pump and have 2 heat sources...

@hot_rod A little earlier I found a drawing you made and attached to a discussion from 2020 showing 2 water heaters piped so they could be used in series or independently. That's what I'm going to do. Thanks!

@Jamie Hall, @Derheatmeister Thanks for your replies. I think I will go from the indirect to the electric but will look into tanks with coils and elements. Didn't know those were available. A heat pump WH is also an option due to the rebates.

Thanks again guys!

EdTheHeaterMan

There is the option to use one water heater as a preheater to room temperature before sending it to the primary heating tank. This way the primary water heater will not work so hard. The first tank will allow the water to get from cold ground water temperature to the boiler room temperature. maybe as much as 14° warmer. That makes the ∆T for the water heater a little less, therefore using less fuel. But selecting which water heater tank to use as the FIRST or PREHEAT tank is always a problem. With 6 valves you can alternate tanks from season to season. Then both tanks will stay online so the water in the non-heating tank will still have fresh water moving thru it in the off season. I have illustrated the piping design in this post from last year.
https://forum.heatinghelp.com/discussion/comment/1711484#Comment_1711484

Joe107

@EdTheHeaterMan Thank you! That's a great solution.

random12345

@Joe107 Ok thanks, I understand a little more now. Good luck to you in making your decision.

Derheatmeister

Joe107 said:

@random12345 When I gave my wife all of our options I mentioned that it was good this didn't happen during winter, we would have had to move out due to the 6-8 week wait to get a new oil DV boiler, she said get propane! There's a local company that will bury a 1,000 tank for me on a lease for only $250 and unless they're lying, their per gallon price for lease customers is very reasonable (and that's not just for the first fill). But now you got me thinking again, we could get the oil DV boiler and in a few years replace our air conditioner with a heat pump and have 2 heat sources...

@hot_rod A little earlier I found a drawing you made and attached to a discussion from 2020 showing 2 water heaters piped so they could be used in series or independently. That's what I'm going to do. Thanks!

@Jamie Hall, @Derheatmeister Thanks for your replies. I think I will go from the indirect to the electric but will look into tanks with coils and elements. Didn't know those were available. A heat pump WH is also an option due to the rebates.

Thanks again guys!

If you are contemplating using a heatpump look at the latento storage tanks...This is a reverse indirect waterheater that will reduce the formation of legionella,it has a parafamin storage medium that will store the BTUs for a longer period that regular H2O ,It has three coils that can be intergrated with geo/boiler/solar... This tank can also be upgraded with a electric resistance coil as a back up or for choosing between different fuel sources depending on the cost associated with them at any giving point.(Seperate control)
Pretty much the Bomb when it comes to keeping occupants safe and and money in their pockets.

Edit: Here is a link to the product:
https://ivt-group.com/en/produkte/latento-solarsystem/

Joe107

@Derheatmeister Thanks for that info. I will research that.

ethicalpaul

The Rheem Marathon is pretty cool, I had one. I keep wishing for a Marathon tank with a heat pump upper on it