# How To Plumb Electric Water Heater With Oil Indirect?



## velvetfoot (Sep 6, 2012)

(I thought it would be better to start a new thread.)

Should the cold inlet of the elec. wh come from the indirect hot water?  Maybe it would pay, to preheat the water the same temperature as the outdoor reset say when a heating zone is on?  The boiler would be up to temp anyway, so what's the big deal in heating up the indirect?   I'd have to figure out how to wire that up.  The reset isn't that much because I didn't think it was a good idea to go too low.  Maybe the excess boiler heat could be scavanged (not sure about the whole condensation thing though - how low to go.)

Thinking about it some more, if I did that, both tanks would wind up being heated up, and there'd be standy losses from both.   Maybe wiring the the indirect to only run when heat is on would not cost much incremental oil so that it wouldn't be a big deal.  The water in the electric would be used first and replaced by warm water from the indirect, so it wouldn't have to run as much.

Maybe plumb it for flexibility in plans, but more complicated than just going whole hog with the electric.

Ideas?


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## kopeck (Sep 6, 2012)

I'm in the same boat.  My ideal setup would be a DHW coil/exchanger in my storage tank piped into a electric, or even better heat pump hot water heater and ditch the indirect all together.  Then if I wanted to I could even dump solar into my tank and use it to preheat the water for the electric heat during the summer.

My wallet isn't going to allow for my ideal setup at the moment though.  I do have an unused electric hot water heater though that could be plumed in.  Just sitting here I can come up with some rather complex ways to switch between the two but then I would have a bunch of money wrapped up in supplies.  I like to dream. 

K


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## avc8130 (Sep 6, 2012)

If it costs more in the summer, it probably isn't THAT much cheaper in the winter.  No matter what, if your hot water usage is consistent, the indirect will call for heat the same % of the day...1.5% for my case.  If the boiler is HOT already from heating the house, the circ will kick on and start stealing your house heat from the boiler.  It all depends on the exact scenario if it MIGHT be cheaper.
If I am wrong (always a possibility):

I would just plumb it in parallel with some ball valves.  Once you are done with the heating season, throw the ball valves to switch from the indirect to the electric.  Vice versa in the winter.


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## velvetfoot (Sep 6, 2012)

I think it's ironic that the very insulation that is an advantage for an indirect, would act against it if it were used as a buffer from the cold well water.


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## Don2222 (Sep 6, 2012)

velvetfoot said:


> (I thought it would be better to start a new thread.)
> 
> Should the cold inlet of the elec. wh come from the indirect hot water? Maybe it would pay, to preheat the water the same temperature as the outdoor reset say when a heating zone is on? The boiler would be up to temp anyway, so what's the big deal in heating up the indirect? I'd have to figure out how to wire that up. The reset isn't that much because I didn't think it was a good idea to go too low. Maybe the excess boiler heat could be scavanged (not sure about the whole condensation thing though - how low to go.)
> 
> ...


 
I would add the electric DHW tank to the cold water line coming in and the HW output to the indirect HW tank.
Just by adding the storage in the basement the new electric tank would pre-warm the water because it would not be as cold as the street or well water. Then you could raise the temp even more with a little electricity up to 70 or 80 Degrees. Then the oil would hardly kick in! That is a good idea, maybe I will do it!


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## TheMightyMoe (Sep 6, 2012)

One thing to consider is electric water heaters have anode rods and build up debris that will make there way into your indirect water heater / coil. Not swapping a anode is a common reason coils built into boilers get plugged up( that and never blowing down a water heater) If it were me I would turn off the boiler and run the electric water heater by itself.

Also if your heating or already on stand by maintaining a boiler temperature, I would just use dwh. Savings using electrical come from turning off the boiler.


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## velvetfoot (Sep 6, 2012)

Ok, thanks.
I will probably maintain the capability of heating with the indirect, but drain it, since I'll probably use the elec. heater all year because, hopefully, the insert will be carrying most of the heat load.


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## TheMightyMoe (Sep 6, 2012)

If it werent for my garage, I would have the boiler on stand-by with no low limit, and be heating water with electricity. But because my garage needs the boiler, I heat the DHW with it it as well.


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## velvetfoot (Sep 6, 2012)

One good reason for me to keep the indirect capability would be to heat water in a blackout.


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## TheMightyMoe (Sep 6, 2012)

Well you shouldn't need to drain it anyways, valve it off, unhook thermostat, and turn off boiler low limit, if it has that option. Leak check often if the boiler never gets turned off. If it leaks you gotta leave it on standby anyways.


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## velvetfoot (Sep 6, 2012)

It's been operating as a cold start so I would think it should be okay, leak-wise.
Would there be a concern for something like Legionaires'?  (On the 'shell' side of the heat exchanger, if that's the right term here, where the domestic hot water resides.)


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## TheMightyMoe (Sep 6, 2012)

Legionaires thrives around 77-113*. You can always drain it to be on the safe side, good time to blow it down too. I'd probably just valve it, when its time to use it, heat the water up to 160* then flush the system.


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## velvetfoot (Sep 7, 2012)

Yeah, I might never use it again though, except in a power outage.

On another note, who'd thought the 40 gallon water heater box would fit in the back of a Mini Cooper...with the hatch closed!


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## BoilerMan (Sep 7, 2012)

TheMightyMoe said:


> Legionaires thrives around 77-113*. You can always drain it to be on the safe side, good time to blow it down too. I'd probably just valve it, when its time to use it, heat the water up to 160* then flush the system.


 
Exactly! Well said sir! Valve it off and drain the indirect in the summer. I'm EXTERMLY cheap when it comes to heating my water also, or anything else for that matter, but it is not worth the risk. The idea of connecting two (EWH and Indirect) together does nothing unless there is flow so say we had two EWH piped in series, the first one (well water in) just heats all the incomming water and has standby losses. The second one just has standby loss as it recieves hot water from the first. The only time the second one would do anything other that maintain itself (standby loss) is if a large enough draw cooled the first tank to the point it'd give the second tank cool water.

A tank as a buffer before a heating apliance will let the temp rise a bit and sweat all over the place rusting itself out. Or you could insulate it (think boilermate) and now the "heat" can't get in.

TS


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## velvetfoot (Sep 7, 2012)

All I can say is, "yup"!


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## velvetfoot (Sep 7, 2012)

I will say that I cut out the sweating on my well and softener tanks by wrapping them in some thin foam underlayment wrap.


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## velvetfoot (Sep 15, 2012)

I plumbed it in parallel with isolation valves so I can switch if I want, and put in some heat traps.
The joints sure don't look pretty but they don't leak.


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## BoilerMan (Sep 16, 2012)

Well done velvet!  Thats how I would have done it.

TS


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## TheMightyMoe (Sep 17, 2012)

Awesome =) I'll figure out this winter if I can turn off my oil completely, then I'll be doing the same thing.


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## velvetfoot (Sep 17, 2012)

Thanks.  I put the water heater on a piece of 2" xps foam I had laying around.  I'll insulate the pipes and maybe put a blanket on it.


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## velvetfoot (Sep 18, 2012)

Here is final picture...although I'm still thinking about putting a blanket on it.
It'll never look as pretty, though.


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## kopeck (Sep 18, 2012)

Looks good!

Every time I see a nice neat job I curse the plumber that did my initial install.  I like to think I'm doing a decent job with the stuff I'm adding on but it's hard when you start with a mess.

K


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## Beauly (Nov 15, 2015)

velvetfoot said:


> Here is final picture...although I'm still thinking about putting a blanket on it.
> It'll never look as pretty, though.
> 
> View attachment 74187


Hi!

I know this is an old thread, but it is about exactly what I am looking to find out.  I have a lpg gas boiler, (Cold start) for hydronic house heating.  I also have a 40 gallon Boilermate for domestic (off the boiler of course). And so in the middle of the summer the boiler is called (from the Boilermate for domestic) and runs for a long time (cold start) to satisfy Boilermate.  This summer I installed an electric hot water heater (EHWH) in the basement right underneath the kitchen sink, (5 seconds for hot water out of kitchen sink, used to be 50 seconds, Boilermate at the far other end of Basement) We fed the EHWH from the supply from the Boilermate.  I turned the Boilermate off this summer. I do not have a bypass in place for the Boilermate.

My question.  Now that my Boiler is starting to run for hydronic heat what should I do with Boilermate?  How low can I set it so to act as "preheat" for EHWH and do I have to worry about Legionairres, if I set Boilermate to less that 120f?

Thanks for any thoughts?


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## velvetfoot (Nov 15, 2015)

"We fed the EHWH from the supply from the Boilermate."
I take that to mean the outlet of the Boilermate goes to the input of the electric water heater?

This is assuming you like to run your wood stoves as much as possible, and so, might be starting up the boiler just to heat up the indirect, which maybe you don't want.

Maybe you could rig things up so that the indirect's aquastat circuit is completed only when there is a call for heat.  If priority was off, then the indirect's pump would stop when the call for room heat shuts off-while minimizing the boiler run time, maybe it wouldn't get the water temp up that high.  If priority was on, the indirect's pump would run until the boilermate's aquastat turns it off, and then the zone would heat up to setpoint.  You'd be storing more heat in the Boilermate, which might be a little weak in the insulation department, and might need a fiberglass wrap.  The Boilermate would then act as a mini buffer tank so that the boiler would run longer, which is usually a good thing, I think.

Edit:  Although, oil is cheap now, lol.  It's hard to get out of the expensive oil mindset.


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## Beauly (Nov 15, 2015)

I take that to mean the outlet of the Boilermate goes to the input of the electric water heater?

_Correct..._

This is assuming you like to run your wood stoves as much as possible, and so, might be starting up the boiler just to heat up the indirect, which maybe you don't want.

_LPG boiler runs radiant in floor, which I am only just starting to trun on and use, up till now I have been using Scan Anderson woodstove in the evening and also the Mini-split a little in the mornings (both in living room which is open to kitchen etc)_

Maybe you could rig things up so that the indirect's aquastat circuit is completed only when there is a call for heat.

_Ahh ok, a frined suggested that i find a thermostat swtich off an old EHWH and attach it to the boiler and use it to swtich on the Boilermate (only when the boiler is on and running) Same thing you are suggesting essentially, correct?_

If priority was off, then the indirect's pump would stop when the call for room heat shuts off-while minimizing the boiler run time, maybe it wouldn't get the water temp up that high.  If priority was on, the indirect's pump would run until the boilermate's aquastat turns it off, and then the zone would heat up to setpoint.  You'd be storing more heat in the Boilermate, which might be a little weak in the insulation department, and might need a fiberglass wrap.  The Boilermate would then act as a mini buffer tank so that the boiler would run longer, which is usually a good thing, I think.

_Any worries about less that 120f water sittingin the Boilermate (eg Legionnaires?)_


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## maple1 (Nov 16, 2015)

Can't you just set the boilermate hotter then?


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## Beauly (Nov 16, 2015)

maple1 said:


> Can't you just set the boilermate hotter then?



hotter then what?  or did you just mean, "Set the Boilermate to a higher temp"?

Not sure exactly what you mean.  Even now, yesterday, running wood stove in house, the radiant is not calling for heat, yet the Boilermate will and so on come the the boiler, running away to heat the Boilermate to whatever temp I set, and meanwhile the EHWH (electric hot water heater) is full of hot water.  It would be great to only have the boiler mate be able to call for hot water if the boiler was already running for heat. That is the trick, I think.


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## maple1 (Nov 16, 2015)

Yes - I was also thinking of the above suggestion to have the boilermate call only when there is a call for heat. Which should be often enough that the boilermate should be able to be heated as hot as you would want, once heating season gets going. DHW is a very small portion of an overall heating load. Plus the hotter you set the boilermate, the more hot water you have available overall, and the less chance of the electric having to be used at all.

But worst case if the boilermate isn't even used at all, electric DHW is pretty economical overall on its own. And re. legionalla, I think as long as the water gets hot enough before it heads for the taps (i.e. in the electric heater), the bacteria won't survive.


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## Beauly (Nov 16, 2015)

Ok,

That is the goal then, setting up the Boilermate so that it can only be "allowed" to come on when the boiler is already at some temp above "cold". hotwater heater thermo switch taped to Boiler, only allowing Boilermate to call when Boiler is already hot.  

I have an Everlast HTP EHWH (otherwise know as worlds most expensive electric hot water heater) which is quite efficient and insulated very well, so I am still spending less in electric than I was when the 165k boiler ran for 45 mins each time the Boilermate called for heat!


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## velvetfoot (Nov 16, 2015)

With that heat sensor taped to the boiler plan you can probably set it so that it extracts more heat from the boiler after it shuts down rather than going up the flue.  Although, with radiant and its lower temp requirements...  Speaking of that, the oil version of this gas vent damper has been working well for me:  http://www.supplyhouse.com/Field-Controls-GVD-6PL-6-Automatic-GVD-Vent-Damper-11703000-p

I have several Ranco digital controllers and like them:  http://www.supplyhouse.com/Ranco-ET...ntrol-w-Sensor-120-240V-Input-Includes-8-Cord
They have 120/240v and 24 v. powered models.  Even if it's powered by 120v, it can still switch 24v.


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## Beauly (Nov 16, 2015)

velvetfoot said:


> With that heat sensor taped to the boiler plan you can probably set it so that it extracts more heat from the boiler after it shuts down rather than going up the flue.  Although, with radiant and its lower temp requirements...  Speaking of that, the oil version of this gas vent damper has been working well for me:  http://www.supplyhouse.com/Field-Controls-GVD-6PL-6-Automatic-GVD-Vent-Damper-11703000-p
> 
> I have several Ranco digital controllers and like them:  http://www.supplyhouse.com/Ranco-ET...ntrol-w-Sensor-120-240V-Input-Includes-8-Cord
> They have 120/240v and 24 v. powered models.  Even if it's powered by 120v, it can still switch 24v.



I do have radiant, but boiler still heats to 180f etc and then radiant heat goes through a mixing valve etc, as I do have two (small) zones of high temp, one for an office space on North corner of first floor with cathedral ceiling and sunlights and 6 foot patio door to deck, that room is not heated enough from radiant so I added a panel rad to the North wall, and then other zone is the fin tube baseboard on 2nd floor bedrooms that is seldom used)

But thoughts for heat sensor:

put that electric hot water thermostat in series with the aquastat on the indirect water heat -

install  it on the supply pipe coming directly out of the boiler - strap in on, insulated it well.

wiring:  disconnect one of the leads leading to the boiler mate (from the indirect aquastat), tie one to one terminal on the added aquastat , tie the other terminal back to the boilermate.

set the "supply aquastat" for about 140, set the indirect aquastat for about 100F.

When the boiler reaches 140F if the indirect is calling for heat  it will then heat to its setting.

Thoughts?


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## maple1 (Nov 16, 2015)

I don't think an electric heater stat would work - it would be closed at lower temps, and it would open when it gets to setpoint (hot). I think that is the opposite of what is wanted?


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