# Install an electric water heater to bypass tankless coil



## Bbowz (Jan 25, 2014)

Hi everybody.  Thank you in advance for any help or advice you can give me.

My wife and I bought a house in September which use(d) an oil boiler for domestic hot water and to operate a hydronic heating system.  We were stunned to see what our oil usage was over the first 3 months we were here.  So we quickly made a great decision and bought a harman accentra 52i pellet insert.  This stove effectively heats our 2200 st ft colonial in Connecticut.  We only turn the heat on in the second floor at night because my wife thinks our 1 year old won't sleep through the night with his door open.

So the heating system kicks on very little.  Now I'd like to install an electric water heater to supply hot water and bypass the tankless coil in the boiler.  I would alter the wiring in the aquastat (Honeywell l8124a) to cold start the boiler and install a ball valve to stop the supply of city water to the boiler coil.  I would drain the coil and leave the tempering valve off to leave a pressure relief inside the coil.

I'd like to also install a ball valve on the supply to the water heater.  I'm thinking doing this would allow me to effectively use the electric heater for 99.99% of our heating but allow me to switch to the conventional tankless coil in the event of a power outage.

Any thoughts on this?  The boiler is a laars Newport approx. 12 years old.  I'm wondering if leaving the coil empty and exposing it to the heat of the boiler (when it does turn on) could cause damage to the copper.

Thank you all so much!


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## Dune (Jan 26, 2014)

Bbowz said:


> Hi everybody.  Thank you in advance for any help or advice you can give me.
> 
> My wife and I bought a house in September which use(d) an oil boiler for domestic hot water and to operate a hydronic heating system.  We were stunned to see what our oil usage was over the first 3 months we were here.  So we quickly made a great decision and bought a harman accentra 52i pellet insert.  This stove effectively heats our 2200 st ft colonial in Connecticut.  We only turn the heat on in the second floor at night because my wife thinks our 1 year old won't sleep through the night with his door open.
> 
> ...



Put the a ball valve on both the in and out pipes on the water heater while you have the house drained. You will be very happy ten years from now when you are replacing it. Other than that, no, you can't use your oilburner as a back up water heater during a power outage unless you have a generator. 

Second, I would just leave the boiler as is. Don't change anything.


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## Bbowz (Jan 26, 2014)

Dune said:


> Put the a ball valve on both the in and out pipes on the water heater while you have the house drained. You will be very happy ten years from now when you are replacing it. Other than that, no, you can't use your oilburner as a back up water heater during a power outage unless you have a generator.
> 
> Second, I would just leave the boiler as is. Don't change anything.



Hi dune, thanks for the good tip for the additional ball valve.  Sorry I left out that we have a generator and transfer switch already installed on the house.  I'd like to run the boiler off the generator in the event of a power outage and just wanted some opinions on whether the tankless coil would be damaged if it were empty , drained and exposed to the heat of the sporadically firing boiler.  I don't really see that it would be a problem considering the heat would be transferred to the air in the coil and out the open tempering valve rather than to the water in the coil as it's set up now.


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## peakbagger (Jan 26, 2014)

Some boilers leak when they are operated as cold start, some don't. Pretty easy to figure out, cold start it manually for a few weeks, if it leaks then cold start isn't an option. My tech recommended that I remove the tankless coil and replace it with a blanking plate. Unfortunately the plate is no longer available for my boiler but may be for yours. If mine ever leaks I would probably make up a plate.


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## Bbowz (Jan 26, 2014)

I don't see how it could leak if I put a ball valve on the dhw intake and drain the coil.  Think the hydronic side would leak?  

I'd like to leave the coil in place to allow a sorce of hot water if I need to use the generator


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## woodgeek (Jan 26, 2014)

The highest temp a dry coil would see, immersed in the boiler water, would be 180°F or so.  Don't know why a copper coil would have a problem with that.

Keep in mind that a well insulated tank would stay warm for 3-5 days, and could hold enough water for 6-10 navy showers.  I personally wouldn't deal with all the plumbing hoohaws for the occasional power failure longer than that.

Personally, if you can run your boiler cold start, you should get a geospring HPWH, retire the oil coil permanently and shut down the oil boiler whenever you don't need the space heat.  With a $30 transformer (120V to 240V), you could run the HPWH on almost any genny.


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## Bbowz (Jan 26, 2014)

Great tip on the transformer!  I had looked hard at the geospring but my wife is stuck on an 80 gallon tank. The 80 gallon heat pump is way outta my price for this deal.
  I called the boiler manufacturer to see how to start this project safely and he was the one to claim the coil would be weakened.  It didn't make sense to me either.


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## woodgeek (Jan 26, 2014)

On second thought, a drained coil could be ok, but a flooded coil closed on both sides (i.e. by valves) could have problems from thermal expansion of the water.


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## woodgeek (Jan 26, 2014)

Bbowz said:


> Great tip on the transformer!  I had looked hard at the geospring but my wife is stuck on an 80 gallon tank. The 80 gallon heat pump is way outta my price for this deal.
> I called the boiler manufacturer to see how to start this project safely and he was the one to claim the coil would be weakened.  It didn't make sense to me either.



You could get an 80 gallon tank, and put an external HP on it.


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## Bbowz (Jan 26, 2014)

Haha yea....problems like BOOM.  I think my plan is good to go


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## Dave A. (Jan 26, 2014)

No experience with it but doesn't sound like a good idea to leave air sealed in the coil.  Leave it active with water in it or remove it, seem the safest options.


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## Bbowz (Jan 26, 2014)

It wouldn't be sealed.  I'll leave the water intake closed with a ball valve way before it goes into the boiler.  No air there.  Ill drain the cool of water through the tempering valve and leave thermostat off all together .  So there would be an open pipe on the formerly heated pipe as it exits the boiler.  Should be plenty of pressure relief.


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## Dune (Jan 26, 2014)

Bbowz said:


> It wouldn't be sealed.  I'll leave the water intake closed with a ball valve way before it goes into the boiler.  No air there.  Ill drain the cool of water through the tempering valve and leave thermostat off all together .  So there would be an open pipe on the formerly heated pipe as it exits the boiler.  Should be plenty of pressure relief.


Why do you think you need to empty the coil? My system has been what you are describing for at least 22 years, without removing the coil. What is the point of removing the coil? 

By the way, a New Yorker is a welded steel boiler, not a sectional cast iron boiler. Cold starts shouldn't be an issue.


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## Bbowz (Jan 26, 2014)

I don't want to remove the coil.  I want to shut off the water flow to the coil, drain it to prevent over-pressure and run an electric water heater.  I want to keep the coil and water connections intact so that I can switch to the oil boiler in the event of a power outage.


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## peakbagger (Jan 26, 2014)

Some boilers leak between cast ron sections when operated as cold start boilers it has nothering to do with the hot water coil.


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## Dune (Jan 26, 2014)

Bbowz said:


> I don't want to remove the coil.  I want to shut off the water flow to the coil, drain it to prevent over-pressure and run an electric water heater.  I want to keep the coil and water connections intact so that I can switch to the oil boiler in the event of a power outage.


Right. Over pressure will only result if you isolate it.


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## Dune (Jan 26, 2014)

peakbagger said:


> Some boilers leak between cast ron sections when operated as cold start boilers it has nothering to do with the hot water coil.


Like I said, a New Yorker is a welded steel boiler, no sections to leak between.


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## Bbowz (Jan 26, 2014)

I have a laars Newport.  Is that the same as a New Yorker?


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## maple1 (Jan 26, 2014)

peakbagger said:


> Some boilers leak between cast ron sections when operated as cold start boilers it has nothering to do with the hot water coil.



The most vulnerable place for leaks on my old one was around the gasgeted sealing surface of the coil. I was almost guaranteed to see water on my floor from there if my boiler went cold.


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## xman23 (Jan 26, 2014)

Yes the domestic hot water from the oil hot water furnace is terrible. We had one as kids, domestic water was so hot it was dangerous. It has to be so you have heat. We would plug the coils every 2 years due to the minerals in the well water. Not to mention the oil consumption, smell and furnace running all summer. 

Not a big deal. I would cut off the water in and the water out . Route the house side to the new electric hot water heater.

 I have a 40 or 50 gal electric that works great, GE I think,  dual elements. It's in our cabin. we have hot water 10 minutes after turning it on. It's still hot after being off for a week. Never runs out of water with 2 showers going non stop. That said we only have 25LBS water pressure at the top of the mountain.


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