With oil over the $4 per gallon mark, I am ready to go get an electric hot water heater for domestic hot water. My Crown boiler is a Bahama model BD-120 wc with a tankless coil. Home heat and domestic hot water.

Can I tee off of the cold water supply to go into the electric WH and simply disconnect the hot water out at the plate on the boiler and plug it?

I would keep the Crown for heating in winter and get year round Dom hot water from the electric WH. I can do all the electric and plumbing work. Just need to get away from heating hot water with oil right now.

Am I ok or will doing this create issues with my system not obvious to me at this point? Thanks for helpful responses.

 

I would suggest cutting both pipes on the tankless coil and then capping them. You may want to first blow out any water in the coil to be sure as not create a high-pressure hydrostatic lock when the boiler comes up to high temperature.

I think what you are doing is fine. My opinion is that tankless coils are a crappy way to heat domestic water, barely better than heating a kettle of water on a wood-burning kitchen range.

 

If you are going to convert to electric hot water, I don't suggest capping both domestic coil pipes unless you leave at least a pin hole in one cap. You will probably want to change the aquastat as well.

 

I might also suggest getting the water heater and making it a circulated storage tank. Use a bronze pump and use the coil as a heat exchanger. Put on a cold start aquastat and an Intellicon 3250 heat manager and you will have something good going on.

Ken

 

While Grady has far more experience in this matter I see no reason to leave the coil open and a good reason to close it tight. I suspect that the reason that he suggests not capping it tight is the fear that when the boiler heats up it will create a high pressure inside a totally capped coil. As long as there is no water in the coil this fear is groundless.

A reason FOR capping it tightly is if the coil were to leak it would then still be contained. If the connections were left open then the boiler water would puke from the open connections.

As for changing the aquastat you may be as well off to simply set the low limit as low as it will go and then turn off the power to the burner/boiler during the non-heating season.

As for KField's suggestion of using the tankless coil with a bronze circulator pump...unless the energy cost for oil is less than the cost for the same amount of electrical energy you are just as well off saving the money that would be spent on the pump, piping and new controls.

 

First question I'd ask is whether you've run the numbers comparing cost of oil vs. electrcity. Where I am, oil is still cheaper.

 

I'll admit I have not run the comparison numbers oil vs electric as xiphias mentions; I'm not familiar with the math or formula to work that out. But the energy dollar cost since having the boiler installed back in 98... I mean,now, it's just incredible. Thank goodness here in New Jersey we haven't had as severe winters this season and the last, as we've had in the past. I had an automatic delivery of oil 150 gallons (middle of last month) @$3.68 gal cost me $552 dollars. ( I shut the heat off at the thermostat immediately following) Right now that same 150 gallons cost $637.5!

Typically, here, I shut off the home heat from May to early October, unless we get really cold September mornings.

So I've only measured based on spending. I don't know what the cost will be when electric pays for the Dom hot water. I just don't know how to compute it; make sense of it.

So that's where I am, and I appreciate the responses you guys have volunteered. Forgive the long post.

 

I run an EWH here... 50 gall ... family of 2, central NJ ... I'm paying about $35-40 for the water heater, but I'm on a separate meter with a small discount (0.02/KWH) on that meter. They don't offer that service option anymore, so you will pay full price.

Maybe this will help for reference ...

 

I did the conversion you are asking about back in Feb and I installed a 50g Electric water heater and my electric bill has increased about $40 per month. Family of 3.5 (college student home on weekends). I capped off both ends of the coil and installed an old press relief valve on one end...no fear of leak and over pressure protected. My amateur cost calculation is this. $40 per month for hot water = $480.00 per year. Oil at 4.10 per gallon...just keeping the boiler hot for DHW from May thru Sep at 1 gallon per day 150 days = $615.00 just in the summer. I would likely save hundreds more over the winter not heating DHW. I did the install it myself and the total cost with the heater and plumbing and electrical supplies way under $400. Good luck!

 

The energy calculation is pretty simple. Number two heating oil has an ultimate BTU rating of about 142,000 BTUs per gallon. If you are really lucky you may get as much as 80% of that transferred to the domestic hot water but realistically the number is probably less.

So take 80% of 142,000 and you get 113,600 BTUs of domestic hot water for every gallon of oil burned. Round that down to 113,000 for ease of calculation. If you were able to adjust for the standby losses of the boiler you would likely be down to less than 100,000 BTUs of domestic hot water for every gallon of oil burned but use the higher figure to make the oil look good.

So, every gallon of oil would release about 113,000 BTUs for heating domestic water.

Now for the electric. Electricity has (by definition) 3,414 BTUs per kilowatt. Electric water heaters are about 97% efficient so a kilowatt of electricity will deliver about 3,311 BTUs to heating the domestic water. Round that down to 3,300 for ease of calculation.

Divide 113,000 by 3300 and you get 34.24. Multiply that by the total cost of electricity per kilowatthour and you get the break even cost of using oil rather than electricity.

For example: the total cost per kilowatt for electricity is 12 cents per kilowatt hour you multiply 34.24 times 0.12 and the answer is 4.11. That means that if the cost of the oil is $4.11 a gallon then the electricity is cheaper. REMEMBER, this calculation is skewed in favor of the oil. If the cost of electricity is only slightly more than the oil the real world cost of heating the water will be less with electricity.

 

Most, if not all, boiler manufacturers specify leaving at least one end of the domestic coil uncapped or removing it & replacing with a blank off plate. I've seen it done both ways & never have I witnessed a problem.

 

... at a time when I really needed clear thinking on this subject you all came through with interesting input. My best to all.

Nelson

 

I'm in the same boat and need to do something about it. Would adding an indirect be a better choice over an Electric WH? If the indirect route, I assume I would need to replace the Aquastat to a High Limit and would I need to add boiler protection like P/S or a bypass?

 

Depends on the related energy prices and how efficient your boiler is. Without knowing those, nobody can advise you.

 

I've read your question and I have the same problem and question. Can I tee off of the incoming water line, shut off the water to the tankless hot water section of the furnace with a ball type valve, and shut off the hot water feed pipe from the oil furnace with a ball type valve? This way I would bypass the furnace and have all my hot water coming from a new hot water tank but still have the option of using the tankless oil hot water heater if I have a problem. What do you think?

 

I"ve read several comments and I'm still alittle confused. According to my thinking, what I need to do to convert from oil heated hot water to electric heated hot water is to: (1) tap off on the incoming cold water and feed the elec. hot water heater. (2) Feed the hot water form the elec HWH to the existing hot water line that feeds out from the existing furnace. (3) Close off the incoming cold water line so it doesn't feed the oil furnace and close off the hot water feed from the oil furnace with ball type valves. This would take care of the plumbing and electrical I can easily understand. Is there anything Iam missing ? I don't want to damage my oil furnace. I thank anybody for a reply.

 

It is best to completely disconnect the tankless coil from the domestic water system.

If you want to retain the option of using the tankless coil under some circumstances then do NOT completely valve off the coil. You MUST allow the coil to either be completely drained of water or have it connected at all times to either the inlet (house cold water line) or outlet (house hot water line).

If you were to completely isolate the coil with water in it the water would try to expand upon heating and break the coil causing you much grief.

If you completely disconnect the coil and drain all the water you can then cap the coil (my recommendation) or leave it open as everyone else here recommends.