Indirect Water Heater, fed by electric?

WilliamME

I'm planning on having my failing steam boiler replaced this summer. It feeds indirect hot water. I'd like to get the boiler offline ASAP as condensate is ruining my masonry chimney, but I need hot water meanwhile. 

My plan was to buy an electric hot water heater to get me through the summer. But I was wondering, if I bought a small, perhaps 50 amp on demand electric water heater, if I could plumb it into the indirect hot water heater as the storage medium, in lieu of hauling a whole other hot water tank down to the basement.

Stupid, crazy, impossible?

Larry Weingarten

Hello, I see nothing that makes your idea impossible, or even crazy! I would be careful about how you tie it in to the existing lines, so you don't get flow when and where it isn't wanted. I have ideas, but am pretty sure others here have dealt with this question. This all assumes you have 50 amps or so available in your breaker box.

Yours, Larry

JohnNY

I've done similar things. If you buy a domestic "water heater", you can use the indirect as additional storage and bypass the coil altogether. Just pump the new heater's outlet into the domestic side of the indirect.

WilliamME

I was initially thinking I could loop the water through the coil, as if it were boiler water, so that it would maintain the tank temperature. I assume it would have a much slower recovery time , since it wouldn't match the BTU of a boiler, but I think I would be okay with that.

If I had the heater dump right in to the storage part of the tank, I wasn't sure how to regulate the temperature.

Full disclosure, I am not a plumber, just a penny pinching home owner, so I don't exactly know what I'm doing, but want to learn

ethicalpaul

As a fellow penny-pinching homeowner, I will say: take this opportunity to separate your domestic hot water from your home heating boiler.

I'm going to assume you have oil, or you could just buy a gas water heater.

So I recommend getting a hybrid water heater using cash incentives that may be available in your area.

If you don't like the idea of really cheap hot water/are afraid of heat pumps, then I would recommend a Rheem Marathon which has great insulation and a plastic tank that will never rust. As much as I hate resistive heating, even this would be better than an indirect. Imagine shutting off your boiler in the summer, what a concept!

WilliamME

Thanks for response. I do have an oil fired boiler, the only reason I like it more than an electric solution is just the ability to have low demand on a portable generator in a power outage. But realistically, I seldom lose power where I live.

EdTheHeaterMan

You know, as soon as you make the commitment to go all-electric for the hot water, That is when you will experience the 7+ Day electric failure.

Just saying!

Another option is an oil-fired water heater. I know they're pricy but you can't beat the recovery, and they do cost less than an electric to operate in most areas. If the fuel line or the venting capacity is restricting you from having 2 oil-fired appliances operating at the same time, you can use a demand relay to shut off the steam boiler for the few minutes the water heater is in operation.

I'm not usually the one to recommend spending someone else's money purely for my own preference. I just offer it as an alternative if you were considering @ethicalpaul's suggestion of separating the DHW from the Space Heating.

Your 50 amp tankless idea is fine in either configuration, you just need the proper circulator pump to generate the necessary flow to operate the tankless. That is where many people run into trouble. The pump you currently use may not be sufficient if you decide to use the heat exchanger coil design you were thinking of originally. Another consideration is: you will be designing a closed system so you will need an expansion tank and relief valve set at 30 PSI in addition to leaving the open system relief valve (usually temperature and higher pressure) connected to the water heater. it does not make sense but it comes with the water heater and you need it in the event of an over-temperature condition.

@JohnNY's suggestion is less complicated, but you need a stainless steel or bronze pump for that design. It's never as simple as you want it to be.

Yours truly,
Mr.Ed

Ahead

EdTheHeaterMan said:

You know, as soon as you make the commitment to go all-electric for the hot water, That is when you will experience the 7+ Day electric failure.

Which is why I always consider backup power (or a backup system for any critical system):) (of course, this would mean that your electrical loads are manageable by a reasonably sized generator)

ethicalpaul

EdTheHeaterMan said:

You know, as soon as you make the commitment to go all-electric for the hot water, That is when you will experience the 7+ Day electric failure.

Just saying!

I guess you're thinking of those solar-powered oil burners that I've heard so much about!

EdTheHeaterMan

ethicalpaul said:

I guess you're thinking of those solar-powered oil burners that I've heard so much about!

You Scoff... Just you wait until my work is completed on the solar-powered, oil-fired, tidal flow, perpetual motion machine is completed. Then we will see who has the last laugh!

neilc

uphill in the snow both ways