Using boiler as backup for Electric water heater

wayngrove

Hello all. I have an itch on my brain and was wondering if any of you fine folk have the knowledge to scratch it, whether it be a link to another post or some brand spankin' new knowledge. Apologies if I'm in the wrong section.

Being in the Philadelphia area, I've had it with the late winter snow, and so has our power company. This upcoming storm will be another possibility that we will lose power. Between the 2 major storms so far this year, we've lost power for a total of 13 days. This is nothing new for my neighborhood, so I have a 7500 watt portable generator and I have a Transfer switch set up for my oil hydronic boiler, deep freezer, kitchen circuit, basement circuit for the sump pumps and living room/dining room for lighting. The big missing piece is my 50 gal, 4500 W electric water heater. No hot water in the winter is not what I'd call glamorous...

My itch is about creating a bypass for our hot water for power outages by shutting out the feed from the electric water heater and opening a feed line from the boiler. My boiler is a Utica UH3KW100Z and my water heater is a Rheem XE50M06ST45YO. We just had this boiler installed in late 2011, and the old clunker before it had a mess of cut copper pipes coming out of it, so I know the house was boiler hot water at one point, but I have no idea what make or model it was.

Question 1; Is what I'm asking to do a somewhat normal setup, frowned upon, or downright idiotic, considering my current setup and equipment?

Question 2; If question 1 is okay or just frowned upon, what else would the setup entail, besides T'ing off the electric hot water feed above the ball valve and tapping into the hot feed (with it's own ball valve) of the boiler?

I'm not concerned with efficiency, as it would be emergency purposes only, and I'm only thinking shower for the hot water, so potability isn't much of a concern either

Ironman

Please, stop! Abandon this idea right now!

What you're proposing is illegal, unsafe and will harm your person as well as your boiler.

nicholas bonham-carter

If I understand what you are proposing, you would be showering with the water from the heating system, which may be a breeding ground for Legionella. In addition, the system would be constantly filled with fresh oxygenated water with its great rust potential. As a result, both you and the boiler would face an early grave.
In order for this not to happen, the hot water heater would have to be hydraulically separated from the boiler water, like an indirect hot water heater, with a separate pump, controls, and heat exchanger.
Generating hot water using the boiler in the winter might have a lower energy cost than using the electric water heater, (depending on electricity cost),which could be an additional benefit. A real hydronic expert could advise you on this.
I would start a new thread on this for details, on the main wall section here, and maybe Erin could move this thread there.—NBC

Erin Holohan Haskell

Moved this thread to the Main Wall.

Great points. This is dangerous. Don't do it.

GBart

" I'm not concerned with efficiency, as it would be emergency purposes only, and I'm only thinking shower for the hot water, so potability isn't much of a concern either"

think again, most of the time when people get upper and lower respiratory infections they got them from their water in the shower

I made this video years ago to explain it, all water heaters should be run to 140F and have a tempering valve to send 120F to the sinks showers to kill bacteria

https://www.youtube.com/watch?v=IY0v5YGZNpc

GBart

More info can be found here and can help contractors convince homeowners and business owners of the need for this set up (140F in tank) and tempering valves.

https://www.sciencenews.org/blog/science-public/case-very-hot-water

GBart

highlights from the above article: On its website, the Department of Energy notes that, “Although some manufacturers set water heater thermostats at 140 ºF, most households usually only require them set at 120 ºF.” For each 10º drop in temperature, consumers can expect to see a three to five percent savings on energy use. Moreover, DOE points out, setting that thermostat to 120º could extend the heater’s lifetime by slowing the buildup of minerals and corrosion within it.

What DOE and other energy-conservation sites don’t point out is that 140 ºF will kill a number of potentially lethal waterborne organisms, like the ones responsible for Legionnaire’s disease and NTM, short for nontuberculous mycobacterial infections. In contrast, 120º provides a nurturing environment for such toxic microbes...........he primary route to respiratory disease from these germs comes through inhalation of the steam associated with showering or hot tubs. Infections due to these home-grown germs are estimated to kill 3,000 to 12,000 Americans annually, Edwards says.

How come we haven’t heard about this? Mistaken for flu, many cases remain off the radar screen,...........

more good news is that the bacteria can also grow in your shower head

Brewbeer

You could add an indirect water heater to your current boiler set-up, and set it up so that in the winter when you are using the boiler, the boiler would heat your hot water. At the end of the heating season, you would operate some valves so that the electric water heater would take over and serve domestic hot water needs for the warm season.

SuperTech

I would install an indirect tank. Your idea would require use of a flat plate heat exchanger and a bronze pump to heat the water heater safely. An indrect tank would be superior to your electric water heater and would be used all year.

Daiel1J

GBart said:

More info can be found here and can help contractors convince homeowners and business owners of the need for this set up (140F in tank) and tempering valves.

https://www.sciencenews.org/blog/science-public/case-very-hot-water

Thank you, this is an interesting article!

hot_rod

Flat plate heat exchangers are very affordable ways to separate heating from potable water.

wayngrove

Thank you everyone for the replies. I am alive and well; no Legionnaires here (although looking over the symptoms, it sounds a helluva lot like what we're dealing with right now). I never moved forward with anything. The wife put the kibosh to all MacGyver plans of mine (we're moving soon! We won't need to do that!).

I'm not sure why, but I never received any notifications about your replies, so sorry if you thought I ghosted the thread. I saw the 1st and 2nd ones the next time I logged in and went about my day. There's a lot of very good info here and wanted to make sure you knew I received it.