Tankless water heaters

Not necessarily. You have a shop at home so you have a 400a+ service right?

Besides, pulling 2/0 cable to a water heater is pretty reasonable cost wise anyhow.

 

Unless the shop has 480V supply... Which would cut the amperage in half. Never seen 480V in residential areas around here but it is common for commercial buildings to have it.

 

As long as they are sized ok a single point of use electric is fine. You can figure out what you need just by: 1) approximate temp of the water 2) what temp you need to achieve 3) maximum water flow from the faucet.

Ok a few more numbers for anyone who wants to calculate this stuff. It is really pretty easy if you know the numbers.
1 gallon of water weighs 8.34 pounds,
It takes 1 BTU to raise 1 pound of water 1*F
1 KW equals 3,412 BTU/h

So we will go with 60* since the water is in the lines and 1.2 GPM since that is a standard bathroom faucet flow. We will also assume that 100* would be acceptable. Here we go:

1.2 GPM x 8.34 = 10 pounds per minuet. 10 pounds per minuet x 60 minuets = 600 pounds per hour.
Now we want to raise that that 600 pounds 40* so we take 600 x 40 = 24,000 BTU/h
24,000 BTU/h divided by 3,412 = 7.03 KW

For another example, if we want to raise that same amount of water 60* we take 600 x 60 = 36,000 BTU/h
36,000 BTU/h divided by 3,412 = 10.55 KW

For point of use you will most likely be in the 7-10 KW range so be thinking of having to run a 40-50 amp 240 volt circuit to it also as this can be a problem. If the power or cost is an issue the point of use 1-5 gallon tanked units do work fine also and only need a standard 120v power. Another option for a long run from a water heater can be one of the on demand recirculation pumps that pump the water from the hot side and dump it back to the cold line.

Two words of caution. When dealing with tankless if you turn the water on and off all the time the "water sandwich" can be an issue to be aware of. Also if you are looking at point of use heaters be aware that most of the cheaper units do not have temperature controls. If it does not have a "thermostatic" control it is full on or full off and it can not control the temperature of the water

 

I installed an electric tankless water heater in my house. I replaced a 50 gallon tank with a unit the size of a briefcase. Had to run three 10-2 with ground romex wires and install three 40 amp breakers in my panel. It will pull 112 amps on high fire. And it NEVER runs out of hot water (120-140*). I can run the tub wide open all day. I had about $800 in it installing it myself. My biggest problem was my extremely hard (well) water. I had to install a water softener also.

It is also possible to preheat the water in a tank heater then boost it with a tankless, but that gets pretty complicated.
I've also heard of using motion sensors in the bathroom and kitchen area to turn on a recirculating pump to get the water up to temp when you walk into the room .

 

112 amps @ 240 volts
It does make the lights flicker a little when I run the tub.
It has a life time warranty too.
I call...they send parts. Nice people to deal with
Eco Smart from Florida

 

Hate to be the safety nazi but I hope that was three 8-2 romex on 40 amp breakers.

10-2 romex can not be put on a 40 amp breaker per NEC in any application except for some a/c, refrigeration, or other special high surge current applications. A resistive heating load would be an absolute no no. And the manufacture states 8 AWG in the manual. Just checking. Be safe.

 

As far as a power outage. I lose everything. Stove, well, oil furnace, heat pump, water heater. That's how I ended up on this site. Just got a woodstove for emergency heat/ auxiliary heat....you know....fteotwawki....lol

I do think I am saving money. maybe 5-10 dollars a month last time checked. But it's hard to tell the way the bills are going up. That and the wife pays all the bills, so I don't really see them...lol

 

First is obviously the size. The tankless is the size of a briefcase and hangs on the wall.
You only heat water when you need it. Go away and it just sits and waits till you get back.
Small but noticeable savings. (should pay for itself in ten years or less)
Lifetime warranty on parts.
Good service from the manufacturer.
On/off switch/temperature dial on the front. Makes for easy adjustments. (no need to remove the cover)
Very easy installation for me. I'm a plumber. And my basement was unfinished. (easy to pull new wiring)
No draining out sediment.
And I saved the best for last. It NEVER runs out of hot water!
Now I'm not saying it's been all unicorns and lollipops! I had a couple problems early on. The good service and warranty took care of that. Has been working fine since.
The unit cost me $525. Wire and three new breakers cost $190. A few fittings to hook it up $20-30. Total $800
Replacing with a standard 50 gallon would have been about $300. If I saved $10 /month. it would pay for itself in about 4 years
As far as a power outage, I don't think your genset will run a standard water heater either. Although if you have city water you could get a quicky shower if needed with a tank type heater.
I you called a plumber and had it done it would cost you more like $1200-1400 (I'm guessing here)

 

MM. sounds like you need a good wood boiler. Plumb that baby in with your existing oil boiler and you'd be set.

 

I know this is a tankless talk but how about the hybrids? I'm pretty sure a 50 gallon hybrid is going in the place of our current 50 gallon lp very soon and that is without some of the fat incentives there are in a lot of places around the country. Recovery time really isn't an issue for us and even if there were a time when it was there is a setting for that.

 

Hi Solar
I'm not familiar with the hybrid water heaters. Which one are you looking at?
Using electric to heat anything is usually expensive.

 

There are a few of them out there but im looking at the ge geospring. They use a fraction of the energy of a normal resistance heater but still have that mode if you need fast recovery on occasion. There are places in the country where they are cheaper than resistance heaters because of incentives. Unfortunately ny isnt one of those places. Still works for me though given the price of propane here.