Point of use/on demand hot water heaters

[TnAndy]

I've thought about that concept also. Go to the shop turn on the air compressor and hot water reverse the process when leaving.
How long from a cold start until warm? What's the amperage draw at 110V?

Don't remember....it's been in there 20 years or so....my guess is standard 1500w element, so (1500/120) probably in the 12-13amp range....whole lot less than an on demand. Doesn't take long to heat up. I killed a pig this morning, and 'field strip' it down at the shop before bringing up to the house and my walk in cooler. Meant to turn it on last night, but forgot. Turned it on when we started skinning, in 1/2 hour, we had plenty of hot water to wash our hands and tools. Only 2 gallons, so it's not long.

You could put it on a timer too if you use it regular enough.

 

[TnAndy]

I think that is right. In the Virginia house I switched to the on demand unit to save space in a 30x64 utility space that had the hot water tank and a washer. With the hot water tank out of the way up on the wall, I was able to install a dryer. I did some calculations, to the best I could tell there was no clear savings on costs maybe the reverse.

I installed a small hot water tank for the sink in my shop here in California rather than an on demand unit. Lower initial cost, simpler installation, and I only turn it on when I need it.

My neighbor is a QC/product testing engineer at local American Water Heater place over in town, and he said the same thing.....despite anecdotal stories of savings, new tank models are so well insulated, heat exchangers more efficient, etc, there is zero energy savings in tankless models...and this from years of testing. Heat pump units, another story......

There are reasons to go tankless, such as space savings, but when I was shopping for a new heater, he said don't go tankless.....because the electronic controls on many, (Big $$ if they go out) plus the fact many require line power (which is WHY I switched to standing pilot, tank model after a multiple week power outage in '93) are reasons to avoid them.

 

[ultrarunner]

The big advantage when these heaters came to market is never ending hot water... as in never running out of hot water.

I agree there are many benefits to tank type heaters and only have tankless at the cabin that is vacant for months at a time.

 

[prichard]

Not appropriate to the op but we did whole house at our last house and loved the endless hour water for really long showers in winter. It was natural gas and no real ode of it saved money but we did take advantage of 30% tax credit. We're planning on whole house propane when we build due to space saving.

 

[PILOON]

I recall reading that ideally a tankless unit was good for about a 40 or deg temp gain and not ideal for cold ground water to hot shower levels.
Would therefor assume that in Florida it would be just fine but not so in northern climates.

 

[ultrarunner]

It gets down to zero once in awhile at the cabin and have a whole house tankless.

Typically place is locked up in winter with the tankless removed from the wall to protect against any chance of freeze damaged... it happened before.

Rated Draw is 24kW and can provide 3 gallons per minute with 100 F temp rise.

It does not work so well with multiple taps open at the same time.

 

[dstig1]

Again, it depends on the situation. For a single shop sink that is rarely used, an electric point of use on -demand is the perfect fit. They don't cost a fortune:
Eemax Electric Tankless Water Heaters , Eemax Tankless Water Heaters , Eemax Tankless Heaters - SupplyHouse.com
$170-200 or so, depending on the power output you want/need. In fact all the small electric tank heaters they have cost MORE than all of the tankless ones. +50% or more:
Water Heater - Hot Water Heaters - AO Smith Water Heaters - SupplyHouse.com (you'll probably have to filter that down yourself to "electric" and then "0-9 gals," as it seems the filters don't come through in the link)

For the 120V tankless units, install couldn't be simpler: Screw to wall near sink, connect HW hose from faucet to output, connect input hose from cold water plumbing tee, plug into outlet. Easier than putting a toilet in. They are making them with normal faucet compression fittings and even supply a Tee so you have to do almost nothing to plumb them in. You just need an outlet (appropriate size) and a cold water supply.

It seems to me people have more opinions on this topic than facts. If you use it frequently, then a 6 gal tank may make a lot of sense. If it is going to sit for a week or month between short uses to wash hands or clean a paintbrush, then a tankless makes a lot more economical sense. Well, my opinion

 

[ultrarunner]

Are you guys in cold country heating your shops in winter to keep the pipes from freezing?

Tank type water heater don't freeze... even the Insta Hot one gallon under counter water heaters.

Tankless very much do freeze if out in the cold.

 

[dstig1]

Mine have an anti-freeze system as long as they are left plugged in (don't have to be turned on). There is an electric heater that will keep it above freezing, if it gets that low. I'm sure there is a limit to how low it can go and keep up, but these are indoor units up here. And besides - if the indoor heater is going to freeze, so will the rest of your pipes...

 

[ultrarunner]

Learn something new all the time...

I installed the cabin tankless in 1983... lost to freeze in 1985 and replaced it... have been taken it out for winter ever since if the cabin is unoccupied...