Electric Tankless Water Heaters

[bob haller]

[clare]

The IDEAL situation, in my opinion, is a central tank type heater with a small (say 5 gallon) point of use tank in the bathroom if it is at the far end of the house. You have 5 gallons of virtually instant hot water on tap - and before that water is depleted, you have hot water from the main tank. No recirc lines, no pumps, no "special" plumbing - and a 5 gallon unit can even be 110 volt and run on a 15 amp breaker. A 2 gallon 1440 watt unit is about $200 at Home Despot. 6US gallon WaiWela heaters are around $160 in the USA.

[HerHusband]

I would think the water would go cold as the small tank runs out, and the cold water in the pipe between the two tanks reaches the small water heater. It seems like you would get hot, cold, and hot again? Then again, maybe the cold water in the pipe mixes with the warm water in the tank. I don't know, I would be curious to hear how that works in real situations.

Of course, a 5 gallon tank is probably all you need for a bathroom sink anyway.

Anthony Watson

[trader_4]

Probably more like hot, warm, hot. If the tank holds 5 gallons, there is probably only a gallon or maybe two of water in the typical pipe, but it obviously depends on the length of the run.

Then again,

I don't see how it would not mix, to some extent.

I

I think that's the application, usage at a sink. If you tried to use it for a shower, it wouldn't work. For the typical sink usage, you only draw a couple quarts, maybe a gallon at a time. It would work fine for that.

[Arthur Conan Doyle]

This is true. Depending on the pump used and the length of the run, it can take up to 30 seconds to have hot water reach the faucet. That said, for anything other than immediate handwashing, pressing the button as you enter the bathroom is usually sufficient.

That's what we have and yes, it does. That's why there is a timer on the pump. Ours is set to run in the morning for an hour, around dinner time and again at night and not continuously. Any other time, you run the faucet and wait.

[Josh]

Agree -- our PG&E gas bill in the summer is $10-$15, and that includes a gas stove, oven, and dryer, and as you point out, the hot water we actually use as well as any minimum charges and taxes.

Tankless at the point of use may make sense, giving the convenience (and less waste) of having hot water immediately, but I don't buy that replacing a properly sized central tank with a central tankless system makes much sense given the cost and drawbacks (sizing of electric/gas source, issues with temperature control when the incoming water is too cold or warm, or the flow is too low). For a vacation home or similar that goes unused for weeks at a time, maybe.

Josh

[clare]

With a 2 gallon heater you get some fluctuation, but remarkably small unless you have a REALLY long run from the main tank, in which case you use a 5 or 6 gallon heater. Half inch copper pipe (the standard in north america) holds just under .1 gallon for 10 feet - so unless you have 500 feet of pipe you will not use all the hot water before the tank is refilled. With 100 feet of pipe and a 5 gallon heater, only 20 % of the hot water will be replaced by , not cold, but "room temperature" water before the pre-heated water comes on line.

Not an issue in my opinion and experience.

[muhipozyurt]

Electric tankless water heaters are very efficient if you pick the right si ze. But you will probably need new circuit breakers and even with that prep are to see your lights flicker when it runs full power. Here is some detail ed info on sizing an electric water heater ans some recommendations:

eviews Note that very efficient does not necessarily translate to lower energy bil ls. Electric is always more expensive.

[sol]

Electric tankless water heaters are very efficient if you pick the right si ze. But you will probably need new circuit breakers and even with that prep are to see your lights flicker when it runs full power. Here is some detail ed info on sizing an electric water heater ans some recommendations:

eviews Note that very efficient does not necessarily translate to lower energy bil ls. Electric is always more expensive.

[Gomez]

Severe weather knocks out my electric power for 2-3 days at a time. How big of a generator do I need to run an electric tankless water heater?

[trader_4]

size. But you will probably need new circuit breakers and even with that pr epare to see your lights flicker when it runs full power. Here is some deta iled info on sizing an electric water heater ans some recommendations:

ills. Electric is always more expensive.

None of that adresses the question asked. The questions isn't even answerable with the info given. But the answer is readily available. Just look up the specs on the tankless of the size in question and see how many watts/amps it uses. That's how much generator capacity you'd need. Then add in anything else that needs to run at the same time, plus some margin.

When you do that, you'll find that even a whole house, $3000 generator, can only barely supply a tankless sized for one bathroom, if even that. If having hot water during power outages is a concern, then a tank type water heater will keep water hot enough for a shower for a couple days. And a gas one that doesn't require power will give you an endless supply. If you don't have gas and need to use electric, even that is way more suite d to run off a generator. It's not the most efficient and will still require a decent size generator, but it's still in the realm of possibilities. If it's going to be tankless and the concern is power outages, then the only practical option is a gas one. Some I think will operate with no electric at all. And even those that require electric too, can run off even the smallest generators.

[CRNG]

On Thu, 18 Sep 2014 04:39:36 -0400, Gomez wrote in

About 15kw to 30kw just for the tank less WH alone, depending on the how water supply rate. That's one of the reasons I avoid them and use natural gas or propane or a conventional electric WH.

A power outage without hot water is a bummer. Plan for more outages as the supply of electricity becomes more green and inadequate.

[Stormin Mormon]

I've got a tank WH, which is gas, and standing pilot. Sure is nice, most power cuts in Buffalo, NY area are winter. Having hot water for shower is good. Brings back life to these old bones.

[Stormin Mormon]

2-3 days at a time. How big of a generator do I need to run an electric tankless water heater?

We don't have enough information.

"I'm going on a vacation, how much money should I bring?"

"Do I have enough gas to get to the store?"

"What size clothes should I buy for my kid?"

[Gomez]

Don't carry cash on vacation. Use a credit card. Haven't you seen those Karl Malden commercials?

Prolly...if you have a Chevy Volt.

Yes

[clare]

Stormy, you have all the information you require. An electric tankless water heater won't run on your typical portable backupngenerator - even a 9000 watt unit.

[clare]

If you read the link, they run 9 to 37 thousand watts.

[Stormin Mormon]

Smallest is 6960 watts.

[trader_4]

wrote in

You can't run a 9KW tankless on any generator? Take a look at HD, they have small tankless starting at 2.4KW and lots of them that are 3 - 5KW. That size unit isn't going to do a whole house, but it will do a sink. Stormin is right, there isn't enough info given. It's not practical to do a whole house one on a generator, but we don't know what they are trying to do, if they live in FL or MI, etc.

I could see someone installing a small point of use on one sink and then using it in an emergency for hot water. With a little creativity, you could even use it to bathe, have a hose that you could connect in an emergency to a small handheld shower. Hell, it's actually starting to sound like a reasonable idea.

[Stormin Mormon]

I've found filament heaters to be a major energy hog. Ideally, there would be some way to burn the gasoline to heat the water, not having to run an engine, spin a turbine, and convert that to electric, which heats the filament. But, that's in a perfect world.

One power cut years ago, I wired my NG hot air furnace into my generator. Took the furnace totally out of the house wiring for a couple days, zero chance of backfeed and kill a lineman. I was comfortable from end to end. The guy next door ran a space heater in the living room, I'd guess he was cold.

For the OP, the ideal thing is a fuel only heater, or a fuel heater such as natural gas with very small electric usage. Usually the NG stays on during power cuts. . Christopher A. Young Learn about Jesus

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