Small Point-of-Use Electric Water Heater Recommendations

[labboy]

Hi Everyone:
We are doing some remodeling of our detatched garage. I would like to install a small sink as well as my KUDS-22 out there. Any recommendations for a small point-of-use tankless electric water heater?

Thanks
Bob

 

[hydralique]

Remember that these can take a lot of power. If your main electrical service comes from the garage then you're OK, otherwise make sure you've got sufficient wiring to the garage. Unless the garage was set up for a laundry with an electric dryer or a previous owner wanted to run an air compressor or something similar it would be unusual to have lots of power capacity in a detached garage.

 

If at all possible I'd recommend a gas tankless.

 

[DADoES]

 
Yes, keep in mind that with tankless the sizing parameter is not how much/what volume (gallons) of heated water is needed ... it's how much temperature rise is needed to attain the desired target output temperature, of which the incoming cold supply water temperature is a factor, and the flow rate.

A "small" 50 amp (12,000 KW) unit for example may produce a 40°F temp rise at 2 GPM flow rate ... which means 50°F incoming water at 2 GPM will come out at 90°F, or 70°F input at 110°F output.  Getting 140°F out of it might require 75°F incoming water on a flow rate of 1.3 GPM.

My whole-house electric unit is 120 amps / 28,800 watts.  The power draw is moderated according to the load (input temp, output temp, flow rate, setpoint) but the circuit must be able to supply the maximum power draw that can occur.

 

[maytagbear]

There are

20 gallon electric tanks.....that may be more suitable....

Just my dos centavos.

Lawrence/Maytagbear

 

[launderess]

Bosch, Ariston and others make small

Under sink tank water heaters with capacity of about five or so. These are heated by electric and can be set at 120F or 140F, and run of regular 120v service.

Pardon Our Interruption...

 

[whirlcool]

Is it just me or is the description the seller put on Laundress' water heater a bit hard to read?

 

[labboy]

Stiebel-Eltron

I think this one or a similar mini-tank unit will be what we go with. The info about the tankless regarding temperature rise and current draw was very helpful.

Bob

http://www.amazon.com/Stiebel-Eltron-SHC-2-5-Mini-Tank/dp/B0048EJXZ2/ref=cm_cr_pr_product_top#productDetails

 

[vacbear58]

Undercounter sink heaters

These are quite common over here in Europe (including the Stiebel Eltron model you are looking at) but there are a couple of things to remember with them.

They can be used with a regular tap, even a mixer tap (although regulations here say that the mixing has to be at the point of exit to avoid potential contamination of the fresh water supply), but in that case they must be used with an expansion vessel, which may be included in the pack with the heater, but will take up some extra room which you will need to consider is space is tight. They also have a pressure release valve which needs a small tundish or perhaps an extension to the stand pipe would do - these you need to consider when laying in the pipes. It maybe that if you are sufficient distance from the nearest outlet/tap you may not need this but do check the installation instructions on line before purchasing. Otherwise they need a special tap which provides a vent to the heater

Will you be using this as a hot feed for your dishwasher? If so it is highly unlikely that the recovery rate will be sufficient for your needs, even in San Diego - in Europe these generally operate at 2000 or 3000 watts at 240 volt. Fine if you only want it for hand washing and the occasional pail or sink of hot water, but much more than that and I doubt it will be suitable for your needs.

Al

 

[DADoES]

 
The model you linked is a 2.65 gal capacity.  I've read that the effective capacity of an electric tank water heater is about 2/3 of the rated capacity, assuming the design of this unit follows that convention.

Being 120v, it draws only 1,300 watts.  The recovery rate (presumably from full usage of the heated supply) is stated as 18 minutes, but doesn't say what input temp and to what setpoint.

Tech Specs | Stiebel Eltron USA

Complete technical specifications for all Stiebel Eltron products.

www.stiebel-eltron-usa.com

 

[revvinkevin]

Yes.... but will 2.5 gallons be enough?

 

 

Bob, here are a couple other things to consider.

 

You are installing a small sink and your KA dishwasher in the garage.   The small 2.5 gallon water heater will be enough for hand washing in the sink, but won't be enough for the dishwasher.

 

Those older KA dishwashers use like 2-3 gallons each time they fill, don't they? 

 

OK let's say it's 2.5 gallons.  The DW fills for the wash and now the water heater is full of cold water.   Can it heat that 70-80 degree water up to 140 degrees in 5 minutes (time of the wash)?     

 

Now, is it able to generate that same 2.5 gallons of 140 degree water in just 2 minutes?   Because that's all the time you have between each of the rinses, around 2 minutes.

 

My point is that small capacity would be fine just for the sink, but if you are planning to also run the DW off that heater too, you may want to seriously consider a larger capacity tank, 5 gallons at least.

 

Kevin

 

[labboy]

5gal

Thanks for all the input...I will definitely consider a larger tank size. 5 would probably be good...the KA also will do some heating which will add to some time for the water heater to recover.

Of course, maybe I should consider an even larger tank and space for more appliances..?

I can see my husband rolling his eyes now...

 

[launderess]

Posted this in another thread

But read an article in an old issue of Popular Mechanics dealing with energy savings. Part of the article was about if homeowners should *allow* their dishwashers to dictate energy use. That is why was it necessary to keep their water heaters at 140F because that is the minimum hot water temp dishwasher makers suggested for proper results.

This was a period when only a few dishwashers had thermostat holds on their timers. That is the cycle would not advance until water reached the proper temperature. IIRC Westinghouse was one brand cannot recall the other. Every other dishwasher needed *HOT* water because that is what helped break up soils, oils and muck.

Long story short writer of article installed an in-line on demand water heater for the home's dishwasher. This allowed the main water heater to be set at 120F but still give "boosted" hot water for dishwashing.

 

[neptunebob]

The best solution might not be a water heater at all!

I would recommend what I advised my sister to get for her bathroom - a recirculating pump that brings the hot water to the sink and pumps the cold water in the pipes back to the water heater. Yes, you will need a line back to the WH but you are installing pipes anyways. In your case, you just have to turn the pump on when you need the hot water so its not that wasteful. Now, my sister's contractor (not a real plumber) told her to do it his way and get a mini water heater instead. 2 weeks later, it gave off bad odors and now its dead and that wouldn't have happened if they did my loop. Took up 2 of the spaces in the breaker panel too.

 

[kenmoreguy89]

Bosch, Ariston and others make small undercounter....

Yes, we have a 8 liters one in our company's kitchen, brand is Boschetti, these small heaters are typically found in oldee homes in Europe not having a central hot water line piping, or just one for bathrooms and not secondary bathrooms or outside sinks.
We have one where I work, water coming out of it about 85degrees celsius (185F)
Due to the output high temperature, which especially in these small models is not always selectable and always reach temps on the 180s degrees...you'll have to put either a warning sign for hot water, or simply install an auto mixing selectable valve that automatically mix hot water to cold one to make the proper temp you select and avoid very rare but potential considerable scalding in certain situations....
For example, where I work we all know how hot the water coming out of our is, as everyone of us knows how hot is in our own homes, so we just set the tap to mix it...sometimes happens that a stranger/customer jumps in our company's kitchen to use the sink and steal a free coffee, and select idiotically hot water all the way, sometimes you hear an "Holy crap!" who's that? It's a customer, but we are happy as next time they'll learn to ask before making their way in "staff only" rooms for a coffee we would have gladly offered anyway, however never seen one going to hospital at all or being seriously or considerably injured by that...find it nearly impossible, but for some people nearly impossible is just not enough, they need to make it impossible...
Of course in ones you can select the temperature, all relies in how much water you need, keep in mind that by setting higher temps you can actually get more water at lower temp,and this change, upon the use you have to do, say if it heats 8 liters at 180-190 degrees, you will get 16 liters at 90-95 farheneit...vs just 8 liters if you set it up to that last temperature, as obvious and granted as it gets...

[this post was last edited: 6/19/2014-08:40]

 

[labboy]

Installed...

Hi Everyone:
I installed a 4 gal Stiebel-Eltron. It is the ideal size for this application. It is on a switch so we only turn it on when needed. The KDS-22 is in place. I ran a load last night and there were no issues with power when both the dishwasher and water heater were on simultaneously. I've forgotten how fast it was and how well it performs. Looking forward to much more use.

It will also be handy to have hot water close to the yard for things like washing the dog outside, etc.

Bob