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#4814 - 10/19/01 04:05 PM tankless water heaters  
bordew  Offline
Joined: Aug 2001
Posts: 142
Vienna,Ohio, USA
Has anyone ever heard of and/or installed a tankless-water heater ? Are they any good ? and is it worth the investment ?

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#4815 - 10/19/01 04:34 PM Re: tankless water heaters  
sparky  Offline
Joined: Oct 2000
Posts: 5,303
Do you mean those 'point-of-use' ones?

#4816 - 10/19/01 07:21 PM Re: tankless water heaters  
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
They've been around in this part of the world for many years. In fact just a day or two ago I was looking at an old trade journal dating from 1966, and there was an ad for a 6 to 7kW over-sink unit.

The biggest drawback is that they raise the temperature THROUGH a number of degrees rather than TO an absolute temperature. Output temperature is dependent upon the temperature of the cold water supply and the flow rate, so to get high temperature output the flow rate is generally much lower than with a conventional system. If the cold temperature and supply pressure are fairly constant, the output temperature will be so as well, but the only way to increase the temperature is to reduce the flow rate so that the water is in contact with the heating elements for longer.

These devices are now very popular here in "instant" electric showers where a lower rate of flow is acceptable, but there are one or two units available now to feed normal basin/sink taps (faucets) as well. These are rated up to 9.5 kW, although I have no idea whether you have more powerful units on sale in America.

I'll dig out some temperature/flow data if you're interested.

#4817 - 10/19/01 08:19 PM Re: tankless water heaters  
Tom  Offline
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
Paul has pretty well covered the ins & outs of these things.

A major drawback is if you use one of these heaters to supply more than one tap, open 2 taps & the water will be lukewarm, open 3 at the same time & you'll wonder what is wrong with the heater.

I installed a gas fueled one in my house some years ago & the gas company came around to see what was wrong with their gas meter, it was obviously reading too low. [Linked Image]

One positive aspect, especially of the gas fired ones, is you will not run out of hot water. A 2 hour shower will be just as hot at the end as it was in the beginning.


Few things are harder to put up with than the annoyance of a good example.

#4818 - 10/19/01 08:20 PM Re: tankless water heaters  
bordew  Offline
Joined: Aug 2001
Posts: 142
Vienna,Ohio, USA
Yes those are exactly what they are, however the ones you mention pale in comparison, I got a call from a customer and he wants to get one but he is talking two 50 amp breakers feeding the thing. The liturture he has talks about 18 kw to 22 kw, I mean these are some large units for a residence. Also, the ccost is between $650 to $750 per unit. Plus with deregulation I would wonder if it would really be worth the investment. From what I have read they are the size of a phone Book, there is no storage capacity, it just heats the water like right now, and the temp depends on the flow rate and incoming water temp. which makes sense.
Yes if you got some charts it would be interesting to see them.
Thanks for the quick reply.

#4819 - 10/20/01 04:43 AM Re: tankless water heaters  
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Wow, 18 to 22kW! That makes my old 6kW shower unit seem like a weakling! Those sort of figures sound more like the equivalent power output of the gas-fired "multi-point" heaters like Tom described.

Here's sthe manufacturer's data for the British Triton TW10i, recommended for up to 2 outlets. I've converted the metric & centigrade measurements to U.S. units, hence the non-round flow figures:

Power: Selectable 6kW or 9.5kW
Dimensions: 7.1 x 11.6 x 3.4 inches
Water in at 50 deg. F, 9.5kW setting:
0.53 U.S. gal/min., 158 F.
0.79 U.S. gal/min., 133 F.
1.06 U.S. gal/min., 111 F.
Water in at 77 deg. F, 9.5kW setting:
0.53 U.S. gal/min., 185 F.
0.79 U.S. gal/min., 160 F.
1.06 U.S. gal/min., 138 F.
Water in at 77 deg. F, 6kW setting:
0.53 U.S. gal/min., 167 F.
0.79 U.S. gal/min., 138 F.
1.06 U.S. gal/min., 120 F.
The cost of this unit by cmparison is £122.50 (about $180) plus tax.

#4820 - 10/20/01 10:37 AM Re: tankless water heaters  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,875
It seems obvious that these heaters should be used with 'low-flow' shower heads. Has anyone found and good ones?

(I'm thinking about the one that Kramer (on Seinfeld show) was using. [Linked Image] )


#4821 - 10/20/01 11:23 AM Re: tankless water heaters  
bordew  Offline
Joined: Aug 2001
Posts: 142
Vienna,Ohio, USA
The company I believe is ' SETS systems ',their E-mail is they have the heads youre thinking about.
As Paulik pointed out rate of flow is key to a high rise in temperature, they assume incoming water temperature to be minimun of 50 degrees F and at optimum flow rate a rise of I think it said 66 degrees, but and supposedly that 50 degrees was an average for the worst case. This I find hard to believe especially in northern climates where older homes do not heat their basements and the outside temps drop as low as -5 to -15 degrees below zero. and in basements where the pipes get cold enough to freeze and dont because of the basement is kept at about 40-45 degrees, any way the rise will not reach the optimum temp.
To All:
IMO a 22kw Electrical heating unit is just plain bad planning.
If a customer has Central Air, electric Range, Dryer,some small appliances ie disposer, dishwasher etc and then adds a 22 kw tankless the combined load is over 200 amps.
I like Tom's idea of a gas fired one seems a lot more economical that a 22kw electric model/ this model and a few others of less power still require two 50 amp breakers, and the manufactureer could not guarantee that the circuit only drew 80 amps, or 75 for a smaller model.
The smaller models as Paulik was talking about sound much more practical.

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