Tankless water heaters

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mgookin

mgookin

Senior Member
Location
Fort Myers, FL
electrofelon said:
I assume because it will be used infrequently is why you are leaning toward tankless? Despite that, I wonder if just getting a small talk unit and setting it low, like 90-100 degrees is worth considering? You would have tank losses, but capital cost would be much less and if set low, losses may be minimal. Just a thought.

I havent been happy with most of the tankless electric ones I have come across. The temp regulation is poor. some (many?) do not modulate the electrons so the output temp depends on the flow rate. Turn the faucet to part way and it gets super hot. Most (all?) have a minimum flow rate that is kinda high. My friend put one in and we had to take off the faucet diffuser to get the thing to kick on. Just be aware of that. Maybe there are better ones out there now.
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Correct. It will be used to wash out a coffee pot, etc. It's an office & manufacturing facility. We may put a shower in one day which would be the biggest draw but that would rarely be used. When we did the buildout we roughed in for a full bath and kitchenette. I was thinking of setting some of the plumbing fixtures over the holidays and that's why the water heater comes into play. We're just doing conceptual planning and budgetary quoting right now.

What you're saying about the inconsistent water temperature makes sense; thanks for that heads up.

The benchmark to get a fair deal is a Rheem 13kW for $209 but that's 240V and we have 208Y/ 120. I wish I could find something that's 3p and 10-20kW in the $200-300 range, but all the 3p heaters are big commercial units costing $1,000's. It seems once you go above that 13kW the price doubles and keeps going up from there. Being in south Florida we don't need anything in the 20-40kW range.
 
hbiss

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
If all you need HW for is to wash out the coffee pot and your hands in the washroom (typical office scenario) I would just put in a small 20 gal water heater. I've seen these up in ceilings that even supply a shower. I think you are over thinking this. We are not plumbers. :eek:hmy:

-Hal
 
Barbqranch

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician Semi-retired
I recently installed one in my shop at home. I probably use 2 gallons a week. It works great. Turn on the hot faucet to get it started, then adjust the cold to set the temperature. For a single utility sink, I think it is the answer.

Ace only shows one little 6 gallon unit that is about $10. cheaper than my instant unit, all the others are a lot more expensive. The reduced capacity due to 208 volts shouldn't make it less usable, just longer lasting.
 
kwired

kwired

Electron manager
Location
NE Nebraska
If you are in a northern area where heating seasons are longer then cooling seasons, I don't see the heat loss from a tank style heater to be that big of an issue. It does increase cooling load, so does cooking appliances, hair dryers, hand dryers and lighting, though in recent years lighting changes have not only used less energy to produce light they also wast less energy as heat. During heating season the inefficiencies of those items lessen the heating system load. You have to factor that in before you call heat loss from the tank a total loss.
 
cpinetree

cpinetree

Senior Member
Location
SW Florida
hbiss said:
If all you need HW for is to wash out the coffee pot and your hands in the washroom (typical office scenario) I would just put in a small 20 gal water heater. I've seen these up in ceilings that even supply a shower. I think you are over thinking this. We are not plumbers. :eek:hmy:

-Hal
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This!!
Never seen a tankless unit last 5 years without leaking, Put a small tank type on a timer from 7:00am to 3pm have hot water all day and not worry about the small difference in electric savings (especially at the FPL rates in SWFL)
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
cpinetree said:
This!!
Never seen a tankless unit last 5 years without leaking, Put a small tank type on a timer from 7:00am to 3pm have hot water all day and not worry about the small difference in electric savings (especially at the FPL rates in SWFL)
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For those purposes, every other day of operation would probably work. Other than my wife, who washes the coffee pot more than once a week or even a month?
 
J

JFletcher

Senior Member
Location
Williamsburg, VA
cpinetree said:
This!!
Never seen a tankless unit last 5 years without leaking, Put a small tank type on a timer from 7:00am to 3pm have hot water all day and not worry about the small difference in electric savings (especially at the FPL rates in SWFL)
Click to expand...

I always suspected there was something in the water in Fl. :D

Agree with Hal here, I'd go with a small tank unit in this case.
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
shortcircuit2 said:
Here are the instructions for a 36kw...

https://assets.nationalbuildersupply.com/ul_pdfs/eemax-711133-installation-instructions.pdf

The chart say it has 4-9000watt elements and to wire 4 circuits at 40-amps each. It seems like it should be 4 circuits at 50-amps considering 9000watts@240volts is 37.7-amps x 1.25 = 46.875-amps...

Anyway thats alot of power to make hot water.
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Unlike some sizes of tanked heaters which are explicitly called out by the code to be treated as continuous loads, there is a strong argument that a tankless is NOT a continuous load and thus not subject to the 1.25 multiplier.
Putting in 50 wiring would certainly be allowed, but the installation instructions may not allow you to have only 50A for OCPD.
 
kwired

kwired

Electron manager
Location
NE Nebraska
shortcircuit2 said:
Here are the instructions for a 36kw...

https://assets.nationalbuildersupply.com/ul_pdfs/eemax-711133-installation-instructions.pdf

The chart say it has 4-9000watt elements and to wire 4 circuits at 40-amps each. It seems like it should be 4 circuits at 50-amps considering 9000watts@240volts is 37.7-amps x 1.25 = 46.875-amps...

Anyway thats alot of power to make hot water.
Click to expand...
Energy is a product of power and time. You can basically heat same amount of water the same number of degrees 8 times faster than you can with a 4500 watt heater.
 
mgookin

mgookin

Senior Member
Location
Fort Myers, FL
Right now I'm thinking no water heater. The main runs for 400' through the bar joists of unconditioned industrial building before it gets to us. In the afternoon it's around 95F coming out of the pipe. Maybe a heater will be Phase II.

Thanks for all the input everyone.
 
O

Open Neutral

Senior Member
Location
Inside the Beltway
Occupation
Engineer
gar said:
If you take a 38 kW heater designed for 240 V and operate it at 208 V, then the output power will drop to 75% of its 240 V specified value. That means for the desired temperature rise that flow rate will have to be limited to 3 GPM.

.
Click to expand...

Can't you buy 208V elements vs. 240 ones? I know you can for stoves.....
 
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