120 gal water heater

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augie47

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
I am looking at a job where a 120 gal storage type electric water heater needs to be relocated to provide clearance for some other equipment.
In discussion with the G/C he advised on another job "an inspector (unknown trade)" required them to maintain a 18" clearance from all points of an identical electric water heater as it "required by the (his words) International Electric Code"

I can find no such requirement in researching Codes I have at my disposal.
Does anyone know of a required clearance for an electric storage water heater (other than working clearance for any controls, etc) ?

On a side note there was some discussions concerning electric hot water boilers. When does an electric water heater become a hot water "boiler" ?
 
G

Gregg Harris

Senior Member
Location
Virginia
Occupation
Electrical,HVAC, Technical Trainer
augie47 said:
I am looking at a job where a 120 gal storage type electric water heater needs to be relocated to provide clearance for some other equipment.
In discussion with the G/C he advised on another job "an inspector (unknown trade)" required them to maintain a 18" clearance from all points of an identical electric water heater as it "required by the (his words) International Electric Code"

I can find no such requirement in researching Codes I have at my disposal.
Does anyone know of a required clearance for an electric storage water heater (other than working clearance for any controls, etc) ?

On a side note there was some discussions concerning electric hot water boilers. When does an electric water heater become a hot water "boiler" ?
Click to expand...

IMC 1004.3 Working clearance is 18 inches for boilers. Section 1002 covers water heaters for potable water and 1002.2 covers water heaters utilized for space heating and does not require the 18 " clearance. unless the manufacturer requires it
 
J

jrohe

Senior Member
Location
Omaha, NE
Occupation
Professional Engineer
augie47 said:
I am looking at a job where a 120 gal storage type electric water heater needs to be relocated to provide clearance for some other equipment.
In discussion with the G/C he advised on another job "an inspector (unknown trade)" required them to maintain a 18" clearance from all points of an identical electric water heater as it "required by the (his words) International Electric Code"

I can find no such requirement in researching Codes I have at my disposal.
Does anyone know of a required clearance for an electric storage water heater (other than working clearance for any controls, etc) ?

On a side note there was some discussions concerning electric hot water boilers. When does an electric water heater become a hot water "boiler" ?
Click to expand...

GoldDigger said:
IMHO that happens when the hot water is used for space or equipment heating (often in a closed system) rather than just as hot water.
I don't think the water has to even get close to boiling. :happyno:

http://www.recampus.com/documents/book12_c01.pdf
Click to expand...

If it is a boiler, it will have an ASME "H" stamp on it and the installation will be required to comply with ASME CSD-1.
 
kwired

kwired

Electron manager
Location
NE Nebraska
And anymore a "boiler" doesn't hold very much water at one time, maybe steam producing boilers do but not domestic / light commercial heating boilers.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Beside the exact aspects of the op. I thought that mechanical had the same dedicated space reqirements as electrical - 3'-0" .

IE -We can't block or cross over any of their equipment panel.
 
Last edited:
renosteinke

renosteinke

Senior Member
Location
NE Arkansas
The Mechanical Code has the definition - over a certain number of BTU's and it's a boiler. That is, classification is determined by the size of the heating element, not by the storage capacity.

120 gallon? Even if this particular one is OK as wired, I'd run oversize wires to the new location. Why? So that a later replacement might be one with a 'quicker recovery,' or larger heating elements.
 
kwired

kwired

Electron manager
Location
NE Nebraska
renosteinke said:
I'd run oversize wires to the new location. Why? So that a later replacement might be one with a 'quicker recovery,' or larger heating elements.
Click to expand...


Best run 3 or 4 60 amp circuits and increase the service size while at it just in case they change to an on demand type heating unit sometime down the road.:happyyes:
 
renosteinke

renosteinke

Senior Member
Location
NE Arkansas
Let's consider, for the moment ....

My 40-gal water heater can easily be fed by a 30-amp circuit. I have not been able to find a 40-gal water heater that cannot be fed by that same circuit. Likewise, the recovery rate of a 40-gal water heater is somewhere near 55gph. You've got two elements, arranged so only one is on at any time.

Up the capacity to 120 gallons, and the story changes - considerably, even within the same series from the same maker.

For example, Rheem has their ES120 series. That model is available (120-gal capacity) in a variety of wattages, from 6KW to 81KW. Put another way, that heater can have anything from 3-2KW elements to 9-9KW elements. The recovery rates vary from 157gph to 558gph.

That last one - 558gph - is notable, because at 276,000-BTU, it's well past the (IIRC) 200,000-BTU line into "boiler" territory. Now the thing is required to be in a special room, and additional controls are required.

At the other extreme, Rheem has a "homeowner" model 82V120-2, which has a 120-gal tank but a puny 21gph recovery. IMO, this is a prescription for trouble; Fill the tub once, and it's wait, wait, wait.

You've got to pull the wire. It's a lot better to do it while the walls are open. Both pipe and wire are rather cheap, in terms of the total job cost. Do you really want the customer to be forced to tear open the walls when he needs a better heater? Wouldn't it be nicer if your pipe was just a size larger, and you could simply pull in the new wires? Or, if you just happened to use #6 instead of #10?

I expect some clever sole is now itching to post "but you can't put a commercial water heater in a house." Wrong. The UMC specifically allows it. Residencial water heaters have to be UL Listed to either the 'residential' OR the 'commercial' (UL1453) standard. See ICC/UMC 1002. No 'listing and labelling' issue here.

The NEC say it's not the code's job to worry about tomorrow. That does not mean it's not your job, either. After all, if 'minimum code complaince' rules the car business, we'd all drive a Yugo.
 
kwired

kwired

Electron manager
Location
NE Nebraska
renosteinke said:
Let's consider, for the moment ....

My 40-gal water heater can easily be fed by a 30-amp circuit. I have not been able to find a 40-gal water heater that cannot be fed by that same circuit. Likewise, the recovery rate of a 40-gal water heater is somewhere near 55gph. You've got two elements, arranged so only one is on at any time.

Up the capacity to 120 gallons, and the story changes - considerably, even within the same series from the same maker.

For example, Rheem has their ES120 series. That model is available (120-gal capacity) in a variety of wattages, from 6KW to 81KW. Put another way, that heater can have anything from 3-2KW elements to 9-9KW elements. The recovery rates vary from 157gph to 558gph.

That last one - 558gph - is notable, because at 276,000-BTU, it's well past the (IIRC) 200,000-BTU line into "boiler" territory. Now the thing is required to be in a special room, and additional controls are required.

At the other extreme, Rheem has a "homeowner" model 82V120-2, which has a 120-gal tank but a puny 21gph recovery. IMO, this is a prescription for trouble; Fill the tub once, and it's wait, wait, wait.

You've got to pull the wire. It's a lot better to do it while the walls are open. Both pipe and wire are rather cheap, in terms of the total job cost. Do you really want the customer to be forced to tear open the walls when he needs a better heater? Wouldn't it be nicer if your pipe was just a size larger, and you could simply pull in the new wires? Or, if you just happened to use #6 instead of #10?

I expect some clever sole is now itching to post "but you can't put a commercial water heater in a house." Wrong. The UMC specifically allows it. Residencial water heaters have to be UL Listed to either the 'residential' OR the 'commercial' (UL1453) standard. See ICC/UMC 1002. No 'listing and labelling' issue here.

The NEC say it's not the code's job to worry about tomorrow. That does not mean it's not your job, either. After all, if 'minimum code complaince' rules the car business, we'd all drive a Yugo.
Click to expand...
I would say that 80 - 90% of the water heaters I have hooked up were in same mechanical room or similar area as the electric panel supplying them, so if there is a need to increase capacity it is not really that hard to do so.

Also when it comes to residential if more capacity is needed usually that means installing an additional 40 or 50 gallon unit instead of replacing the 40 or 50 gallon unit with a 120. Not all that uncommon around here to see a water heater that feeds a bathroom with a large whirlpool tub and nothing else, and additional water heater(s) for other portions of the house.
 
sparkyrick

sparkyrick

Senior Member
Location
Appleton, Wi
kwired said:
Best run 3 or 4 60 amp circuits and increase the service size while at it just in case they change to an on demand type heating unit sometime down the road.:happyyes:
Click to expand...

Might as well throw in a back-up generator too
evilB.gif
 
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