demand of point of use water heaters

Status
Not open for further replies.
masterinbama

masterinbama

Senior Member
Location
Huntsville Alabama
I have a job where the customer wants to add 5 point of use water heaters 2 twelve kw 1 nine kw and 2 eight kw whats the demand for these heaters my code book is on another jobsight and i just need a rough calculation to know if I need to order material for a service upgrade I'm hoping the 200 amp service will be large enough because the 400amp meter sockets we have to use are very expensive and have a long delivery time
 
To get a better understanding of the load calc, please include the gallon size(s). NEC 2005 422.13 states storage-type water heaters 120-gallons or more must be considered a continuous load and calculated at 125% (422.10).
 
BTW I come up with 204 amps for that collection, I don't think any demand factor would keep you under 200 amps once you add the rest of the load calcs.
 
necnotevenclose said:
iwire how did you get 204A without knowing the voltage and phase(s)?
Click to expand...

LOL....I guessed.

I assumed 240 volt single phase.

Questions about these point of use hot water heaters are fairly common here at the forum and the common voltage has been 240 1 PH.

I think the power companies are very worried about these units becoming popular.
 
iwire said:
LOL....I guessed.

I assumed 240 volt single phase.

Questions about these point of use hot water heaters are fairly common here at the forum and the common voltage has been 240 1 PH.

I think the power companies are very worried about these units becoming popular.
Click to expand...

ahh the one voltage I did not check.....dang it.

are point of use water heaters also called insta-hots or are they completely different?
 
necnotevenclose said:
are point of use water heaters also called insta-hots or are they completely different?
Click to expand...

I am not sure, most 'Insta hots' I have worked with have a small storage tank, a gallon or less.

The point of use water heaters do not have any storage, they use brute force to heat water only as needed.

As soon as a flow switch senses water flow the elements are energized and they stay energized until the flow stops.

Some whole house units require two 60 amp feeders.
 
You can get them in all flavors 120, 277, 208, 240, single or three-phase. I've heard of some POCOs making the customer pay to upgrade the pad mounted transformer when using the whole house models.
 
insta-heat

insta-heat

they are becoming more popular in this area, but, for the most part, only those folks who went for the higher end k-w are happy. I've not seen a sucessful installation yet that didn't require kissing a 200 amp service good-bye.
 
augie47 said:
they are becoming more popular in this area, but, for the most part, only those folks who went for the higher end k-w are happy. I've not seen a sucessful installation yet that didn't require kissing a 200 amp service good-bye.
Click to expand...
If you have to draw that much current to heat water, why not us a gas fired instant unit?
 
Psychojohn said:
If you have to draw that much current to heat water, why not us a gas fired instant unit?
Click to expand...

It is not always available.

But I agree, electricity is a poor choice for water heating.
 
These units drive me nuts with my load calcs!!! And after they are installed, unless they are a 6KW or greater, the better term is ' Insta-warm", not "Insta-hot". I finally got our Plumbing engineer to understand this and start specifying 5-10 gallon EWH's.
 
insta-warm

insta-warm

boater bill said:
These units drive me nuts with my load calcs!!! And after they are installed, unless they are a 6KW or greater, the better term is ' Insta-warm", not "Insta-hot". I finally got our Plumbing engineer to understand this and start specifying 5-10 gallon EWH's.
Click to expand...

"insta- warm" amen :)
 
necnotevenclose said:
To get a better understanding of the load calc, please include the gallon size(s). NEC 2005 422.13 states storage-type water heaters 120-gallons or more must be considered a continuous load and calculated at 125% (422.10).
Click to expand...
Actually, it is 120 gallons or less, not 120 gallons or more.

A 120 gallon point of use water heater would be pretty big. :)
 
ryan_618 said:
Actually, it is 120 gallons or less, not 120 gallons or more.

A 120 gallon point of use water heater would be pretty big. :)
Click to expand...

well you got me on less not being more....so does that mean that a common residential water heater needs to be calculated as a continuous load?
 
Status
Not open for further replies.
Top