Hot water tanks

Status
Not open for further replies.
B

Big Guns

Member
Good Morning

If you have a 80 gallon electric hot water tank @ 208 volts with two elements @ 4500 watts a piece non simultanious. do figure the amps @ 4500 watts or 9000 watts.
 
It should have a min OCP - max OCP listed on the data plate...

So the question is: 3 Phase or single phase? Anyway I would do it at 9000VA - unless there is something else that should be known.
 
Big Guns said:
Good Morning

If you have a 80 gallon electric hot water tank @ 208 volts with two elements @ 4500 watts a piece non simultanious. do figure the amps @ 4500 watts or 9000 watts.
Click to expand...

For non simultanious useage just go by one element like your qoute stated so go with 4500 watts or 4500 va.

That is the key word if it was simultanious then you will have to go with 9000 watts or 9000 va.

Merci,Marc
 
I kinda question the 'simultaneous' part - on a water heater??? Say Upper and lower at a cold start.... Does it have some sort of interlocked dual thermostat??? It might be 'non-continuous'????
 
E57.,

You did bring up good point so let me make it clear on this one.

Ok ., for the simultaneous operation it mean it will useally have single thermosat to control both heating element in the water heater.

For non simultaneous operation yes there is interlock thermosat on upper element plus there is a lower thermosat as well so when the water heater tank is cold the upper element will come on first and heat the upper half first when it get warm up to the point the thermosat call the heat off it will do two functions one is turn off the upper element and the interlock will change the circuit connection to the lower lower element. { sorta like DPDT switch }

And yeah all the water heater do have limit switch that useally located at the upper element { if have dual element tank } otherwise at lower element location { single element tank }

that item that what I describe it will work with both single and three phase two element water heater tanks { three phase multi elements will use single thermosat with contractor }

Oh yeah the other thing the water heater can be contionuis useage due if used alot of hot water.


Merci,Marc
 
Last edited:
Thanks Marc....

Just googled '3 phase water heater schematic' and found some - example on page 16 of 16 Which has 3 phase and single phase schematics - I get it now... ;) So then - if it is interlocked - it would act as a single 4500VA load - I've seen a few other thing likes it - but the 208 threw me - 3 or single - I was thinking 3 phase "V" set up (Like an open V transformer) there is one on that page too...
 
Sure anytime E57.,:cool:

by the way not too often you will run into three phase with two heating element set up unless this is found in commercal location. { they useally are a specail order item IIRC } and yes they run in open delta format with this set up and keep in your mind the B phase will have higher current drawage if both elements are on.

Typically 1.73 X amps on other two phases.

Merci,Marc
 
frenchelectrican said:
yes they run in open delta format with this set up and keep in your mind the B phase will have higher current drawage if both elements are on.
Click to expand...
Thats why I questioned it. ;) You know... Often we get only some of the info - and sometimes can give a wrong answer based on that. Sometimes we get all the info - and still the wrong answer if it is missed if presented the wrong way...

Merci - Mark ;)
 
Nobody mentioned the size, as far as I know, that's what determines it, not the thermostat.

A WH less that 125 gallons in considered continous duty.

A wh more than 125 is considered non continous.

4500 watts, continuous, makes you run a #10 for the load
 
mcclary's electrical said:
A WH less that 125 gallons in considered continous duty.

A wh more than 125 is considered non continous.
Click to expand...

I believe it's 450 L (120 gal). ;)

A small distinction but I do remember a post from a while back where someone had come across a water heater on a job that was something like 121 gallons and thought it was a odd number.

But apparently it was manufactured with 422.13 in mind, so that it just crossed the threshold into non continuous.
 
Dave58er said:
I believe it's 450 L (120 gal). ;)

A small distinction but I do remember a post from a while back where someone had come across a water heater on a job that was something like 121 gallons and thought it was a odd number.

But apparently it was manufactured with 422.13 in mind, so that it just crossed the threshold into non continuous.
Click to expand...



So true, again my memory failed me.
 
Had a similar situation recently. I checked out the Rheem site and found this http://globalimageserver.com/fetchDocument.aspx?id=7522ff8d-b9a6-420d-ba77-3263d7148f76. (check out pages 8 and 20 of this PDF) The heating elements are interlocked so that they can't both operate at the same time. In my case I had (2) 4500 watt elements, non-continuous with a 3 wire outlet. Customer currently has a 2-pole 20 amp circuit to the heater that the plumber installed (replaced). It won't pass inspection and I've already told them they'll have to replace the wiring and disconnect. Will the wiring burn up before they decide that I'm right. :confused: Who knows;)
 
goldstar said:
Had a similar situation recently. I checked out the Rheem site and found this http://globalimageserver.com/fetchDocument.aspx?id=7522ff8d-b9a6-420d-ba77-3263d7148f76. (check out pages 8 and 20 of this PDF) The heating elements are interlocked so that they can't both operate at the same time. In my case I had (2) 4500 watt elements, non-continuous with a 3 wire outlet. Customer currently has a 2-pole 20 amp circuit to the heater that the plumber installed (replaced). It won't pass inspection and I've already told them they'll have to replace the wiring and disconnect. Will the wiring burn up before they decide that I'm right. :confused: Who knows;)
Click to expand...



If it's 240 volt,and non continuous, the 20 amp circuit is big enough
 
mcclary's electrical said:
If it's 240 volt,and non continuous, the 20 amp circuit is big enough
Click to expand...
Not the way I read the chart. It requires a 25 amp circuit so the next highest trade size breaker is 30 amps and # 10 wire. If you do the math 4500/240= 18.75 amps. 80% of a 20 amp breaker is 16 amps so you'll have to go to the next size up the way I see it.
 
goldstar said:
Not the way I read the chart. It requires a 25 amp circuit so the next highest trade size breaker is 30 amps and # 10 wire. If you do the math 4500/240= 18.75 amps. 80% of a 20 amp breaker is 16 amps so you'll have to go to the next size up the way I see it.
Click to expand...

Actually 25 amps is a standard sized breaker, 240.6. We use a 30 amp for convenience.
 
goldstar said:
Not the way I read the chart. It requires a 25 amp circuit so the next highest trade size breaker is 30 amps and # 10 wire. If you do the math 4500/240= 18.75 amps. 80% of a 20 amp breaker is 16 amps so you'll have to go to the next size up the way I see it.
Click to expand...



I'm not talking about the chart. I'm talking NEC. The op said non continous.

Why can't I load a 20 amp breaker past 16 amps? Pleaase provide code article.
 
Status
Not open for further replies.
Top