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1. Originally Posted by ballvalve
Obviously it depends on the distance. And the wire and its temperature rating of insulation. It goes as high as 130 amps.

http://www.thelenchannel.com/1amps.php

The manufacture says #2, so it can be used. NEC don't seem to care about the length, even tho it is part of the formula.
I go by voltage drop when I install wire.

2. Originally Posted by ballvalve
Obviously it depends on the distance. And the wire and its temperature rating of insulation. It goes as high as 130 amps.
Wow. Really?

No, NOT really. An electric boiler with a draw of 100A simply CANNOT use wire rated for 100A.

3. Originally Posted by Speedy Petey
Wow. Really?

No, NOT really. An electric boiler with a draw of 100A simply CANNOT use wire rated for 100A.
If the wire is rated at 75-90degs C, You may could get by with it. But not using 60 deg wire. Should use 90C for good measure.

4. Originally Posted by DonL
If the wire is rated at 75-90degs C, You may could get by with it. But not using 60 deg wire. Should use 90C for good measure.
The rating of the wire has NOTHING to do with it.
An electric boiler like this has to be figured @ 125%. So the ampacity of the conductor must be at least 125A.

How do you figure temp has anything to do with this? I never mentioned wire size, just ampacity.

5. Originally Posted by Speedy Petey
The rating of the wire has NOTHING to do with it.
An electric boiler like this has to be figured @ 125%. So the ampacity of the conductor must be at least 125A.

How do you figure temp has anything to do with this? I never mentioned wire size, just ampacity.
I thought that we were talking about #2 ?

You say Temperature does not mater ?

That unit has bank switching and would very rarely (If Ever) require 100 amps to operate.

You also have to add < 10 amps for the rest of the system.

6. Originally Posted by jwelectric
2 copper NM-B or 2 SE-R copper is good for 95 amps. As long as the boiler ampacity is below 76 amps then installing it using #2 with a 100 amp breaker will be fine.
If the heating elements are rated at more than 48 amps and the boiler does not have an ASME stamp on it then the maximum ampacity cannot exceed 60 amps. If the boiler does not have an ASME stamp and the elements are rated more than 48 amperes the load has to be divided into loads that does not exceed 60 amps. This can be done inside the control panel of the boiler by having fuses or breakers that subdivide the loads.

Once again please do a service load calculation to be sure that it will handle the new load. Remember that the boiler is to be figured at 125% of its ampacity.

7. Originally Posted by jwelectric

Exactly.

Also the manufacture says #2 , It is UL listed, so its got to be correct. Right ?

8. Originally Posted by DonL

Also the manufacture says #2 , It is UL listed, so its got to be correct. Right ?
You keep saying this. WHERE are you seeing that the mfg recommends a #2 branch circuit for a 24kW heating load?

9. Originally Posted by DonL
Exactly.

Also the manufacture says #2 , It is UL listed, so its got to be correct. Right ?
If the boiler is rated at 24KW then it will require a conductor rated at 125 amps regardless what the installation instructions say.
The more strenuous rule will take presence.

Remember that the NEC is a minimum safety standard so to do anything less than what it calls for leads to an unsafe installation.

10. Originally Posted by jwelectric
If the boiler is rated at 24KW then it will require a conductor rated at 125 amps regardless what the installation instructions say.
The more strenuous rule will take presence.

Remember that the NEC is a minimum safety standard so to do anything less than what it calls for leads to an unsafe installation.
I Don't really think that it is going to Be using 24KW that is just a selling point that people fall for. Bigger is better ?

The True rating is in BTU, Then when you do the math, their own figures don't add up.

It works just like a water heater, Well it is one, and all Heating elements will not be in operation simultaneously.

11. Don,

How do you figure? At 24KW, I get ~81,900 BTU (thermal) per hour, which agrees with the 82,000 BTU/hr listed earlier. Maybe you are looking at a different unit?

Even if it doesn't pull 100A 100% of the time, the wiring needs to be sized for a 100A load (really sized for 125A).

As I (and others) brought up earlier, we don't know that this house even needs a 82k BTU/hr unit. We also don't know anything about the "new house" either. One of the smaller units might get the job done and will cost less for the unit as well as the wiring, breaker, etc.

12. Originally Posted by DonL
I Don't really think that it is going to Be using 24KW that is just a selling point that people fall for. Bigger is better ?

The True rating is in BTU, Then when you do the math, their own figures don't add up.

It works just like a water heater, Well it is one, and all Heating elements will not be in operation simultaneously.
A boiler is different than a water heater. The boiler is designed to allow all the elements come at one time. On the first start up when the water is cold it is possible for all the elements to draw current at the same time.

The NEC requires that the KW rating of the boiler to be multiply by 125% for sizing the conductors. If the name plate on this boiler says 24KW then it is 24,000 times 125% for sizing conductors.

13. You guys are exactly correct.

When you look at the units Controller Sequencing a different story is told.

14. This is NOT a boiler its a flo thru water heater - no steam. And no 'bungalow' needs a 100 amp water heater.

http://s3.pexsupply.com/manuals/1255..._PROD_FILE.pdf

15. The link you posted on the cover of the manual is calls it a boiler

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