heating chart?

[Merleti]

I'm sorry if some one has posted this before, but is there a heating chart for kw to gal with temp and time? I searched but could only find formulas that had 2/3 of the answer.

 

[aspiffymofo]

Here ya go.
It wouldn't upload the .xls file so I re-named it to .xml

View attachment electric-heat.xml

 

[thargrav]

There are problems with the spreadsheet.

For example:
The maxumim load for a 15 Amp breaker & #14 AWG house wire is 15 Amps, not 12 Amps.
The maximum load for SJOOW #14, 300V, 3 wire extension cord is 18 Amps, not 12 Amps.

And this statement is incorrect:
"Always use an extension cord the same size as the wire on the Sizing chart or heaver. A smaller extension cord will cause a voltage drop and may cause a fire. If the cord gets warm it's too small and don't use it!"

 

[Merleti]

aspiffymofo thanks for the sheet.
thagray thanks for the corrections.

 

[Merleti]

I'm not exactly computer savvy. So bear with me. I could not open it because it said it said it had problems with the content.

 

[AllanMar]

There are problems with the spreadsheet.

For example:
The maxumim load for a 15 Amp breaker & #14 AWG house wire is 15 Amps, not 12 Amps.
The maximum load for SJOOW #14, 300V, 3 wire extension cord is 18 Amps, not 12 Amps.

And this statement is incorrect:
"Always use an extension cord the same size as the wire on the Sizing chart or heaver. A smaller extension cord will cause a voltage drop and may cause a fire. If the cord gets warm it's too small and don't use it!"

The sheet is using the 80% rule, another highly debated topic.

 

[thargrav]

The sheet is using the 80% rule, another highly debated topic.

The 80% rule is accurate - it's what derates #14 house wiring DOWN TO 15 amps. Applying the rule to derate the current again after it's been applied once does not make since to me.

 

[AllanMar]

The 80% rule is accurate - it's what derates #14 house wiring DOWN TO 15 amps. Applying the rule to derate the current again after it's been applied once does not make since to me.

You'll have to excuse me as I mostly deal with the CEC but....

In the case of 14AWG wire, the NEC mandates a maximum 15A over current device. The over current devices we use (on a residential scale) are all only rated for 80% continuous load. If the load is continuous (which I usually argue in our case it is not) then the 80% applies to the over current device rating (aka 15A->12A in this case).

The spreadsheet is not going to cover all cases in details, and is not meant to replace the advice of a professional. ...

 

[thargrav]

You'll have to excuse me as I mostly deal with the CEC but....

In the case of 14AWG wire, the NEC mandates a maximum 15A over current device. The over current devices we use (on a residential scale) are all only rated for 80% continuous load. If the load is continuous (which I usually argue in our case it is not) then the 80% applies to the over current device rating (aka 15A->12A in this case).

The spreadsheet is not going to cover all cases in details, and is not meant to replace the advice of a professional. ...

Look closer at your 15 Amp breakers - the 15 Amps is 80% of the continuous load! That's why if you overload a 15A breaker to something like 18 Amps it does not trip immediately.

Breakers are designed this way so that intermittant loads, like the compressor in the fridge in your kitchen that draw a strong surge current on start-up don't trip the breaker every time they start.

 

[AllanMar]

15A is the breaker's rating. The NEC states for continuous loads (which again I disagree that this is, but many believe it is) you cannot exceed 80% of the over current device's rated current (aka 15A).

The 80% your referring to always applies, where this rule only applies to continuous loads.

Rule 220.20

(A) Continuous and Noncontinuous Loads. Where a
branch circuit supplies continuous loads or any combination
of continuous and noncontinuous loads, the rating
of the overcurrent device shall not be less than the noncontinuous
load plus 125 percent of the continuous load.
Exception: Where the assembly, including the overcurrent
devices protecting the branch circuit(s), is listed for operation
at 100 percent of its rating, the ampere rating of the
overcurrent device shall be permitted to be not less than the
sum of the continuous load plus the noncontinuous load.

So for a 15A rated breaker, you cannot have more then 12A of continuous load. Your average residential breaker does not have the 100% rating according to the NEC.

I over simplified to say the breakers are only rated for 80% load (they're still tested/certified for 100% load), it is infact the NEC's requirement that only specific breakers listed for 100% load may bypass this rule. The extra testing just certifies that it can survive prolonged usage (heat/etc) without tripping at 100% of its rating,

How and when they trip (surge currents, etc) is to do with the trip curve, this rule is about the NEC being overly cautious.

 

[Merleti]

I'm not exactly computer savvy. So bear with me. I could not open the file because it said it said it had problems with the content.

 

[AllanMar]

rename it to electric-heat.xls

 

[Merleti]

It still comes up with invalid content. It might be that I have Window 8?

 

[thargrav]

The issue is likely the version of Office you are running.

 

[AllanMar]

I PM'd you a google docs version you should be able to open in your browser. (If i posted link anyone could edit it while your using it)

 

[Merleti]

AllanMar I received the chart and it is way better than expected. Thank you!