application of demand factors

[bigrockk]

Well I have to put my two cents in.
If the stove is used as intended supper will be nice and hot. One has to remember that it is extremely unlikely that all elements will be on high at the same time. As such the load from each element will be cyclic, so highly improbable that the stove will ever draw 12KW even if the whole family is home for dinner.

Aspencade: In your first post you ask: That seems to mean that for calculations of service the conductors or breaker do not have to be de-rated to 80%. Does this apply to branch circuits as well?

No this does not apply to branch circuits. Rule 8-200 applies to Services and feeders only, not branch circuits. Rule 8-104(3) applies to branch circuits, and in my experience this means it is considered "a continuous load" unless you want to take the time to prove to the Safety codes officer (Inspector) that it is not continuous. There are exceptions but they are stated quite clearly in Section 8, such as 8-300.

It would be rare to find residential hardware (service box, fusible switch, circuit breakers or panel boards) marked for continuous operation at 100%. So in most residential cases rule 8-104(5) will apply.
Just my two cents....

[aspnecade]

Originally posted by twh:
You got me on 8-300. I was wrong. However, the breaker does trip - even the replacement. I insist that supper will be cold, but only when the whole family is there.

If you are relying on the handbook, I can't respond. I don't have a copy, and I have never had a rejection based on the handbook.

<font size="2" face="Verdana, Helvetica, sans-serif">Why do you think supper will be cold? This is the standard procedure for a range installation. In almost every case a 40A breaker is installed on #8 conductors to feed the 50A receptacle. In many cases the new ranges are around 12Kw. If supper was going to be cold the safety authority would have long since changed the demands in 8-300.

As to the handbook it is produced by the CEC authority for the explanation and application of the rules.

What is your opinion on PS Knight's books? Have you ever used them? I remember years ago when he first wrote them his name was "mud" with most other inspectors. Rumour had it that if one of his books was found on a job site it would mean an instant rejection on something! He also has a lot to say about section 8 and how it applies to dwellings. Anyway ... enough about demand factors...my dinner is ready...oh darn...its cold! [img]graemlins/cry_smile.gif[/img] (just kidding) Thanks for the discussion.

[aspnecade]

Originally posted by bigrockk:
Well I have to put my two cents in.
If the stove is used as intended supper will be nice and hot. One has to remember that it is extremely unlikely that all elements will be on high at the same time. As such the load from each element will be cyclic, so highly improbable that the stove will ever draw 12KW even if the whole family is home for dinner.

Aspencade: In your first post you ask: That seems to mean that for calculations of service the conductors or breaker do not have to be de-rated to 80%. Does this apply to branch circuits as well?

No this does not apply to branch circuits. Rule 8-200 applies to Services and feeders only, not branch circuits. Rule 8-104(3) applies to branch circuits, and in my experience this means it is considered "a continuous load" unless you want to take the time to prove to the Safety codes officer (Inspector) that it is not continuous. There are exceptions but they are stated quite clearly in Section 8, such as 8-300.

It would be rare to find residential hardware (service box, fusible switch, circuit breakers or panel boards) marked for continuous operation at 100%. So in most residential cases rule 8-104(5) will apply.
Just my two cents....

<font size="2" face="Verdana, Helvetica, sans-serif">If you look at the rules you will see that the equipment would not have to be rated for continuous use. If a load is non continuous then the equipment can be loaded to 100%. You are right though about "most residential circuits" but only because almost every kind of load you could install is covered by another area of the code that ammends section 8.

[twh]

bigrockk, I'm pretty sure my range is intended to heat food. My range trips my breaker and it does draw more than 40 amps.

[bigrockk]

THW
If your range is tripping the breaker and all your doing is cooking dinner (as opposed to heating your house) I would be looking for a problem with the range.

Under what circumstances is the breaker tripping? Is everything turned on high when the breaker trips? I have yet to come across a properly working range that trips a 40-amp breaker under normal usage.
How about some more details.

[twh]

About an hour before it's time to eat:
- Take the turkey out of the oven so it can cool before you carve it. Cool turkey carves nicely, instead of coming apart in chunks. Leave the ham in the oven to continue cooking.
- Take the cabbage rolls off, but leave them in the pot. They will stay warm enough.
- Put the pot of potatoes on high.
- Put the pot of carrots on high.
- Put the water for the perogies on high.
- Put the pot of turnips, or whatever other vegetables, on high.
- Pour yourself a big glass of wine and take a little break, you earned it. There's plenty of time to reset the breaker, later.

My ex liked to have big meals and this breaker tripping problem followed us from house to house, even when the appliances didn't. It isn't normally a problem, but when you have 20 people in your house, waiting to eat, it is; and, you have to start planning your cooking around the 40 amp limit.

When the children visit, with their children, the hot water heater doesn't cycle either. Neither does the air conditioner in the summer, nor the clothes dryer.

Normally, though, the dog is home alone. He doesn't use much electricity, so it's okay to undersize the circuits.

[bigrockk]

TWH:
Good Analogy!! I see your point.
If nothing else at least I had a good laugh, thanks!!
Maybe the trick is too get half a dozen dogs and give up on the kids and relatives.
At least dogs don't mind cold food.
[img]wink.gif[/img]

[u2slow]

I guess the CSA guys like baked potatoes, and microwave their vegetables! [img]wink.gif[/img]

[bigrockk]

All I know for sure is all this talk about food is making me hungry!!!
I think I have to work on TWH for an invite to dinner...Love cabbage,turkey,ham.....etc.YUM!! [img]biggrin.gif[/img]