LeafMan66_67 wrote:
Depending on the rating of the element, the current (I) will change based on voltage (E), since the resistance (R) of the element is a constant.
Example:
If the element is rated 4500W @ 240V, calculated current is 18.75A. Resistance of the element is E/I = 12.8 ohms. As the voltage decreases, the current will also decrease because I = E/R and R is constant for the purely resistive load. So, once you know the resistance, you can calculate the new current at different voltages. So, at 235V, current would be 235/12.8=18.4A but the element would only be 4314W. As well, at 220V, I=220/12.8 = 17.2A and the element would only be 3781W.
The key is paying attention to the actual rating of the element, whether it is 4500W@240V or 4500W@220V or somewhere in between. From there you can determine the current based on your actual voltage. Hope it helps. That's all I got for a Sunday morning.
Well put, this is what I was getting at, although on second look for some reason I used 4700W and not 4500W....
Kal likes to talk about this rule a fair bit, although you will also find many that disagree. Similar to the previous conversation regarding GFCI breakers, code application here is not so simple. The easiest argument as to why the 80% rule doesn't apply here is it refers to continuous current.LeafMan66_67 wrote:CEC states that an overcurrent device can only be loaded to 80% of its capacity. You can get 100% rated breakers, but you are looking at larger frame sizes with solid state trip units, costing lots of extra money.John G wrote:I don't know what the code is here in NS, but Kal from theelectricbrewery.com site mentions that many places stipulate that you must have a supply of at least 125% of the maximum rated amperage of what will be used for continuously operating appliances such as hot water heaters. Based on that, regardless of how you calculate the above you'll likely need to go to a 40A double pole breaker in your panel instead of 30A. I'm not an electrician though, so don't listen to me.
So if you choose to follow the 80% rule, if you plan to run both elements for more then 1 hour in a 2hour period...The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load
unless it can be shown that in normal operation it will not persist for
(a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or
(b) a total of more than 3 h in any six-hour period if the load exceeds 225 A.
Surely we've all plugged a 15A power tool into a 15A outlet at some point....
IMHO Kal is dictating good practice, not required practice. You can get away with 30A for a 4500W & 1500W, in fact P-J's DWG you posted calls for a 30A feed. As I said before, weigh this against the effort required to upgrade your service. Its unlikely anyone's brewery (including Kal's) is going to meet CEC compliance due to the lack of certifications, which he himself does state but rather that he is just trying to follow good practice.
This is not my field of expertise, so take my advice with a grain of salt.
It's 16"x14"x6" so should be a good size for what i'm doing. Anybody got any suggestions or tips on the layout of the controls in it? Rubbertoe, what did you use to cut your's?