Why don't we take that into account? How is a breaker that trips 25% higher than nameplate for at least 5 months of the year, in my area, a code compliant installation?In cold environments, thermal magnetic breakers will carry more current, is that what you are referring to? But for the most part the 'up North here' nobody takes the characteristics into consideration. There are thousands of multi-metering applications installed where no adjustments have been required.
The emergency disconnect, like the meter disconnect, probably would not need to be rated to close into a fault condition, and may not even need to break bolted fault conditions, unlike a service disconnecting means.
Based on the lack of any significant number of reported issues with this type of installation, I would guess the NEC tables for conductor sizing are sufficiently conservative and therefore the overcurrent protective device performance is satisfactory.Why don't we take that into account? How is a breaker that trips 25% higher than nameplate for at least 5 months of the year, in my area, a code compliant installation?
It code permitted increase is not as much as the increase in the trip point. The maximum multiplier in 310.15(B)(2)(a) is 1.15. Also, in many cases only a very small part of the conductor run is outside. Square D shows a 25% shift for their larger breakers in a 50°F ambient. While there would be some slight increase in the interior of the enclosure, I expect that in my area, a single main breaker in an exterior enclosure would operate at or below 50°F for about 5 months of the year.Doesn't conductor ampacity also increase under those conditions?
For derating purposes, you need to find the temperature derating curves and not simply shift the standard TCC. Use their publication called "Current Carrying Capacity In Special Applications" (0100DB0101).
QOT 20A trips around 22A,
QO 20A trips around 26A
QOM100A trips around 125A
QOM 200 trips around 260A
My copy of this publication is from July 1988 (#SD361 R1) and has the same curves as the link I provided.
The dashed lines on the trip curve should be based on the NEMA standard AB-2 for a single pole breaker, rather than on the actual breaker. This is probably a worse case 'long time delay', but honestly, I have never seen a clear explanation of when/how this reference would be used.
UL has told me that this is a 110.3(B) instruction and prohibits the installation of the breaker in an outside location in my area.Square D circuit breakers can be applied in ambient temperatures within the range of -10°C to 60°C (14°F to 140°F). This document provides guidelines to follow when adjusting for ambient conditions.
The dashed line is not a characteristic of the breaker shown in the TCC. It is representative of a generic worst case device.How is the dashed line different from the 40°C trip band on the same trip curve?
So we shouldn't use breakers outside where it gets cold. With the emergency disconnect rule, I think we will see a lot more outside service overcurrent protective devices. Maybe an Informational Note should be added to 230.85.The dashed line is not a characteristic of the breaker shown in the TCC. It is representative of a generic worst case device.
I can't think of any breaker that would not be somewhat affected by temperatures below 14°F. Many greased mechanism parts tend to be sluggish at 'negative' temperatures.
I didn't say that.So we shouldn't use breakers outside where it gets cold.
If the circuit breaker panel is located outside and has a main breaker, can this main breaker serve as the above mentioned main service disco?I was talking to an inspector from my area yesterday and he mentioned there may be a new requirement to have a main service disco on the residence(outside, on side of building) for 2020. Presumably for first response reasons but I don't know for sure. Anyone know more about this?
But I did say that and the manufactures publications are 110.3(B) instructions. Just because we have not had seen problems does not mean there is not a code violation.I didn't say that.
Our industry has 50+ years of outdoor breaker installation history, particularly with multi-meter centers. I have no significant amount anecdotal evidence of outdoor breakers not offering appropriate protection except when they overheat in sunshine.