lazorko
Member
- Location
- Philadelphia
I could use some advice:
A church had a 100A single phase 120V/240V 20/24 circuit subpanel supplying lighting loads in the sanctuary. Complaints were that several of the breakers were getting very hot, accompanied by burning odor. Each of (3) 20A breakers served (2) ceiling fixtures lamped witth (9) 100W incandescent lamps. We calculated the load on each branch to be 1800W or 15A - within the 80% continuous loading on a 20A branch; measurements revealed that actual loads ranged from 16A - 17A on the three breakers. Neutral currents for each circuit were identical to currents on the hots.
We found that the panel bus insulation had begun to burn under the three breakers and replaced the panel with a new copper bus 125A panel and wired (6) new switches to control the lights (they had previously been controlled by flipping the breakers).
The three circuit breakers are still getting hot, getting noticably warm within several minutes of loading. The heating starts at the point of contact between the breakers and the panel bus - not at the screw terminal or #12 THHN.
We advised replacing the incandescent lamps with comparable compact flourescents to reduce the loads, but are concerned that this is occuring in the first place. Why is the panel getting so hot? Would the 1A (on the load drawing 17A) difference between permitted continuous loading of a 20A circuit and the actual continuous load make the differrence between a safe installation and a fire hazard? What about the circuits loaded to only 16A, 80% of the circuit rating?
We would appreciate your thoughts and advice.
A church had a 100A single phase 120V/240V 20/24 circuit subpanel supplying lighting loads in the sanctuary. Complaints were that several of the breakers were getting very hot, accompanied by burning odor. Each of (3) 20A breakers served (2) ceiling fixtures lamped witth (9) 100W incandescent lamps. We calculated the load on each branch to be 1800W or 15A - within the 80% continuous loading on a 20A branch; measurements revealed that actual loads ranged from 16A - 17A on the three breakers. Neutral currents for each circuit were identical to currents on the hots.
We found that the panel bus insulation had begun to burn under the three breakers and replaced the panel with a new copper bus 125A panel and wired (6) new switches to control the lights (they had previously been controlled by flipping the breakers).
The three circuit breakers are still getting hot, getting noticably warm within several minutes of loading. The heating starts at the point of contact between the breakers and the panel bus - not at the screw terminal or #12 THHN.
We advised replacing the incandescent lamps with comparable compact flourescents to reduce the loads, but are concerned that this is occuring in the first place. Why is the panel getting so hot? Would the 1A (on the load drawing 17A) difference between permitted continuous loading of a 20A circuit and the actual continuous load make the differrence between a safe installation and a fire hazard? What about the circuits loaded to only 16A, 80% of the circuit rating?
We would appreciate your thoughts and advice.