Our facility is installing new out door MV switchgear consisting of several sections joined together. The last switch gear section contains the batteries, battery charger, an AC load panel and a DC bus distribution panel. The enclosure is large enough to walk into. The enclosure opens from both sides. The batteries, installed on a 3 tier rack, consist of 92 wet cell NiCad cells in series that creates a 130V, 175Ah bus to power the protective relays, the trip and close motors and all the associated controls. Several issue have come up about this system and the enclosure.
1. Since the enclosure can be entered and the front of the battery rack is accessible while inside, does the working space requirements of 110.26 apply? Currently there is only 18" of clearance between the battery bank and the side wall of the enclosure. From one side of the enclosure with a door open, there is plenty of clearance if the perspective is from the outside of the enclosure. It is when the perspective is from a worker standing inside the enclosure that the working space is obstructed between the battery bank the the enclosure side wall. A majority of the battery maintenance would need to be performed in the area with the 18" of clearance. Is this in violation of the working space requirements?
2. Should we be concerned about hydrogen accumulation? A simple vent exists near the top, on one side of the enclosure opposite the battery bank. The batteries are not below this vent. Any hydrogen would accumulate in the ceiling pockets and can also migrate to the adjoined medium voltage sections. I understand that under normal conditions, the hydrogen emission is somewhat low. However, I am concerned about the abnormal conditions such as thermal runaway, and charger malfunction. There is no hydrogen detection sensor or powered ventilation.
3. Should we be concerned with high temperatures? There are no environmental controls on this outdoor enclosure, in direct sun, and summer time temperatures can reach +110F. The maximum battery temperature rating is 124F. I would expect the inside of this enclosure to greatly exceed this maximum.
1. Since the enclosure can be entered and the front of the battery rack is accessible while inside, does the working space requirements of 110.26 apply? Currently there is only 18" of clearance between the battery bank and the side wall of the enclosure. From one side of the enclosure with a door open, there is plenty of clearance if the perspective is from the outside of the enclosure. It is when the perspective is from a worker standing inside the enclosure that the working space is obstructed between the battery bank the the enclosure side wall. A majority of the battery maintenance would need to be performed in the area with the 18" of clearance. Is this in violation of the working space requirements?
2. Should we be concerned about hydrogen accumulation? A simple vent exists near the top, on one side of the enclosure opposite the battery bank. The batteries are not below this vent. Any hydrogen would accumulate in the ceiling pockets and can also migrate to the adjoined medium voltage sections. I understand that under normal conditions, the hydrogen emission is somewhat low. However, I am concerned about the abnormal conditions such as thermal runaway, and charger malfunction. There is no hydrogen detection sensor or powered ventilation.
3. Should we be concerned with high temperatures? There are no environmental controls on this outdoor enclosure, in direct sun, and summer time temperatures can reach +110F. The maximum battery temperature rating is 124F. I would expect the inside of this enclosure to greatly exceed this maximum.
