422.12 violation?

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tommyrice

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Recently I wired 8 gas fired hot air furnaces on 4 multiwire branch circuits.Later I saw that 422.12 required central heating equip. to be on individual branch circuits.Each multiwire branch circuit consists of 2 20 amp breakers with handle tie . 12-3 mc to j-box then 12-2 mc to ssy with 15 amp fuse to each furnace.Why would this present a problem ?
 
tommyrice said:
Recently I wired 8 gas fired hot air furnaces on 4 multiwire branch circuits.Later I saw that 422.12 required central heating equip. to be on individual branch circuits.Each multiwire branch circuit consists of 2 20 amp breakers with handle tie . 12-3 mc to j-box then 12-2 mc to ssy with 15 amp fuse to each furnace.Why would this present a problem ?
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I think you may be okay

210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article
shall be permitted as multiwire circuits. A multiwire circuit
shall be permitted to be considered as multiple circuits.
 
tommyrice said:
Recently I wired 8 gas fired hot air furnaces on 4 multiwire branch circuits.Later I saw that 422.12 required central heating equip. to be on individual branch circuits.Each multiwire branch circuit consists of 2 20 amp breakers with handle tie . 12-3 mc to j-box then 12-2 mc to ssy with 15 amp fuse to each furnace.Why would this present a problem ?
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4 MWBC is the same as 8 individual circuits, assuming 2 hots & 1 neutral. 422.12 is not calling for individual neutrals. Your install is fine.
 
Sounds fine, except the handle tie kind of stinks. If you need to shut off just one circuit you'll end up knocking out two boilers.
 
both furnaces wouldn't shut down

both furnaces wouldn't shut down

handle tie is required on multiwire circ. the ssy's have 15 amp fuse which would probably trip if there was a problem with one of the furnaces
 
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