Adding a panelboard when no more breaker space is available in the MDP

[vincec]

I want to add a 225 amp panelboard, but there is not enough breaker space in the MDP but adequate capacity. The MDP has a 600A bus but a 500 amp MCB. My thoughts are to legally tap either the bus after the MDP main breaker or if necessary tap the conductor on the primary side of the MCB. In either case an 200 or 225 amp device would be installed to protect the wire if necessary. If the new panelboard had a MCB could I use the tap rule if it is within 25' if I am able to tap on the load side of the MCB of the MDP?

What are my options?

 

[infinity]

Is there a reason why you would choose a line side tap over a load side tap after the 500 amp OCPD? For clarification the MDP is not a service?

 

[vincec]

I think that, if possible, a bus line side tap would be preferred. If not possible, then line side which would be the service conductors.

 

[infinity]

A 200 amp panel with 200 amp conductors and a main CB would fall under the 25' tap rule if the conductors are tapped on the load side of the 500 amp CB.

 

[augie47]

Although it's done all the time, tapping the buss, I believe, requires manufacturers approval which is basically impossible to obtain.
To me, the buss tap is preferable to a line side tap and you should be fine with the 25ft tap rule.
A possible third option would be a sub-feed lug kit in MDP moving breakers to the new panel to provide space for the kit assuming a kit is available