Regs/guidance for large holes in an internal load-bearing wall

[ffelt]

I'm looking to get a ducted air conditioning unit fitted in a utility room and have the hot/cold air ducted into the neighbouring rooms.
According to the AC company, I would need to make 2 or 3 150mm holes through an internal load-bearing wall:

I'll then create an insulated box and fit a slot diffuser on the front of it:

Fortunately, the joists run parallel to the wall.

It's fairly typical to core out 100mm holes for ventilation and soil pipes through load-bearing walls without much thought, but is there a rule-of-thumb to know how many holes, size of holes and spacing of holes are allowed before I would need to fit a lintel?

 

[noseall]

is there a rule-of-thumb to know how many holes, size of holes and spacing of holes are allowed before I would need to fit a lintel?

I doubt you will incur any structural integrity issues with a few cored out holes, no. As long as you don't remove any material directly beneath any point loads i.e. lintel, joist or beam-ends etc. And the core holes are away from corners and say 300mm apart etc. When you think that you can build a structure upon pillars or with doors and windows i.e. lots of big gaps in the masonry, then you'll get the idea.

 

[freddiemercurystwin]

You should be using fire dampers on any fire resistant walls if applicable.