Will I be able to replace an existing "under the bridging unit" extractor hood (which vents directly out the back through the wall) with a chimney-style extractor venting through the same hole? (i.e do the chimney-style extractors have the option of venting out the back as well as upwards?) Or will I have to cut another hole in the external wall? Ta, Simon
Yes, just use a 90 degree bend,or flexible aluminum ducting, & most chimney-style extractors now use 6" ducting for best effiency & performance. http://www.fantronix.com/acatalog/Plastic_90_Degree_Bend.html
Might potentially be a problem in that the bottom edge of canopy to fan spigot might be a lot more than the height of your existing Hood. You may need to set your new hood lower than existing one to use same outlet hole or re-core!! Double check before buying!!
Was going to add that, but lost connection again. Use rigid pipe through the wall, might get away with a rigid 90 degree bend, or use a thread hose connector to connect flexible pipe to rigid pipe through the wall.
Thanks both, you've both hit the nail on the head. I suspected that the fan unit might be taller and vent from the top, rather than straight out the back and this does seem to be the case on most models. Looks like I'm going to have to re-core...
it may be a good idea to rebrick up the the existing core hole prior to drilling a new hole if they will be in close proximity, once set recore a new hole. Go for 150mm ducting and use an appropriate sized core drill. You may have to hire the bit and drill if you haven't got anything suitable. Try to find similar sized and stock of brick and carefully stitch drill out any un whole brick to be replace with new full bricks.
Thanks Jitender, I've been having a very similar conversation with a builder pal. Someone did suggest that you could use the new core to plug the old hole but I'd rather go for the replacement bricks myself.
I don't think a 152mm core drill will allow for 150mm ducting to go through, so may have to use a 162mm core bit, this is the drill size I have. Some ducting is internal diameter measurement only. Best to allow the mortar to fully set and harden before coring out the new hole as the bricks could loosen up with all the vibration.
Oh yes it does! Slightly off topic Silvavent 150mm wall fan,uses a larger hole than the usual 152mm diameter, just been caught by that.