chasing in oval conduits and filling in chases advice please

[Guest112]

Hi guys, before starting this thread I have searched old threads on this site and had no luck finding a good one. I started a thread a few weeks a go my house rewire and now im after a bit of advice on filling chases.

I rarely do domestic electrical work so have barely touched on chasing, the jobs that i have done/been on in the past involving chases have been done by labourers.

im going to chase in oval conduits and would appreciate advice on how you guys fix the conduits in before filling, a colleague of mine says he pins in the conduits using nails to hold the conduit before filling with a sandy concrete mix leaving 3mm for skimming after. Does this sound good?

as far as chasing the drops im either going to borrow a wall chaser if i can or use a grinder with diamond disks and scutch out the center.

to cut out the boxes im going to use a grinder to cut the square and chisel out the centers by hand after fixing the metal backboxes and running in the conduits i plan to fill the chases and cuts with a concrete mix with 1 part sand to 3 parts concrete and leave the 3mm gap for skimming over.

a few things im wonderingn are first of all is there anything wrong with anything ive said and also what cables will fit down a flat 20mm conduit? im guessing i need 25mm drops for the 2 2.5mm twins for the rings

thanks in advance guys

 

[Guest112]

ye ive seen them mate was debating getting them or not my only worry was they might bring the conduit off the wall by a few mm so would have to chase deeper but as ive said im completely new to chasing and oval conduits like

(i hope i get a chaser lol going to be a nightmare with a grinder)

also can anyone tell me how they chase up to the ceiling because the chaser can only reach so far any tricks at the top or just good old fashioned hammer and chiseling??

cheers guys advice has been great so far

 

[Ponty Massive]

Peter

I'd use a chaser withdust extraction rather than a grinder. A LOT less mess and both chases are spot on. Use the chaser as high as possible then scutch chisel on the end of an SDS drill (hammer) to chase the tops.

Also for back boxes, I tend to mark the box on the wall, use some insulation tape and mark the correct depth of the back box on a drill bit, drill a load of holes around the box to the correct depth, then again scutch chisel on SDS to knock it out. A bit of practice and no need to fill around the box..

 

[VoltzElectrical]

Peter

I'd use a chaser withdust extraction rather than a grinder. A LOT less mess and both chases are spot on. Use the chaser as high as possible then scutch chisel on the end of an SDS drill (hammer) to chase the tops.

Also for back boxes, I tend to mark the box on the wall, use some insulation tape and mark the correct depth of the back box on a drill bit, drill a load of holes around the box to the correct depth, then again scutch chisel on SDS to knock it out. A bit of practice and no need to fill around the box..

I use this method called 'stitch drilling' for lots of masonry applications. Works a dream. For the amount of work here though, a trip to speedy hire or the like, and a day's hire of a wall chaser and extract unit every time.

 

[Guest112]

thanks guys great advice so your saying literally using a say 5-6 mm bit drill the outline of the box and then knock out the center and then your pretty much spot on size wise

i was going to cut the square and fil the lines where they go beyond the box size for the depth but by the sounds of it my idea very messy using a drill MUCH tidier and you get your depth spot on, cheers guys again very good advice thank you

 

[MarkieSparkie]

Hi Peter,
There is an alternative to purchasing/hiring a chaser. Grinder guards with extraction port and depth stop, with a "Henry" vacuum cleaner make a cheap set-up which will minimise the dust, but it's still going to messy like all chasing. This is the kit I used for 2 years after getting started and still use this type of set up for some specialist chases.
You will only need 4.5" angle grinder with a diamond blade. 9" angle grinders are over-kill and extremely difficult to use for chasing due to the weight of the tool and the gyroscopic effect.
Bosch do a guards for most of their models, with extraction port and depth gauge, see link below:
Angle Grinder Dust Extraction Guards | Miles Tool & Machinery Centre

 

[Mfctitch]

We done a job recently and used large round conduit. and was glad that we did as trying to get 2 number 2.5mm t&e down an oval conduit after we had plastered the wall up would have been a nightmare.
Just a thought.

 

[Guest112]

cheers markie didnt know these existed i noticed the one wher you can actually set the depth (by the look in the pic) very good mate fingers crossed on the chaser but definatelyt a good buy if not thanks for than mate

 

[Mr.Si]

We done a job recently and used large round conduit. and was glad that we did as trying to get 2 number 2.5mm t&e down an oval conduit after we had plastered the wall up would have been a nightmare.
Just a thought.

Why that way around? I would have thought you'd run cables before plastering!

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[Guest112]

had a go chasing a double backbox in one of the bedrooms using the sitch drilling method and chiseled out the middle with a flat sds chisel worked really well very tidy way of doing it not much dust in the air and as mentioned tidy enough to not need to fill around the backbox when its in place, oredered a circular sds cutter but not the square box cutter as ive read about how useless they are on red brick but the circular cutters are meant to be pretty good worth a try at £16 anyway

 

[bodders22]

Hi I recently bought a Erbauer wall chaser from screwfix for £99.99. Its a great bit kit for the money, connected to my henry the dust was almost non existant. Use it for what you want then stick it on ebay you should get a good price, but I wouldn't be suprised if you keep it after using it. Tip though dont pull the chaser out of the wall until the discs stop keeping vacuum going.

 

[Mfctitch]

you are right, but I learnt a valuable lesson which is that you can easily get 2 number 2.5 down a large round conduit but not oval. So it makes it better if something goes wrong.

 

[sparc]

Hi I recently bought a Erbauer wall chaser from screwfix for £99.99. Its a great bit kit for the money, connected to my henry the dust was almost non existant. Use it for what you want then stick it on ebay you should get a good price, but I wouldn't be suprised if you keep it after using it. Tip though dont pull the chaser out of the wall until the discs stop keeping vacuum going.

I was going to "dust was almost non-existent" sounded a bit of an exaggeration - I use a Sparky chaser + Henry combination and can only minimize the dust. However, I haven't tried the your tip on letting the discs stop - will try that next time.

If I can't clear the whole room and there's only chasing to do on a couple of walls I staple plastic sheeting to the ceiling, to form a wall around the work area. That works very well and doesn't take long to rig up. When you pull out the staples a dab of caulk hides the tiny holes.

 

[Mr.Si]

This has got me thinking. A while back I asked about replacing existing cables and asked if it was allowed in the cavity.

I was told the cables needed to be suitably supported.

Does that mean that running in oval conduit with no clips on the cable qualify as a suitable support then?



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[Jel]

You can fix it by using a 5.5mm SDS raw plugs, penny washers and a philips screw. Just drill next to the chase and use the washer over the top of the conduit to hold it in place.

 

[Guest112]

as far as im concerned when my conduits are covered in bonding and the finishing plaster theyll be pretty secure and my cables will be clipped up to the drops so secure enough imo tbh