8mm copper to 15mm copper on TRV's and Rads help

[gimli]

Hi all, have a question and cant find a clear answer too in the forum

We have recently had our house dry lined throughout and now the time to put the rads back on the walls is almost here. (At last, its damn cold at this time of year)

A new boiler has just been added and tied into the existing manifolds feeding the 8mm pipes to the existing heating, new 15mm to the other new rads in the house.

Question 1: Is it possible to use a 15mm TRV with a short run of 15mm copper pipe to under the floor boards or into boxing, then use a compression or solder fitting to reduce down to the existing 8mm pipe work. I am unsure if this is a good idea or not due to possible noise etc and I have heard a lot of complaints about using 8mm reducers in TRV's due to leeks etc. Also, 15mm looks better running up to the valve.

Question 2: Fixing the rads to dry lined walls. lots of suggestions here, plywood panel behind rads, cut through the dry lining, add timber supports and fix brackets to them or use a standart methods with 100mm to 125mm No12 screws. The cavity behind the boards is around 25mm. Have been around and seen many fittings done with normal screw method, good if we decide to alter Rad positions at a later date I guess.

Any advice here would be greatly appreciated, just need to get on again with stuff now, (but in the heat I hope)

Thanks All

 

[gas4you]

1) Yes, no problems

2) It's up to you what fixtures you use. I tend to use DRIVA plasterboard fixings and run a bead of silicone behind the rad brackets for large/heavy radiators.

 

[gimli]

Thanks Gas4you,

I was quite worried about noise from the pipe work the flow rate changed from 8mm to 15mm. I also think the finish of the 15mm pipe looks so much better than the 8mm, no matter how straight you try and get it. Someone once told me that mini bore or micro bore does not work well when you fit say a 90º angle fitting, would this be OK to do at the base of the 15mm or should I allow a short tail of 15mm again after the elbow before reducing down to the 8mm?

Thanks also for the wall fixing advice, did not much fancy 'hacking' holes out of my new walls to fit support battens!!!

 

[gimli]

Sorry Dave, any reason why silicon and not something like no nails? apart from easier to remove at a later date maybe.

Cheers again

 

[namsag]

Why not use 8mm trvs instead of messing about with different pipes

 

[gimli]

Its a largeish house, and better deals are available on 15mm TRV's, the 8mm pipe looks untidy, the TRV's are usualy standard or 10mm with reducers which have a tendency to give a poor seal and the 8mm pipe is easily deformed if kicked accidentally by kids etc.

Just looking for alternative methods that best suit the situation whilst maintaining a nice visual appearance.

 

[Whitespirit66]

Re. Fixing to dry lining. Where there is brick/block behind the board you can get some extra long plugs and screws (B&Q etc). I have used some approx. 5 inch long ones to mount some heavy rads in the past.

The extra length means that it doesn't matter that the outer end of the plugs are situated in the plasterboard and cavity, there is enough of the plug in the block/brick to carry the weight.

 

[kevindgas]

Why not use 8mm trvs instead of messing about with different pipes

because they are more expensive?

if we change to TRV on microbore we use 15mm TRV with a reducing set as it costs less than a 8/10/12mm TRV

 

[gimli]

Thanks Whitespirit66

I have a load of 10mm frame fixings about the house somewhere, the kind used to install windows etc, they must be about 125 - 150mm from what i remember ordering, how about them? they would span the void between board and brick like you explained.

CHeers

 

[gimli]

Thanks also Kevindgas

What make do you usually use and any problems with bad seal using reducers?

 

[gas4you]

Make sure you don't overtighten them, otherwise you can pull the brackets into the plasterboard.

 

[gimli]

Hell dave, my wife would kill me if that happened lol

 

[kevindgas]

we use Plumbfix for TRV's last lot were around a fiver each and Plumb center for the reducer sets (3 part) check the bags as they are sometimes mixed up!

 

[namsag]

plumbcentre bulldog (terrier valves)or pts boss trvs are the same price whether 15mm or 10mm with 8mm reducing sets in them £39 for 5 including lockshields, never have a problem with them sealing just dont mix the nuts up

 

[gimli]

Ok thanks all, will get some prices and see how we get on, thanks for all te sound advice, great forum and any other issues and i sure will try here first.

Have a good week