10mm or not 10mm that is the question...

[scatmanjohn]

45yearsagasman - I'm struggling to see why a 15mm ring with 10mm tee'd off to each rad individually would be an issue? I know that there would be a (approx) 2500w limit to the radiators used but other than that... Is there anyone else that can contribute with a more "constructive" comment?...

Ahhhh...i get it. You have already decided what the answer is and just want confirmation.
Thats called "Confirmation Bias" in psychology.
http://en.wikipedia.org/wiki/Confirmation_bias

Here you go....10mm will be fine sir..fill ya boots

 

[lowster]

Errr yeh Scatmanjohn - think you're looking for a different forum (amateur psychology for begginers!) either that or you've been sampling too much of the local "produce"

I wasn't trying to suggest that I had already decided the answer - Merely that the comment quoted below didn't provide any advice as to why not choosing that particular method. It's the motor mechanics equivilant of sucking his teeth and not telling me what the issue is!
I'm obviously no expert in Plumbing and haven't once suggested that it was for the simple mind - that's why i'm on this forum asking for help...

"15mm ring and tee down to 10mm drops? I wouldn't go there.Get your pipe sizing right from the start and save a lot of heartache."

 

[Onetap]

I'm obviously no expert in Plumbing and haven't once suggested that it was for the simple mind - that's why i'm on this forum asking for help...

Yes, the answer was that you should calculate the required pipe sizes. There's no point in trying to explain how to do that here on a DIY forum, you'd need a book. If you don't want to go to the trouble, then you need to employ someone who has studied such books. These people are called 'plumbers', 'heating engineers', 'mechanical engineers', etc..

I bought and diligently studied a book about this black art when I first started doing it. After much studying, I realized that the book was wrong (irrelevant but true). It's not (very) hard. It is very tedious doing it manually.

What you're proposing is just whacking in 15 and 10mm pipework. It may work, though I have doubts, and you won't be surprised if it doesn't heat effectively. If it doesn't heat effectively, it is worse than useless, you'll have to rip it out and do it again.

 

[oss]

If you have not started why not run the flow and returns in 22mm and the droppers in 10mm[to avoid cutting out the brickwork behind the plaster].plastic coated 10mm is readily available [plaster can corrode copper].I would not use denso, the oils could later stain the plaster.

 

[D_Hailsham]

Will I be ok to have a 15mm ring upstairs under the floor boards and then tee off using 10mm pipe 2.5 meters down to each radiator?

Small Bore Heating Systems explains how the carrying capacity of different size pipes are calculated.

WB Pipework Sizing Guide gives recommendations based on a velocity of 1m/sec.

Copper Tubes in Domestic Heating Systems explains how you calculate the required pipe sizes for an installation.

Many installers will not bother to calculate sizes, they just use their "experience"!

 

[lowster]

Just want to say; big thanks to the above two posts - found them helpful cheers. I'm going with 22mm flow and return and dropping down in 10mm. Am I best to go with a manifold or a reducing tee? If the latter; do 22mm down to 10mm exist? As I can't find them online, should I go for a 22mm reduced to 15mm and then off 15mm pipe reduce down again to 10mm?...

 

[oss]

When i,ve done it in past ,i used 22mmx15mm tees ,then 15 mm to 10 mm reducers,I found it reduced the runs of 10mm.

 

[Andygasman2010]

As everyone has said, there are many factors to take into account when pipe sizing but from what you've said, 22mm circs with 10mm drops in the walls will most likely be fine (at the risk of being a little controversial, 8mm would do )

Use as little 10mm as poss, only in the walls. Use 10mm kutalex or barriered plastic (no joints in the wall unless soldered)

Chase them quite deep and use PVA, bonding coat then finishing. It'll still eventually crack with the heat so you'll not be able to have a painted finish unless you wallpaper first.

If you have an empty house and don't mind hard work and lots of mess, how about running the pipes in ducting in the floor? Then you could drop down in 22mm somewhere discrete and use 15mm to the rads.

 

[craig51]

and to finsh it off, use some inhibitor and fit a filter. Seem to spend a lot of times with a foot pump and 8mm/10mm microbore clearing blockages.

 

[lowster]

Do you think covering the chase with 0.95mm plasterboard and then skimming over would prevent any heat related cracking? Or is that a bob idea?

 

[oss]

Should be ok,covering the chase will allow for thermal expansion.

 

[george07]

i have a 15mm drop clipped onto to a breezeblock wall that will be dot n dabbed over ? before any plastering work should i chase it into the breezeblock wall and cover with something is yhat what you guys reccommend here cheers + as majority of my rads are done in 15mm pvc piping (22mm from boiler upstairs to 1st 2 rads) how much time should they heat up in to confirm that i do/dont have a problem

 

[gasafengineer]

) how much time should they heat up in to confirm that i do/dont have a problem

Well , if D-Hailsham specced the heat load using a 6kw boiler then i suspect those rooms may take a lifetime to reach temp.

 

[D_Hailsham]

) how much time should they heat up in to confirm that i do/dont have a problem

Well , if D-Hailsham specced the heat load using a 6kw boiler then I suspect those rooms may take a lifetime to reach temp.

Where did I say anything about a 6kW boiler?

 

[Agile]

IF, and thats a big IF, the system has been properly balanced then the returns from each rad will already be starting to get warm within about 5-10 minutes.

Thats a general figure and only applies to normal pressed steel rads and NOT to cast iron or other types with a high water content.

Tony