secondary return copper or speed fit

[jonnyswamp]

I think I know the answer but I'll ask all the same, has any of the manu's brought out something for sec rets recently?
Just about to start a farm house with 4 bath/shower rooms and cyls in the middle of building on top floor with all outlets fairly close (within 8 m) Now they want the cyls in leanto building (boiler house) off the one pine end, so now need a sec ret, was going to use plastic for first fix as there is a load of full width 10 x 12 oak beams with 25mm above and below them for pipe runs etc
Its going to be an absolute tw@ to run copper, I'm OK price wise as its a client (architect) alteration, just could do with not being there any longer than I originally allowed (other jobs etc)
So.......copper or plastic

 

[SimonG]

Speedfits not rated for secondary return applications.

 

[lame plumber]

think you'll find you cant use plastic on 2ndry returns, been the rule since plastic came in use, manufacturers ruling not regs.

 

[jonnyswamp]

I was hoping they may have came up with something by now, seeing how they want us to use their shyte
Copper it is then

 

[jonnyswamp]

Is it not recommended for the full length of the hot water system or just from the last draw off back to the cyl?

 

[lame plumber]

Is it not recommended for the full length of the hot water system or just from the last draw off back to the cyl?

cant use on 2ndry returns full stop

 

[Ermintrude]

None of it. Copper copper copper. If your struggling for secondary return route. Not best practice but if short use 10mm microwhore

 

[EPH]

This is news to me!!

Makes no odds because I use copper, but why not in plastic?

 

[SimonG]

I was told its the heating and cooling cycles with the oxygenated water.

 

[Ermintrude]

It bursts. Only rated for 2 bar ish at 65 c. Breeding ground for liggonella. Copper kills it!

 

[Nostrum]

How about pex or tectite flexible metal system?

 

[townfanjon]

Jonny, don't forget a quality non ret valve at the cylinder .

 

[SimonG]

And insulation and a decent means of control.

 

[Ermintrude]

Pex = not copper

 

[Nostrum]

Pex = not copper

no ****,but an entirely different plastic that may be rated for the task. Check with manufacturer.

 

[hammers4spanner]

tektite apparently ok for sec return ,

installed sec return for large mechy company in upon or before

 

[jonnyswamp]

How about pex or tectite flexible metal system?

Just had a quick read through "qualpex" spec sheet and it states that it can be installed on hot water systems that are continuously used at the following parameters,
12bar @ 20c, 4 bar @ 82c, 3 bar @ 92c and short term up to 114c, but I couldn't find anything specific to secondary returns maybe worth a phone call for future ref

edit all done today in copper now

 

[markfxy]

Hep2o can be used on secondary returns where the temperature does not exceed 65°

• Hep2O® should not be installed
in ringmain installations.
A ringmain is a water-replenished
circulating system maintained at a
constant high temperature to
provide a permanent source of hot
water to its distributing pipes.
Typical locations where ringmain
systems are used are hospitals or
hotels which distribute constant hot
water to wards or rooms at a
distance from heat source.
This restriction does not apply to
domestic systems operating
intermittently at temperatures less
than 65°C where a design life of 50
years as detailed in BS 7291: 2001

copied from Hep2o Technical manual

 

[nicro3]

The MI will reveal the way forward or ring the technical dept. Its as simple as that:confused5:

 

[Ermintrude]

But erv 6 bar so could be 86c at 6 bar - tprv blows at 10 bar or 90c. Pipework isn't allowed to be weaker than safety valves. Ask plastic telecoms to explain that one

 

[Nostrum]

Could link secondary pump to high limit stat to get around it if required?

 

[Nostrum]

and I presume a one off fault condition is not the problem, it's the constant high temp's that it's not tested against?

 

[Ermintrude]

No pipework should be designed to withstand 1.5 times highest fault pressure. Begs the question why u can use plastic on dhw..... Because when it's hot it's got an open end - drawing water off.

 

[markfxy]

86° wouldn't go through through the return if your controls turn it of at a lower temp the fault temp would be in the tank not the return pipework

 

[Ermintrude]

Controls are assumed not to work in a worst case

 

[smhstu]

So what if you time the return?
10 mins in morning 10 mins evening?

 

[Ermintrude]

What? Why would u even bother with one?

 

[Nostrum]

Controls are assumed not to work in a worst case

Where is this information please?

You'd have to be pretty unlucky to have every single control fail, boiler stat, overheat stat, high limit stat. I think the least of your worries would be whether or not you used hep.

If if this were the case then we'd have to assume the t&p relief failed as well, so we'd better only install unvented cylinders in blast chambers.

 

[markfxy]

if everything failed the pump wouldn't run your hep return would be safe as houses:smartass:

 

[Ermintrude]

T&c is last level of protection, but if the system is going to fail before it goes off what's the point?