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?

 

[Ermintrude]

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

No it wouldn't it would be at 10bar and 85c

Try engineering design or hazop & hazan for a start.

 

[markfxy]

wouldn't be 85° in the pipework if the pumps not pushing round the circuit

 

[Nostrum]

The only thing going around and around is this conversation by the looks of things

 

[Nostrum]

No it wouldn't it would be at 10bar and 85c

Try engineering design or hazop & hazan for a start.

Unless i'm mistaken, these do not fall under the remit of our trade.

It reminds me of a friend of mine who was forced (by an engineer customer) to pressure test the entire system to 3 x the maximum working pressure of the system before fitting the new boiler.

At 7 bar the old radiators blew open and showered the elderly mother who was sat in the chair minding her own business with black sludge.

 

[rpm]

Love it !

 

[Ermintrude]

Designing pipework to withstand 1.5 max pressure is well within job

 

[Ermintrude]

wouldn't be 85° in the pipework if the pumps not pushing round the circuit

Ok so there won't be any hot pipes coming off the cylinder made of plastic? No because the naughty hot water will stay on the inside of the cylinder and the good safe low pressure cold water outside. Because the pump is off.

 

[markfxy]

you've got it, cylinder cupboards done in copper, plastic pipework elswhere:smartass:

 

[Ermintrude]

Secondary return is right into ac and isn't supposed to be plastic for the reason that the halfwhits that use plastic all day cut corners and don't know enough to do job properly and the plastic ends up on cylinder. Also how exactly do u join copper to plastic under the floor and still meet building regs and the WRAS codes of practice ? You know in-accessible mechanical couplings on services? Especially those subject to high thermal variations and pump vibrations?