secondary return copper or speed fit

[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?