Main pressures for unvented cylinders

[TFGplumbing]

I've got a job to price for an unvented hot water cylinder, I have taken water pressures as follows

Standing 4bar
Dynamic 0.5-0.8
flow rate of 22ltr/m

The incoming main is 25mm mdpe.

I know most manufacturers recommend a dynamic pressure of 1.5 bar, what do you guys think?

Thanks

 

[kris]

Your flow rate and incoming pressure look spot on, how did u work out your dynamic pressure ???

 

[TFGplumbing]

Hiya Kris

due to the fact its a new build and there's only a stopcock no sink or anything, I rigged up an length of 22mm with a tee which had my pressure tester attached and after that I reduced down to 15 and used a standard service valve as an out let.

Service valve open water running = dynamic pressure

probably not the most scientific method but not a lot of options

Thanks for the reply

 

[lame plumber]

most practical method though

 

[TFGplumbing]

every single manufacturer says different mega flow say 3 bar inlet, WB say 1.5 dynamic, glenhill say 3 bar dynamic... my recordings fall foul of all

 

[Ermintrude]

Do what I recently did and launch it in . F100 the regs and mi.

How far was the 15mm outlet from tee? Usually need a bit of back pressure, a 1/2 open cheap ball valve usually best.

 

[Ermintrude]

I've just remembered d1 still like that...[emoji23]

 

[TFGplumbing]

The 15mm out let was about 1.5 meter away from the tee, enough to pop out the kitchen window haha

Ahh damn I measured it when fully open maybe I should have left it half open?

 

[Ermintrude]

5/8th open is best. 1/2 is a bit unprofessional

 

[TFGplumbing]

5/8th open is best. 1/2 is a bit unprofessional

Just as well there was only sparks there today, they wouldn't know the difference lol

 

[TFGplumbing]

5/8th open is best. 1/2 is a bit unprofessional

Just as well there was only sparks there today, they wouldn't know the difference lol

 

[AWheating]

Put in the small print on the quote that the water supply is assumed adequate and the responsibility of the builder/ main contractor to ensure its suitable.