Using Balanced cold

[Mgrant]

Hey, do people tend to use the balanced cold connection on unvented hot water systems. To feed all the cold supplys on a house,bar the kitchen sink tap which is taken straight of the mains. Or is balanced cold not often used? I often see it just capped off on the composition valve in the cylinder cupboard.

 

[Mgrant]

Ideally, in a all new job, the mains will go straight to where the unvented cylinder is & to a stopcock, cylinder PRV & all cold supplies are from this PRV.
On your question of gravity vented hot & mains cold in houses, - yes, - it can & will cause issues as the mains can push back into hot pipes at mixers & if you have a faulty pin holed mixer, the mains will go to vented copper cylinder & up the cylinder cold feed into cwt & keep overflowing it.

So even toilets would be taken off balanced cold? Have seen that a lot of cylinder manufactures prefer you to have a uninterrupted cold feed to the cylinder.

 

[Best]

So even toilets would be taken off balanced cold? Have seen that a lot of cylinder manufactures prefer you to have a uninterrupted cold feed to the cylinder.

Yes, all supplies to bathrooms etc to be balanced.
By uninterrupted cold supply to cylinder the manufacturers will have two reasons for that, - no robbing of the higher pressure mains before it reaches the cylinder & also balanced supplies to everything from the units PRV point so that no higher pressure water can come back to the unit & overpressure it.

 

[Mgrant]

I was speaking to one rep for unvented cylinders who told us to fit a prv after the stop tap in the kitchen set to about 5 bar. Take the cold for the kitchen off this, as it was a long way to come back from the cylinder to feed. Then take the cold to the cylinder to feed the hot through the prv on the cylinder. Then instead of using the balanced cold connection fit a prv to 3 bar on the cold after its tee'd of to the cylinder and take it back to all the cold draw offs as this would give a better flow then using the balanced cold connection. I wonder why he stated we should fit a 2 prv though. It is a high pressure area around 9 bar.

 

[Best]

Problem IMO with fitting other PRVs is that you will have all these PRVs to check if working correctly & service. They are not always reliable. Also the big worry is some of the mixers - like shower valves & mixer taps, if faulty can put the cold through the hot pipe & to the unvented cylinder.
The idea of putting a separate PRV set to 3bar for the house cold pipes is okay if you really have to in a change over from an existing vented system, but not ideal.

 

[Best]

All the unvented cylinder manufacturer requires is that their unit is safe & is also protected from over pressurising.

 

[topman870]

So i have a house with 3 showers across 3 floors, all have thermostatic showers controls and the sinks have mixers... So my questions is would you feed a new cold supply to all the toilets? or would you take this from the balance cold feed

 

[Old Account]

If you ask me I'd install all with the balanced cold water even though it's not a mixer. Ideally you take a balanced cold for not having pressure differential.