Having an unvented cylinder installed - do I need pressurised central heating?

[dilalio]

I didn’t even read the whole OP... too long, just picked up on others responses

 

[EAST61]

directed at OP not you Dilalio

 

[Adam Fell]

You can’t get more out of less (apart from more aggro out of a less than perfect installation ).

If you have “15lpm” coming into your property, that is all you have and will be subdivided by each outlet/demand that is imposed upon it.

You need to calculate your own flow-rate, within your boundary using a container of known volume and a stopwatch, you can then do some simple math to calculate what litres-per-minute you are getting.
This needs to be done from the least restricted outlet that you can access - typically an outside tap or washing machine valve... kitchen taps are often restricted by flexi-hoses and internal gubbins to shape spray pattern etc.

Once this figure has been obtained you can then ask your water supplier to carry out a similar test at their stopcock, to your property. This will show if it is worth upgrading your main from the street to your internal stopcock.

That seems sensible and very good information thank you. I will measure the flow rate from the outside tap and washing machine valve and report back.

I'm annoyed that neither plumber seemed concerned about my flow rate and only performed rudimentary checks and one of them told me I needed to pressurise my heating system!

 

[fezster]

A good summary (albeit biased) on open vent vs sealed heating systems:

http://www.miketheboilerman.com/openorsealed.htm

 

[Adam Fell]

Thanks for everyone's help. I was finally able to do a test on the outside tap and got between 24-26 litres per minute so I'm satisfied that the water pressure is sufficient to go ahead with an unvented cyclinder. I don't see the need to have a pressurised central heating system as that seems to be an independent decision. Thanks again.