Unvented cylinders

[Cooperman1]

I am looking at getting an unvented cylinder to replace my existing traditional vented system with cold water storage tanks. Water pressure into the house is 5 bar at a flowrate of 18 ltrs/min. I am concerned about getting a Megaflo as with a relatively low flowrate I understand that the Airgap will need to be recreated occasionally. Would it be better to use another make like Range Tribune, which has an external pressure vessel, and then I won't have any "Airgap" issues ?

Thanks for your help in advance

 

[justlead1]

Hi. Either the calculations are wrong or your first work must be a new supply pipe. As with a head of 5 bar and a 15 mm supply pipe say 30 m run from mains one would expect somewhere about 42 litres / min

 

[Cooperman1]

Thank you justlead1, but my initial question is around preferences for the Megaflow with its airgap and other systems with built in or external pressure vessels. My question is, why should you need to re-pressurise or "recreate the airgap"? What circumstances make this necessary?

Updating my current heating system which can be left completely unaided (with perhaps the intermittent yearly or so service) to a "current" "modern" system which has some temperamental nuance of worrying about airgaps - seems a bit of a backward step in technology!


Look forward to any help.

 

[Toddyplumb]

Its no big deal resetting the air gap, drain and fill. If going with an expansion vessel , it will be checked for pressure periodically as well. Any one with unvented will be able to sort.
As an add on , I tend to agree with just lead with 5bar and only 18ltres you have a valve not fully open , a blockage or the tap you flowrate at is very restricted, depending on which it is it is not necessarily a problem