Y plan or S plan central heating

[quintain]

My Stanley 20yr old gas powered (AGA style) boiler/cooker/central heating boiler has thrown a few faults lately.
Over the years I have 'tinkered around with it' but I have now decided to get in the local experts.

The first piece of advice was I should change the pipe and electric system from the existing 'Y' plan to the simpler 'S' plan.
Apparently this will require modifying the 22mm copper pipes and replacing the 3 way mid port 22mm pipe control unit and also electrically rewiring the new 22mm units.

QUESTION (eventually)
(1) is the Y plan no longer a recommended system
(2) is the S plan a better system
(3) is it a required procedure that gas boilers can only go faulty at the most inconvenient of times

Best regards to all
Richard (AKA) quintain

 

[Spectric]

The old Y plan worked because you only had hot water and a single heating circuit, now we use multizoned systems it is easier to use the S plan where you have a zone valve for each circuit. Along with this you want to look at a smart pump, something from Grunfoss because apart from the energy savings it gives a controlled flow which is very beneficial with multi zones. I would also suggest going for an unvented system with a system boiler rather than a combi.

Using an S plan system means you will also need a bypass circuit for the boiler overun, the old Y plan valve always had an open port and I use the three way valve as my bypass in my system. If going down the sealed system route then fit the pump in the return to the boiler, the lower temperatures give the pump an easier life.

This is my wiring for the boiler where I am using an OSO cylinder.

 

[Sideways]

I think Spectric nailed it above.
Having done this change in 2023, I don't feel like the S plan system is simpler that Y plan, just different. You end up with 2 motorised valves not 1 and the added automatic bypass valve. In my case some of the gear is now under the stairs with the new tank while the CH 2 port valve and the magnet filter remain upstairs near where the old gravity fed tank was removed from. The upside is I no longer have a header tank getting in the way in the loft and we have space to extend the bathroom because the HW tank doesn't have to be upstairs any longer. The downside was a LOT of disruption lifting floors and accessing behind kitchen cabinets in order to route new pipework to a different part of the house.

If you go for a mains pressure hot water tank, be sure to first check that you have enough flow + pressure because your incoming cold water main dictates what you can draw from both hot and cold hot water at the same time e.g. when filling a bathtub. They become linked. Open the cold tap and the hot water flow reduces a little.

 

[Spectric]

I suppose having a system layout would also be helpful, this is a single zone as I am in a bungalow. The airing cupboard loop has two functions, it helps reduce the return flow temperature to keep the boiler in condensing mode whilst warming the cupboard and on bypass it uses the extra pipe run to drop the boiler temperature by transfering the heat into the airing cupboard.