Central Heating 'S' verses 'Y' plan
- Thread starter Diyisfun
- Start date
i have always been led to belive there is less flow restriction with an S plan so better for larger systems
That's what I thought. Then I saw the figures for one of the common makes, Danfoss I think. The resistances are exactly the same!
Is does make sense in that in a 2 port valve the water has to go all the way round the "ball" if that's what's used, whereas in a 3 port the water changes direction with less obstruction. I would have thought the figures would be better on the 2 ports where they have a rotating "shoe", as with Sunvic and some Danfoss.
ALso, some 28mm valves are surprising, in that they have exactly the same bits inside as the 22mm versions, and the resistance is therefore identical.
Moral - go look it up.
There is the "bypass" issue - do a search on that, it's been covered a lot.
Is does make sense in that in a 2 port valve the water has to go all the way round the "ball" if that's what's used, whereas in a 3 port the water changes direction with less obstruction. I would have thought the figures would be better on the 2 ports where they have a rotating "shoe", as with Sunvic and some Danfoss.
ALso, some 28mm valves are surprising, in that they have exactly the same bits inside as the 22mm versions, and the resistance is therefore identical.
Moral - go look it up.
There is the "bypass" issue - do a search on that, it's been covered a lot.
As someone who mainly does fault finding on systems and combi boilers, I have to say that its much quicker for me to work on a system with two port valves.
Thats particularly so with valves which have failed internally from a ball coming off etc.
Tony Glazier
Thats particularly so with valves which have failed internally from a ball coming off etc.
Tony Glazier
Its marginally cheaper to use a three port valve, marginally quicker to fit.
Marginally longer to wire up.
Even the two port valve can be fitted reversed and let by a bit.
Much easier to fault find.
Much easier ( if you know how ) to operate manually if anything fails.
But most installers are cheapskates and do a bad job to save £12.
Why dont many installers put an outdoor drain cock?
Tony
PS ChrisR did not really put the 3-port in backwards ! Its just someone said that he never gets anything wrong, so he is trying to pretend that once a year he does something wrong.
Marginally longer to wire up.
Even the two port valve can be fitted reversed and let by a bit.
Much easier to fault find.
Much easier ( if you know how ) to operate manually if anything fails.
But most installers are cheapskates and do a bad job to save £12.
Why dont many installers put an outdoor drain cock?
Tony
PS ChrisR did not really put the 3-port in backwards ! Its just someone said that he never gets anything wrong, so he is trying to pretend that once a year he does something wrong.
I exclusively use s plan, in most cases that I'm fitting a cylinder it's unvented so there has to be a zone valve on the hot water side anyway.
The mid position valve is doomed to failure long before the zone valves. Do a google search for mid position valve to see why it's a flawed system.
The mid position valve is doomed to failure long before the zone valves. Do a google search for mid position valve to see why it's a flawed system.
Thanks for the suggestion. I came up with the UK.DIY FAQ section, which is presumably what you meant. Very interesting stuff, I learnt a lot about function of mid position motorised valve, amongst other things.Paul Barker said:
The Achilles' heal of the mid position valve is presumably the fact that the motor can remain energised during "off" periods. I accept this point, but it does depend on the timing of hot water relative to heating, so it can be minimised (for example by ensuring there is at least a brief period of hot water function before long idle periods).
On the other hand, the mid position is not energised on hot water function, where the zone valve is, so there are swings as well as roundabouts.
I have not read the link.
A two port valve and a three port in one of its positions all leave the motor energised and stalled.
In the mid position the motor ( a multipole ac syncronous motor ) is fed with raw dc which "locks" it in that position.
Neither of these situations gives any significant causes for concern as its what the unit is designed to do.
The saving using a three port is a bit less than the pure hardware cost because the wiring and checking time is longer. The wiring is less "obvious" and few people can wire them from memory without a connection diagram.
Tony Glazier
A two port valve and a three port in one of its positions all leave the motor energised and stalled.
In the mid position the motor ( a multipole ac syncronous motor ) is fed with raw dc which "locks" it in that position.
Neither of these situations gives any significant causes for concern as its what the unit is designed to do.
The saving using a three port is a bit less than the pure hardware cost because the wiring and checking time is longer. The wiring is less "obvious" and few people can wire them from memory without a connection diagram.
Tony Glazier
Yes if I'm honest Tony it's the simple flow of the s plan that I find most attractive. We can all do y plan from the diagram but we don't need a diagram for s plan, and if s plan ever went wrong it would be a lot easier to trouble shoot. Any time I've had to fix a control problem involving the valves it has been mid position valve. I still think two port valves are inherently more reliable. I have y plan at home but I didn't put it in.
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