which plan,Y or S ?

[outinthestix]

Wondered if anyone had any thoughts on the following ? Went to service a 100k btu Stanley cooker/boiler which went fine but the owner said they had never had great heating performance out of it. The property was a LARGE open plan farmhouse with approx. 18 LARGE rads. Some of the rads were not getting hot enough. I suggested they may need balancing but the owner was insistant that they had been balanced previously.None of the rads had cold spots and all were getting diferent degrees of warmth.
Pump was working but noticed the system was a Y plan. Will a Y plan have a good enough flow of water for an installation of this size ? I can't help thinking two motorised valves are better than one in this case. Any thoughts please ?

 

[wilhelm]

put a 2 gallon nozzle in, and let em fry.

 

[chrishutt]

Some of the rads were not getting hot enough.

Need balancing then!

 

[ChrisR]

I looked it up once - a 3 port has exactly the same resistance in the valve as a 2 port. When it's mid pos of course you only have half the flow..
That was Danfoss I believe.

What IS a con is the size of the hole you get in a 28mm valve. Looks the same as a 22mm! Depends on make I guess though.

 

[outinthestix]

Thanks fellas.

 

[Prof.plumb]

With out a shadow of doubt S plans are far more superior to Y plans. They do not flow share are more reliable and much easier to fault diagnose. electronically Y plan valves can cause some real nonsense faults.

 

[ChrisR]

Why do Y's not share the flow?
How are S's more reliable when there is more to go wrong?
Neither is any difficulty to diagnose faults in for a heating engineer, easier for DIY though.
The only "electronics" is a diode, which can very rarely fail, but shows an obvious fault.
None of it is nonsense if you take a couple of minutes to understand how it works!

 

[Prof.plumb]

Well Chris i can tell you are a very knowledgeable man and i am not undermining or contesting what your saying. But just from experience i get called to 3 times more problems regrading y plan valves. S plans do rarely go wrong you know that. WIth three ports you find they are always passing either on the hot water or heating because the ball has had it. And, generally, flow rate through 2 ports is superior to the 3 port in mid position.

 

[weareleeds]

A 22mm y plan valve will carry the equivelant of 60,000 btu's to htg whe fully powered (ie dhw port closed) so a 100,000 blr needs to bo on s plan with 22mm valve for water & 28mm valve for htg

 

[outinthestix]

It's sad i know but i find this all too interesting and in need of further advice.As a fairly new entrant to this line of work i have never converted from Y to S plan before (really i just maintain oil boilers, part time).Can i simply do away with the three port and add 2 two ports close to the same place as the 3 port or do i need to move the valves eg closer to the cylinder ? or should i just balance the system and tell them to get a plumber ?

 

[Kettle 3]

I am experiencing a similar problem with y-plan, boiler in loft, pump & 3 way valve in airing c/board, downstairs radiators only getting warm? switched hot water off, found still getting constant supply of hot water? felt pipe that feeds cylinder always hot? took lid off 3-way valve, functioning as it should, i am going to change complete valve, thinking ball is not seating properly, (25 years old) and sharing the flow.[/img]

 

[ChrisR]

Balls in 2 ports are under exactly the same strain and chemical attack as balls in 3 ports!
With the same spring holding them closed in the same sized orifice, they are no less likely to let by than one on a 3 port. And let by they do.
The force on the CH port in a 3 port valve will be different, but if it's the ball which has failed it'll make little difference what the force is.

I was surprised to find that the 3 port was no more resistive than the 2 port of the same make which I looked up. I suppose it's because the water only has to go past the ball and not all the way round it. Having said that I think it was a Danfoss, which would have had a paddle or a shoe and not a ball! Other valves may be different.

Must be 80% or so of valve failures are dud motors? So if you have 2 valves, you might expect more failures! Plenty of 2 ports on CH stick shut in the autumn!

And, generally, flow rate through 2 ports is superior to the 3 port in mid position.

Good, you've measured it. What flow rates did you get?