Y plan or S plan for unvented cylinder and boiler

[nogoodatfaultfinding]

Yes he does - You can still run an unvented from a combi boiler

Yes you can and yes i have.
Done few systems like this and when my boiler came up under the scrappage scheme i decided to keep the cylinder.

 

[sambotc]

Y plan is suitable up to 26kw only.

Never heard that before! Can you explain please?

http://customer.honeywell.com/techlit/pdf/95c-00000s/95c-10820.pdf

Sorry should have said Honeywell Y plan, not sure on other manufacturers, but would be interested to know. We only fit honeywell gear though so may have jumped the gun.

This was kindly pointed out to us and the customer after one of our job's worth engineers carried out a service plan visit to one of our installs. As it goes the motorised valve was existing, we just upgraded the boiler, pump and controls.

Have seen them fitted on much larger sytems with no problems but but the red tape brigade would probably want to know, and as such we only fit S plan's, partly due to this reason.

Sam

 

[Happyplumber]

Pube i have converted loads of systems ,where the installer has gone in and chucked a combi,the customer realising it isn't up to the job in and the hot water isn't up to the job and nothing like their previous system


It is relatively simple job to convert a combi to run a Unvented cylinder.Its also very easy to zone a house and should be explained and done where possible too

 

[D_Hailsham]

Y plan is suitable up to 26kw only.

Never heard that before! Can you explain please?

http://customer.honeywell.com/techlit/pdf/95c-00000s/95c-10820.pdf

Sorry should have said Honeywell Y plan, not sure on other manufacturers, but would be interested to know. We only fit honeywell gear though so may have jumped the gun.

Thanks for the link. Pity that info is not available on Honeywell's UK site.

I think the 26kw (suggested) limit may have something to do with the pressure drop through the valve.

 

[gmack34]

I still do not understand why anyone would ever install a Y plan system. The design is just crap althought the idea of using dc to stop the motor is ok in principle. S plan is far better.

 

[ctp]

with the s plan you should fit an auto by pass valve ....

 

[Happyplumber]

No sh.it sherlock!!!

 

[mysteryman]

Advantages of a Y Plan:

You don't need a bypass because there is always a path open, which is also important for pump overrun. The purpose of pump overrun is to dissipate residual heat; an auto bypass merely sends it back to the boiler.

It is simpler to plumb.

It is simpler to wire.

It costs less.

There are fewer parts to go wrong.

 

[gmack34]

How on earth do you manage to figure that the Y plan is easier to wire? The S plan dont even need thinking about and an electrician should not even need a drawing its so simple

 

[vulcancontinental]

Advantages of a Y Plan:

You don't need a bypass because there is always a path open, which is also important for pump overrun. The purpose of pump overrun is to dissipate residual heat; an auto bypass merely sends it back to the boiler.

It is simpler to plumb.

It is simpler to wire.

It costs less.

There are fewer parts to go wrong.

Personal opinion-

Most MI request or show a bypass and an auto bypass is better. If you use the cylinder as a bypass the hot water has the danger of overheating though this can happen to some extent anyhow.

Personally I don't think so, the logic of S is easier to follow though neither are difficult.

S is far easier to fault find - simple series of switches

S is far easier to fit into a narrow cupboard as F & R can be configured in any arrangement or direction and the valves to not stick out so far into the space.

Easier to zone (though I'm not a big fan of zoning anyway).

 

[scorch]

Advantages of a Y Plan:

You don't need a bypass because there is always a path open, which is also important for pump overrun. The purpose of pump overrun is to dissipate residual heat; an auto bypass merely sends it back to the boiler.

It is simpler to plumb.

It is simpler to wire.

It costs less.

There are fewer parts to go wrong.

true but on unvented cylinder with additional safety zone valve, in event of cylinder overheat the Z/V will close. if C/h not required then flow has nowhere to go and boiler will likely overheat too. Therefore an autobypass will be required too.
Y plan on unvented cylinder appears to be a messy waste of time. (imo)

 

[Longtallted]

Re the reference about Y plan being suitable only upto 26kw - I've got a Vaillant ecotec 637 which I believe is rated upto 40kw (largest number rating I found in the specs) but it's been installed in a Y plan (with a Megaflow hot water tank, I think it's a 250 litre item), all in a house with 15 radiators and two bathrooms.

Would I be better off with an S plan setup as I'm looking into having this done?

Thanks!