the combi boiler explodes, and the plasterer dies

[Gasman77]

If you read Tony's old posts, most of what he says isn't relevant

 

[matt1e]

[
Just to clarify for the hard of thinking reading this thread, what Danny stated regarding the 'Y' plan, this refers to a mid-poss valve; this valve will never not have an open port, even when all thermostats are satisfied, the hot water port will remain open, so this will even accommodate pump over-run. Therefore no by-pass valve is required.

And if an unvented cylinder is fitted on a y-plan and its overheat stat has tripped????

just food for thought /discussion

Matt

 

[Andygasman2010]

[
Just to clarify for the hard of thinking reading this thread, what Danny stated regarding the 'Y' plan, this refers to a mid-poss valve; this valve will never not have an open port, even when all thermostats are satisfied, the hot water port will remain open, so this will even accommodate pump over-run. Therefore no by-pass valve is required.

And if an unvented cylinder is fitted on a y-plan and its overheat stat has tripped????

just food for thought /discussion

Matt

This is why an unvented cylinder must have a spring-closed zone valve fitted and wired up to the overheat stat. Even if it is a Y-plan/Mid-position

 

[matt1e]

And if an unvented cylinder is fitted on a y-plan and its overheat stat has tripped????

just food for thought /discussion

Matt

This is why an unvented cylinder must have a spring-closed zone valve fitted and wired up to the overheat stat. Even if it is a Y-plan/Mid-position

Precisely!! Andy which makes this statement

Just to clarify for the hard of thinking reading this thread, what Danny stated regarding the 'Y' plan, this refers to a mid-poss valve; this valve will never not have an open port,

Incorrect, well in certain circumstances/situations anyway
Matt

 

[DeltaT]

But that statement is a fact my little Engerland Geordie chum, a 'Y' plan never has both outlet ports closed, if anyone is daft enough to fit two valves to control the HW cylinder, well, they need medication.......................An unvented cylinder should always be on an 'S' plan.

 

[The Baker]

where do u live

In Wigan. Ashton in Makerfield to be a wee bit more specific.

There is a nice youngish lad whome I know who lives in leyland, he does a good job, partly because his father watches over him.

If you would like his details please call me on 07860 568 147,

Although I live in Preston (20 miles north of you) I am not able to offer to help at the moment as I am doing my house up.

Tim

 

[matt1e]

But that statement is a fact my little Engerland Geordie chum, a 'Y' plan never has both outlet ports closed, if anyone is daft enough to fit two valves to control the HW cylinder, well, they need medication.......................An unvented cylinder should always be on an 'S' plan.

Hi delta
s-plan would be my preference too TBH

but.............................it doesn't make your statement fact,
a mid position valve always has a port open, true but what I'm saying is there are y-plan systems that can have all flow blocked off(unless you have an adequate bypass)

unvented cylinders can and do get installed on y-plans, especially cylinder upgrades i.e vented to unvented on an existing y-plan
it does not matter if you yourself always install/convert to s-plan when fitting them,other installers might not,and they would be daft not to fit the safety 2-port to close off the 3-ports hotwater connection on overheat
Ps I will admit to being slightly pedantic if you admit your slightly wro.....

Matt

 

[DP]

matt1e wrote

a mid position valve always has a port open, true but what I'm saying is there are y-plan systems that can have all flow blocked off(unless you have an adequate bypass)

Under whar circumstances? When? Not haveing a dig at you, mearly looking for furher education/ information.

 

[matt1e]

matt1e wrote

a mid position valve always has a port open, true but what I'm saying is there are y-plan systems that can have all flow blocked off(unless you have an adequate bypass)

Under whar circumstances? When? Not haveing a dig at you, mearly looking for furher education/ information.

Hi DP
all unvented cylinders must have a spring return to closed, 2-port valve fitted in line with the heating coil, this valve is connected to the cylinder overheat stat which will remove all power to the valve thus blocking off flow to the cylinder when the overheat stat trips, it is a safety device.
If you have a s-plan system as long as the 2port feeding the cylinder is spring return (not momo) and connected via the overheat stat then no other valve is required, this is another reason why s-plan is better
Now if the cylinder is connected to a y-plan because of the fact a 3-port valve always has the hw outlet open when unpowered( ie you need to motor the valve to close the port) then you have to have a secondary spring return safety valve in line with the 3-port and connected to the overheat stat.
It must be said that under normal operating conditions a y-plan incorperating an unvented cylinder will still always have a port open its only under certain fault conditions that it won't, so to answer your question "under what circumstances will all flow be blocked on a y-plan"

answer
unvented is fitted on a y-plan, with no bypass fitted
the cylinder stat has failed (stuck on)
the overheat stat has operated and removed power to the safety valve thus blocking off the flow to the coil (or the HW outlet from the 3-port if you like)
the room stat is satisfied so the ch port is closed
the boiler is on pump over run but has no internal bypass
so.....no flow
hope I expained it ok
Matt

 

[Nige F]

That`s useful about the Unvented cyl. Should I want to get registered The rest of the 9 pages looks like a bunch of Y-Fronts ( or plans) arguing

 

[chr15]

Worcester Ri Mi's do state that 'generally a bypass is not nesessary on a Y plan system as one of the ports is open to flow'.

Just some common sense required I think. Chris

 

[DP]

Matt, Y plan and UV cylinders is an anomaly which for all intent and purposes is really an S plan.

Discussion if I can remember correctly 9 pages on, is to do with Y plan as in vented cylinder and TRVed CH zones, needing a bypass.

S plan for CH and unvented is really a UK requirement (I suspect) as I have seen unvented coupled to Vaillant VCW with a diverter valve. Can provide written proof.

 

[matt1e]

Matt, Y plan and UV cylinders is an anomaly which for all intent and purposes is really an S plan.

no mate, control wise its a y-plan(the safety valve will normally be held permenantly open on time control whilst the cyl stat will control the 3-port as normal) maybe it should be given another clasification y/s-plan perhaps!

Discussion if I can remember correctly 9 pages on, is to do with Y plan as in vented cylinder and TRVed CH zones, needing a bypass.

no,around the 5th page discussion moved on to Y plan as in cylinder and TRVed CH zones, needing a bypass- niether vented or unvented were mentioned,hence my first post

And if an unvented cylinder is fitted on a y-plan and its overheat stat has tripped????

as I mentioned earlier I was being pedantic and wanted to give a little

just food for thought /discussion

Worcester Ri Mi's do state that 'generally a bypass is not nesessary on a Y plan system as one of the ports is open to flow'.

Just some common sense required I think. Chris

nail on head chris


Matt

 

[transam]

Saw something on the general disscusion forum , thought it was amusing ?

The premature ejeculation society is holding it's annual dinner , there is no dress code , just come in your pant's

 

[transam]

And on that note , we will end this disscusion ???? or have I come to this conclusion to early ???