motorized valves 2 & 3 way

[kenny101]

If installing a 2 way zone valve for CH & HW would this have to be fitted on the 22mm return before the first rad and a 22mm branch before the zone valve going to the HW cylinder or does a 3 way valve do the same job without having to put in a 22mm branch pipe.Hope someone out there can make sense of what asking. or maybe not.
system is oil fired pumped open vent.

 

[PaulAH]

Hope someone out there can make sense of what asking

Well I can't for one.

By "2-way valve" do you mean two-port? In which case

If installing a 2 way zone valve for CH & HW

is a contradiction. A 2-port can only control one circuit.

Also, it is best practice to fit these valves on the flow, not the return.

You need to think harder about how to express this type of question. You can't expect others to de-code it AND give a sensible answer.

 

[oilman]

Despite that, here's a (sensible) answer

Look up Y plan and S plan.

 

[chrishutt]

it is best practice to fit these valves on the flow, not the return.

Why would this be, in the case of two port valves? I would have thought that they would work just the same in flow or return, with the slight advantage of lower water temperatures in the return.

 

[PaulAH]

Why would this be?

Oilman told me to

Also, most circuit diagrams (including the Honeywell) show the valve on the flow. I guess it's because this stops the hot in its tracks. Placing it on return could cause a significant amount of thermal drift into the system. Only guessing - what do I know?

Here are (sensible) links:

http://content.honeywell.com/uk/homes/Technical/Splan Installation Guide.PDF

http://content.honeywell.com/uk/homes/Technical/Yplan Installation Guide.PDF

 

[megawatt]

Doesn't make any difference IMO, block the flow no water transfer, no water transfer no heat transfer and the flow can be blocked anywhere in the circuit ... Same thing applies with electricity.

Its useful to have standards for isolation though to help predict where circuits would be expected to be live (or full of hot water in this case ) but there is no excuse for checking anyway before disconnection just in case the muppet who commissioned the system had a problem conforming to standards

Besides, many combi's have the 3 port changeover valve on the return internally within the boiler

 

[PaulAH]

Same thing applies with electricity

With the greatest respect, Megawatt, electricity and water don't behave in the same way. Water is affected by turbulance, convection, radiation and all manner of unpredictable behaviour.

I have a kitchen towel rail which in theory shouldn't work. It's connected in parallel with the return from upstairs, which is a separate zone. Even when upstairs is turned off fully (ie most of the time!) the towel rail gets piping hot. This must be due entirely to convection plus a little conduction. It's close to the boiler, so whenever another part of the circuit is active, some stray heat works its way back up this isolated return to the towel rail.

If it was an electrical circuit the "bulb wouldn't light".

 

[chrishutt]

most circuit diagrams (including the Honeywell) show the valve on the flow.

This is purely because 3 port valves do need to be fitted in the flow, since if fitted in the return the pressure of pumped water would tend to lift the ball off the orifice that it was closing.

This problem does not arise with 2 port valves because they can be fitted according to the direction of flow, irrespective of whether it's flow or return. However the 2 port diagrams provided by Honeywell (et al.) follow the layout appropriate for 3 port valves simply as a matter of clarity.

 

[PaulAH]

However the 2 port diagrams provided by Honeywell (et al.) follow the layout appropriate for 3 port valves simply as a matter of clarity.

Are you, dare I say, assuming this?

The towel rail that shouldn't work, does. That's not an assumption - try touching it! Admittedly it feeds back into the same return pipe so there is some kind of closed circuit for the water to move around if it wants. But if you looked at the layout you'd say it would probably stay cold.

Say you had a rad in a bedroom directly above the boiler with the valve fitted to the return, wouldn't get at least a bit warm, even with the valve closed?

 

[oilman]

....................

Say you had a rad in a bedroom directly above the boiler with the valve fitted to the return, wouldn't get at least a bit warm, even with the valve closed?

True, but it would get a "bit" warm even if it was disconnected from the system just as the room above the boiler would get a "bit" warm. It would be a rather small "bit" though.

It would get much warmer though if you had a 28mm pipe connected to it. (Only one end needed)

 

[chrishutt]

Are you, dare I say, assuming this?

Yes, I am, because there doesn't seem to be any evidence to suggest any other reason for it.

Of course gravity circulation can take place in certain circumstances, but this could almost as easily occur on the return pipe as the flow pipe, so I don't think that really counts as an general argument for locating 2 ports on the flow pipe.

 

[kenny101]

Thanks all for for your comments and deciphering my very poor description of topic,went into honeywell web as advised and got info.Has to be the best forum by far.

 

[esra_ptrap]

I'm with megawatt on this one as our boiler (Worcester Highflow) has the diverter valve fitted in the return not the flow

PaulAH wrote:

If it was an electrical circuit the "bulb wouldn't light".

Electricity displays many of the characteristics of piped water and the two have far more in common than you'd think ... Try standing underneath high voltage pylons holding a fluorescent tube ... It shouldn't light but it does

Regarding your misbehaving towel rail ... I thought we connected things in parallel to ensure that they do work independant of each other?

Ho Hum ... Time for bed said Zebedee

 

[PaulAH]

Of course gravity circulation can take place in certain circumstances, but this could almost as easily occur on the return pipe as the flow pipe, (my itals)

Very good point, Chris. I buy it.

Electricity displays many of the characteristics of piped water and the two have far more in common than you'd think ... Try standing underneath high voltage pylons holding a fluorescent tube ... It shouldn't light but it does

Indeed they do. But electricity lacks the equivalent of convection and turbulance, both highly significant in fluid mechanics.

Also the effects of electrical radiation are small at normal voltages (less so magnetic, which has no liquid equivalent). When it comes to conduction, you can provide an extremely high level of non-conductivity in an electrical circuit (eg switch) which cannot be achieved so easily in fluid systems (eg valve).

The water analogy is one I have often used to explain electrical principles but, in the practical world, there some glaring differences.

 

[megawatt]

PaulAH:

electricity lacks the equivalent of convection and turbulence

You're confusing effects here ... Convection is a property of heat and is the same irrespective of source i.e. when wires get hot they emit convected heat in the same way heat is convected through hot fluids ... This is why light bulbs are hot, ovens work etc?

Also electrical turbulence is significant in many areas, the human heart being quite a significant one if you value breathing Electrical turbulence causes ventricular fibrillation (irregular heartbeat where the heart does not effectively pump blood) and makes the ECG machine start beeping and people come running from all parts of the hospital shouting "can I have some help here please" (c) Holby City

Also the effects of electrical radiation are small at normal voltages

You should work for a mobile phone company ... They've been saying that for years but no-one actually believes them

less so magnetic, which has no liquid equivalent

Not true, high magnetic fields reduce water flow rates by altering the surface tension of the water (water is repelled by high magnetic fields).

When it comes to conduction, you can provide an extremely high level of non-conductivity in an electrical circuit (eg switch) which cannot be achieved so easily in fluid systems (eg valve).

Sorry, wrong again, same principles apply ... Increase the voltage the greater the air separation required to prevent flow ... Increase the pressure the beefier the valve required to prevent flow