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SPECIFICATION FOR 3 WAY MODULATING VALVES( APPLICABLE FOR ALL F.C.US AND A.H.US)

General :

The intention of this specification is to highlight themain features which should be taken intoconsideration when choosing the 3 way valves.

The right selection lead to achieving the goals ofautomatic temperature control which areincluding but not limited to the following :-

- Smooth temperature control to maintain thehighest levels of comfortable atmosphere

conditions.

- Energy saving as one of the major objectivesof the automatic temperature control.

- Reliability and high performance arenecessary to get the best results at certainexisting conditions such as ambienttemperature, system pressure and electricalfactors.

Technical specifications :

Operating pressure :

Operating pressure should not be less than 240 psi.

While test pressure should be 280 Psi and above.

The above pressure figures are the minimum requirements

and is for normal condition. In cases, where higherpressure is required it is the responsibility of thecontractor to calculate the required pressure byfinding the static pressure, the pump head and Selectthe valve accordingly, valve operating pressure shouldbe 1.5 of the total pressure.

Ambient temperature :Valve actuator should be able to operate at ambient temp

up 50 deg.c, at the normal conditions, and when motoris installed In shaded areas.

For the special conditions where the valve is installedoutside the building, contractor should select

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valves / motors to operate under these conditionsor to make the necessary shading.

Material :

Valve body should be of forged brass or bronze forvalves less than 1 size. For bigger size valves,brass or cast iron with corrosion resistanttreatment.

Motor should be of thermoplastic type or aluminium.Motors with clear transparent covers should notbe installed in direct sun to avoid over heating.

Leakage :

Leakage should not be greater than 0.01 % for valvessmaller than 1 size, and should not be greaterthan 0.03 % on the main port for the bigger sizes.

Valve selection :

Contractor should submit valve sizing selectionschedules. Which should take 3 factors in mind atthe time of selection :-

(a) water flow(b) coil pressure drop(c) field practical requirements.

Electrical & control specifications :

Power supply :

24 vac (+ 25%) (-15%) valve motor should operate

Safely without over loading in the fluctuation ofvolt between 20.5 to 30 vac.

Control signal & feed back :

Valve actuator should be able to receive control signals0 - 10 v dc and 4 - 20 ma. Field selection of theoperating control signal by normal tools should bepossible. The selection of the control signal will bemade depending on The surrounding conditions.

Such as distance between motor and controller,electrical interference factors etc.

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Others features :

* Valve should have manual facility to open or closethe valve with or without power supply.

* Motor should receive a feed back signalwhich locates the position of the valve. Thefeed back signal can be through electronicbuilt in circuit or through positive orpotentiometric feed back.

* The electronic board of the motor should beprovided with leads to show different status

such as valve opening or closing, zerocalibrating, low power indication and motorfailure. These leads will help commissioningand maintenance specialists to do theirwork efficiently.