2 port Motorised valve

Two port ones don't, but three port ones do - I guess that's what you mean.

There is a paddle or ball inside on a shaft which is rotated by a geared motor in the head. A spring in the head drives the mechanism to one end of its travel if no power is applied to the motor. When power is applied, the motor runs and moves the ball or paddle to the other end of the travel, diverting the flow the other way. The motor is held in a stalled position all the time that the flow this way is needed.

There is an auxiliary microswitch which is used to control the boiler and probably the pump as well.

More details on the Honeywell web site. Look up W plan and Y plan

.andy

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So what does a 2 port one do ?

Novice

It's a simple on/off

Some systems have two or more of these instead of a diverter valve and the Honeywell arrangement is then called S-Plan or S-plan Plus.

.andy

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Answer: It is a simple open/closed peice of pipe. See the Main FAQ.

Except for the Sunvic ones which motor the valve both ways and so don't take power all the time. They are meant to be better than the type that fight the spring, less likelihood of burning out the motor as it only runs for a short time.

Many of them used to be like this and it's a shame that the design was changed. However it does mean that you can't drop one of them into a system wired for the spring return type.

.andy

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The sunvic one can. BTW my B&Q Warehouse have sunvic if you want to look at the datasheet with the valve or

Presumably it must have a relay or special contact arrangement to achieve this......

.andy

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In message , Novice writes

Do you mean a 2 port or a 3 port?

A two port valve is effectively an on-off switch

In message , Malcolm Reeves writes

Sunvic make both types

In message , Andy Hall writes

No, it's controlled by a microswitch on a cam