TC903-4FMSA FCU Room Thermostat

Wyman_Yeung · ‎2021-12-02

We have a project using TC903-4FMSA and will using AO to control the FCU fan speed.

But the customer require TC903 thermostat to repeat the Fan status.

Can we use the DO point (dry contact) to represent the Fan running status?

What is the DO point used for?

Please refer to attached wiring diagram.

Thx for advise?

Gary · ‎2021-12-03

Hello Wyman,

Re: Please refer to attached wiring diagram.

I do not see any attachments?

Wyman_Yeung · ‎2021-12-03

We have a project using TC903-4FMSA and will using AO to control the FCU fan speed.

But the customer require TC903 thermostat to repeat the Fan status.

Can we use the DO point (dry contact) to represent the Fan running status?

What is the DO point used for?

Please refer to attached wiring diagram.

CraigEl · ‎2021-12-06

Hi Wyman

I suspect that the ECM fan requires some sort of PWM control and that is why the DO is required.

Wyman_Yeung · ‎2021-12-08

Well noted and many thx.

Emmerich · ‎2022-01-17

Thanks for sharing i was curious to know about it and this was true and solved my issue thanks for your support.

Myloweslife

PetZeri · ‎2022-04-12

The advanced indoor regulator are only for room temperature control in 2-lines and 4-pipes FCU cooling frameworks with 3-speed fan and a couple of water valves. Highlights: - Designed for control a 3-speed fan and a couple of water valves with fan speed auto or manual change selectable.