Fan coil unit speed controller specification

[marko333]

Hello,

I am trying to write a standard spec. for a fan coil unit fan speed controller. Speed controllers on fan coils are potentiometer operated for balancing air flow. The fans we use are normally two speed(then BMS controlled). FCU's are single phase and 240V mains powered. The fans are up to 2.5kW.
But all of a sudden, new fan coil units have speed controllers that burn out! When comparing these new style speed controllers to the old ones, they have different components. I dont know how they work, but i suspect the old controllers are a TRIAC controlled but the new controllers have a huge 125V, 6Amp potentiometer, rather than a small pot that controls the TRIAC in the older version. It is the contractor that has substituted an inferior product it seems.

What is the best style of speed controller to specify for a fan coil unit that is single phase and up to 2.5kW? What are the key criteria a speed controller should meet?

Thank you
Marko

 

[HVACctrl]

I would look into Nailor Industries. They have factories in the US, Canada and the UK. One option for them is an ECM or "electronically commutated motor". These devices are very versatile. They essentially function like a motor and VFD. The speed of the morot can be controlled by had or by a control signal. There is a control package that can be supplied with the unit that will modulate the fan and the chilled water valve based on demand and thereby save energy.

In addition, these ECM motors don't only modulate the speed, but they can be set in the factory to put out desired air volume. This makes balancing a snap. There are internal torque and speed calculations that enable the motor and its controls to determine the air volume supplied.

It really is a neat system. Other companies have it also. But I don't believe their control and air volume preset capabilities are up to speed with Nailor's.

Ed