Variable Frequency Drive (VFD) and Plant Safety

250degC is approaching the melting point of solder, and is probably above the design maximum temperatures of many of the components within the VFD's circuits.

Discuss the proposal with the VFD manufacturer.

A standard VFD will NOT survive temperatures approaching 250 deg C. Discuss with the VFD manufacturer and if possible locate the VFD in a heat-protected enclosure and/or away from the expected high temperatures if you expect the area near the VFD to get this hot in a fire.

I'm way out of my domain here, but why do you want ventilation DURING the fire? Wouldn't that feed oxygen to the fire, making it harder to extinguish and helping it spread faster? I understand the need to ventilate smoke immediately after the fire, but I've always figured you want to minimize air exchange during the fire.

I was thinking the same thing. We close all vent and fan during a fire.

I agree. All of our fans are tied into the fire alarm system and will shut down if there is a fire signal. This includes supply air and exhaust air. The last thing you want is to increase airflow.

CFD Report has been generarted for FIRE Mode scenario and as per LIFE & FIRE SAFETY report we have to put this fans and due to space contraint these fans are used for both normal and smoke exhaust purpose.

Hi,

With "Smoke Spill" fans, from what I understand, the cable needs to be fire rated not the VSD or motor starters. I doubt the VSD will be the issue but rather the cables that also feed the 'Essential Services MSB', the contactors and the controls. The purpose of the fans is to remove smoke to allow the safer egress of people and I guess reduce smoke damage. You will need to consult with someone familiar to the local building code and requirements for such equipment.

If the VSD is questionable for the purpose of fire smoke, but is required for normal day to day extraction, then use DOL contactors for the fire condition and override the VSD, and use a contactor to isolate the VSD.

Rgds,

Trevor.

The VFD should be located in a fire /smoke rated enclosure , as close as possible to the exhaust fan .

Disclaimer: I am not a fire suppression engineer nor do I or have I played one on TV.

Years ago I worked on fire detection and suppression equipment. It is not uncommon to have forced ventilation for stair ways and hallways which are part of an evacuation route. This is why doors to evacuation stairways and hallways all have automatic closers and must not be blocked open. This is also why stairways must be kept clear of flammable materials. In some cases, it is acceptable to use automatically released spring closing doors which remain open until fire is detected.

I do not know your local codes, but my non certified opinion is that fans for evacuation stairways should be run on a contactor and not a VFD when in fire mode. In this case it seems that we have not only the VFD but the control equipment that feeds the VFD in an unprotected area. In my worthless opinion, the system should be setup to fail into fire ventilation mode upon failure of the VFD or the control equipment which controls the VFD.

Mirz,

I don't understand why you are making any assumptions when you haven't told us where the VFD is located in reference to the exhaust fan. If it is located in the path of the heat and smoke being exhausted you have to consider one set of variables, but if the VFD is mounted to a probe that is operating the fan and the VFD is nowhere near the area where the smoke and heat are, then you only have to worry about the cabling and probe being damaged (another set of variables).

gsmcten