Multiplex a Softstart

I have a application with about 15 roof fans that are bel driven and in hard to reach areas. We are looking at softstarts for these such as the AB SMC series since it has bypass contactor overload and everything in one compact package.

These are all 5 HP motors but they may only start once a month or less on avaergae because unless the power blinks they pretty much stay running all the time 24/7/365

But the units we have without softstarts we change belts on twice a year on average and we think with softstarts we may get once a year or even better from a belt change.

Most of the units you have to get a boom lift to get to or put up scaffolding in some areas and every fan counts in this place.

Is there some possible way to start al15 fans one at a time with 1 softstart and the switch it over to a regular contactor and start another?

We have some yaskawa drive with a 3 contactor bypass system and that is where I got this idea.I was hoping it could be done for less than the cost of softstarts for each unit which are around 700.00

The SMC soft starters are price competitive with NEMA starters. I think that with all the extra contactors for a multiplexing scheme you would pretty quickly eliminate any savings. You would need two contactors and an extra overload per motor, plus timing, interlocking, and wiring.

However if you are rarely starting and mostly running and going through belts then you may have another problem. Five or six starts should not destroy a belt.

I agree with everything Troy said...either something is wrong (belt/sheave alignment, size, matching lengths), or there are many more starts that are not accounted for.

With that said, I have a couple of the cheap SR22 units for exhaust fans that seem to be just fine. I would also not hesitate to try their other models. Even without bypass contactors, they should be easy enough to replace if there's a failure, especially you you put nice manual motor starters as OL relays upstream in the power circuit.

I would find any way possible to avoid doing the multiple motor thing...I looks good on paper or in the imagination of some bean counters, but in practice it will be more costly in most cases...

I like soft starters on fans though, it can end that startup belt chirp that catches the ear of every supervisor, and they can allow more frequent starts without faults if sized properly up front.

EDIT: Safety note: the SR22 has one hot leg at all times, so only use it where a strict lockout procedure or local (downstream) disconnect isolates all three phases for electrical repairs.