Indoor generator

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dahualin

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I am doing a pump station design with an indoor generator. In generator room, there are two louvers for generator inlet air and air out. Our mechanical engineer wants to put motorized damper for those louver in order to keep it shut in winter time. Because we put a gas fired unit heater to keep everything from frozen. In that case, the motorized damper shall be interlocked with generator and powered by generator. So there are a lot of control staffs shall be involved in it and I am concerned about if the damper doesn't work and it will stop generator and affect the intent of power back up.

Any thought is appreciated.
 
This is a very common installation and is really not complicated.

We use power open, spring close damper motors, we power the damper motors from a an emergency panel and run through the auxiliary contacts on the transfer switch.

Or sometimes we make a tap off of the generators output and feed the damper motors directly off that tap (with proper OCP)

If the louvers fail to open the generator will likely kick out on over temp in a short time.

Along with the unit heater the engine should have a block heater if it is suppling emergency loads.
 
Along with what Bob said, you also would place a position switch to indicate that the damper is open when it is supposed to be open, if not, very load horn outside the gen room (until the gen goes out on over temp).
 
dahaulin
I have been down this road many times. Made a mistake or two along the way. The best design we have come up with for powered louvers is this: Install power-to-close spring-to-open louver motors. Connect them to a normal power circuit that is NOT powered by the generator. This way when utility power is lost, the louvers will open prior to generator start-up and the louvers will not be damaged by engine radiator fan pressure. The motors on these louvers are designed to withstand locked rotor current continuously. So they spend their entire lives in a locked rotor state with power flowing through them. Not a problem - these are very small motors that consume low current when locked. When power to the motor is lost, the springs will spin the motors backwards opening the louvers. On our first big generator job (600KW Diesel Cummins Indoor at a municipal water pumping station) the engineer had designed the motors to power open, spring close and he put them on a normal power circuit. At first start-up of the generator, the louvers got sucked into the radiator and destroyed them. As soon as they were replaced, the engineer wanted us to reconnect power to an emergency circuit. Our generator tech realized this would not work because the louvers were destroyed before emergency power was available. So he had us do what he called a standard arrangement of spring-to-open, power-to-close as I have described above, and we have had no problems since. Only other requirement is that a relay must be put in the circuit to kill power to the louvers while the engine is running so that the louvers will not close when utility power returns. This relay also opens the louvers when the engine is tested or run manually for any reason. We have had no problems with this arrangement at any of our installations! Good luck
 
Thanks ramdiesel3500. It is a great idea.

Do you know how quick the radiator fan start to work when generator starts? If it doesn't start when generator starts, I don't think it is going to damage the motorized damper on emergency circuit.

You mentioned a relay to kill power louvers while the engine is running so that the louvers will not close when utility power returns. Could you please tell me who is going to power the relay, auxiliary contact of ATS or genertor? Thanks.
 
Most generator engine fans are either solidly driven or clutch driven. Either way, the fan is usually spinning full speed at start-up. So you need to have those louvers opened prior to engine start-up. I suppose there are a hundred ways of doing this correctly. Just be sure you carefully plan the control of those louvers so that they are never closed when the engine is running! If you have remote cooling (like, say, generator in the basement and radiators on the roof) with electric driven fans, then louvers are not a problem anymore.
Good luck with your installation!
 
Oh, and as for the relay. The best way I know to deal with that is to have a 12 volt relay coil that is powered from the run circuit of the generator. You will need a timer in the circuit as well so that the louvers are held open for several seconds after the run circuit opens so that the engine has time to stop turning. This takes some careful control circuit design.
 
I have always assumed the louvers (and their control) were part of the package provided by the generator manufactuer. So I have never really had to deal with this, but I would have expected these to be gravity louvers: gravity closes them, and the pressure from the radiator fan would open them.

I am also supprised that one generator pulled the louvers into the radiator. Doesn't the radiator fan blow out away from the radiator? I would expect the louvers to open against the spring or motor before ripping out of their housing.

If the problems you have experienced are common, Ramdiesel, than this is an enlightening thread.
 
a easy control circut can use an engine oil pressure switch to control the relay. (there might even be one already on the engine already)
 
with the power to close louvers,when the utility power goes out the louvers open. then the oil press switch holds the contacts open.
 
Steve66
Thank-you for the memory jarring reminder!! :) After reading your reply, I made a call to the project manager for that job. We did this install prior to Y2K. As you suspected, my story was a bit in error. The louvers we had a problem with were not at the radiator. The radiator louvers were gravity type that get blown open by the fan! The problem louvers were the air intake louvers at the opposite end of the generator room. Those louvers had to be reworked. The mechanical contractor changed them so that they were power-to-close and spring open. The project manager also told me that they connected the control circuit to sense engine oil pressure so that the louvers would stay open after normal power returned so long as engine oil pressure was up -- just as referred to by E150club! Since that time, we have done other jobs the same way. This method of louver control is, according to our generator equipment supplier, the preferred method of operation for motorized louvers.

I want to apologize to all for my inaccuracies in my previous post. I hate it when untrue stories are told. I especially hate it when my memory fades with time causing me to relate an inaccurate account of a past occurance! Thank-you Steve66 for questioning my story. You helped me to get it right!

Take care all!
 
Take it easy. Ramdiesel3500.

Human being makes mistake. If something doesn't make sense to us, we will keep asking and thinking.

For the pump station project, I am going to use spring-close power-open louver and activated by ATS auxiliary contact. Because the whole pump station will be backed up by the generator.

I can't wait to see what is going to happen.
 
IMO I would take it at battery voltage from the start/run circuit right out of the generator to control a relay for 120 or what have you. And use louvers that are spring loaded to open when power is removed - much the way smoke dampers will close when powered off. As during excersize cycles and maintenance they will need to open as well. Remember the engine can start without any voltage out of the generator at all. This way they will open as the glow plugs heat up before the starter kicks in, and stay open until it is shut off.

And I'll say this.... If they dont open - it'll start anyway. It may not cool itself right and unless the room is air tight - really tight - it'will continue to run by sucking air through the weather-stripping or any other crack.
 
Thanks David!
I was just mad at myself for posting the story of an incident in my past and not relating it accurately! I am glad someone pointed it out to me!
I would suggest that you be sure the motorized louvers are constructed sturdy enough to withstand the pressure of the engine fan running while they are closed and be sure they can open under that pressure. The short time they are closed during start-up will not hurt the generator at all.
Take care!
 
A small rubber flap over a hole in the fan cowling will pretty much guarantee pressre has a place to escape - but off the start/run it would not be nessesary.
 
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