MEP-003A with PLC controlled auto start

[sewerzuk]

I actually built this and shot the video several months ago, but I've been to lazy to post it up here.

I had a really nice low hour -003A that I had been using to power tools at remote job sites, backup power for my shop, etc. I was just loading it onto my flatbed trailer as needed, but I decided that it would be fun to build it into an enclosed trailer (which doubles as lockable tool storage). I wanted to make its operation as simple as possible, so my employees could start it without needing a course on MEP operation. My goal was to be able to safely start and run the entire trailer with the push of one button. It came out perfect; here are the details:

I used a TECO PLC and wrote a program to control the generator, a magnetic switch (to isolate the generator's output from the load center), and the air compressor's blowdown valves. The PLC displays messages to the operator about what it is doing (for example, "engine cranking, low oil pressure bypassed," "warming up, please wait,", etc.) The start sequence goes like this:

1. Operator pushes green start button
2. PLC energizes fuel pumps, manifold heaters, and glow plugs for 40 seconds (I found this was the time needed to start the set when it was near zero degrees outside)
3. PLC energizes a relay which bypasses the low oil pressure switch, and cranks the engine (same as holding the start switch in start) for 15 seconds
4. Once running, the PLC disengages the start relay and allows the set to run unloaded for 1 minute
5. The PLC closes the magnetic switch, energizing the load center
6. Once every minute, the PLC opens solenoid valves on the compressor blowdown valves, preventing a buildup of moisture
7. To completely shutdown the system and ready it for the start sequence again, the operator simply pushes the red button

Some cool features:
1. The generator can still be started manually with the control panel switches, in the event the PLC doesn't work properly
2. I have a 110v marine grade power inlet box that keeps 1 circuit live. On this circuit I have battery tenders for the generator's batteries, a heater to keep the trailer above freezing, and a small dehumidifier. This circuit automatically switches over to generator power as soon as the generator is started, ensuring that it is always live
3. I have programmed an auto start feature into the PLC; whenever power is lost to the 110v circuit, it begins the start sequence. I currently have this feature disabled, as I do not have an automatic transfer switch in my shop, so it doesn't help me out much. It may be handy in the future...
4. I added a full power 50A RV style receptacle on the outside of the trailer; this is the same style plug I have on my house generator, and PTO generator for my tractor, so it allows me to plug into my shop or the house. I also have a few spider boxes, and 100' of 6/4 SOOW cable in case a lot of power is needed a long distance from the trailer
5. The air compressor I am running in the trailer is a 3 phase machine, so the genset is set up to run 120/208 3 phase, and I have a 3 phase panel installed in the trailer. The full power outlet receives 120/208 single phase (all of my tools, appliances, etc. run fine on 208v). However, if the full power of the set is needed in single phase (wife wants to dry clothes and cook dinner at the same time), then the genset can be switched to 120/240 single phase. In this condition, the magnetic switch for the load center will still close, but will leave 1 phase "cold" in the load center. All of the single phase loads are still powered, but the air compressor's mag starter is disabled, preventing damage to the motor, breaker trips, etc.
6. The trailer is equipped with LED lighting, so no flashlight necessary for startup
7. I have a cord reel set up near the back of the trailer, supplied by the convenience receptacle on the generator
8. Not shown in the pics and movie is the air system; the compressor is a 3 cylinder, single stage, 25 CFM 3 phase curtis compressor. It has solenoid valves for the moisture separators and tank valves, which blow down every minute. There is an air manifold with an additional moisture separator, regulator, and lubricator (for air tools), and a separate 3 stage dessicant air dryer/filter/regulator.
9. The generator can be run for about 30 minutes at full load with the trailer closed up. It is actually very quiet. Any longer than 30 minutes, and the doors need to be opened to allow for some ventilation. In the future I may add an RV style roof fan to allow the doors to remain closed.

The pics and video were taken a while ago (a few things have changed since then), but it gives you a good idea of the setup.

[media]http://www.youtube.com/watch?v=52dkk7QrmUA[/media]

 

[R Racing]

Sweet setup. Just curious why you have it in a trailer ?

 

[NDT]

Very nice! I was considering something similar but I am very concerned that there would be too much heat buildup in the trailer on a 100 degree day, as the engine is air cooled, and may start to recirculate the air in the trailer. Any thoughts on this?

 

[Carl_in_NH]

Nicely done.

 

[glcaines]

Very nice looking job - I'm impressed!

 

[sewerzuk]

Sweet setup. Just curious why you have it in a trailer ?

It allows me to leave the genset/compressor and any other tools at a jobite because the doors can be closed and locked. And, it keeps everything out of the weather...

Very nice! I was considering something similar but I am very concerned that there would be too much heat buildup in the trailer on a 100 degree day, as the engine is air cooled, and may start to recirculate the air in the trailer. Any thoughts on this?

9. The generator can be run for about 30 minutes at full load with the trailer closed up. It is actually very quiet. Any longer than 30 minutes, and the doors need to be opened to allow for some ventilation. In the future I may add an RV style roof fan to allow the doors to remain closed.

I have run it for longer in the closed trailer; for a few hours at a time. The trailer isn't insulated and it seems to shed enough heat to keep the set operating normally. However, if I plan to run the set at a full load or for an extended period of time, I do open both doors. There is more than enough ventilation then to keep the set cool. I have thought about adding a roof vent in the trailer with a small electric fan and some kind of louvered air inlet on the floor or low on a wall; this would allow me to keep the trailer closed up for a longer period of time.

 

[Bighurt]

I like it...what keeps someone from taking the whole trailer?

 

[sewerzuk]

I like it...what keeps someone from taking the whole trailer?

A big Master hitch lock!
I suppose they could still rig up some way to chain the trailer tongue to the hitch, but it makes it difficult enough that I don't expect anybody to try...

 

[Speddmon]

Nice job!

One question though...did you program a few rungs to flash the field in the event that the generator is running and not producing power on it's own?

 

[sewerzuk]

Nice job!

One question though...did you program a few rungs to flash the field in the event that the generator is running and not producing power on it's own?

I didn't; that isn't something that had crossed my mind...

I suppose it would be easy to add, but I'm not really sure when it would be necessary. The PLC does flash the field for a full 15 seconds on startup. My thought was that if it wasn't producing power after that, something must be faulty and the lack of power would clue me in to the problem.

I am wondering why you asked this...have you run into situations where a running genset loses its field?

 

[RichardR]

Very nice setup! Thanks for posting this with the video.

 

[rosco]

Great job on a great project!

 

[Speddmon]

I am wondering why you asked this...have you run into situations where a running genset loses its field?

A running genset, no. The time I was talking about is right after start-up, sometimes they don't start generating on their own. Several members have reported having to flash the field right after start-up because the generator didn't start producing on it's own.

I intend to so something very similar, but it's going to be mounted as a dedicated house back-up with automatic start and automatic switch-over. But rather than bypassing the oil pressure switch and such like you did. I'm going to parallel my PLC outputs with the appropriate wires on the generator master switch and the generator will take care of bypassing the temp and oil switches for me.

 

[ARYankee]

That is a sweet setup..... You get that TECO from Automation Direct? I have a SLC 500 that I plan on using if I can ever get a generator.

 

[sewerzuk]

A running genset, no. The time I was talking about is right after start-up, sometimes they don't start generating on their own. Several members have reported having to flash the field right after start-up because the generator didn't start producing on it's own.

I intend to so something very similar, but it's going to be mounted as a dedicated house back-up with automatic start and automatic switch-over. But rather than bypassing the oil pressure switch and such like you did. I'm going to parallel my PLC outputs with the appropriate wires on the generator master switch and the generator will take care of bypassing the temp and oil switches for me.

I didn't describe it in detail in my initial post...but that's exactly what I did. The PLC's outputs are tied directly into the generator's switch (via the appropriate terminal boards). The PLC operates the set almost exactly the same way that the master switch would, utilizing the relays, wiring, etc. inside of the control box. The only difference is that the fuel pumps run during the preheat cycle (that was just for ease of programming, and it sounds cool while you are waiting for the preheat).
For the start cycle, the PLC energizes a standalone time-delay relay (I had to use a standalone relay because I ran out of output relays on the PLC and I needed at least 2 electrically separate poles). I used an off-delay relay with a 2 second delay because I found that if it was really cold out or the batteries were partially discharged, the internal relays on PLC would flutter due to the voltage fluctuation, causing the solenoid, K1 and K3 to drop in and out. This probably could have been remedied by using bigger batteries, a standalone power supply for the PLC, or several other ways...but the easiest and cheapest way was simply to add the off delay to the relay...so it "ignores" the flutter from the PLC. That standalone relay operates the relays in the control box just as the master switch would; they take care of bypassing the low oil pressure, cranking, field flash, etc. And, that allows the overspeed switch to operate as designed as well...so it doesn't really matter how long it actually takes to start the generator. Once it comes up to speed, the starter motor drops out, but the low oil pressure is still bypassed and the field flash continues as long as the PLC remains in cranking mode.

If you are interested, I can snap a pic of the inside of the control box. All I did was drill a small hole in the side for some 3/4" flex conduit, and I ran the appropriate wires right into the box. I was even able to sneak them into the existing wire bundles without removing the zip ties. They run through the harness down to the appropriate terminals on TB5 and TB6.

 

[sewerzuk]

That is a sweet setup..... You get that TECO from Automation Direct? I have a SLC 500 that I plan on using if I can ever get a generator.

I got it from here:

Home - FactoryMation

I buy lots of stuff from them for my projects...always been happy with their prices, shipping, etc.
Probably spent over $10k there in the last 5 years for mag starters, PLC's, relays, etc.

 

[steelandcanvas]

Nice job sewerzuk! I knew someone on this B/B would make a PLC work with a MEP.

 

[PeterD]

I agree, this is way cool... I have used these controllers in the past, with good results (not controlling a generator, but would do that just fine). They are very reliable (the one I have has been tough) generally. And what I like is that the prices are very attractive as well... I'd wondered about that extra timer, thanks for explaining why you did that. I suspect on things like my MEP-004 I would not need that at all. In fact, I bet I could come up with a controller setup without any extra parts other than perhaps a relay or two (and maybe a voltage sensor).

 

[Carl_in_NH]

I got it from here:

Home - FactoryMation

I buy lots of stuff from them for my projects...

I've been purchasing VFDs for my three phase metalworking machines and other componenet from the folks at FactoryMation since about 2006; I'm also very happy with them. Only once did I have a small problem with something they shipped, and they bent over backwards to make it right once I called it to their attention. I can't say enough good about them.

 

[bimota]

First, great work. I love to see this kind of real re-use rather than these once expensive and well built machines sitting in the yard, rusting. So much hardware gets wasted.

The more important sharing is the wiring diagram. I use a more standard auto start called the Dynagen GSC 300 which costs about $300 plus 24 volt relays. You could help us out by scratching out and posting a basic wiring diagram. We don't need the PLC coding since that is not an option for most of us but a basic MEP-003 auto start wiring diagram would be huge!