Pictures of a backup power systems replacement evolution at one of our clients. The old generator was a Katolight 45FGH4, circa 1990. The new generator is a Cummins Power GGHE-1503557 60 KW 3 phase. Unfortunately, when the Katolight generator was moved from the previous studio location in 1998, it was never installed correctly. The 500 gallon propane tank was undersized, the gas tubing was undersized, etc. We fixed those items, but the damage was done. After running too lean under load a few times, the head gasket blew and there is oil in the antifreeze and antifreeze in the oil. It is a Ford straight six engine, and sure, we could rebuild it, but why bother. This is a major group of stations in a very lucrative market, it makes much more sense to replace the entire unit.
Katolight Genset hooked up to the crane, ready to move
In addition to the head gasket problem, the load on the generator has increased. Since the old generator was installed in 1998, two more stations have been added to this facility. That means another air studio, another production studio, more computers, servers, air conditioning etc. Thus, the new generator is rated for 60 KW.
Cummins Power Generator delivery
Cummins generator lift
After the GENSET is placed, connections for remote start, battery charger, block heater and AC power output are made. We were able to reuse the existing conduit and cable, thankfully the electricians used 3/0 AWG cable for the AC power connections to the transfer switch.
Cummins Power generator in place
It appears that they have dropped the Onan name, but not the color, completely.
Radio facilities, particularly mountain top transmitter sites, are prone to power transients. The causes can be varied, but most often, lightning is the culprit. Long power transmission lines to the site are vulnerable to direct strikes and EMF induced spikes from nearby strikes. Other issues, such as switching transients, load fluctuations, and malfunctioning equipment can lead “clear weather” outages. Of course, the best way to deal with such things is prevention.
Power line surge suppressors have been around for quite some time. They usually take the form of a MOV (Metal Oxide Varistor) connected between the hot leg and neutral or ground. There are a few differences in designs, however. Typically, most facilities employ a parallel surge suppressor. That normally take to form of an enclosure hung next to the main power panel with a group of MOV modules in it. The MOVs are feed from a circuit breaker in the panel. Like this:
LEA parallel or shunt surge suppressor
This is an LEA three phase 208 volt shunt surge suppression unit, which has MOVs between all phases to ground and each other. That is connected in parallel to the electrical service with the circuit breaker disconnect. These function well enough, provided there is a good bit of series inductance before the unit and also, preferably after. The series inductance can come from many sources, including long secondary leads from the utility company transformer or electrical conductors enclosed in metal conduit, particularly rigid (verses EMT, or FMC) metal conduit. The inductance adds a bit of resistance to the transient voltages, which come in higher than 50 or 60 Hz AC waveform.
A better method of transient protection is the Series Surge Suppressor. These units are installed in line with the incoming service and include an inductor to add the required series resistance coupled with MOVs and capacitors. Most series surge suppressor also filter out harmonics and RF by design, something desirable particularly at a transmitter site. Series surge suppressors look like this:
LEA DYNA systems series surge protector
This is a LEA three phase 240 volt unit. As in the other example, all phases have MOVs to neutral and each other. There are MOVs and capacitors on the line and load side of this unit (line side is the bottom of the inductor). A basic schematic looks like this:
Series surge suppressor basic schematic
A few things to note; MOVs have a short circuit failure mode and must be fused to protect the incoming line from shorts to ground. MOVs also deteriorate with age, the more they fire, the lower the breakdown voltage becomes. Eventually, the will begin to conduct current at all times and heat up, thus they should also be thermally fused. MOVs that are not properly protected from over current or over temperature conditions have the alarming capacity to explode and/or catch on fire. From experience, this is something to be avoided. Matched MOVs can be paralleled to increase current handling capacity.
The inductor is in the 100 µH range, which adds almost no inductive reactance at 60 Hz. However, it becomes more resistive as the frequency goes up. Most transients, especially lightning, happen at many times the 60 Hz fundamental frequency used in power distribution (50 Hz elsewhere unless airborne, then it may be 400 Hz).
Capacitors are in the 1-10 mF range and rated for 1 KV or greater as a safety factor. The net effect of adding capacitance is to create a low pass filter. Hypothetically speaking, of course, playing around with the capacitance values may net a better lowpass filter. For example, at 100 uH and 5 mF, the cutoff frequency is 225 Hz, or below the fourth harmonic. Care must be taken not to affect or distort the 60 Hz wave form or all sorts of bad things will happen, especially to switching power supplies.
These units also need have a bypass method installed. If one of the MOV modules needs to be replaced, power to the unit has to be secured. This can be done by connecting it to the AC mains before any generator transfer switch. That way, the main power can be secured and the site can run on generator power while the maintenance on the surge suppression unit is taking place.
Power loss is a critical failure, thus much money is spent to prevent or mitigate commercial power interruptions in broadcast facilities. Backup generators and Uninterruptible Power Supplies (UPS) are the first line of defense against commercial power interruptions. It is prudent to research products and check reliability and interoperability when specifying and installing these systems. However, even the best mechanical and electrical systems will fail, often at the worst possible time. The UPS has a startling tendency to shut down, often at the worst possible moment, due to some internal control circuit or something similar. This can happen when commercial power is being supplied without interruption. The net result is some critical piece of equipment is now dark and the station is off the air.
Eaton Automatic Transfer Switch and UPS
There is a solution: The Eaton EATS EPDU TPC 2234-A Automatic Transfer Switch.
Eaton EATS EPDU
With this unit, the primary plug is connected to the output of the UPS, the secondary plug is connected to the commercial power source. If the UPS fails, the load is automatically transferred to the commercial power. Typically, the commercial power is also backup up with a generator. The secondary plug can also be connected to a second UPS. In theory, having two UPSs connected in parallel via an Automatic Transfer Switch would increase the Mean Time Between Failure (MTBF) by 50%.
UPS Eaton ATS EPDU block diagram
The Eaton products come with a variety of options, including basic network monitoring, advanced network monitoring, switching and management. Those features are available via Ethernet or serial data port.
Multiple layers of redundancy is the best method to avoid those late night, weekend or holiday phone calls.
Never a good mix, unfortunately, it usually turns out bad for the mice and sometimes the equipment. This is a Onan GGMA 20 KW propane generator installed in a rural area, not that the location matters that much. Mice will find what they perceive as a safe secure spot to hold up for the winter.
Onan GGMA20 propane generator
Unfortunately, the mice decided that the generator cooling fan was a good place to make a nest. It probably was until the generator started, then the mice had a quick lesson in centripetal force.
Mice and generator
This will require some additional maintenance in the spring time when I change to oil. By that time, the carcases should be mostly dried out and easier to deal with.
Onan generator mice
The mice are generally a nuisance, getting into ATU’s, transmitters, electrical panels, spare parts boxes, etc. Once in place, they begin to bread and reproduce. The gestational period for a mouse is 21 days, which means populations rapidly increase creating further problems. If left alone, mice will chew through electrical insulation, control wires, cardboard boxes, packing material and so on. They tend to carry diseases like hantavirus and bubonic plague.
I don’t usually agree to using poison to get rid of pests, it tends to linger in the environment and accumulate up the food chain. However, judicious use of some type of poison is usually the only way to effectively get rid of a mouse infestation.
Wherever possible, make sure that all openings and holes into equipment and buildings are sealed up. Do not kill snakes and other predators, who will assist in keeping the mice in check. Employ traps and wear gloves when removing dead mice and mouse parts. Beware of fleas.
An issue I had to deal with recently; an unstable generator/UPS relationship. When the generator was running under load, it surged repeatedly causing the UPS to drop out and not recharge. Eventually, the UPS ran out of juice and shut down, killing the power to the Sine Systems remote control and telephone system. Of the two, the remote control was the biggest pain to fix, as it lost it’s timed commands and would not reduce power at sun set for the associated class D AM station.
What went wrong? This is a chart of typical problems with generators operating UPS loads:
|Fail to “lock on” to generator power
||Improper generator frequency or voltage
Poor generator regulation
Unrealistic performance requirements
|Instability of generator
||Voltage regulator sensitivity
Control loop compatibility
Governor or AVR problem
|Fail to sync bypass
||Frequency or voltage out of range
Poor frequency stability
Unrealistic performance requirements
Changes to total load on the system
Generator output voltage distortion
|Instability at specific load levels
||Control loop compatibility
|Instability at load changes
||Control loop compatibility
||Generator output voltage distortion
|Loss of voltage control
||Excess capacitance in filters vs. load
Table courtesy of Cummins Power Generation.
Generator excitation methods can be the culprit in many of these situations. Generators often use one of three types of excitation for their field coils:
- Shunt excited SCR (silicon controlled recifier)
- Shunt excited PWM (pulse width modulation)
- PGM (permanent magnet generator)
Of the three, permanent magnet generator is the most stable since the AVR (automatic voltage regulator) is powered by a separate small generator which is unaffected by the load on the main generator output. SCR and PWM both use the generator output windings, which makes them susceptible to load inducted voltage distortion brought on by non-linear loads. Therefore, in locations where large UPSs are known to be part of the load, PGM excited generators are the best choice.
PMG generator diagram
Sometimes, the generator is already in use before the UPS is installed. In that case, there are some remedial steps that can be taken. The speed which the voltage regulator reacts to changes in the load is often the culprit in many of these situations. It may seem counter intuitive, however, the faster the AVR reacts, the more fluctuations there will be in the voltage and frequency. A UPS can operate under a wide range of voltages and frequency, provided they do not rapidly change.
Depending on other loads, it may be necessary to dampen the gain on the AVR to slow it’s reactions down. This will work if there are not large intermittent starting loads on the generator such as air conditioning compressors.
Another method would be to delay the UPS transfer to generator power until after all the other loads have been satisfied. This will ensure that the generator voltage and current fluctuations are damped by the existing load.
The generator’s size needs to account for the equipment attached to the UPS and the battery charging load. With a larger UPS, the battery charging load can be significant. Generators that are improperly sized will not be made to work under any circumstances, hence the “unrealistic performance requirements” noted in the chart above.
You can read the entire Cummins Power white paper on generators powering UPS loads here.
I was fortunate enough to acquire this generator last fall. It was new in 1969 and has unknown hours on it, but it appears in decent shape. I am going to do a level two overhaul and install it as backup power for my house/shop. The first order of business is a complete inspection. I discovered a few problems; the starter didn’t crank, the distributor was loose, and the carburetor had some burned out chunk of metal attached to it.
Onan 12JC4R generator
First, the starter: These units use a Prestolite MEO3006 starter, which is common to several Chrysler products from the late ’60s and early ’70s. This is obviously a replacement unit, as it is not “Onan Green.” When I hooked a battery up and tried to turn the motor over, the start relay clicked but nothing else happened. I dismounted the starter and removed the starter solenoid. The interior of the starter motor looked in good condition, which points the solenoid. Sure enough, I removed the back of that unit and found two wires burned through and a large blackened area. While I had the starter off, I hooked it up to a 12 volt battery and it worked fine. A new starter costs $469.00, a new solenoid cost $59.00. I opted for the solenoid.
Onan 12JC4R burned out generator starter solenoid
The next thing is the distributor. I was checking the points and contemplating replacing the breaker points with an electronic ignition when I discovered the distributor could turn 1/8 of a turn in each direction, as when making timing adjustments.
Onan 12JC 4R distributor clamp
I used a 3/8 box wrench and tighten up the clamp holding the distributor shaft. It took several turns and makes me wonder why it was loose. I will have to check the timing with a light once I get it running. This also could be why the generator was not running when we took it out of service.
Onan 12JC 4R rotor and breaker points
As for the points, they look brand new, as does the rotor and distributor cap.
Onan 12JC 4R generator spark plug, champion H8C
The spark plugs look well used and the plug wires look original.
Finally, there was an electric choke mechanism on the carburetor which is completely unnecessary for a propane fueled unit. The choke plate itself was wired open. The electric choke was was burned open, so I removed the assembly. I then spent some time at the local NAPA cross referencing parts. Here is a tune up list:
||Onan part (old)
||Onan part (new)
|Plug wire #1
|Plug wire 2,3,4
|*Electronic ignition set
|**Ignition coil W/PRX 1545
*Condenser and breaker points can be substituted for electronic ignition kit, either Onan 166-0825 or Pertronics 1545 with Pertronics PRX 405011 coil.
**Pertronics electronic ignition must be used with Pertronics coil
***Champion RH8C plugs should be used with replacement wires without noise suppression plug boots.
This is for an Onan 12JC generator circa 1969 with a Studebaker engine. Other models/years may vary. The other issue with this unit is there is no supervisory monitoring and control. There is no oil pressure loss, overheat or overcrank faults. This is why the starter solenoid failed. To remedy that situation, I started to design a better control circuit. Then I looked around on the inner tubes and found somebody had already done this. DynaGen makes the GSC400p which has can monitor oil pressure, engine temperature, frequency, engine RPM, hours, voltage and current. It can fault for any out of tolerance condition, as programmed by the user.
Retrofit generator controller
I plan to install this in the original control box, leaving the original control circuit intact by using the remote start/stop connections. I keep the original remote/start/stop switch and hand crank switch in place for use if the fancy controller fails.
The WICC transmitter site, Pleasure Beach in Bridgeport, has been cut off from normal access since the bridge to the island burned in 1996. Since that time, access has been by boat with a 0.93 mile walk from the dock to the transmitter building.
Last summer, LVI Construction, under contract from the Town of Stratford, put in a temporary road and began removing the burned out cottages. While that road is in place, the radio station has been able to access the site and get many important things accomplished. These include:
- Replacing the vandal damaged top beacon on the South tower
- Removing several decades worth of stored crap, garbage, obsolete and unused equipment
- Repair the electrical service to the building
- Replace the generator transfer switch
- Repair the Sonitrol building alarm
- Replace the old Onan Generator
- Have the power company replace the 3 phase circuit from the point where the under water cables come ashore to the transmitter building.
All of these projects should greatly improve the reliability of the station. This should make Bill, happy, who appears to have a WICC chip implanted in his brain because every time the carrier is interrupted he posts about it on the radio-info.com website.
The biggest issue with the site was the utility feed from the shore to the transmitter building. The original circuit was installed in 1936 when the station moved to the island. It was old and the poles were all rotting and had horizontal cross arms. Ospreys especially like the horizontal cross arms as they made good nesting spots. That is, until the nest shorts out one of the phases catches on fire and burns the top of the pole off. This has happened several times over the years causing many hours of off air time.
WICC new utility service
United Illuminating, the local utility company, was very cooperative and installed new utility poles, wires, breakers and transformers, this time with a vertical phase arrangement, which should keep the Ospreys off of them. Additionally, the cottage removal project included installing Osprey nesting poles.
Pleasure beach cottages removed
With almost all of the cottages now removed, the area looks much better than before. Actually, it should be a nice nature preserve and hopefully, the absence of the buildings might reduce the number of vandals in the area. The work is almost done, so the road is about to be taken up. This means we need to wrap up the work out there, so the final push is on.
WICC transmitter building
In the last three weeks, 10 truck loads of junk have been hauled out of the transmitter building and generator shack. Over 1,500 pounds of scrap steel, 640 pounds of insulated wire, 2,000 pounds of particle board furniture, old t-shirts and hats (something called “Taste of Bridgeport” which, if anyone knows what that was let me know), old propane tanks, batteries, etc. We also managed to fix the fence and gate in front of the building, cut down the over grown yew bushes and bittersweet vines.
The old Kolher transfer switch was also an issue. There was no place to mount a new switch inside and mounting one outside is out of the question, so the guts from the Kohler switch were removed and replace with an ASCO unit. This was done in the summer of 2009. The breaker on the right side is the main service disconnect for the building, which was installed in September.
Onan 12 KW 12JC 4R air cooled generator, removed from service
Today, it was time to replace the Onan propane generator. The old generator is an Onan 12JC-4R air cooled propane unit which was installed on April 4, 1969 at a cost of $1,545.00 new. For many years, this unit gave reliable service, but it has many, many hours on it and it lacks the fault/self control circuits needed for remote (read desolate) operation. Several times over the last few years, the generator would run out of gas or the propane tank would freeze up and the starter would crank until it burned out.
It was cold out on the island, with temperatures in the twenties and a bitter west wind blowing right into the generator shack. All of this conspired to make working conditions difficult. Wind chill readings were in the single digits all day long, and in spite of long johns and extra layers, by 3 pm I was shivering and even several hours after coming inside, I still feel cold.
Using tractor to move new generator
The new generator is an Cummins/Onan 20GGMA which is rated for 20 KW. We used a John Deere bucket tractor to move the generator from the flat bed truck to the generator building, then push it inside. The old generator wiring to the transfer switch was reused, but a piece of flex was used to connect to the generator instead of the solid conduit. The building fan was also wired up so that it will run whenever the generator is running.
The generator load with all possible things switched on and the transmitter running at full power is about 12,000 watts, but this would mean the air conditioner and tower lights were on during the daytime. More likely, the transmitter will be at low power when the tower lights are on and the AC will be intermittent on/off at night. At full load, this generator uses slightly less than 2 gallons of propane per hour. At half load, I’d estimate that to be 1.4 or so gallons.
Cummins Onan generator in new home
100 pound propane gas tanks
HOCON gas came out and connected six 100 pound propane tanks in series, which should prevent tank icing. Propane weights about 4.11 pounds per gallon, therefore the fuel supply should last about 100 hours, or 4.5 days, give or take. Why 100 pound tanks? Because we will have to shuffle them back and forth between the dock and the generator shed, a journey of about one mile, in a cart. Anything larger would be impossible to deal with. Even so, refilling the propane will be a 2 person job and will likely take all day.
File under some new everyday. Yesterday, there was an area wide power outage in Woodstock, NY. The backup generator failed to start, however, WDST remained on the air until the UPS batteries ran out several hours later. Then my cellphone rang. Alas, yet another Sunday on the job.
Upon arrival, I found the power had just come back on, so the DJ (yes, there was a live person in the studio, on Sunday) was restarting the NextGen system and getting the station back on the air. I restarted the rest of the servers, streaming computers and what not. While I was there, I figured I might as well see why the generator didn’t run.
Pressing the start switch led to the “click, click, click, click…” which normally indicates the battery is dead. Deciding that I should dig a little deeper, I got the volt meter out. Battery voltage, no load 13.8 volts. A normal reading. Flick the starter switch and measure the battery voltage again, under load 13.7 volts. Hmmmm, now that is not what I suspected. If the battery were bad, the voltage should drop down under load.
Cracked Battery Terminal
I grabbed the negative cable and it came off in my hand. Another one of those “ah ha!” moments. Upon closer examination, the terminal connector is cracked in half.
Cracked Battery Terminal
I went to the local Ford dealership and bought a heavy duty truck battery cable. Since the battery itself is six years old, I decided to bring it and have it checked, and sure enough, the battery was going bad too. Rather than suffer through another power outage without generator, I went ahead and replaced the battery.
Why the terminal cracked in half in the first place, I don’t know. Perhaps it was over tightened, or some type of manufacturing defect.
Broadcasters historically have tried to remain on the air during emergency events like major storms, earthquakes and other forces of nature. Often times, commercial power is interrupted, and thus, the backup power generator is installed. Propane powered generators for medium duty (powers up to 45 KW) are popular because of the decreased environmental hazards, availability and expense of fuel, ease of maintenance and repair. This sized generator can run the critical loads of a studio facility or a transmitter site with TPO’s between 5 and 10 KW.
Katolight 45 KW generator w/outside housing
Most propane generators use a gasoline engine modified to use propane. These generators can also use natural gas, however, because natural gas has slightly less energy, the generator’s service rating is reduced by about 10 percent.
Ford inline 6 cylinder engine
The biggest error I consistently see with propane generators is improper fuel tank sizing. It might seem just fine to plop a 500 gallon tank down next to a 45 KW generator and expect everything to be just fine. 500 Gallons may sound like a lot of fuel, but the more important consideration is tank vaporization, that is to say, how fast can the liquid propane can be removed from the tank for use. Propane fuel companies should be able to sizing these things correctly, most of them have books and charts that tell what capacities and sizes are needed. However, as a general trouble shoot guide, the following information is provided:
Generator manufactures will specify how many BTU per hour a generator will require under full load. If not, these are some conservative rules of thumb:
- For every 1 KW of electrical generation, 2 horsepower of engine is needed*
- Under full load, each horsepower will consume 10,000 BTU per hour*
- Propane has 92,000 BTU per gallon
- Propane weighs 4.2 pounds per gallon
*Note: These are not the figures you will find in your engineering handbooks, they are adjusted for generator winding and engine efficiency.
Propane Tank Vaporization Rates (Continuous BTU/hr vs volume at tank temperature):
|Size propane in a tank (assumes 1/3 full)
||Maximum continuous BTU/hr at degrees F
Note: Tank vaporization depends on fuel level, tank temperature and withdrawal rate. The above chart is a conservative generalization and represents a safe median value.
If a propane tank cannot vaporize fuel fast enough, the generator will begin to run lean, eventually overheat and shutdown. The vaporization rate depends on the tank temperature, which drops as fuel is withdrawn. For the above cited 45 KW generator called to duty after a sever winter storm, the tank would need to vaporize: 45KW x 2 HP = 90 HP. 90 HP x 10,000 BTU/hr = 900,000 btu/hr. A 500 gallon tank is too small for that size generator.
As the tank temperature drops a propane tank can develop frost on the outside of the tank, even on a hot summer day, which compounds the problem.
The correct size tank for a 45 KW generator is a 1000 gallons. This can also be two five hundred gallon tanks connected in parallel via a high pressure line.
45 KW propane generator with two 500 gallon tanks
Also note, the generator’s radiator is facing the tanks so that when the unit is running, hot air is blowing on the tanks, warming them up. This particular generator is about 25 years old, which is why it looks a little worn. It still carries the load and mechanically is in sound condition.
Most propane fuel systems have two regulators; one high pressure regulator on the tank, which takes the variable tank pressure and steps it down to about 10 PSI, and the vaporizor which steps the pressure down to a few ounces per square inch (or inches water column) and adds air creating propane gas for the generator to burn.
High pressure propane tank regulator
It is important that the vaporizer be mounted above the snow line and that there is a little screen on the air intake, otherwise mud wasps will build a nest in the air intake and the next time the generator is required to run, it won’t start.
Low pressure propane regulator/vaporizer
Fuel piping is also a concern, if the low pressure lines are not large enough to handle the required BTU, the generator will run lean, creating the same problems of an improperly sized tank. Different piping has different capacities, see the following charts:
Propane Schedule 40 steel pipe sizing diagram
Propane copper-K pipe sizing diagram
Assumes pressure less than 1.5 PSI, one MBTU is equal to 1,000 BTU per hour.
Once the generator is installed, maintenance is required. As a minimum:
- Exercise engine bi weekly for 15 minutes. Propane generators do not need to run under load.
- Check fuel, oil, and antifreeze levels monthly, more often if heavy use.
- Change the oil, oil filter, air filter, check antifreeze freeze point, battery electrolyte specific gravity yearly
- Change out belts and hoses as needed, pay close attention to the block heater hose, this is where leaks often develop
- Clean out mice nests and droppings as needed
Mice love generators.