Generator Control Wiring

[mkgrady]

I'm wiring up a Generac 20 KW. The fourth one in the last month. Every one of them has had a very long run to the ATS and much of it is outside the house. The runs have been about 100 feet long with lots of changes in direction. Conduit and multiple JB's would be way too much work so I have been running #1 Aluminim SER for the power and switching over to copper in a JB with Carflex and #3 copper for the final connection.

The control wiring consists of three low voltage (12 volts) wires and three line voltage wires for voltage sensing of the normal and generator power. The minimum size wire is #18. I have been running 18-3 sunlight/weather resistant for the low voltage and 14-3 UF for the line voltage. I have run these cables to a WP JB and switched over to 1/2" with THHN and carflex for the last few feet The cost of the UF and running a seperate 18-3 seems like more work and cost than it should be.

If the runs were much shorter I would run conduit for everything. The changeover from AL to CU would be eliminated and I could run all the control wires in one conduit (6 # 18 thhn in 1/2 inch). I'm looking for suggestions on how to combine the control wiring into one cable. As far as I know I can't buy 18-6 UF cable. Is there anything I'm missing?

 

[infinity]

What is the Class of the 12v, low voltage wiring? If it's Class 2 it must be seperate from the line voltage conductors so a hybrid cable or single raceway won't help much.

 

[hillbilly1]

Has Generac changed their control scheme? The last 20 kw I hooked up has been a few years ago, but they had only two 12 Vdc wires to control the transfer switch, two 240 volt wires for utility sense, and two 240 volt wires for the charger. You had to do a separate 120 volt circuit for the block heater. Onan uses three 12 volt wires from the generator to the transfer switch to power the switch electronics and start function, Generac must be doing the same thing now.

 

[mkgrady]

What is the Class of the 12v, low voltage wiring? If it's Class 2 it must be seperate from the line voltage conductors so a hybrid cable or single raceway won't help much.

I don't know the class of the 12v wires and I'm not sure how to figure it out. The instructions (Generac) show all the controls wires in the same conduit and they specifically say to keep them seperate from the generator output wires.

 

[mkgrady]

Has Generac changed their control scheme? The last 20 kw I hooked up has been a few years ago, but they had only two 12 Vdc wires to control the transfer switch, two 240 volt wires for utility sense, and two 240 volt wires for the charger. You had to do a separate 120 volt circuit for the block heater. Onan uses three 12 volt wires from the generator to the transfer switch to power the switch electronics and start function, Generac must be doing the same thing now.

Yes the control scheme is different in the new models. Not sure when they made the switch.

 

[ceb58]

Has Generac changed their control scheme? The last 20 kw I hooked up has been a few years ago, but they had only two 12 Vdc wires to control the transfer switch, two 240 volt wires for utility sense, and two 240 volt wires for the charger. You had to do a separate 120 volt circuit for the block heater. Onan uses three 12 volt wires from the generator to the transfer switch to power the switch electronics and start function, Generac must be doing the same thing now.

They are using n1 n2 as the utility sensing and the other is T1 it is the ungrounded wire for the batt. charger you pick up the neutral in the generator to complete the circuit

I don't know the class of the 12v wires and I'm not sure how to figure it out. The instructions (Generac) show all the controls wires in the same conduit and they specifically say to keep them seperate from the generator output wires.

Most of Generac's instructions state if you go over the 30ft factory whip or do not use it then they must be separated. As long as the insulation rating is over the voltage being produced then they can go in the same conduit. I know that you must follow the Mfg's instructions but there is no real reason the wiring must be separated. The control wires are running 240v utility voltage. If utility drops out a set of contacts close and the gen. starts. The ATS and gen are not "talking" to each other so EMFs wouldn't bother any thing.

 

[jim dungar]

I know that you must follow the Mfg's instructions but there is no real reason the wiring must be separated. The control wires are running 240v utility voltage.

On long runs, there may be a problem with capacitive coupling between the conductors, resulting in 'incorrect signals' to the sensing equipment.

 

[mkgrady]

They are using n1 n2 as the utility sensing and the other is T1 it is the ungrounded wire for the batt. charger you pick up the neutral in the generator to complete the circuit



Most of Generac's instructions state if you go over the 30ft factory whip or do not use it then they must be separated. As long as the insulation rating is over the voltage being produced then they can go in the same conduit. I know that you must follow the Mfg's instructions but there is no real reason the wiring must be separated. The control wires are running 240v utility voltage. If utility drops out a set of contacts close and the gen. starts. The ATS and gen are not "talking" to each other so EMFs wouldn't bother any thing.

These generators have not been supplied with a factory whip. The runs from the gen to the ATS is about 100 feet.

I don't think I am going to find a cable that has 5-#18 rated for 240 volts and suitable for outdoor installation. If I could I would save a lot of time and expense

 

[mkgrady]

On long runs, there may be a problem with capacitive coupling between the conductors, resulting in 'incorrect signals' to the sensing equipment.

I know next to nothing about capacitive coupling but is it likely in this case? I assume the control wires in question carry next to nothing in actual current. CEB's post above describes what each wire is used for.

 

[electricmanscott]

I've been running two 14/3's for the control wiring. To a jbox with nonmetallic liquid tight and from there to the gen.

 

[jim dungar]

I know next to nothing about capacitive coupling but is it likely in this case? I assume the control wires in question carry next to nothing in actual current.

Actually devices that require realtively low current are susceptable to capacitive coupling, which is why most communication and many signal cables are twisted.

 

[ceb58]

These generators have not been supplied with a factory whip. The runs from the gen to the ATS is about 100 feet.

I don't think I am going to find a cable that has 5-#18 rated for 240 volts and suitable for outdoor installation. If I could I would save a lot of time and expense

OH, you can find it. Its the $1.50 or more per ft thats the killer.

 

[mkgrady]

OH, you can find it. Its the $1.50 or more per ft thats the killer.

I should have said 18-6. What would this cable be called? I'd like to get a price on it just to see how much I would actually pay for it. I don't think I can buy 18-6 UF cable.

 

[ceb58]

I should have said 18-6. What would this cable be called? I'd like to get a price on it just to see how much I would actually pay for it. I don't think I can buy 18-6 UF cable.

I use and only because it is what is specked. 18 ga stranded, 8pr, individually shielded, direct bury cable. I do not run 240 volts in it but I think it is rated for 300v like SJ cord. Our price is something like $1.20 per ft if I buy it in 1000ft spools.

 

[hurk27]

The last couple I installed was the Nexus models, and have 5 class 1 conductors for control and battery charging (if you locate the battery charger in the transfer switch which they provide the components to do this with)

N1 = L1 utility sense
N2 = L2 utility sense

0 = battery negative and is grounded in the generator panel to the ground block and is not needed if you don't mount the battery charger in the transfer switch
194/15B = battery positive, and positive for charger when mounting in transfer switch
23 transfer signal to transfer to generator after time delay, return of utility power will transfer back from signal received at transfer switch.

The kit to install the charger in the transfer switch comprises of a male spade terminal to mount on the neutral block with a self tapping screw provided, a male spade terminal that goes on the utility side of the transfer switch again with an included self tapping screw, a fuse block with a 2 amp fuse matching the two installed fuse blocks, and a jumper to go from the terminal you install on the transfer switch load side, and this fuse block, to which the charger connects to and the terminal on the neutral block you installed, the output side of the charger connects to the negative- 0 terminal, and the positive to the 194/15B terminal, this leave 5 control wires to run between the generator and the transfer switch, which I don't see a problem with using a direct burial listed tray cable, but again cost might be a factor, Generac told me that over a 60' run I should use at least a 16 awg for these control conductors and 14 awg after 100' while I have not as of yet used a DB cable for installation as I use PVC for most, I have always ran two conduits, a 1/2" for control, and 1 1/2" for the generator supply. N1 and N2 was always in with the controls as there is very little current on them and they are protected by a 2 amp fast blow glass fuse in the transfer switch.

The reason the battery charger has to be fed from the load side of the transfer switch is because on the non-water cooled generators, (20kw and below) there is no charger on the motor to charge the battery while the generator is running, and if a long term outage happens the battery can go dead causing the generator to die. water cooled units has a 30 amp alternator on the motor. older Generics had a charger built on the main board that would charge the battery while the generator was running but nothing to maintain the battery while standing by from the utility, well that didn't work, so they started supplying a cheap trickle charger that was fine if you used a maintenance type battery that you could add water to, but most would install a maintenance free battery and the trickle charger would just burn the water out of it, because they didn't shut off when the battery was charged, so after many complaints they now use a float charger, that shuts off when the battery is charged.

This is also why it is easier to mount the float charger at the transfer switch because it saves running a 120 volt circuit to the generator.

 

[mkgrady]

The Generac generators and ATS instructions were silent on where the battery charger is located. I hope that is typical because I did not install a charger and I sure hope there is one in the ATS or the Gen. The ATS is a RTSX200A3. I'm installing them for a plumber that found the customers and hired me to wire them. If the batteries go dead he gets the call but I do wonder where that float charger is.

 

[Dennis Alwon]

Call generac and ask what the class wiring is for the control cir. It is probably written on the transformer or the controls that they connect to. Many are class II and thus should be separated from the power.

 

[hurk27]

The Generac generators and ATS instructions were silent on where the battery charger is located. I hope that is typical because I did not install a charger and I sure hope there is one in the ATS or the Gen. The ATS is a RTSX200A3. I'm installing them for a plumber that found the customers and hired me to wire them. If the batteries go dead he gets the call but I do wonder where that float charger is.

I went to Generac's web site, and pulled up the spect sheet on the Gardian 20kw, and your right, it looks like they put it back into the Nexus control board, looks like it is fed from the N1 and N2 utility sense feed from the transfer switch. they are for ever changing their system:roll: wonder how they are charging the battery with the generator running? maybe a relay that switchs the supply to the generator when it's running? could be done just don't know why they didn't think of this before.

As you can tell I'm not fond of Generac after they went to dealer for parts, they wont even allow you to talk to their tech deparment if you have a question, I cant even get a tune up kit or filters unless I'm a dealer or a tech for them, and to become one they want you to stock a whole bunch of parts you may never use, sorry don't have that kind of money, so now if a customer buy's one I'll install it, but I spell it out service or repairs to be done by others.

 

[hurk27]

Call generac and ask what the class wiring is for the control cir. It is probably written on the transformer or the controls that they connect to. Many are class II and thus should be separated from the power.

thats the problem, no transformer, 12 volt starting battery for the 12 volt controls with a 7 amp fuse in the control panel front, and the N1 and N2 utility sense is supplied from two 2 amp fuses in the transfer switch, yes 120 volts to ground, and 240 volts between, but they got (somehow) a UL listing on there instructions that allow the N1 and N2 in the same conduit with the 12 volt DC control

 

[dclauria]

I did a 20kw Generac install last summer with similar difficult installation - through the basement and underground for a ways. I had a piece of leftover underground lift pump wire - I think it had six #12 THHN wires. The lift pumps on some houses we do come with a 100' whip - we cut off the extra and keep it for a rainy day. Just a thought.

I also wondered about the need to separate the conductors. The Kohler 10kW HD generator I hooked up today showed 2 separate conduits but specified 18ga twisted pair 300V wire. Why?? I couldn't find anything like that.