Generator Install Questions

Reply

  #1  
Old 03-26-06, 05:44 PM
OSD
OSD is offline
Member
Thread Starter
Join Date: Mar 2006
Posts: 4
Generator Install Questions

I am getting ready to hardwire a military surplus 12KW diesel genset and have a few questions I wasn't able to find answers for after searching. I have a 200A meter w/service disconnects in the same box below the meter. There is a 60A to the main panel, 60A for the inside air handler unit, and 30A for the outside heat pump unit. My plan is to install a GenTran R5020 transfer panel (rated as service disconnect), replace the 3 CB in the meter box with a 150A CB, and move the 3 CB in the meter to load side of the transfer panel. I will control the load to the generator through the breakers in the main panel. Does this sound like a workable set-up? I would go with a sub panel next to the main except the meter/service disconnect is on the opposite side of the house from the main panel and the A/C CB's are service disconnects at the meter. Being in FL, I would like to have the option of running the A/C.

I have isolated the neutral in the genset so it is now unbonded or a floating neutral, correct?. This genset does not have a plug for a cable connection. Instead, there are 4 wire lugs, 3 power and 1 neutral (this genset can be configured for 120v single phase, 120/240v single phase, or 208v 3 phase). There is no provision for hook-up of a ground. There is, however, a hook-up on the frame for connection to the ground rod (not installed). Should I run my ground from the frame connection to the transfer panel? I was told that I should run the neutral from the genset to the ground bar instead of the neutral bar in the transfer switch and not worry about the ground, but this doesn't seem right.

Any help or advice will be greatly appreciated.
 
Sponsored Links
  #2  
Old 03-26-06, 07:08 PM
Banned. Rule And/Or Policy Violation
Join Date: Feb 2006
Location: North of Boston, MA.
Posts: 2,113
alot of info, Some may be trying to desifer and come up with answers. You have not been lost in the great Abbis
 
  #3  
Old 03-27-06, 03:42 PM
Member
Join Date: Mar 2006
Posts: 13
Generator Install Questions

I]I have a 200A meter w/service disconnects in the same box below the meter. There is a 60A to the main panel, 60A for the inside air handler unit, and 30A for the outside heat pump unit. My plan is to install a GenTran R5020 transfer panel (rated as service disconnect), replace the 3 CB in the meter box with a 150A CB, and move the 3 CB in the meter to load side of the transfer panel.[/I] [/COLOR]
OSD, I will be glad to help you but I am having a hard time figuring out what exactly you are trying to do with your service and breakers.
If you could include some pictures of your existing service this would help me greatly.
In regards to the neutral and ground from the genset to the transfer panel the neutral does need to be "floating" at the genset I.E. it does not connect to the frame of the genset but it does connect to the neutral bar in the transfer panel. The equipment grounding conductor would connect to the frame of the genset and to a seperate grounding bar at the transfer panel. This is based on that the transfer panel is a "feeder" from the main service.

This is where I need to know exactly what you are trying to do with your existing service and the Gentran panel.

Also you would be connecting the generators armature for 120/240 single phase. You will need 2 - hot conductors (L1 & L2), 1 - neutral (white)and 1 - equipment grounding conductor (green) from genset to transfer panel.
 
  #4  
Old 03-27-06, 05:33 PM
OSD
OSD is offline
Member
Thread Starter
Join Date: Mar 2006
Posts: 4
sruffin,

I appreciate the help. Here is a picture of my service disconnect. The meter is just above these breakers in the same enclosure. The 60A on the left is the service main feeding the distribution panel and the 30A and 60A on the right are for the heat pump. My plan is to remove the 3 breakers, put a 150A double pole breaker in their place, and put them in the transfer panel. I will then take the power leads out of the 150A to the utility side of the transfer panel, the 3 breakers will be load out to the main and heat pump, and genset will connect to generator side. The GenTran 5020R power center is rated as a service disconnect and transfer switch. The info for the power center is available here. Like I said in my first post, I will control the load on the genset from the main panel and I want to have the option of running the A/C.

As for running the wires from the generator, I don't have a problem with that. I just wanted to verify that the ground should be attached to the frame of the genset.

Thanks again.
 
  #5  
Old 03-28-06, 04:18 PM
Member
Join Date: Mar 2006
Posts: 13
Generator Install Questions

OSD, The picture and the data sheet helped me understand what you are trying to do along with your last post. What you are proposing to do will work and here are some things to consider.
1. Mounting the gentran panel besides the existing and feeding it with a 150A circuit breaker makes the transfer panel a subfed or feeder panel. The transfer panel does not have to be service entrance rated like this one is. I am not familar with gentran products but if they make another transfer panel comparable to this but not SE rated and it is cheaper then I would consider going this route if it was me. Most mfgs charge extra for SE rating.
2. The feeds coming out of your existing panel will have to be extended over to the transfer panel as you know. It appears that the existing circuit breakers are Siemens and gentrans data says that there panel is compatible with this type so there should not be an issue there. I also see that the conductors on both of the 60 amp breakers are aluminum. There is nothing wrong with using alum. conductors like this as long as they are sized and terminated properly. It appears they are sized correctly for 60 amps. What I do not like is the amount of insulation that has been stripped back where they connect to the breakers. The proper way to terminate alum. conductors is to only strip back enough insulation so bare conductor fits into lug. There should be no bare wire showing like in your picture. Also when you strip it you make sure that you do let the stripping tool (knife) dig into the conductor. Alum. is very soft compared to copper. And lastly a antioxidant compound should be applied to the bare conductor before putting it into lug. A common trade name is "no-lox" made by Ideal Industries that is available at an electrical distributor or another product equal to it.
Okay the alum. feeder wires you have now may or may not be long enough to go over to transfer panel and terminate. If too short then they have to be spliced with matching conductor size and type which opens up another can of worms.
3. Another alternative way to do this installation would be to replace your existing panel with the gentran unit. This would eliminate the 150A breaker and having to reroute the feeders over to the transfer panel. You would have to make sure that existing conductors going up through the meter to the weatherhead or rated for 200 amps and if not replace accordingly. This is probably beyond the capabilities of a DIY and should be done by a licensed electrician. But it would eliminate having two panels and not having to splice the alum. feeder cables.

Also you need to go to where the two 60 amp feeder cables terminate on other end and inspect how they were terminated. If they are like in panel they need to be reterminated properly as indicated above. The other issue about alum. conductors is that the connections need to be checked like once a year for getting loose. This happens due to when the current goes up it creates heat on the conductor and then when the current goes down the conductor cools off. Alum. contracts and expands a lot compared to copper and this is how the connections get loose. This is why you only strip back enough insulation as I describe above because when the connection gets loose it starts tracking back on the insulation when the current goes up and it will start charring the insulation and can cause a fire. This is the issue with alum. wire that you hear about. Your connections do not indicate any tracking or overheating at all from what I can see in picture.

Adding or retrofitting transfer panels or switches to residential services is not as easy as most people think it is due mainly to the way the original service equipment was installed and the particulars involved.
Good luck on your installation and I hope I have been informative and not to long winded.
 
  #6  
Old 03-28-06, 06:08 PM
OSD
OSD is offline
Member
Thread Starter
Join Date: Mar 2006
Posts: 4
Sruffin, Thanks for the help. I have been looking for something other than the gentran panel, but so far nothing I've found will handle the 3 double pole breakers. Maybe I'm just not looking in the right places. I have been looking at ways to keep the cost down, but I do like the idea of having the meter enclosure changed out eliminating the extra breaker. You've also given me plenty of other good advice regarding the existing aluminum wiring. I'm still not sure which way I will go with this, but it's good to know that at least I was in the ball park.

Thanks again. You have been a big help.
 
  #7  
Old 03-30-06, 01:06 PM
Member
Join Date: Mar 2006
Posts: 13
Generator Install Questions

OSD, Yes it is very difficult to find a transfer switch that has space for branch breakers. Most transfer switches or just that and do not have this type of provision. The feeder cables coming out of the wall are what has got you. Another alternative is to put a transfer switch only under your meter and then refeed your existing panel. This would entail moving your meter can and riser over to the left or right side if feasible based on how your service is done now. If your riser cannot be relocated due to going through roof or etc. you could take nipple and wiring from bottom of meter can to panel out, blank off top of panel and bottom of meter can. You could nipple out of side of meter can into top of transfer switch with like a LB fitting and then nipple from side of transfer switch back to existing panel. It will not be aesthetically appealing as relocating meter and riser but would work. I see in your original write up that you are installing a permanent mount 12 KW genset. I am attaching a link (http://www.eatonelectrical.com/unsecure/cms1/PA01602001E.PDF[/URL] for an automatic transfer switch from a company called Cutler-Hammer. What they have done is taken one of there type BR N3R loadcenter enclosures and installed a transfer switch mechanism with auto controls and a 200 amp main circuit breaker which makes it service entrance rated. The controls are real simple and it has an exercise timer built into it. You could have your genset rigged up to where it starts automatically on a power failure and switches over to genset power. You could control your AC load by the circuit breakers as you mentioned before. I have one of the units on my house and it works great and is simple.
Thats all I have for now.
 
  #8  
Old 03-31-06, 06:20 AM
OSD
OSD is offline
Member
Thread Starter
Join Date: Mar 2006
Posts: 4
Sruffin, Thanks for all your help. I decided not to go with an automatic setup since there are times when we are out of town for extended periods and often get short notice before leaving. The last thing I need when that happens is to have one more thing to remember to do (like shutting down an auto sw). I just found out today that an assiciate at work has a brother that is a local elect. contractor and he will do the install for material cost and a dinner at Carraba's. We are hoping to keep the cost down below $850 for everything. I will be getting with him this weekend. I think we are going to replace the meter box and use the GenTran as the sw and service ent. I wish I could move the meter to the other side of the house, but the house is wired overhead from the pole. I have found lots of things done during construction to save a penny here and there that have hampered improvements. I know next time around I will be going with a custom build.

Thanks again for everything.
 
  #9  
Old 03-31-06, 08:51 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
I'm not going to comment on the discussion of the transfer panel wiring.

However you stated that this is a 12KW genset. 12KW at 240V is a continuous load of 50A. You have also stated that your AC system requires both a 60A breaker and a 30A breaker. Depening upon the actual power handling requirements of the AC system, the genset may not be capable of running the AC system.

This is not an obvious conclusion one way or the other, because motor loads such as AC units can require breakers rated in excess of twice their normal running amps in order to provide reliable starting. You will need to examine the manuals and 'nameplates' for the equipment in question in order to determine the running amps. You will also need to determine the motor starting capability of the genset; this unit should be able to supply a couple hundred amps momentarily to start the motors; if the genset cannot supply the necessary starting current, then when the AC compressor starts it can stall the genset.

I would strongly suggest that you consider only running your main house load on the genset, and then use a small window AC to keep one room cool, rather than run your whole house central air system.

-Jon
 
  #10  
Old 03-31-06, 11:56 AM
Member
Join Date: Mar 2006
Posts: 13
Generator Install Questions

OSD, I understand your situation and agree. It sounds like you have a good plan and best of luck to you.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'