Generator wire, conduit and house penetration question
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Generator wire, conduit and house penetration question
My daughter and family (including mom-in-law) just moved up here (Rhode Island) from Texas, bought a house and moved in. So far so good, but there's a new reality dawning now that they consider their water is pumped in from a well, that it gets real cold here in winter, and that there will almost certainly be occasional power outages. This combined with the fact that they travel, leaving mom who is barely mobile, alone for as much as a week, makes a backup generator neccesary for peace of mind if for no other reason.
With that prelude I’ll cut to the chase:
14kw Kohler generator to be sited 25’ from house with 4 day propane supply.
Transfer switch (14 or 16 circuits, not sure which) mounted inside next to main box.
Specs state that the unit has a 70 amp breaker. I think I’ll have to use #6 THWN wire but would be happier with #8 if code permitted.
I Plan to trench and bury the wire in flexible conduit. What conduit size is adequate for three wires (#6 THWN)? Need to also bring over control wires plus 120V power for battery and heaters – my guess is that will require a separate conduit – any thoughts on that?
I’ve wired up a transfer switch before so feel OK doing it myself. A local inspector will check the project from beginning to end.
My agita is the penetration into the house through clapboard siding, having never done that before. I know it should be straightforward, but I’ve screwed up “straightforward” jobs in the past and I don’t want to butcher this one. I don’t even know what fittings to ask for at the electrical supply! I’ll just throw myself on their mercy and hope they treat me like family.
Any thoughts will be appreciated.
With that prelude I’ll cut to the chase:
14kw Kohler generator to be sited 25’ from house with 4 day propane supply.
Transfer switch (14 or 16 circuits, not sure which) mounted inside next to main box.
Specs state that the unit has a 70 amp breaker. I think I’ll have to use #6 THWN wire but would be happier with #8 if code permitted.
I Plan to trench and bury the wire in flexible conduit. What conduit size is adequate for three wires (#6 THWN)? Need to also bring over control wires plus 120V power for battery and heaters – my guess is that will require a separate conduit – any thoughts on that?
I’ve wired up a transfer switch before so feel OK doing it myself. A local inspector will check the project from beginning to end.
My agita is the penetration into the house through clapboard siding, having never done that before. I know it should be straightforward, but I’ve screwed up “straightforward” jobs in the past and I don’t want to butcher this one. I don’t even know what fittings to ask for at the electrical supply! I’ll just throw myself on their mercy and hope they treat me like family.
Any thoughts will be appreciated.
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14kw Kohler generator to be sited 25’ from house with 4 day propane supply.
Transfer switch (14 or 16 circuits, not sure which) mounted inside next to main box.
Specs state that the unit has a 70 amp breaker. I think I’ll have to use #6 THWN wire but would be happier with #8 if code permitted.
Transfer switch (14 or 16 circuits, not sure which) mounted inside next to main box.
Specs state that the unit has a 70 amp breaker. I think I’ll have to use #6 THWN wire but would be happier with #8 if code permitted.
Are you considering a transfer PANEL?
I Plan to trench and bury the wire in flexible conduit. What conduit size is adequate for three wires (#6 THWN)? Need to also bring over control wires plus 120V power for battery and heaters – my guess is that will require a separate conduit – any thoughts on that?
My agita is the penetration into the house through clapboard siding, having never done that before. I know it should be straightforward, but I’ve screwed up “straightforward” jobs in the past and I don’t want to butcher this one. I don’t even know what fittings to ask for at the electrical supply! I’ll just throw myself on their mercy and hope they treat me like family.
#3
This combined with the fact that they travel, leaving mom who is barely mobile, alone for as much as a week, makes a backup generator neccesary for peace of mind if for no other reason.
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A smaller generator would give you more run time. I run a 7 Kw auto generator and it has no problems running the well pump and all lights and outlets. But I do not have AC, heat pump, stove or dryer wired to my transfer switch.
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Thanks for responding.
The peak continuous load is unlikely to exceed 7 kw so 14 kw will provide a 100% margin. Peak transient load may come from the well pump but I haven’t checked that out yet.
Furd, you mention four wires in the power bundle. I plan to drive a ground rod next to the generator and thought that I would need to run just three wires into the house. Appreciate your advice re PVC vs. flexible conduit.
The local Propane supplier suggests a four day supply based on their ability to refuel in that span if necessary. As it is, there will be two 120 gal tanks next to the unit.
Yes there will be a transfer switch and a panel of selected circuits.
The peak continuous load is unlikely to exceed 7 kw so 14 kw will provide a 100% margin. Peak transient load may come from the well pump but I haven’t checked that out yet.
Furd, you mention four wires in the power bundle. I plan to drive a ground rod next to the generator and thought that I would need to run just three wires into the house. Appreciate your advice re PVC vs. flexible conduit.
The local Propane supplier suggests a four day supply based on their ability to refuel in that span if necessary. As it is, there will be two 120 gal tanks next to the unit.
Yes there will be a transfer switch and a panel of selected circuits.
#6
You normally don't connect the generator to a ground rod. In any event the ground rod is only for a GEC (Grounding Electrode Conductor) which handles atmospheric electrical charge buildup. The fourth wire (if used*) is the EGC (Equipment Grounding Conductor) that provides a low resistance path to clear faults (shorts) by tripping the OCPD (breaker or fuse). GEC is often not a low resistance path and can not substitute for an EGC.
*Note in the case of a generator you shouldn't use an EGC if the neutral and ground are connected at the generator.
*Note in the case of a generator you shouldn't use an EGC if the neutral and ground are connected at the generator.
#7
Have you talked to a Kohler dealer? I'm sure they can answer your questions (along with an installation manual that should come with the unit). The warranty on the Kohler unit requires that a dealer be used for installation and startup for the labor portion of the warranty to be valid. You can probably bargain for some DIY labor in the installation to help with cost.
Generac does not require dealer installation for full use of their new 5 year warranty. Their 14kw unit comes with a connection box with how to instructions to mount at the entry point when used with the packaged 14 circuit switch. Code may also require a disconnect if the generator is located at a distance from entry.
Look into the warranty issue if you want to go with Kohler.
BTW, I think you still need all 4 wires to the house, plus control wires. Grounds all need to be connected. Control wires can be in the same conduit if insulation rated at the same voltage and the manufacturers instructions permit. You really need to comply with both installation instructions from the manufacturer as well as electrical codes. You need to discuss all this with a qualified electrician.
Generac does not require dealer installation for full use of their new 5 year warranty. Their 14kw unit comes with a connection box with how to instructions to mount at the entry point when used with the packaged 14 circuit switch. Code may also require a disconnect if the generator is located at a distance from entry.
Look into the warranty issue if you want to go with Kohler.
BTW, I think you still need all 4 wires to the house, plus control wires. Grounds all need to be connected. Control wires can be in the same conduit if insulation rated at the same voltage and the manufacturers instructions permit. You really need to comply with both installation instructions from the manufacturer as well as electrical codes. You need to discuss all this with a qualified electrician.
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My 7 Kw Generac system came with an 8 circuit auto transfer switch and instructions for installation. It did require 4 wire power since it is not bonded to neutral. It also said to use a ground rod at the generator. LP consumption is 0.82 gal/hour at half load and 1.47 gal/hour at full load.
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My Generac had "INSTALLATION GUIDLINES". Even the guidelines can be vague.
exp.
Connect an approved grounding conductor to the grounding electrode terminal on the corner support and to an approved earth ground or grounding rod as specified by local regulations.
So it's your guess as to what the inspector will or will not call a manufacture requirement.
exp.
Connect an approved grounding conductor to the grounding electrode terminal on the corner support and to an approved earth ground or grounding rod as specified by local regulations.
So it's your guess as to what the inspector will or will not call a manufacture requirement.
#12
Right. That depends on what part of the sentence "as specified" refers to, likely the "or" just preceding it. "Connect" is a command as opposed to "If required by local regulations, connect...". The English language can easily be subject to various interpretations. A comma after the word support would make it clear if it were meant to be a requirement.
#13
exp.
Connect an approved grounding conductor to the grounding electrode terminal on the corner support and to an approved earth ground or grounding rod as specified by local regulations.
Connect an approved grounding conductor to the grounding electrode terminal on the corner support and to an approved earth ground or grounding rod as specified by local regulations.
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Thanks for all the help
Thanks for all your responses. They've really been helpful.
Here's where I (think) I am at this point.
- 14 kw Kohler RESA
- 200 Amp transfer switch (going with whole house service, it's what they want and it beats rewiring 16 circuits into a panel).
- Will pound in ground rod. If nothing else it will ease tension.
Still have some details to nail down:
- Use end lugs to connect #6 stranded wire? Have to buy special crimping tool that I'll probably never use again?
- Generator sited 45 feet from house - Require external disconnect? - will check with inspector. Anyone run into this?
Just sat down and listed all the stuff I need for this job and undoubtedly missed some. Intimidating.
power wire – AWG #6 – THWN-2 --- 2 black, 1 white, 1 Green (60’ each)
control wire – AWG # 14 or #12, need 150 – 250 feet (divided into 4 lengths) depends on Kohler supplied control wires – get colors to match Kohler’s colors if available
Power wire for battery/heater - THWN-2 AWG # 12 - at least 60’, maybe double
PVC (Sched. 40) pipe for power and for control (buried in trench) plus connectors
Probably five 10’ lengths each (1¼ inch for power, ½ inch for control)
PVC (Sched 80) pipe/adapters/connectors to bring wires out of trench
PVC pipe cement
Large/small flexible conduit for final run to Gen., into house and to transfer switch – about 15’ each
adapters to connect flexible conduit to Sched 80 pipe
fittings to penetrate generator housing
fittings to penetrate house
ground rod/strap/connector
wire stripper for AWG #6 stranded wire
may need end lugs for wire. If yes, need 4-8 lugs and crimping tool
200 Amp Service Cable – to go from transfer switch to main box – 10’ ?
Penetration fittings for transfer switch – supplied by Kohler???
Caution tape - required by inspector to inspect open 18" trench!
Thanks again guys.
Here's where I (think) I am at this point.
- 14 kw Kohler RESA
- 200 Amp transfer switch (going with whole house service, it's what they want and it beats rewiring 16 circuits into a panel).
- Will pound in ground rod. If nothing else it will ease tension.
Still have some details to nail down:
- Use end lugs to connect #6 stranded wire? Have to buy special crimping tool that I'll probably never use again?
- Generator sited 45 feet from house - Require external disconnect? - will check with inspector. Anyone run into this?
Just sat down and listed all the stuff I need for this job and undoubtedly missed some. Intimidating.
power wire – AWG #6 – THWN-2 --- 2 black, 1 white, 1 Green (60’ each)
control wire – AWG # 14 or #12, need 150 – 250 feet (divided into 4 lengths) depends on Kohler supplied control wires – get colors to match Kohler’s colors if available
Power wire for battery/heater - THWN-2 AWG # 12 - at least 60’, maybe double
PVC (Sched. 40) pipe for power and for control (buried in trench) plus connectors
Probably five 10’ lengths each (1¼ inch for power, ½ inch for control)
PVC (Sched 80) pipe/adapters/connectors to bring wires out of trench
PVC pipe cement
Large/small flexible conduit for final run to Gen., into house and to transfer switch – about 15’ each
adapters to connect flexible conduit to Sched 80 pipe
fittings to penetrate generator housing
fittings to penetrate house
ground rod/strap/connector
wire stripper for AWG #6 stranded wire
may need end lugs for wire. If yes, need 4-8 lugs and crimping tool
200 Amp Service Cable – to go from transfer switch to main box – 10’ ?
Penetration fittings for transfer switch – supplied by Kohler???
Caution tape - required by inspector to inspect open 18" trench!
Thanks again guys.
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A trick for installing a ground rod is to just fill a small hole with water and lift and drop the rod in that water. It worked great for me (8 foot rod). Also my control wires only needed to be 20 AWG but I used 16 AWG. Are you mounting your starter battery inside the house? Mine is mounted in the generator housing.
#16
Still have some details to nail down:
- Use end lugs to connect #6 stranded wire? Have to buy special crimping tool that I'll probably never use again?
- Use end lugs to connect #6 stranded wire? Have to buy special crimping tool that I'll probably never use again?
- Generator sited 45 feet from house - Require external disconnect? - will check with inspector. Anyone run into this?
Just sat down and listed all the stuff I need for this job and undoubtedly missed some. Intimidating.
power wire – AWG #6 – THWN-2 --- 2 black, 1 white, 1 Green (60’ each)
power wire – AWG #6 – THWN-2 --- 2 black, 1 white, 1 Green (60’ each)
control wire – AWG # 14 or #12, need 150 – 250 feet (divided into 4 lengths) depends on Kohler supplied control wires – get colors to match Kohler’s colors if available
Power wire for battery/heater - THWN-2 AWG # 12 - at least 60’, maybe double
PVC (Sched. 40) pipe for power and for control (buried in trench) plus connectors
Probably five 10’ lengths each (1¼ inch for power, ½ inch for control)
Probably five 10’ lengths each (1¼ inch for power, ½ inch for control)
Hot tips: Lay the pipe with the bells pointing toward the end where you will feed the wire in. Also, if you don't have a pull tape, feed a length of mason's twine or jet line through each run as you make it up. Finally, always upsize pipe for ease of pulling. 1/2" conduit, especially, can be a PITA to pull through.
PVC (Sched 80) pipe/adapters/connectors to bring wires out of trench
We use a female adapter or a male adapter plus a rigid coupling to transition to a rigid 90 on each pipe at the generator end, but you don't have to.
PVC pipe cement
Large/small flexible conduit for final run to Gen., into house and to transfer switch – about 15’ each
adapters to connect flexible conduit to Sched 80 pipe
adapters to connect flexible conduit to Sched 80 pipe
fittings to penetrate generator housing
fittings to penetrate house
ground rod/strap/connector
wire stripper for AWG #6 stranded wire
may need end lugs for wire. If yes, need 4-8 lugs and crimping tool
200 Amp Service Cable – to go from transfer switch to main box – 10’ ?
Penetration fittings for transfer switch – supplied by Kohler???
Caution tape - required by inspector to inspect open 18" trench!
Sounds pretty complete. Phase tape, or are you buying colored wire for the 6 AWG?
Last edited by Nashkat1; 10-06-13 at 02:25 PM.
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The hole and water trick sounds great but it won't work here in Rhode Island shale. The last time I drove one my friend and I pounded it with hand sledges for about 30 minutes.
Nashkat, really appreciate detailed response to the list! Very helpful.
The idea of using flexible conduit at the house penetration is because my plumbing skills are modest and I thought it would be better to have some play there.
The battery is in the generator housing, so the battery/heater wires will have to be pulled along with the control wires. Thought it would be easier to use single THWN wires in that case; had planned on using 1/2" PVC but will upsize if a test run is tight.
No KO's on the housing. The installation manual specifies a site for penetrations and provides a template for drilling or punching holes.
The transfer switch is going on a corner wall 1-2 feet from the main, close to where the service line comes in. I think (hope) I can reroute the service line to the TS without making any additional connections.
Don't know what I was thinking running cable back to the main. Will definitely use individual wires in conduit.
Thanks again guys. You are really a great resource.
Fred
Nashkat, really appreciate detailed response to the list! Very helpful.
The idea of using flexible conduit at the house penetration is because my plumbing skills are modest and I thought it would be better to have some play there.
The battery is in the generator housing, so the battery/heater wires will have to be pulled along with the control wires. Thought it would be easier to use single THWN wires in that case; had planned on using 1/2" PVC but will upsize if a test run is tight.
No KO's on the housing. The installation manual specifies a site for penetrations and provides a template for drilling or punching holes.
The transfer switch is going on a corner wall 1-2 feet from the main, close to where the service line comes in. I think (hope) I can reroute the service line to the TS without making any additional connections.
Don't know what I was thinking running cable back to the main. Will definitely use individual wires in conduit.
Thanks again guys. You are really a great resource.
Fred
#21
Generator sited 45 feet from house - Require external disconnect? - will check with inspector. Anyone run into this?
#22
Do we have to dig so low that the top surface of the conduit is 18" down?
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New Info (maybe just to me)
Just called a wire distributor for price per foot on THWN #6 wire. Nice guy let me know that they sell by the reel but that what I wanted was available at HD although they might not know they had it. Seems that new wire standard is THHN-2 which is rated 90 deg C both wet and dry. I was at HD and both the sign and electrical guy said that they carry only THHN so will go back and check that out tomorrow.
#25
Just called a wire distributor for price per foot on THWN #6 wire. Nice guy let me know that they sell by the reel
I was at HD and both the sign and electrical guy said that they carry only THHN so will go back and check that out tomorrow.