Suggestions for RV panel install, long run
Greetings, everyone! I tried a forum search but could not find what I wanted. I recently purchased my 1st trailer and joined this group. I'd like to set up RV hookup on my sister's property in the ...
Forum Discussion
I would go with either copper or aluminum and oversize it to allow for voltage drop to suit your situation. UF type cable is about as economical as you can go and can be direct buried. Conduit & wire is usually more. Big cost jump from 1 to 1-1/2" conduit and you may get away with 1". Note that there is a min. code burial depth and unless you're young & strong, will need to hire someone to trench it with a backhoe. A 240' run isn't really that long and you'll often find that in CGs. HD, Lowes, etc. will have what you need. Sometimes electrical wholesalers will sell directly to the public and you can save a lot when you need a lot of stuff.
Nothing wrong with aluminum if installed properly. The ground wire doesn't need to be the same size as hot & neutrals and the NEC will give you the min. size allowed. If using conduit, max. 4 90 degree bends are allowed (or equivalent total) in a run and if more, you'll need a pullbox. Pulling 240' of wire in conduit can be a challenge. Just go UF cable!
Voltage drop should def. be considered. Check a voltage drop table. Start with the actual voltage at the house's panel under load (like in summer with AC running), not nominal 120/240 volts. Include the shore power cord length and any ups/downs at the house (not line of site distance). There is no code allowable maximum % voltage drop, it's only a recommendation and 3% what you normally want to aim for which is only 4 volts (at 120 volts). Voltage drop in a CG usually gets waay more than that, especially in the summer due to many ACs running and often in the 105-110 range.
You don't want to unnecessarily oversize the wire due to cost. Do you really want/need the full 50 amps @ 120/240 volts available? You might well be able to use smaller wire. I wouldn't allow more than a min. voltage of 105 volts which is 12.5%. An EMS or Surge Guard will automatically shut you off at 104 & 102 volts. Voltage less than 105 can lead to AC unit damage over time.
Another consideration could be voltage drop during the startup of an AC unit. An RV AC unit has a momentary inrush current of around 50-60 amps and with long wiring runs can cause ACs to struggle to start. A hard start capacitor can help that in some cases. Inrush current would be added to whatever else happens to be running in the RV at the same time.
A Hughes autoformer may be an option which will automatically boost voltage it it gets too low. Another option would be to use a step up transformer at the house to 480 volts and step down at the RV to allow smaller wire. You would want an electrician to do that, however that added cost of electrician and transformers would probably negate the benefit.
Nothing wrong with aluminum if installed properly. The ground wire doesn't need to be the same size as hot & neutrals and the NEC will give you the min. size allowed. If using conduit, max. 4 90 degree bends are allowed (or equivalent total) in a run and if more, you'll need a pullbox. Pulling 240' of wire in conduit can be a challenge. Just go UF cable!
Voltage drop should def. be considered. Check a voltage drop table. Start with the actual voltage at the house's panel under load (like in summer with AC running), not nominal 120/240 volts. Include the shore power cord length and any ups/downs at the house (not line of site distance). There is no code allowable maximum % voltage drop, it's only a recommendation and 3% what you normally want to aim for which is only 4 volts (at 120 volts). Voltage drop in a CG usually gets waay more than that, especially in the summer due to many ACs running and often in the 105-110 range.
You don't want to unnecessarily oversize the wire due to cost. Do you really want/need the full 50 amps @ 120/240 volts available? You might well be able to use smaller wire. I wouldn't allow more than a min. voltage of 105 volts which is 12.5%. An EMS or Surge Guard will automatically shut you off at 104 & 102 volts. Voltage less than 105 can lead to AC unit damage over time.
Another consideration could be voltage drop during the startup of an AC unit. An RV AC unit has a momentary inrush current of around 50-60 amps and with long wiring runs can cause ACs to struggle to start. A hard start capacitor can help that in some cases. Inrush current would be added to whatever else happens to be running in the RV at the same time.
A Hughes autoformer may be an option which will automatically boost voltage it it gets too low. Another option would be to use a step up transformer at the house to 480 volts and step down at the RV to allow smaller wire. You would want an electrician to do that, however that added cost of electrician and transformers would probably negate the benefit.
