NEC 551 RV Parks - 208 volt

[tszalai]

Here's the question first and the back story below: Has anyone ever experienced an electrical/motor problem due to undervoltage (of a 230-volt motor) with an RV connected to a 208 volt RV park?

We are working in California with the authority having jurisdiction, Housing and Community Development (HCD), over RV parks. HCD does not adopt NEC 551 and instead has its own state regulations (Mike Holt - please adjust CA's safety grade downward one point :dunce. HCD does not allow the pedestals to be connected at 208 volts because of the potential to have problems with 240-volt appliances. HCD - now made aware that NEC started allowing this in 2005 - is concerned that the NFPA got this wrong and is putting RV's at risk for failure/fire due to undervoltages.

Specifically the issue would be with line-to-line appliances which will most often be the air conditioning. The issue here would be the larger rigs that have a 50-amp line-to-line connection which are newer and should be built to the 208/230 requirement; how many older rigs are there that have 50-amp line-to-line connections that are only rated at 230 volt?

The standard in CA at least is for the pedestal to have single-pole 20A and 30A receptacles, so older rigs at 30A would be 120-volt; only the 50 amp units would be 208 or 240 volt.

As NEMA 230-volt rated motors are intended to be functional at +/- 10% of voltage, the low end at 207 volts is right on the threshold and it is likely that most RV's in a park would have less than 207 volts at the pedestal with voltage drop.

I have sent HCD the 2005 NEC Handbook explanations to 551.40 noting that manufacturered RV equipment needs to be 208/230-rated.

HCD is checking with the Recreational Vehicle Industry Association and I will be checking the related NFPA/ANSI standards.


(I'm not particularly trusting of HCD's state regulations as they currently require the EGC and the grounded conductor to be bonded together to a ground rod at every RV pedestal. I've told them this is an NEC 250 violation, which they do adopt - they're essentially creating parallel neutrals... Mike - minus one more point... :slaphead


This issue is of concern for some RV parks in CA which have been 208 volts since they opened 30+ years ago without known issues, where HCD won't allow them to continue to operate at 208 volts or stay at 208 volts if they upgrade. It's a utility issue as 240-volt services are generally not available above 600 amps, so a 480 volt service must be taken and transformers used for larger parks. It's also a cost issue as three-phase 208Y/120 feeders are more cost-effecting than single-phase 240/120 feeders, and three phase 240/120 is not a good idea for distribution in the parks with the 208V stinger.

This is one of those local issues that I would appreciate hearing others' experience and/or knowledge on the subject. I was hoping to bump this to the Mike Holt (guru) directly or indirectly to at least get an opinion if the NFPA is indeed out to lunch for allowing 208 volt parks...

Thanks in advance! - Terry Szalai, P.E. - Summit Engineering in Santa Rosa, CA

 

[Npstewart]

Seeing how nobody has responded yet, I will at least reply to send this to the top of the list.

There probably wouldn't be any problem with supplying 208v to the motor homes. Most of these loads are 120v anyway. That being said, the two I have done in the past, voltage drop becomes an issue pretty quickly so I would definitely try to get the 240v service that way you have some room to breath.

As you stated, it might be a problem getting a 240V service greater then 600A, but there is nothing preventing you from doing (2) or (3) runs to the transformer and having (3) 600A mains or (6) 600A mains if need be. The last one I did, I had (2) 600A mains which fed distribution panels centred between the group of pedestals which worked out great. You wouldn't want a 1200A main anyway on something like this. Just group your mains together and have them feed 600A distribution panels, or several 400A/200A.

As for you writing the HCD and NFPA, I personally think you are spinning your wheels. Your quest will just end with a disappointing response which resigns whomever wrote it of absolutely any responsibility because chances are that nobody cares about this issue as much as you do. I have written the NFPA about the NEC in the past, and the response usually doesent take a side and will just point you in the direction (generally) of the code you were already looking at.

 

[tom baker]

Its a NEC violation to use a 208 volt motor on a 240 system

110.4 Voltages. Throughout this Code, the voltage considered
shall be that at which the circuit operates. The voltage
rating of electrical equipment shall not be less than the
nominal voltage of a circuit to which it is connected

You mentioned 230 volts, NEMA rates motors intended for 240 v systems at 230 volts and 208 at 200 volts to allow for voltage drop.

 

[tszalai]

NEC 551 RV Parks - 208 volt - reply

NEC 551 RV Parks - 208 volt - reply

Thanks, Npstewart -

Multiple mains still depends on the serving utility and ours doesn't offer large 240 volt services without large dollar penalties to the owner (special facilities).

Also - NEC 551 allows 208 for RV parks only, not mobile home parks (NEC 550).

Voltage drop is not that significantly impacted at 208 as compared to 240 and jumping up a wire size and still using three-phase feeders can still be more economical than using single-phase feeders. Usually the issue is for existing parks with existing wiring and equipment - not at all economical to change from 208 to 240...

NFPA has not been much help so far but IMHO they have already done their work with updating 551 to alllow 208 volt in 2005 NEC...

Sidebar comment - one of the NFPA committee members voted no to the 2005 change (to allow 208V in RV parks) because two legs from a 208 three-phase circuit (120 degrees between phases) won't balance like 240 single-phase (180 degrees between phases), so RV circuits that are ground-referenced to the neutral would experience more unbalanced 'tickle' voltage. Only two problems with this - just because 240 single phase can be balanced doesn't mean it will be with several RV's with single-pole loads on the same feeder - two legs from a 208 feeder may not be any less balanced... also, the neutral should not be tied to any ground per 551.54(C) so there shouldn't be any tickle voltage caused by the neutral. I'm sure there are improperly-wired RV's out there, but it shows that there is a lack of understanding of this issue...

 

[tszalai]

reply - 208V RV Parks

reply - 208V RV Parks

Its a NEC violation to use a 208 volt motor on a 240 system

110.4 Voltages. Throughout this Code, the voltage considered
shall be that at which the circuit operates. The voltage
rating of electrical equipment shall not be less than the
nominal voltage of a circuit to which it is connected

You mentioned 230 volts, NEMA rates motors intended for 240 v systems at 230 volts and 208 at 200 volts to allow for voltage drop.

Hi, Tom - not sure if you meant 230V motors on 208V system or the reverse as you stated...? The question here is regarding RV's and if many out there have 230V line-to-line appliances.

The RVIA (which appears to the be the largest national RV manufacturer organization) uses NEC and NFPA 1192 (which refers to NEC) for their standards; since NEC back in 2005 specifically allowed RV parks to be 208 volt and required that RV's be manufactured to accept 208/230 volt, I would submit that NFPA believes there is not a significant risk of RV's with 230-volt only appliances connecting to a 208 volt park... and I'm trying to show the California folks that this is indeed safe. From what I have read there are some manufacturers (i.e. Prevost) that actually provide 230-volt appliances, but most of even the large RV's have only 120-volt appliances spread across the two phases.

 

[kwired]

I am not around RV's that often, but the ones I have been around never had and 240 volt equipment installed in them, even if supplied by a 50 amp 120/240 circuit. If you supply these units with a cheater adapter for say a 30 amp 120 volt supply cord everything still works, you just can not run as much without overloading the 30 amp breaker. Many larger units with 50 amp supply cord will have two air conditioners but they are still 120 volt units. That all said, I have no problem supplying these units from a 208/120 supply because the only loads are all 120 volt anyway. Now I could be wrong and there maybe is 240 volt equipment installed in these RV's somewhere, but I have never seen it.

 

[curt swartz]

I am not around RV's that often, but the ones I have been around never had and 240 volt equipment installed in them, even if supplied by a 50 amp 120/240 circuit. If you supply these units with a cheater adapter for say a 30 amp 120 volt supply cord everything still works, you just can not run as much without overloading the 30 amp breaker. Many larger units with 50 amp supply cord will have two air conditioners but they are still 120 volt units. That all said, I have no problem supplying these units from a 208/120 supply because the only loads are all 120 volt anyway. Now I could be wrong and there maybe is 240 volt equipment installed in these RV's somewhere, but I have never seen it.

I agree. All of the motor homes I have been around are 120 volts. When you supply them with 120/240 volts you are simply supplying them with (2) 120 volt circuits.

 

[tszalai]

208V RV Parks - update

208V RV Parks - update

For any interested, I spoke with the chief electrical consultant for a national campground organization (over 500 parks), and in his experience, much less than 1% of RV's have line-to-line voltage appliances. He has worked on several 208 volt parks without issue. Hoping I can convince the CA authorities to come aboard with the rest of the country on this issue.

 

[tszalai]

CA HCD approves 208 volt on limited basis

CA HCD approves 208 volt on limited basis

Update - CA has allowed us to utilitize 208 volts on a limted basis ("alternate approval") :thumbsup: as long as a permanent label is affixed to each pedestal noting the voltage, as they are still concerned about the occasional 240 volt appliances. We will propose to use label language something like the following:

NOTICE: 208/120 VOLT PEDESTAL
Do not operate 240-volt appliances.
Contact park staff with any questions.

FYI - thank you - Terry

 

[kwired]

Update - CA has allowed us to utilitize 208 volts on a limted basis ("alternate approval") :thumbsup: as long as a permanent label is affixed to each pedestal noting the voltage, as they are still concerned about the occasional 240 volt appliances. We will propose to use label language something like the following:

NOTICE: 208/120 VOLT PEDESTAL
Do not operate 240-volt appliances.
Contact park staff with any questions.

FYI - thank you - Terry

I'd bet any occasional 240 volt appliance you may find would work just fine @ 208 volts, many of them maybe even would be rated 208/240 volts.

 

[GoldDigger]

I'd bet any occasional 240 volt appliance you may find would work just fine @ 208 volts, many of them maybe even would be rated 208/240 volts.

Which is a decision that the RV operator can make after talking with the park management to figure out what the sign meant.
As long as it keeps the state happy.

BTW, operating a 208/240V appliance is just fine according the sign. It is just 240V appliances that are cautioned against. :happyyes:

And I agree that it would be a rare 240 volt appliance which would not work just fine (although maybe slower heating) on 208 volts.
The only thing I could think of would be a purely motor appliance which runs the motor to its full load. A 240 volt trash compactor maybe? Running continuously.

 

[kwired]

Which is a decision that the RV operator can make after talking with the park management to figure out what the sign meant.
As long as it keeps the state happy.

BTW, operating a 208/240V appliance is just fine according the sign. It is just 240V appliances that are cautioned against. :happyyes:

And I agree that it would be a rare 240 volt appliance which would not work just fine (although maybe slower heating) on 208 volts.
The only thing I could think of would be a purely motor appliance which runs the motor to its full load. A 240 volt trash compactor maybe? Running continuously.

And the park attendants are going to be well knowledged in electrical theory and able to have these discussions? I would like to be a fly on the wall in most of those conversations, would be a little like hanging around big box stores and eavesdropping on customers asking the "experts" questions about their home electrical projects.:happyyes: