2005 version of 680.74

[ryan_618]

From the 2005:

680.74 Bonding. All metal piping systems and all grounded metal parts in contact
with the circulating water shall be bonded together using a copper bonding
jumper, insulated, covered, or bare, not smaller than 8 AWG solid.

As I'm sure you will notice, this is a substantial cahnge in wording from the 2002 NEC, which specifically references the motor. I am having a bit of a difficult time fully understanding the ROC comment of the submiiter. I have never claimed to be the expert on voltage gradients, but reading the substantiation, it seems as though UL (and the CMP) are of the opinion that a motor (double insulatd or not) will not create a voltage gradient.

Could someone clarify for me whether the motor is to be bonded under the 2005? Here is the ROC substantiation:

Recommendation: The Panel Statement regarding the rejection of proposal
17-152 indicated they believed a double insulated whirlpool bath pump provided
an increased level of safety. Although this is the case for above ground
storable and non-storable swimming pool pumps, I believe it is not the case
with whirlpool baths utilizing double insulated pumps. The pump designs and
their installations are different.
Whirlpool bath pumps are not accessible by the bathtub occupants and are
required by UL 1795 to have their live parts above the mounting service in the
event of a leak. They are also required to have their internal metal parts that
might become energized in a failure (the motor shaft in particular) isolated
from the water. An internal failure of the motor would not produce the same
hazards as an outdoor storable pool unit that is accessible and may have wet
surfaces. The grounding of internal dead metal parts, therefore, is not needed.
Due to the requirements on the double insulated bathtub pumps and their
mounting in UL 1795, the text from 680.74, ?and providing a means for
grounding internal nonaccessible, non-current carrying metal parts? should,
therefore, be deleted.
Substantiation: Present text requires substantial modification of the pump
motor without an overall increase in the safety of the complete whirlpool bath.
Panel Meeting Action: Accept in Principle

And the panel statement:

Panel Statement: The need for bonding in a bathroom differs from the need
for bonding in a pool area. Electrical equipment of a hydromassage bathtub is
not accessible to users of the tub. Only parts that can cause a voltage gradient
in the bathtub need to be bonded. Section 680.74 has been concisely reworded
to require the bonding of only the parts that present a risk of creating voltage
gradients in the hydromassage bathtub. The panelʼs action on 17-183 supersedes
the panelʼs action on ROP 17-153.
Number Eligible to Vote: 10
Ballot Results: Affirmative: 10

 

[bphgravity]

Re: 2005 version of 680.74

It appears to me that according to the UL "NCHX.GuideInfo" a pump motor assoicated with hydromassage bathtubs has its internal metal parts isolated from the water that is circulating within it. It also apears that this is required regardless if the pump is Double-Insulated or not. Therefore, even if the motor is provide with a means of grounding with an EGC, there is no possibility of a voltage potential being created between the motor and the water, and therefore no bonding would be required. Only parts in contact with the water or accesible to the tub users would be. Right?

 

[iwire]

Re: 2005 version of 680.74

Ryan I would say no, you are not bonding the motor for a whirlpool tub under the 2005.

The motor is not in contact with the circulating water.

 

[ryan_618]

Re: 2005 version of 680.74

Well, thats what I'm reading too. When I went to a code update class (2005) this was went over VERY quickly, and I don't think anyone really noticed or thought about the text.

I fired off an E-mail to a friend of mine with UL who will be looking up the 1795 standard and give me his opinion (an opinion that I think very highly of, BTW), and I'll see what he has to say as well.

If this is the case, this is pretty big change, considering that the typical bonding is from the motor to the pipe. Now without the motor, there is nothing to bond!!!

 

[dana1028]

Re: 2005 version of 680.74

This is a follow-up to Ryan's effort to get some feedback from his UL contact.


Topic: 680.74 - 2005 NEC
dana1028
Member # 24 posted December 17, 2004 06:22 AM
Ryan - back in Sept. you posted a comment in the Mike Holt forum indicating you would speak about this matter with a friend of yours at UL. Have you heard any more on this subject or a reply from your UL friend?

David Newton


ryan_618
posted December 17, 2004 06:32 AM

Hi David. I spoke with Mark Ode via E-mail on this. This was the question I asked him:

quote:My question is regarding the new language of 680.74 in the 2005 NEC. In my opinion, the 2002 requirement for bonding a hydromassage tub was pretty straightforward, and it specifically addressed the tub motor. In the 2005 it no longer does. I read the ROP and ROC and I believe I understand the change, but I am so surprised by it that I am doubting myself! The way I read it, is that only ??all grounded metal parts in contact
with the circulating water shall be bonded together?.?. Since the UL standard that governs these motors doesn?t allow any metal parts of the motor to touch the water, under normal or fault conditions, it seems to me that you would never have to bond the motor, even if it is not double insulated. Is this the way you are reading it as well?

And his response was:

quote:I think you are reading it correctly. There have been double insulated pump motors with internal components that were not movable but must be connected to an equipment grounding conductor that was installed as a part of the cord supplying the motor. Internal metal nonmovable parts were then connected to the equipment grounding conductors. Some pump motor manufacturers were still supplying a three conductor cord to double insulated pump motors but were not connecting the equipment grounding conductor to anything inside but simply floating it inside. We have been discouraging this since a double insulated motor with no metal parts does not need this three conductor cord. Any metal part that could be energized and in contact with the water must still be connected to an EGC even for a doulbe insulated motor.

Relating to the Panel 17 action, I wholeheartedly agree that a double insulated motor must not be bonded since trying to bond it would result in defeating the double insulation on the motor. All other circulating motors in a hydromassage bathtub are connected using a nonmetallic piping system, and again, the possible leakage to the water of any current affecting the user would be almost impossible.
Mark

--------------------
Ryan Jackson, Salt Lake City
Inspector, Instructor


Just thought I'd provide this feedback as this has been a point of contention for quite some time.

For what it's worth: My information on the subject indicated that it never was the intent of the NEC to require bonding to the hot/cold water pipes that supply hydromassage tubs. The original intent was to require the one and only manufacturer who produced these tubs with metal piping for the circulating system [vs. plastic recirc piping] to bond their pipes.

 

[electricmanscott]

Re: 2005 version of 680.74

This is interesting. The copper pipes that supply the water are not actually in contact with the circulating water. So it seems that there won't be the need to bond anything on these anymore.