Single point ground and ECM modules

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David Goodman

Senior Member
Location
Pahrump, NV, USA
I'm new to this forum. I work in HVACR. I've been getting some great information from the HVACTalk forum for refrigeration side of things. I am here to get the same quality of information about the electrical side of HVACR. The electrical and motors topics typically have the lowest scores for NATE and other industry tests for HVACR people. So, I want to learn more in those areas.

My question concerns EMC motors and their control modules. Several HVAC people have been complaining about the control modules acting up in a variety of ways.

Could a failure to maintain a single point ground (isolated ground) cause control problems with these ECM motors, or are these control modules not electronic proportional controls and therefore aren't affected?
 

David Goodman

Senior Member
Location
Pahrump, NV, USA
I'm new to this forum. I work in HVACR. I've been getting some great information from the HVACTalk forum for refrigeration side of things. I am here to get the same quality of information about the electrical side of HVACR. The electrical and motors topics typically have the lowest scores for NATE and other industry tests for HVACR people. So, I want to learn more in those areas.

My question concerns EMC motors and their control modules. Several HVAC people have been complaining about the control modules acting up in a variety of ways.

Could a failure to maintain a single point ground (isolated ground) cause control problems with these ECM motors, or are these control modules not electronic proportional controls and therefore aren't affected?

I just reread my post. I might have thrown people off with a typo. "EMC motors" should have been ECM (electronically commutated motor)
throughout.

I'm still hoping for a response.
 

user 100

Senior Member
Location
texas
I just reread my post. I might have thrown people off with a typo. "EMC motors" should have been ECM (electronically commutated motor)
throughout.

I'm still hoping for a response.

So you're wondering if an isolated egc is necessary with these motors?

If that's the case the IEEE 1100 more or less says its a waste of time for a lot of electronic stuff, iirc.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Could a failure to maintain a single point ground (isolated ground) cause control problems with these ECM motors, or are these control modules not electronic proportional controls and therefore aren't affected?

First off, I have no idea what you mean by an "isolated" ground.

People think "better" or "more" grounds will solve all kinds of problems but the reality is they usually don't do all that much.

The code allows for receptacles to have what is referred to as isolated receptacles (250.146(D)) but all it really allows you to do is run the equipment grounding conductor (EGC) on the receptacle somewhere upstream like to the service point. I don't recall there is any provision for such a thing except via a receptacle.

A "single point" ground is about as far from being "isolated" as you can get. A single point ground is a single location, often a stud or a small copper bar where all the EGC terminate for a particular piece of equipment. There is some evidence that this can reduce certain types of electrical noise, although it is by no means a panacea.
 

David Goodman

Senior Member
Location
Pahrump, NV, USA
First off, I have no idea what you mean by an "isolated" ground.

People think "better" or "more" grounds will solve all kinds of problems but the reality is they usually don't do all that much.

The code allows for receptacles to have what is referred to as isolated receptacles (250.146(D)) but all it really allows you to do is run the equipment grounding conductor (EGC) on the receptacle somewhere upstream like to the service point. I don't recall there is any provision for such a thing except via a receptacle.

A "single point" ground is about as far from being "isolated" as you can get. A single point ground is a single location, often a stud or a small copper bar where all the EGC terminate for a particular piece of equipment. There is some evidence that this can reduce certain types of electrical noise, although it is by no means a panacea.

I was reviewing course materials from RSES on Electronic Proportional Controls. Lesson 10 covers Power Supply and Grounding practices. In that section "single point ground" and "isolated ground" are used to mean the same thing. The use of those terms confused me a bit also, and obviously still does. Eliminating either noise or electromotive potential between multiple ground points would seem to be the intent.
[h=2][/h]It is possible I need to think the question/problem through a little more before requesting help.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
....It is possible I need to think the question/problem through a little more before requesting help.
Nothing wrong with asking the question the way you did, just be prepared to get some answers you never expected around this forum.

There is so much hoodoo voodoo around grounding and bonding you can off the deep end real fast. Thing is properly wired, code compliant circuits don't need a visit from voodoo grounding high priest.
 

David Goodman

Senior Member
Location
Pahrump, NV, USA
Nothing wrong with asking the question the way you did, just be prepared to get some answers you never expected around this forum.

There is so much hoodoo voodoo around grounding and bonding you can off the deep end real fast. Thing is properly wired, code compliant circuits don't need a visit from voodoo grounding high priest.

FM interference (flip'n magic) does seem to apply at times with electrical devices.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I was reviewing course materials from RSES on Electronic Proportional Controls. Lesson 10 covers Power Supply and Grounding practices. In that section "single point ground" and "isolated ground" are used to mean the same thing. The use of those terms confused me a bit also, and obviously still does. Eliminating either noise or electromotive potential between multiple ground points would seem to be the intent.

Keep in mind also that other trades and some manufacturers and their engineers don't understand grounding so it's possible that you have been getting confusing or erroneous information. What some manufacturers require is not Code compliant and even dangerous.

-Hal
 

cuba_pete

Senior Member
Location
Washington State
Shielding

Shielding

In the gov't/military sector we refer to MIL HDBK 419A, Grounding, Bonding, and Shielding for Electronic Equipments and Facilities (and other references similar to that). We also rely on the IEEE Green and Emerald books (and current IEEE 3000 series) as a resource and reference. The IEEE books delve deep into single point, multi-point, SRG's, etc. with decent references to various studies for various environments.

The title itself sums up the concerns for engineers, electricians, and installers.

I believe that key to most issues which may relate to your question is shielding.

Some people try to make the grounding and bonding work as a means for shielding. It is important to retain the proper grounding and bonding scheme consistent with codes and AHJ requirements for the sake of personnel and property safety.

Not all equipment is tested and verified in all possible environments, so expecting a manufacturer to provide equipment which may need further protection from stray fields is expecting too much.

Applying practical shielding methods consistent with codes, rules, regulations, and common sense can be an art form in and of itself.
 

David Goodman

Senior Member
Location
Pahrump, NV, USA
In the gov't/military sector we refer to MIL HDBK 419A, Grounding, Bonding, and Shielding for Electronic Equipments and Facilities (and other references similar to that). We also rely on the IEEE Green and Emerald books (and current IEEE 3000 series) as a resource and reference. The IEEE books delve deep into single point, multi-point, SRG's, etc. with decent references to various studies for various environments.

Thank you. I'll check out those references.
 
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