ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 16 guests, and 14 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Panel Meter Question #43414
10/12/04 09:43 PM
10/12/04 09:43 PM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
I recently installed a panel meter on a single phase load of 10 hp, 230 volt, FLA 55. My local supply house sold me a 0-75 amp meter, and 75-5 amp donut transformer. I installed these as I have a few in the past. The running load on my Fluke is 22 amps. However the meter only reads about 5 amps. The only thing I can figure is either a defect. or possibly the donut is to close to another load. Is anyone familar with these things. Thanks.

Work Gear for Electricians and the Trades
Re: Panel Meter Question #43415
10/13/04 01:51 AM
10/13/04 01:51 AM
E
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Emon-demon? Are the donuts and meter a match for eachother and calibrated? Also, the placement of the donut is crucial. If it is sitting on the side at an angle to the conductor you'll get false readings. They should be as centered and squared on the conductor, which can be hard to do in most panels.


Mark Heller
"Well - I oughta....." -Jackie Gleason
Re: Panel Meter Question #43416
10/13/04 03:18 AM
10/13/04 03:18 AM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Also,
Has the Ammeter got the correct shunt attached to it?.

Re: Panel Meter Question #43417
10/13/04 07:35 AM
10/13/04 07:35 AM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
e-57,

I don't know if they are matched, this is what my supply house sold me so I assume so. It is sitting pretty square although it is laying on top of other wires in a very crowded box.

Trumpy,

What do you mean by a shunt?

Thanks for the reply

Re: Panel Meter Question #43418
10/13/04 01:04 PM
10/13/04 01:04 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Merlin,
Quote
What do you mean by a shunt?

An ammeter only carries a very minute amount of current, compared to the amount that it may be measuring.
A shunt is a resistance that is lower than the resistance of the meter movement itself, this shunt is placed in Parallel with the meter movement.
In this way, when connected to the circuit, the majority of current is passed, or Shunted, through the Shunt resistance.
Thereby ensuring that the meter only recieves a small proportion of the total circuit current and prevents the movement being damaged.
Hope this helps. [Linked Image]

Re: Panel Meter Question #43419
10/13/04 03:08 PM
10/13/04 03:08 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
Quote
My local supply house sold me a 0-75 amp meter, and 75-5 amp donut transformer.


Check the meter carefully. Did they actually sell you a 0-75A meter, or a 0-5A meter with a 0-75A scale? You need a 5A meter for use with the CT.

Other than that, check the orientation/centering of the conductor in the CT window, and make sure all the secondary CT wiring is OK. Insert another ammeter in the CT loop, and verify how much current is being developed on the 5A side.


Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Scott35
Scott35
Anaheim, CA. USA
Posts: 2,708
Joined: October 2000
Show All Member Profiles 
Top Posters(30 Days)
Admin 20
sparky 16
Potseal 15
Popular Topics(Views)
243,583 Are you busy
180,379 Re: Forum
170,856 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.014s Queries: 14 (0.004s) Memory: 0.9754 MB (Peak: 1.1222 MB) Zlib enabled. Server Time: 2018-01-21 22:31:31 UTC