A CL320 adaptor is the meter-head interface for a heavy-duty lever-bypass socket. The name is the jaw family, not the service amp rating. That is why utilities spec it on a 200 A PowerBack as well as on a 320 A can.
Lever bypass is not a 320 A-only thing. Heavy-duty clamping-jaw sockets are built from 100 A through 320 A. A plain AM or AG head does not seat in that block. The CL320 adaptor does.
What lever bypass actually is
A normal ring or ringless socket holds the meter by the cover and the spring of the jaws. To pull the meter, the service opens.
A lever-bypass socket adds a handle. In bypass, the load stays fed through a bypass path while the meter is out. On a heavy-duty can, that same handle also releases jaw tension so the meter blades can come out of clamping jaws.
Two mechanisms get called “lever.” Only one of them takes a CL320 adaptor.
| Socket | What the handle does | Adaptor |
|---|---|---|
| No bypass, ring or ringless | Nothing. Cover and jaws only | AM or AG |
| Medium-duty lever | Slides a bypass link. Jaws stay spring type | Not a CL320 callout |
| Heavy-duty clamp-jaw lever | Bypass plus jaw release | CL320 adaptor |
Milbank’s heavy-duty line is 100 A to 320 A, lever operated, jaw clamping. The lever on a U3741-style 200 A can only slides the bypass. That is medium duty. The lever on the HD and on 320 A jaw-clamping cans clamps the blades and runs the bypass. Those are the sockets a utility means when it writes CL320.
If the spec says CL320 on a 200 A PowerBack, the can in front of the crew is the heavy-duty clamp-jaw style. It is not “any handle on a 200 A socket.”
Why the name says 320
Class 320 is where this block was tooled. Deeper jaws. Bypass rotor. Jaw-release linkage. Ringless cover that has to capture the plug-in. A 200 A heavy-duty can uses that same block.
What those cans share is the block, not the amp rating.
| 200 A heavy-duty lever | 320 A lever | |
|---|---|---|
| Jaw family | Clamp jaw, jaw release | Same family |
| Bypass | Lever, visible | Lever, visible |
| Cover | Ringless, captures the plug-in | Ringless, captures the plug-in |
| What is actually 320-specific | Optional rejection clip is not on this can | Rejection clip can narrow the upper-right jaw |
| PowerBack adaptor | CL320 | CL320 |
The short tab is the 320-specific piece. The rejection clip that narrows the upper-right jaw lives on Class 320 sockets, and it is optional. A 200 A jaw is full width. The narrow blade still enters a full jaw, so one adaptor covers both.
Utilities are not asking you to put a 320 A part on a 200 A service. They are asking for the lever-bypass base. That base was tooled around the Class 320 blade.
Older Brooks and Servisavor notes say the same thing: the lever adaptor is for Class 320 sockets and for the newer 200 A lever-bypass sockets.
Who is moving to this can
The shift is away from horn bypass and toward a clamp-jaw lever, including on residential 200 A.
Central Maine Power. A residential 100 A to 200 A socket does not require a bypass. A single-handle lever is permitted, and CMP recommends it where a meter change should not drop the house. A residential 320 A socket requires a lever that locks the blades in the jaws. Non-residential self-contained sockets require a bypass. At 200 A and 320 A non-residential, that bypass has to lock the blades.
Ameren. Horn bypass is no longer allowed on permanent services after January 6, 2015. Clamp-jaw lever bypass is required on residential single-phase through 320 A, and on non-residential single-phase through 320 A. The socket they call out for a 200 A service is the heavy-duty style: Milbank HD-5 or HD-7, or Siemens / Talon HQ-5 or HQ-7. Jaw tension release. Bypass action visible.
Co-op lists. Approved lists put 200 A residential lever sockets next to the 320 A ones. Corn Belt’s list includes 200 A residential lever sockets such as the Milbank U9551 beside the 320 A cans. Same jaw problem. Different nameplate.
| Utility move | What the crew sees | Adaptor |
|---|---|---|
| CMP residential 320 A, or non-residential 200 A / 320 A | Locking lever, jaws clamp the blades | CL320 |
| CMP residential 100 A to 200 A | Lever allowed, not required | CL320 only if that can is heavy-duty clamp jaw |
| Ameren permanent service through 320 A | Horn out. HD or HQ clamp jaw | CL320 |
| 200 A lever on a co-op list | Often the same block as the 320 A can | CL320 |
Not every territory has made this switch. A ring or ringless 200 A without a clamping lever is still an AM or AG job. Read the can, not the service size.
How it sits on a PowerBack
The CL320 adaptor is used with the AM or AG metering head. It is not a third head that lands alone.
Lever-bypass can: utility installs the CL320 adaptor, then the AM or AG head on top of it. The adaptor matches the clamping jaws and the cover capture. The head is still the PowerBack interface.
| Landing | When |
|---|---|
| AM head | Ring-type socket, no clamp-jaw lever |
| AG head | Ringless, no clamp-jaw lever. Common where a utility has standardized on AG |
| CL320 adaptor, then AM or AG | Heavy-duty lever bypass, 200 A or 320 A |
A 200 A PowerBack with a CL320 callout is still a 200 A restore. The adaptor is how the head seats. It does not change the kVA or the breaker.
What to tell the crew
- Look at the handle, not the sticker amps.
- If the lever only slides a bypass link, it is medium duty. Do not force a CL320.
- If the lever releases the jaws and the cover has to capture the plug-in, use the CL320 adaptor under the AM or AG head.
- The short blade is for the optional Class 320 rejection clip. It still fits a full-width 200 A jaw.
- Bypass before the meter comes out. That is the point of the can.
FAQ
Is a CL320 adaptor only for 320 A services?
No. The name is the jaw family. It fits heavy-duty lever-bypass blocks on 200 A and 320 A sockets.
Why do we spec CL320 on a 200 A PowerBack?
Because that utility’s 200 A can uses the same clamp-jaw block as the Class 320 socket. Ameren’s 200 A callout is the Milbank HD or Talon HQ style.
Does every lever on a 200 A can need it?
No. Some 200 A levers only slide a bypass link and do not release the jaws. Those are medium duty. CL320 is for the heavy-duty clamp-jaw socket.
Does the CL320 adaptor replace the AM or AG head?
No. It goes on the lever-bypass block. The AM or AG head connects on top.
What is the short tab for?
The optional rejection clip on a Class 320 socket. A 200 A jaw is full width. The narrow blade still enters it.
Where is it made?
Shelton, Connecticut, with the PowerBack metering heads.
Product callout
Bridgeport Magnetics CL320 adaptor
Lever-bypass interface for heavy-duty clamp-jaw sockets, 200 A and 320 A. Used with the AM or AG metering head on PowerBack. Not a 320 A-only part.
Phone: (203) 954-0050
Email: [email protected]
bridgeportmagnetics.com/powerback
