Uncertainty regarding retention specs for U Ground Type receptacles

CSA's Standard C22.2 No.42-99.

Entitled: General Use Receptacles, Attachment Plugs and Similar Wiring Devices.

Paraphrasing CSA's Standard C22.2 No.42-99. It includes Clause 7.7.6 that stipulates that standard receptacles and connectors (Not Hospital Grade) that are not going to be tested as per clause 7.16.3 (Hospital Grade) shall be capable of withstanding for 1 min a force of 1.1 N or (112.1688 grams) applied to the test blade normal to the face of the specimen and in a direction that tends to remove the test blade.

With reference to this CSA Standard, clause 7.7.6, we can then generalize that using CSA standardized test pin (See Figure 10 below), which is inserted into the ground contact of a receptacle that is facing towards the floor and the weight of this test pin (113 grams) or 4.0 Oz with the help of gravity would not dislodge itself from the face of the receptacle more than 1.0 mm unless it has to be tested as per clause 7.16.3 if it's a Hospital Grade Device.

That is the standard method used by CSA & UL to test if the ground contacts have a minimum contact retention of 4.0 Oz or 113 Grams or 1.1 Newton's. This test is achieved by letting the static weight of the test pin withdraw itself from the ground contact.

Most manufacturer's receptacles are engineered to exceed this minimum value and maintain this value after years of abuse in the real world.

If the retention of all 3 blades were too high, it would require high forces to insert a plug into new receptacles and it would also be impractical to remove plugs from receptacles.

Some new types of standard receptacles now incorporate a Stainless Steel spring to help preserve the retention of ground pins subjected to everyday abuse. (See photo)

This spring is external to the contacts and wraps the sides of the ground contacts thus preventing undue stress to the contacts by keeping the contacts in a closed position at all times. Ground continuity and retention are maintained under severe use.

I would like to explain what additional tests are required by CSA in order to meet Hospital Grade Classification.

Paraphrasing CSA's Standard C22.2 No-42-99 it also has a specific test for Hospital Grade Devices.

Clause 7.16.3 Grounding Pin Retention - Hospital-Grade Receptacles and Cord Connectors

7.16.3.1
The ability of the grounding contact in hospital-grade receptacles and cord connectors to withstand conditioning from an oversize-grounding pin without losing retention of a conventional grounding pin shall be determined.

7.16.3.2
Previously untested hospital-grade receptacles and cord connectors shall be tested using each outlet. Using a hardened steel pin 5.17 ± 0.01 mm in diameter, the grounding contact shall be conditioned by 20 insertions and withdrawals.

After conditioning, a 113 g (4 Oz) pin having a 4.680-± 0.006 mm diameter (see Figure 19) shall be inserted in the contact, with the force of the weight applied in a direction normal to the face of the receptacle and tending to withdraw the pin from the device.

7.16.3.3
Each receptacle shall retain for 1 min without displacement in excess of 1 mm the 113 g pin. (See Figure 19).

These are real world situations and receptacles can withstand this abuse with very little reduction in performance.

I receive many calls about a new standard that many Institutions are referencing when commissioning a new area in Hospitals etc or have being asked by Specifying Engineers if receptacles can comply to Can/CSA Z32-99 standard.

Can/CSA Z32-99: Electrical Safety and Essential Electrical Systems in Health Care Facilities

This is not a manufacturing standard or certification standard but is a guide to follow for hospitals etc in patient care areas when a new installation takes place or maintenance is performed and is also very similar to NFPA 99 -1999 in the USA.

Can/CSA Z32-99 is entitled: Building Electrical Systems in Patient Care Areas

Paraphrasing the scope if this standard, it applies only to patient care areas intended to be used in providing patient diagnosis, treatment, or care, involving intentional electrical contact of any kind between the patient and medical electrical equipment.

Paraphrasing clause 8.6.1.3 of Can/CSA Z32-99

It references the Canadian Electrical Code (CEC) Part 1 Section 24 that mentions that all 15A & 20A nonlocking receptacles in patient care areas be hospital grade and that these receptacles resist removal of a test pin and test plug as required by CSA Standard C22.2-No 42-99 by a pull of up to 1.1N (4 Oz) using a round test pin in the ground slot.

This test is not practical to perform in the field since the receptacles are usually already installed and the power may or may not be present.

The 113 Gram test pin (1.1N)/(4Oz) used in CSA C22.2 No 42-99 as referenced above is intended to displace itself by the effect of gravity when the face of the receptacle is facing the floor. It is attached to a test jig and not held in someone's hand.

Many manufacturers provide spring-loaded types of portable instruments to measure the approximate retention of the ground contacts, but the results/values or (Pass/Fail) are subject to the users method, like angle of removal and speed of withdrawal.

What is the diameter & material of the test pin? What's its finish? Does it meet the criteria's of CSA's standard test pin? What calibration process is required to maintain these conclusions? All these factors must be taken into consideration.

The results from these types of test equipment are usually only approximate (Pass/Fail)
Springs have a percentage of error or accuracy. Past history has shown that some institutions are wanting to reject (New and Old) receptacles because of ground retention issues. All questionable samples were found to exceed minimum requirements when tested.

Prior to discarding absolutely good product, please consider how and to what test method is being used to decide if the ground retention is not meeting you're expectations.

“With the permission of Canadian Standards Association, material is reproduced from CSA Standard C22.2 No 42-99, General Use Receptacles, Attachment Plugs and Similar Wiring Devices, which is copyrighted by Canadian Standards Association, 178 Rexdale Blvd., Toronto Ontario, M9W 1R3. While use of this material has been authorized, CSA shall not be responsible for the manner in which the information is presented, nor for any interpretation thereof”.