Contributed by Tom Pierson
On several follow-up trips to my church’s sites in the Yucatan, I kept noticing that the hot terminal on the RO receptacle was burnt and causing a poor connection, necessitating replacement. The older higher pressure membrane RO’s (160 PSI) draw over 18 amps @ 120 volts running and surge to three to four times this when starting. This switched receptacle is rated at 15 amps. During start-up arching occurs on the hot terminal, and over time will create a poor connection and reduce RO performance. See photo below.
One solution is to replace this male/female connection with a twist lock male plug and matching receptacle. The example below is a male 20 amp (220 volt) plug, commonly used on small emergency generators and available at home centers for about $30.
Another solution is to replace the existing plug and receptacle with a hard-wire 30-50 amp HVAC non-fused service disconnect box. You can find an example by looking on the outside wall of your house near your air conditioning compressor. This will give you the ability to quickly disconnect the RO for service and provide you good screw type connections between the Romex feed wire and the flexible service cord going to the unit. There are several styles of disconnect boxes, including the pull type, shown below, the old style side lever and one that appears to have a double breaker, which is actually just an on/off double pole switch. The pull type costs $10-$12.
Service disconnect boxes are easy to wire for either a 110 volt or 220 volt RO. Make sure you make the flexible cord is long enough so the RO can be moved away from the wall for easy service access, once the unions are disconnected. The flexible cord could also be attached to the box with a special type strain connector, instead of a Romex clamp, to avoid accidentally pulling the wires loose. A simple trick is to also make your ground wire length shorter than the hot and neutral wires, to take the initial strain of accidental pull.
The 110 volt box is shown below.
The 220 volt box is shown below.
Pre-Wired Yucatan Ready Disconnect Box