Safe to Plug iMac Into Surge Protector That Is Attached To Three Prong Adapter?

The UPS will probably want an earth connection.

benh911f said:

I have a very old house, that has 2 prong outlets into the wall. My question is, if I plug the iMac into a surge protector, then plug the 3 pronged surge protector into the 2 prong outlet using a 3-to-2 prong adapter, is this safe?

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Human safety means layers of protection. You will be eliminating one. However, code (and common sense) says you can replace that two prong outlet with a GFCI type three prong outlet. That will 'restore' human safety.

The protector does nothing useful - as its numeric specs state. And a UPS is not a surge protector. Again, the second poster need only read its numeric specs to appreciate the obvious.

Install that (maybe $12) GFCI. It will come with a label that reads something like "No equipment ground". That stick-on label must be affixed to the new GFCI receptacle.

Likely not worth spending money on a surge protector that shunts overvoltage to ground, when the ground isn't hooked up.

An electrician might be able to update the outlet to a 3 pronged outlet, and run a ground to a rod sunk in the ground right outside the wall. (can't really use pipes anymore since repairs may have used plastic/rubber sections that break the link to ground).

If you are doing that might also update all the other outlets on that circuit and/or the breaker to a 2 pronged ungrounded GFCI installation.

You still need a connection to ground for a GFCI to work properly.

Cost of having an electrician install it depends on where you live; I've had it done in my study where I have my computer and it cost about $100 to run a new line from the circuit box in the basement. the electrician did not touch the old outlet; he simply put in a new one next to it. The house I live in was built in the 1950s and strangely the wiring goes up through the attic then down through the walls to the basement circuit box. For the electrician, it was easy to go from the study on the first floor right down to the basement then over to the circuit box. You wouldn't want to do it yourself.

benh911f said:

1) Is a GFCI able to be installed right in the place of the old plate? When I unscrew the current outlet plate, won't there still be only two inputs for a two pronged cable?

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Learn some basics.

1) One layer of human safety is provided either by that receptacle's third prong - safety ground. Or by a GFCI. GFCI obviously needs no safety ground to operate. So code permits a GFCI when a safety ground wire does not exist. And code also requires that stick-on label.

Either spend $hundreds to connect a new three wire cable back to the breaker box. Or spend $tens for a GFCI to replace the two prong receptacle. Inspect these in a hardware or big box store to understand this.

2) No earth ground can connect to any receptacle. Receptacle must have safety ground. That means it connects to the ground bar inside a breaker box - not to an earth ground rod. Receptacle ground is a safety ground; not an earth ground. Only the breaker box connects to earth ground - for human safety, transistor safety, and other reasons.

3) GFCI needs no ground to operate. To provide human safety.

4) A protector cannot shunt surges to earth via a receptacle safety ground for a long list of reasons. For example, the connection is too long (ie exceeds 10 feet) to earth. A plug-in protector also does not claim protection from destructive surges. Read its numeric specs. No protection claims.

5) You need surge protection for everything - not just a computer. Only protection that is effective for all circuits - two wire or three - is one 'whole house' protector that connects short to earth ground. Same solution is effective for all house wiring - 1930 or 2010 vintage. That means a protector that costs about $1 per appliance (compared to $tens or 100 times for plug-in protector). And connects to an earth ground that both meets and exceeds post 1990 National Electrical code.

One 'whole house' protector protects from all types of surges. One 'whole house' protector, properly earthed, means even a direct lightning strike causes no damage even to the protector.