Electronics + motor on same breaker ... ?

[Blake Patterson]

I have just finished a basement room that has 3 outlets fed by one line from the breaker in the fuse box. I have a sump pump plugged into one of the outlets and the rest will be computer hardware. All computer hardware will be on fairly high quality APC surge protectors. When the sump pump kicks on for its few seconds, I can detect a slight dimming of the lights - but then there is a light dimming when the heat or AC kicks on, and its on a separate breaker...

What I'm wondering is whether or not there is danger to the computers in having them on the same breaker as the sump pump. It's not easy for me to set it otherwise. I've not tripped the breaker in this setup as yet.

And as a side note - I have 6-7 lights in the room (lots of light!) using lots of low-wattage (40 watt maybe) bulbs - do they draw much power as far as going towards tripping the breaker for the room?

Thanks.

bp

[SQLit]

If you have or can borrow a min/max VOM (volt ohm meter) plug it in at the computer and record the low then the high voltage. Voltage should never go below 115 v ac. Surge protectors usually do nothing for voltage dips, (lights dimming). Check all the connections in the panel (main circuit breaker off, first). IMO if tightening does not help then it is time to consider running another circuit for your computers. Basements typically do not have a lot of circuits because a lot are improved after the original construction Another suggestion is to get a UPS and power up the processor, you do not care if the screen dims but the processor could lose information on a voltage dip. Printers do not need to be on the UPS either. UPS's are typically you get what you pay for. Small units

[trebor4258]

When the pump (or any of the other things with a significantly sized motor in them) kicks on, you may or may not read a measurable voltage drop with a DVM. It'll be pretty fast, and DVMs are notoriously slow. I think that it is the inductance of the load that you're seeing. The instant it powers up, it looks like a dead short to the line so you probably do get a voltage drop and some funny phase effects between voltage and current. (IIRC if the load is inductive, then voltage leads current and if the load is capacitive current leads voltage.)

The surge protector isn't going to do anything about or for this. Most of them are just MOVs designed to short to ground if a relatively high voltage spike comes down the line.

Also, most breakers trip on much longer over-current conditions, so you're probably never going to see that happen unless the pump fries.

If it's bad enough to even threaten your computer gear, you might fix it by spending a few bucks. I've seen rather large capacitors that are made to go along side motors to provide them with the initial "kick" that they need and to prevent any problems from the momentary phase shift. (That may only work for DC motors, and if that's the case, then I'm way out of bounds.)

Off the top of my head, I can't recall a manufacturer, but maybe someone else can provide that info.

If your computer gear is really critical and/or expensive, consider a UPS and you might want to replace some of the lights with CFs (equal light rating and less power consumption).

trebor

[I-zheet M'drurz]

(snipped)

You've got some good explainations and some mixed advice so far.

Yes, you're seeing a temporary voltage drop caused by the startup and continuous draw of the sump pump. Is it harmful? Not likely, if it hasn't caused your computer gear to reboot as of yet.

I tend to agree with anyone who says get a simple (cheap) UPS and use it for one of those surge-protected power strips and plug all of your CPU boxes into there. No monitors, no printers, etc. And yes, get one that always runs off the batteries (not the *real* cheap ones).

Beyond that, as things stand now, there's no need to add extra circuits (you told us that's not something you can easily do) and there is absolutely no reason to change your lighting. 7*40W = 280 Watts = ~2.3A which isn't going to drop a whole lot if you replac them with 7*15W flourescents. (105W, ~.9A) The difference of 1.5A is not the problem, it's the 10A+ that the sump pump is probably drawing.

Leave your bulbs alone, put away the Yellow Pages, and get ye to BestBuy, WalMart, etc for a UPS. JMHO, of course.

[Joseph Meehan]

Let's just say, I would not have my computer on the same circuit as a sump pump. It is just not that hard or expensive to add a good circuit.

My computer is on it's own circuit. I might add I also have a UPS on it.

[mark Ransley]

A UPS will may well see the voltage drop from the pump as a failure in line voltage. It would be hard long term on the ups.

[I-zheet M'drurz]

But we don't know that. He did mention that adding a new circuit wasn't a god option (can't remember exact words, sorry) who knows, maybe it's a finished basement and the computer area is totally on the other side of the room from the panel?

A good UPS takes the line voltage fluctuations (big and little, miliseconds to minutes) out of the picture. I still say that's all he needs for his situation.