Ask Me Help Desk - Metering a well pump

Metering a well pump

Hi all,

My brother lives in a housing complex consisting of 5 attached houses that share a huge, common backyard. Several years ago, they chipped in and hired someone to put a sprinkler system in the yard. The guy drilled a well to provide the water, and the pump was connected to the subpanel in one of the resident's basement. Since that person is getting billed for all the electricity used by what is actually a "communal" pump, the guy who installed it told them that it costs approx. $100 a year, so every summer the other 4 residents (my brother included) pay the first resident $20 each.

However, they are not very comfortable with the idea of estimating the cost at $100 a year - the one who's paying the bill is worried that it actually costs more, while the other neighbors contend that perhaps it costs less. So they would like to have some method of metering how much electricity it is actually using.

I had been thinking of unwiring it from the panel, attaching a plug to the end, and using a Kill-a-Watt device. The problem is that the pump apparently has two 15-amp breakers linked together, leading us to believe that it is a 240-volt device (there is always the possibility that it's actually two separate 120-volt circuits that are linked together due to code requirements, but that seems unlikely), and the Kill-a-Watt device is only good for 120 volts.

So our next idea was: why not get a hold of a meter socket, and an old meter from someplace (perhaps eBay), and rig the pump up to that? After all, when my brother had his basement finished as an apartment, the electrician did just that to the basement subpanel, so my brother can read the meter and bill his tenant for the electricity accordingly.

What I would do is turn off the power; disconnect the incoming wires from the pump from their breakers, and connect them to the meter socket terminals; connect another two wires from the other two meter socket terminals to the original breakers; plug in the meter; and turn the power back on. Can anybody see any flaws with that plan so far?

Now, I've been looking around a bit on eBay, and I found these two meters which look like one of them might work. The question is, how do I know if it is compatible with a particular socket? Are all four-connector sockets made with the same standard dimensions, or are there different types/sizes? i.e. would this used one or this new one work?

Or does anyone have any better ideas for measuring the amount of electricity used by the pump over the summer?

By the way, these are their priorities for whatever metering system I install:
-It should be as cheap as possible (preferrably $50 or less)
-It can even be an older, cheaper meter (i.e. harder to read, and perhaps slightly inaccurate) - the main point is to get a basic idea of the price, even if it's off by a couple of dollars.
-Although it should be installed in a safe, code-approved manner, they don't mind violating a couple of codes that are for technical reasons (i.e. codes that were established as a matter of fire safety, they care about; but not codes that are just in place to keep things uniform and standardized or whatever - for example, someone might tell me that it's illegal to place a device such as a meter downstream from the panel, but violating that would not result in a fire hazard).
-And, of course, it should work. ;)

Thanks in advance,
Moishe

I am sure the pump is 240 volts, so really should have a 2 pole breaker. You are on the right track, you need a 240 volt single phase meter.

Your plan to insert the meter just for the pump branch circuit is fine.

The meters you found are not the correct ones for residential use, they are 240 volt , but Delta, which is a 3 phase system.

Try this one:

And there is no problem with code installing a meter anywhere beyond the utility meter, just needs to be wired safely, just like anything else.

Quote:

Originally Posted by tkrussell

I am sure the pump is 240 volts, so really should have a 2 pole breaker.

As matter of fact it probably IS a 2-pole breaker, and not two separate ones connected - I did not see it myself; my brother described it over the phone as "two fifteens, with the handles connected". My reference to "two 15-amp breakers linked together" may have been a bit misleading.

Quote:

Originally Posted by tkrussell

Try this one

Thank you very much! I will bid on that one as soon as I confirm it with my brother...

What about a meter socket, though? How do I find a compatible one? Can you please recommend one on eBay that's relatively cheap?

Thanks again,
Moishe

OOps sorry forgot about that, the 125 amp meter socket you found is fine.

OK, I've placed both bids. Thank you very much!

Hey TK,

I've been outbid. Will this one work? Considering the price that the other one is up to, I'd rather bid on this one, since it's new. But will it work? And what exactly does "ringless" mean, anyway?

A cheaper, but less accurate solution would be an hour meter. Hours x volts x amps/1000 = kwh. An amp reading would be more accurate than using the name plate.

Quote:

Originally Posted by labman

A cheaper, but less accurate solution would be an hour meter. hours x volts x amps/1000 = kwh. An amp reading would be more accurate than using the name plate.

We're not trying to read the nameplate or even to find out average hourly consumption - that's what we would want to do as a last resort, but it would not be easy to calculate the price, since there is no easy way to calculate how long the sprinklers are running - there are timers (and maybe sensors) controlling them, so the pump is not necessarily running constantly, nor is it running for a known, fixed amount of time. Therefore, ideally, we would like a setup that keeps a running total of the electricity used throughout the entire summer. Then, at the end of the summer, the meter can be read, and the total cost calculated.

In the meantime, since I've been outbid on the other socket, I'm waiting for TK to tell me if this one is also good.

Cheers,
Moishe

An hour meter on the pump would give you the total hours the pump ran for the summer. From there, you could easily approximate the cost of electricity used by the pump for the summer. I guess it wouldn't give the cost of electricity for the timers, etc. but that surely can't be much.

Quote:

Originally Posted by labman

An hour meter on the pump would give you the total hours the pump ran for the summer. From there, you could easily approximate the cost of electricity used by the pump for the summer. I guess it wouldn't give the cost of electricity for the timers, etc., but that surely can't be much.

Ahhhhh... I'm sorry, I misunderstood you. I thought an hour meter allowed you to measure the pump's average current consumption over a period one hour (as opposed to the "instant" reading provided by a standard current-measuring device, which could vary over time), and then you have to multiply the result by the number of hours the pump is used.

Although I'd rather install an old-fashioned meter in this case, the hour meter sounds like a good idea for some of my other projects. Approximately how much do they cost? Where can I get them? And what brand do you recommend?

May need to do a search unless somebody else can help. They are just something I have seen, but never paid much attention to.

I'm amazed that you think that $20.00 a year is a lot to water your lawn. It's seems that you would spend more to find out the actual cost than to pay what I consider a real bargain. Why don't you, the five of you just compare electric bills. I assume the homes are pretty much the same, correct? You could certainly determine an average usage by looking at one years bills. I assume you keep records, since that $20.00 a year seems to bug you so much.

Quote:

Originally Posted by labman

May need to do a search unless somebody else can help. They are just someting I have seen, but never paid much attention to.

Something cheaper than the hour counter is a motorize clock (120V) , if you can get the one with date and month on it