| Author | Message | ||
| David Anderson (168.215.176.201) Rating: N/A |
I want to put 0-50 amp ammeters on each leg of my genny. I found panel mount ammeters at www.shuritemeters.com The meters had no instructions in the box. It has two 5/16" lugs on the back for wiring connections. Logic tells me that those lugs shouldn't carry 50 amp loads and the meters need current transformers. On the website, it appears that transformers are needed. I emailed Shurite, and a tech wrote me back that they do not need CT's, but he didn't give any info on hooking them up. How does one hook these up? Does one leg go to hot and the other to neutral? Should the circuits be fuse protected? What size wire? I don't like doing things without reading instructions. Any ideas??? David Anderson | ||
| Larry (208.18.102.180) Rating: N/A |
You will need to use a CT, info wth Ct will tell you the number of wraps you need for the power leg (Now this is the eary style,new stye has lugs to handle power load thru CT) the two small lugs go to amp gauge. You might want a time delay shunt relay to keep the start load inrush load down on amp meter. | ||
| Ed Jewett (Kristinsgrandpa) (67.74.15.225)
Rating: N/A |
Dave, the tech was right. You don't need CT's. One lug goes to the genset and the other goes to the main breaker at your panel. That type of ammeter is in series with the load. The genset load goes thrugh the ammeter. Hooking one to the hot wire and one to the neutral would be a dead short and might do serious damage to the genset. It would be better if you could go from the genset to the main breaker first, then thru the ammeters, but this might be hard to do if your main is in a breaker/distribution panel. If you want to monitor the load from inside the coach then you should get a CT type ammeter. since the wiring to the gauge will be significantly smaller. Size depends on distance from genset to where you want to mount the ammeters. HTH Ed. | ||
| Larry (208.18.102.230) Rating: N/A |
Never told him to do that. But would still use CT and do it right. Must not read anything about running neutral threw it. You do want the gen load don't you? My assumtion is you do want it mounted remote, but would still CT it, then you have a very safe circuit. Generators will cook the works if you don't watch what you are doing. Don't short cut here. Also a three position selector switch on the ampmeter side of the CT would let you run one ampmeter and read each leg Pending 3 legs? Or two position for 2 leg. The instrument side of the CT is very low actual current, but the shunt relay permits you to use a smaller ampmeter than inrush current might normally permit. | ||
| Larry (208.18.102.230) Rating: N/A |
Hate to keep beating the banwagon but don't use an inline unit as ED says it will be a big heat sink and a high dollar Item. Tooooooooooo dangerious. | ||
| Larry (208.18.102.230) Rating: N/A |
David, Which ampmeters are you looking at? That would be the best way to help you. Rather than going off in all different directions here. | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
David, What's the part # on these? I can tell you if they require CT or not. Parts #7503z-50 and #8503z-50 require a CT. Parts #7506z and #8506z are direct-read units and you would run the hot through it (line side to one lug, load side to the other). They have other part #'s as well for 0-50a AC meters, but I'm guessing you have one of these four. Bear in mind that NEC rules require all the hots, neutral, and ground for any given circuit to travel together wherever they go. So you will need to run all four main wires from the genny to wherever the meters are and then back to the load panel if you have the direct type. As has already been pointed out, the CT type are better choices for remote installation. Also, CT meters would allow you to use one meter and switch it among two or three different CTs -- just remember to short the unused CT's using a make-before-break type of switch. -Sean | ||
| David Anderson (168.215.176.225) Rating: N/A |
Thanks for the replies, I was considering the 8506Z. From what I read above, that isn't the way to go. CT's are a must in this application, as this will be remote mounted by my genset start switch and gauges. I don't want to run big current carrying conductors from the genny to the gauge. Sean, you appear to have the catalog. Could you or someone else tell me which 50 amp gauge and companion CT to get? It appears that Shurite had some CT's that just circle the wire, the same as my handheld amp tester. I want to measure both legs simultaneously, so I need two right???? I'm working with ATEX Electronics in San Antonio. They don't have the CT's in stock. Besides them, what type of store would carry this? Most people give you a "deer in the headlight" look when you ask for this kind of stuff. Therefore, I'm pretty much on my own in setting this up. David Anderson | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
David, Actually, I got my info from the web site you mentioned earlier. Clicking one of the links on the left brought up the appropriate catalog page. The 8503z-50 is a 5-amp full-scale meter. Since it is calibrated from 0-50amps, you will need a 50:5 CT. It doesn't matter who makes the CT, as long as it is 50:5 (that's the way it will be described in the catalog). I'm sure that Shurite will sell these to you, but you can also find them at Newark, Mouser, Allied, and probably Grainger as well. Also, they come up periodically on eBay (search on Current Transformer). The ratio described by the 50:5 designation is a turns ratio. So this would be the same as 100:10, or 10:1 for that matter. However, ammeters for use with CT's tend to run 5-amp full-scale, so the second number in the ratio is almost always a "5." You can get away with different turns ratios on the doughnut, often called the "secondary," by wrapping the current-carrying lead (the "primary") through the doughnut more than once. For example, I have a 100:5 CT, but I am using a meter that runs 10 amps full-scale, so I wrap my mains through the doughnut twice (meaning the meter will see twice the current). With a 5-amp full scale meter calibrated to 50 amps, you could use a 100:5 CT (probably easier to find than 50:5) and wrap the hot lead through it twice, just as I did. Since you want to measure two hot legs, you will need two CT's. Some people also find it useful to measure the current on the neutral as well, so that would be a third CT if you wanted to do it. You could install two meters to go with the two CT's. If you want to either save a few bucks on a second meter, or save a few square inches of real estate wherever the meters are mounted, you can get by with just one meter. To do this, you will need a DPDT switch (or a 3P3T switch in the case of three CT's) to switch the meter between the CT's. All the CT's and the meter share a common lead (which ideally should also be grounded). One pole of the switch connects the remaining lead of the meter to the other lead of the chosen CT, and the other pole(s) of the switch apply a short between the leads of the unused CT(s). This is a critical step, to avoid burning out the CT. Also, the switch must be a make-before-break (shorting) type, to ensure that there is never an open circuit between the two leads of any CT, even for a fraction of a second. If you poke around, you can find some diagrams of this type of setup on the 'net. If you can spare the bucks and the panel space, it's easier (and more informative) to just have two separate meters. Hope this helps. -Sean | ||
| David Anderson (168.215.176.218) Rating: N/A |
Sean, Great explanation, thank you. I do have an electrical engineering 101 question for dummies, however. If I have 240volt setup on my genny, and I measure the amps on phase one and phase two; example, say phase one has 25 amps and phase two has 27amps, wouldn't the neutral only carry the unbalanced portion of the load, ie, 2 amps? If that is the case, couldn't I always figure the difference of the phases to get my neutral load without a meter? Now, back to my application. Shurite meter #8503Z-50 would best fit my needs. Could you go back to the Shurite catalog page and tell me which CT would best suit my installation? I assume I will have to put a juction box on my genny wiring between my genny and panel. Or, could I just thread each number 6 wire through each CT in the panel box fed by the genny, just above the wiring lugs in the box? From the pictures in the catalog, I cannot really tell how to secure the CT to a stationary object. The CT catalog page number is: http://www.primetechnology.com/docs/shurite_docs/ShuriteCat.pdf It is page number 14 of 16. Thanks, David Anderson | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
David, The catalog does not show specific part numbers for the various CT's, it only lists the "styles." From the pictures and the specs, I personally would choose the "RCT" style, which is a doughnut-shaped style (as opposed to the bulkier square ones) that clearly has mounting ears. The catalog says this model can be had in a 50:5 ratio, which is what you want. I would ask the dealer for a 50:5 RCT and see what he says. That having been said, I'm guessing you can find cheaper 50:5 CT's elsewhere. This is a commodity item -- any 50:5 CT will work. As far as location and mounting, you can certainly put a j-box somewhere between the genset and the panel to mount the CT's, or you could just put them inside your distribution panel if there's room. If you choose the latter, make sure you maintain NEC-required clearances and maximum fill within the panel. If you get CT's with mounting ears, you would just screw them down to the panel back with sheet metal screws and position them such that the hot leads have a more-or-less straight shot from where they enter the panel, through the CT's, and to the main lugs. If you go with the somewhat cheaper (and also, usually, smaller) plain doughnuts with wire leads (I did not see these in the Shurite catalog), I recommend you go with a 100:5 CT. That way, you wrap each #6 hot in a loop through the doughnut (so the hot line wraps _around_ once, but passes _through_ twice). The stiffness of the loop of #6 will thus hold the doughnut firmly in place. Lastly, you are correct that the current on the neutral would normally be just the difference between the phase currents. Since you are using a hard-wired generator with these, that should always be true. If you were also using these for shore power, there are times when you will find that both hots of the shore line will actually be on the same phase, in which case the neutral current would be the sum of the hot currents rather than the difference. If you were to use only one meter and a switch to read the various loads, you might find it more useful, in such a situation, to monitor the neutral, as it would be reading the total consumption. -Sean | ||
| David Anderson (168.215.176.213) Rating: N/A |
I just found a good graphic illustration of current transformers at: http://www.teicontrols.com/cts.html I still haven't found a place that sells the 8503Z-50 meter and appropriate CT. I've found other brands of meters, but they are $80 and up. The Shurite meters are in the mid $20 range. David Anderson | ||
| David Anderson (168.215.176.213) Rating: N/A |
Thanks again Sean, I too felt the RCT transformer was the most appropriate. I'll keep looking. David Anderson | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
David, My Allied Electronics catalog (www.alliedelec.com) shows the Shurite meters for around $20, and donut-style CT's for around $30. I doubt you'll do much better on either the meters or the CT's except from surplus dealers or auction sites such as eBay. The Shurite direct-read meters are about the samae price as the CT-driven ones, so if the $30 apiece for the CT's is a big issue for you, you might want to rethink where the meters will mount and go for the direct-read style. If you were going to mount them on or near the distribution panel anyway, the direct-reads should not present too much of a challenge to install. -Sean | ||
| David Anderson (168.215.176.218) Rating: N/A |
I am comfortable with their prices. I want to mount the meters near my genny control panel, to be monitored with an easy glance. CT's are in order for my application. They don't seem to have the 8503Z-50 meter 50/5amp. I may call them to see if they can get it. Thanks for your help David Anderson | ||
| Larry (208.18.102.73) Rating: N/A |
Another thought to the use of CT'S is you are not running high current all over the place creating a possible fire hazard do to high current shorts. Eliminating induction and a hoist of other unwanted problems related to remote mounting amp meters. I'll back off now, good luck. | ||
| David Anderson (168.215.176.241) Rating: N/A |
I called Allied Electronics on Monday 2-2-04. They had to call Shurite to get the meter I want. 8503Z-50. That is a 5 amp meter with a 50 amp scale and requires a 50/5 CT. Allied doesn't stock the meter. Allied has the 50/5amp donut CT's (made by Fisher) in stock. So, I'm waiting to hear from Allied about special ordering the meter. I'll let you know what happens. | ||
| David Anderson (168.215.176.170) Rating: N/A |
Allied Electronics ordered the 8503Z-50 ammeters for me today. $21.31 each. The CT's are about $30 each. Everything is on its way. A sales tech named Denise helped me through this. She was really helpful. If you need anything like this, I recommend them highly. Thanks for all your help in this. It will make good archive material. http://www.alliedelec.com/Search.ASP David Anderson | ||
| David Anderson (168.215.176.207) Rating: N/A |
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| David Anderson (168.215.176.207) Rating: N/A |
Well, I finally got it all installed. I had to make a junction box for the CT's. They were 3" in diameter, pretty big. It took me about 10 hours to do all the wiring. I had to rewire my jenny from terminal to the safety switch, so everything came out and was replaced. I spent $121 for the meters and CT's, and I spent about another $60 for J box, wiring, etc. I cranked up the genny and found that I had the phases pretty well balanced. When the Trace SW2512 maxes its battery charging amps to the house batteries, it is the only time that phase gets way out of balance. I can just turn on a big load on the other phase to keep the phases within 10 amps of each other. All in all it was a lot of work to have these gauges. Probably not really important, but they look cool and professional, none the less. David Anderson | ||
| Peter Broadribb (Madbrit) (67.136.89.229)
Rating: N/A |
David, If you are trying to post an image, make sure it is under 20kb in size. Peter. |