EEVblog Electronics Community Forum
Products => Other Equipment & Products => Topic started by: adam1213 on February 07, 2013, 11:10:32 pm
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Does anyone know if there are any power meters rated for wet environments. I am looking for something of the type that plugs into the power point then has a plug go into it. I would like to monitor the power usage of some pool pumps and chlorination. Currently I have been able to do this on parts of the day when the area is dry and only temporary. Often the area where the pump plugs in has water dripping on it.
Ideally the meter would be something like http://www.jaycar.com.au/productView.asp?ID=MS6115 (http://www.jaycar.com.au/productView.asp?ID=MS6115) but more able to stand water and more accurate. I want something that stores power usage while its turned off and later back on. (the pool pumps are run on a timer)
In case anyone is wondering the pool pumps are IP44 / IP55 rated and the power points are also rated for wet conditions are are mounted on wood off the pool water.
*IP 44 = protected against objects greater than 1mm Most wires, screws, etc, Water splashing against the enclosure from any direction shall have no harmful effect. - http://en.wikipedia.org/wiki/IP_Code. (http://en.wikipedia.org/wiki/IP_Code.)
The area gets wet through a number of ways: watering system above leaking water, rain including on days after it has stopped raining when the pool has too much water. Additionally water from the pool likely gets to this area.
I have been able to estimate the amount of power used based on the hours the pump runs / measured power but these estimates are not exact. Also if the timer gets changed / the power is run for longer the amount of power usage per quarter varies significantly.
I will likely be getting a meter put on the entire pool circuit in not too long but was wondering if any devices exists to measure the individual devices.
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Denzo tape may be your friend :-//
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denso tape -"for corrosion protection, sealing and waterproofing of metal above and below ground. Protection of pipeines, fittings, cables, tensioning members. Denso Tape is part of the Denso Petrolatum System, a multi purpose corrosion protection system for pipes and fittings." - http://www.tapesonline.com.au/denso-tape/denso-tape.html (http://www.tapesonline.com.au/denso-tape/denso-tape.html)
I like your suggestion of putting something around a power meter. Though I don't think denso tape is suited to this task.
To use that I would need a wireless power meter to be able to read the power. It would also might make it hard to change the power cord with that e.g. if the pump fails. Given denso tape is for pipes, fittings and metal I don't think I could rely on it to seal plastic to plastic.
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Shouldn't be too hard to build that really. Just a replacement and waterproof cord grip going through a plastic outdoor electrical box, then a outdoor receptacle mounted on the other side.
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Maybe something like this (http://www.littlegreenhouse.com/accessory/electrical.shtml) could help?
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Perhaps something like this http://www.elv.de/energy-master-expert-i-komplettbausatz.html (http://www.elv.de/energy-master-expert-i-komplettbausatz.html). It's in German, but I think you understand what I mean.
/stefan
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York electrical box with a clear insert, and wire it to place a standard socket inside it to plug the pump in, and a free plug to a waterproof socket outside, supply being from a cord to a plugtop. then plug any power meter that you want in it.
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Two extension leads, put the power meter where it wont get wet and then connect it with the extension leads, or just use one lead and a socket that is in the dry.
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This is totally against Australian law ect ect.. But you can make up a short extension lead around 1 to 1.5 foot long and you remove the main insulation around the cable so all you have is active, neutral and earth cable and just put an IP rated clamp meter on the active wire and it will show your power usage..
Make sure you keep the main insulation on so no exposed copper...
(http://img405.imageshack.us/img405/179/cordt.jpg)
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Two extension leads, put the power meter where it wont get wet and then connect it with the extension leads, or just use one lead and a socket that is in the dry.
I might try this at some point. Most of the area around the pool occasionally gets wet though. Though I could probably put it in a box to prevent water getting to it. Though preventing water getting to the power meter would probably require a special box. e.g. sealed on top, drainage holes and external screws
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This is totally against Australian law ect ect.. But you can make up a short extension lead around 1 to 1.5 foot long and you remove the main insulation around the cable so all you have is active, neutral and earth cable and just put an IP rated clamp meter on the active wire and it will show your power usage..
No, it will show the current usage.
Power measurement requires simultaneous measuring of voltage.
Note: A normal mean or RMS measurement is not good enough, you need to measure much faster than that on both current and voltage.
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No, it will show the current usage.
Power measurement requires simultaneous measuring of voltage.
Note: A normal mean or RMS measurement is not good enough, you need to measure much faster than that on both current and voltage.
Great point. measuring power accurately does requiring simultaneous measuring of voltage and current. Though most of the power meters which use current clamps that I have seen only measure current and do not measure the voltage at the same time. These power meters likely assume the voltage to be constant. If the power meter assumed it was 240v then it would be out by about 5% where I am.
e.g. http://www.efergy.net.au/index.php/au/products/e2v2-monitor-au.html (http://www.efergy.net.au/index.php/au/products/e2v2-monitor-au.html) only includes a current clamp with no capability to measure voltage at the same time.
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If the power meter assumed it was 240v then it would be out by about 5% where I am.
That is not correct, it can be out by many 100 percent. The problem is power factor, not all equipment draws current in phase with voltage.
You could connect a capacitor as load, it would register a current, but the actual power would be nearly 0 (For a ideal capacitor it would be exactly 0, even if it was drawing 100A).
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If the power meter assumed it was 240v then it would be out by about 5% where I am.
That is not correct, it can be out by many 100 percent. The problem is power factor, not all equipment draws current in phase with voltage.
You could connect a capacitor as load, it would register a current, but the actual power would be nearly 0 (For a ideal capacitor it would be exactly 0, even if it was drawing 100A).
Power factor is a good point. The pump motors will likely act as inductors.
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You assume voltage is 240, you can measure it. Then to see if power factor is coming into equation just see normal running amps on the motor and check to see if it's close enough
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My electrician told me that it is fine to leave a plug in power meter connected in the pool pump area as the RCD should trip if there are any issues. They also recommended checking it every few days to ensure it was not corroding. This will be a much easier solution.
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I worked in the food industry for a number of years, and have had a lot of experience with wet and electricity. If you have some sort of compressed air supply nearby you might think about a waterproof enclosure supplied with a small amount of compressed air. We used to run 480v 3phase motors under water for pumping brine. It works, but it must be monitored every now and then.....like once a week.
You could trust a GFI....but...........