nautilus

I appreciate that several exist, but like many things they don't quite do the job. For example the above calculator doesn't work in anything other than IE. I use Firefox on Ubuntu. It would be alot of hassle to get M$ windows and install IE to use something that when written correctly will work across all browsers. It also seems to me that the above calculator suffers from information wash, it gives too much detail when the basic question being asked is: "What size cable to I need to power a device of nominal N amps D metres away.

I have decided to utilise some solar priciples onboard my 70' narrowboat. That is to say when you have the ability to obtain heat do so....and store it for later use. To this end I have a 170Ltr thermal store (with 20Ltr expansion tank), This sits on the centre line close to midships. Think of this as a huge calorifier. An Aarrow becton 7 with backboiler loops into the store, in addition a Solartwin thermal solar panel also feeds this system (when finances allow a calorfier from the engine will also be added). The stove +should+ operate on a gravity feed system, but I've installed a pump to assist, with a thermostat attached to the back-boiler flow. The thermal solar panel has it's own integral PV panel 30cm x 18cm to drive a small and almost silent pump for this system so no power drain and only operates when there is sufficient energy to heat water (which can be done even on a slighty grey cloudy day.). The pump is tiny, slightly larger than a tabacco tin, and is commonly used in medical applications (so I am informed). This thermal store then provides domestic hot water (via a HEx coil from the pressurised cold feed), and also provides hot water for the rads. The thermal store can also be fitted with an electric (240v AC) heater element if required. The theory is all there, and I've seen it all work in land based installations very effectively supplying 3 and 4 bed houses. I'll let you know if things are different on a boat!

This is the figure I have used in the calculator (Opm 0.01725 / CSA mm), as the commonly accepted 'norm' on the site. If you keep the voltage constant (from a battery, for example), then your question becomes: Does temperature affect resistance of a copper wire. The answer is yes. Ergo, the temperature used as the datum point will affect the published resistance of a given conductor. Then there is the purity question of the conductor. Current is the sum effect of electrons moving through the copper wire. When the wire heats up, for example, by a torch, or higher AMBIENT temperature, it causes increasing chaos in the wire. This chaos causes the electrons to bump around more than before. Therefore, flow is with less ease. This means that the copper wire now has a higher resistance. (This is true for all metals except one! It's NOT copper! ) But by how much, you may ask. OK, most metals increase their electrical resistivity by about 0.005 Ohms per degree. Thefore a change of 5 degress can lead to a significant numerical change in the resistance, for a given length and CSA.

People may find this helpful: http://www.fridge-and-solar.net/fridgetest1.htm

Hi, I'm sure there will be more feedback, bugs etc. I would propose to wait until I have a few of these then make some alterations. But doing the watts / voltage option would seem like a good one to do. Just did the last one quickly with the basics. Having thought about it, the layout of results might be confusing therecommended cable size seems HUGE, but this is the technical answer having a voltage drop of under 0.25v, and is above the results for the users voltage drop (actual and as a %), hope it is clear these figures are the ones that are calculated on the users input, NOT based on the recommended cable size. I find it useful as I can decide what VD (voltage drop) I will accept, and then quickly play with the cable size to see what I can use. E.g I'll take upto 10% on lighting etc, but no more than 4% on critical equipment. You can temper all this with the duration of the load too, eg. Horns (not a prolonged and constant load). Is it online somewhere? Could you supply the URL. Can you just paste in the source code (I presume from the HTML page). Would be interesting to look at. I've used what seems to be the commonly accepted resistive value (at least on this forum and most other UK references). I do sometimes worry about manufacturer supplied data, as they will always tend to show the best performance results that can be legally demonstrated (inverters are a good example of this). Although it might be possible to amend the calculator (read: Without too much work) to use the resistance of the cable you have / will use.

Had a look at this one, gives the incorrect values for UK use as it bases the calculations on the converted metric sizes which are rounded and incorrect. It's prettty hard to find the metric sizes they use (with suppliers) and then you need to examine the results to round manually with your preferred margin. The tables are designed with US AWG (American Wire Guage) sizes. They also appear to use values of temperature of 25 Celcius (77 Fahrenheit), where as this 1.) Seems high and 2.) European examples use 20 Celcius as the calculation baseline.

Here's a little HTML / Javascript simple app that should do the job, copy the code into notepad, save it as 'cablesizing.html' and that should be it. Open in a browser and away you go. All normal caveats apply. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <html><head> <title>DC Cable Sizing</title><script language="JavaScript"> </script></head><body leftmargin="10" topmargin="10" alink="#ff8000" bgcolor="#ffffff" link="#008000" marginheight="10" marginwidth="10" text="#000000" vlink="#004000"><font color="Black" face="Arial" size="3"> <!-- POWERTEXT ELEMENT (3) START ------> <table border="0" cellpadding="0" cellspacing="0"><tbody><tr width="552" height="91"> <td align="center" height="91" valign="top" width="552"><table border="0" cellspacing="12"><tbody><tr><td> </td></tr> <tr height="190"><td height="190" width="35"></td><td height="190" width="54"></td><td height="190" width="1"></td><td height="190" width="70"></td><td height="190" width="100"></td><td colspan="1" rowspan="1" align="left" height="190" valign="top"> <!-- InternalHTMLElement ELEMENT (20) START ------> <table border="1" cellpadding="0" cellspacing="0" width="400"><tbody><tr width="450" height="181"> <td height="181" valign="top" width="381"><font color="#000080" face="Arial" size="1"> <script language="JavaScript"> function calcsize(form){ // var input=0; // input=form.amps.value; // alert("Hello " + input + "! Welcome..."); var CableImpedence = 0.01725 form.result.value = (form.crun.value * form.amps.value * 0.04) / ( ( form.volts[form.volts.selectedIndex].value * 5 ) / 100 ); form.voltdropresult.value = (CableImpedence / form.csa.value) * (form.amps.value * form.crun.value); form.voltdropresultpercent.value = (CableImpedence / form.csa.value) * (form.amps.value * form.crun.value) / form.volts.value * 100; } </script> </font><form name="myform"> <select name="volts" size="3"><option value="12" selected="selected">12v</option><option value="24">24v</option><option value="48">48v</option></select><font color="#000080" face="Arial" size="1"> System Voltage <br><br> <input name="amps" value="" type="text"> Amps (Watts/Voltage) <br><br> <input name="crun" value="0" type="text"> Cable run in metres: (There and back) <br><br> <input name="csa" value="0" type="text"> Cross Sectional Area of Proposed Cable <br><br> <input value="Calculate" onclick="calcsize(this.form)" type="button"> <br><br><br><br> <input name="result" value="0" type="text"> Recommended Cable Size (mm2) <br><br> <input name="voltdropresultpercent" value="0" type="text"> Voltage Drop as % <br><br> <input name="voltdropresult" value="0" type="text"> Voltage Drop </font></form></td></tr></tbody></table> </td></tr> <tr height="20"><td height="20" width="35"></td><td colspan="5" rowspan="1" align="left" height="20" valign="top"> </body></html>

Just what I was looking for! Many thanks for this post. I may try to write a little Visual Basic Application that takes the data you have and outputs various suggested results, e.g: Dia of Cable required, Voltage Drop, % utilisation of cable load capacity etc. Would anyone find this useful, if so, I'll produce and post as a freebie tool. Used at you own risk, estimate only, don't put your dog in a microware, try using some common sense type caveats will apply as usual.

The real problem in regard to grey water, is what does the pump out station do with it? many of these use septic tanks, these have calculated volumes. Too much 'water' degrades the efficiency of the system and the tank fills faster, and therefore requires more frequent emptying. It would therefore seem that a major infrastructure program would be required to deal with this. Also septic tanks use a enzyme / biological treatment system, these are affected by detergents and other chemicals that could be contained in grey water. This potentially could cause the treatment cycle to stop (in biological terms, as required bacteria and enzymes were killed by grey water chemicals). This could take upto 8 weeks to re-start. A previous poster points out all water waste is ultimately discharged into rivers and other courses, we are currently cutting out the middle man.

Hi Gary, Thanks for the post, which I unfortunately only just read as I thought I had sybscribe to the topic, but I hadn't (so I get auto notifications about replies). Here's my last to Stan Hesketh (he's been lots of help) on a private thread.

Hi John, I suppose I just see engines as a means of propulsion. I'm not really a 'look at how the flange connecting rod piston returns into the seating cavity void' kind of person. I like reliable, easy to maintain, engines. Many thanks.

I was after info on hose connections, specifically the intake (cooled water) and output hose locations for the cooling system, their locations on the engine, and where they would connect on the skin tank. Just want to confirm mine has been installed correctly. Also I would be interested in knowing what is the size (dimensions) of your skin tank, if this isn't too much trouble? Many thanks.

Hi All, I'm looking to contact anyone who has a Vetus M4.17 engine installed, and where cooling is provided via a keel cooling tank. Also (I know this is like a piece of string, and comparing apples and oranges), does anyone have any personal recommendations on an appropriate engine for a 70' narrowboat. Hope to hear from someone. Craig M.

Hi Bottle, Seems you were spot on. I've had to get in a marine surveyor to help resolve this and a number of other issues I'm having. He put the leaking down to capilliary action as the drains weren't welded the full length along the back edge of the top section. To ensure this was the case (before arranging for the proper welds to be done) I applied some plasticine in the place of weld. Low and behold, it's rained, no leaking. Thanks once again for everyones comments on this.

Hi Bottle, Thanks for taking a look again. As it has now rained again I now have new puddles, and as it was hard rain, 3 of them. It does appear to be as you say, capillary action due to the hinges. What I'm asking then, in your opinion: Is this design acceptable for an external unit? Is it reasonable that these pigeon boxes leak in this manner, from new? If seals are required should these have been supplied with the boxes, from new? Most inportantly, is it a fixable problem? Thanks for everyones help and comments on this to date.