PaulD Posted February 27, 2022 Share Posted February 27, 2022 I've got a 700m run to an electric gate and been advised by the gate company they need 6 amps and to run a 6mm armoured 3 core cable. Obviously cost of this cable length is £££, could I run 6mm for say 400m and then 2.5mm for the final 300m to reduce cost ? Yes I know this is probably a question for an electrician but any advice would be welcome. Link to comment Share on other sites More sharing options...
TonyT Posted February 27, 2022 Share Posted February 27, 2022 You will probably need 25mm2 to allow for the volt drop.. Link to comment Share on other sites More sharing options...
PeterW Posted February 27, 2022 Share Posted February 27, 2022 Ask them for the spec on the gates and ask if they do a battery backup version. I’ve seen this before and you basically run a 1A battery charger on the gates (or even solar) and then use the batteries for the grunt as they only need the power to open and close. Lots of farm gates have similar setups due to exactly this reason. 2 Link to comment Share on other sites More sharing options...
Ajn Posted February 27, 2022 Share Posted February 27, 2022 6A is a one HP motor. It must be a big gate. As has been stated the problem is voltage drop and the reguired start current if it is a 1hp motor. 25mm cable is goingto be very very expensive. Thing is, if the gate company is any good they should be aware of all this. Link to comment Share on other sites More sharing options...
PaulD Posted February 27, 2022 Author Share Posted February 27, 2022 @PeterW ... great advice thank you .... yes I've seen solar solutions for remote farm gates ... that might be a consideration ... guess it depends how the figures stack up. What cable would be required for a 1 Amp trickle charge I wonder over 700m ? Link to comment Share on other sites More sharing options...
Radian Posted February 27, 2022 Share Posted February 27, 2022 Vdrop=I * R so from these tables Resistance per metre of copper conductors at 20°C Conductor cross-sectional area (mm²) Resistance per metre run (m ohms / m) 2.5 7.41 4.0 4.61 6.0 3.08 for 2.5mm2 cable the round trip would present a resistance of 1.4*7.41 = 10.37 Ohms and a therefore a volt-drop of 6*10.37 = 62.24V ditto 4.0mm2: 1.4*4.61 = 6.45 Ohms and a therefore a volt-drop of 6*10.37 = 38.72V ditto 6.0mm2: 1.4*3.08 = 4.31 Ohms and a therefore a volt-drop of 6*4.31 = 25.87V Starting current will probably be the issue. They seem to be happy with something in the region of 200V to get the motor started but you might be able to get them to tell you the minimum voltage. You should be able to see that for a 1A charger on 2.5mm2 you'd get a volt drop of 10.37V which would be fine for a battery charger. Link to comment Share on other sites More sharing options...
JohnMo Posted February 27, 2022 Share Posted February 27, 2022 Solar powered? 1 Link to comment Share on other sites More sharing options...
Ajn Posted February 27, 2022 Share Posted February 27, 2022 5 minutes ago, PaulD said: 1 Amp trickle charge You need a lot more information from them. e.g. is that 1A at 240v (10A at 24v) or 1A into the battery which requires a lot less. Also where you run the cable has a lot to do with the load you can put on it i.e in the air, on a fence or underground. This is because the loss in the cable results in heat. You would also need a local earth at the gate. Even if the supply is PME most distribution network operators (DNOs) do not allow the export of an earth. Link to comment Share on other sites More sharing options...
PeterW Posted February 27, 2022 Share Posted February 27, 2022 These are standard off the shelf items on every major manufacturers list - it’s rare for any of the motors now to be 230v, the majority are 24v and have transformers in the control boxes. And at 700m from source I am a bit surprised they have requested a mains supply. @PaulD how are you controlling the opening from the property ..? 700m is too far for CAT5, is this being done by GPRS ..? Link to comment Share on other sites More sharing options...
Temp Posted February 27, 2022 Share Posted February 27, 2022 26 minutes ago, JohnMo said: Solar powered? +1 Google suggests there are several companies selling solar powered gate systems for farm entrances. Link to comment Share on other sites More sharing options...
joe90 Posted February 27, 2022 Share Posted February 27, 2022 I have a neighbour with solar powered gates and SIM card controlled. Link to comment Share on other sites More sharing options...
Radian Posted February 27, 2022 Share Posted February 27, 2022 (edited) 1 hour ago, joe90 said: I have a neighbour with solar powered gates and SIM card controlled. Too bad 3G about to be switched off ? LoRa is supposed to be workable to 10km (in ideal conditions) - that would be my preferred communication system. Even if the motor is 240V it could be powered by a 24V inverter connected to a 24V LifePo4 battery + charge controller + 250Wp PV module. Probably costing less than the drum of SWA. Edited February 27, 2022 by Radian Link to comment Share on other sites More sharing options...
Temp Posted February 27, 2022 Share Posted February 27, 2022 WiFi with directional aerials both ends should work. If not companies make dedicated point to point links for 1km, 3km etc. Think they would be around £150. I don't think ethernet over the mains will go that far but might be worth trying if you already had the kit. Link to comment Share on other sites More sharing options...
PaulD Posted March 1, 2022 Author Share Posted March 1, 2022 Thank you everyone for the comments and replies. I've decided to go off grid with a solar/battery powered gate and 4G intercom/camera. Thanks again ! 1 Link to comment Share on other sites More sharing options...
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