24v pure sine wave inverter.

[Tom Bell]

Upon searching for advice on this subject, google returned a few results ( old ) from this forum, so I hope this is both the correct board to post on, and an appropriate topic.

I drive an Artic. I have been using a MSW 1000w inverter that plugs into a 15amp rated 24v socket in the cab. It is able to power, sat nav, laptop, mobile phone charger, plus ( when required ) a 600watt pump ( for pumping chemicals ). As it is ageing and requiring maintenance from time to time I decided to upgrade, and managed to find a 3000W PSW inverter, which should power everything I need, without strain/overheating. I would imagine the inverter is similar to one you might use in a small solar install.

My question is that the PSW inverter has 2 + and 2 - DC inputs on the input side ( the old inverter had one of each ). Now, as my cab has 3 different ( seperately wired and fused ) 15amp sockets, would it make sense to connect one 24v socket to one + / - input, and the another 15 amp socket to the other + / - input, theoretically splitting any load required by the inverter over 2 sockets instead of it all coming out of 1 socket.

The inverter, if it helps is like this one on ebay
http://www.ebay.co.uk/itm/3000W-PUR...818?pt=LH_DefaultDomain_3&hash=item19e7fe95ea

Thanks, in advance for your help.

 

[Marvo]

Yes, looking at the pictures of your inverter I'd guess you could supply it from 2 separate inputs to spread the load. It probably wouldn't be a bad idea because if you run the thing at it's 3KW max load you'll need a 130 Amp constant 24V DC supply. I'd be careful not to overload your truck wiring if I were you, check the fuses on the 15A sockets are the correct size because melted wiring is a possibility if the fuses have been replaced with larger than they should be.

 

[Tom Bell]

Thanks for your response, the inverter won't be run at max, and I won't be likely to be running much more than I currently run through the 1000w msw inverter ( which connects via 1 of the 15amp fused lighter sockets without blowing the fuse ). The cab is new, so none of the fuses have been replaced with higher ones. The 3000w spec is more to cope with power surge on startup of items ( particularly the chemical pump ), and of course, being PSW it should be kinder to my electrical equipment .. lol

 

[Lucien Nunes]

I think those two pairs of terminals might be internally connected together (some inverters have two pairs of cables that are not, for circuitry design reasons). If they are connected, it might not be a good idea to use two plugs. When one plug is connected the other becomes live, and if it shorts to the vehicle or itself will cause sparks and blow fuses. Also, the load won't be guaranteed to share effectively, depending on the contact resistance of each plug and the vehicle wiring length, one might take 3/4 of the load and the other 1/4, you wouldn't know. Also, if one negative makes poor contact, the current from both positives will be returned to the other negative and this would allow the rating of the cable to be exceeded under high load.

However, there's something suspicious there (other than the very wonky english). The so-called 'Warning Lable' (table?). It shows a whole list of appliance types with what I presume is the maximum wattage permissible for a particular size of inverter. Some of the limitations I can accept, some are nonsense, but the kettle and heater are especially odd. Both are near perfect resistive loads with virtually no inrush. Yet the 3kW inverter is only recommended for maximum 1kW of either.

For my money, a 3kW inverter that can't run a 3kW heater isn't a 3kW inverter!

 

[Tom Bell]

I think those two pairs of terminals might be internally connected together (some inverters have two pairs of cables that are not, for circuitry design reasons). If they are connected, it might not be a good idea to use two plugs. When one plug is connected the other becomes live, and if it shorts to the vehicle or itself will cause sparks and blow fuses. Also, the load won't be guaranteed to share effectively, depending on the contact resistance of each plug and the vehicle wiring length, one might take 3/4 of the load and the other 1/4, you wouldn't know. Also, if one negative makes poor contact, the current from both positives will be returned to the other negative and this would allow the rating of the cable to be exceeded under high load.

However, there's something suspicious there (other than the very wonky english). The so-called 'Warning Lable' (table?). It shows a whole list of appliance types with what I presume is the maximum wattage permissible for a particular size of inverter. Some of the limitations I can accept, some are nonsense, but the kettle and heater are especially odd. Both are near perfect resistive loads with virtually no inrush. Yet the 3kW inverter is only recommended for maximum 1kW of either.

For my money, a 3kW inverter that can't run a 3kW heater isn't a 3kW inverter!

So, presumably to check whether they are connected, I would connect a 24v supply to one set of terminals, and see if there is current at the other set ?

 

[Besoeker]

So, presumably to check whether they are connected, I would connect a 24v supply to one set of terminals, and see if there is current at the other set ?

Voltage, not current.
But you simply do a continuity test.