Inverter probs

Submitted: Thursday, Jun 01, 2006 at 19:22
ThreadID: 34511 Views:2242 Replies:5 FollowUps:2
This Thread has been Archived
Sorry, first timer here with problems! I have a 1000w MSW inverter powered by a 115ah Trojan. I am trying to run a bar fridge in my on road camper trailer. The bar fridge draws 77w or 0.5amp. I understand it may need 500w to start hence the 1000w inverter with 2000w surge. Anyway most of the time either the audible fault indicator on the inverter is triggered or the "thermal cutout"(probably wrong terminolgy) on the fridge kicks in.
After testing with my you beaut tester I have 14.1v at the inverter and 238v at the switch to the fridge.
Any ideas?
Back Expand Un-Read 0 Moderator

Reply By: lunchbuckett - Thursday, Jun 01, 2006 at 19:57

Thursday, Jun 01, 2006 at 19:57
Wilankurgab if it is compressor type and the size of the capasitor by my calc it will take 1500 w to start
AnswerID: 176186

Follow Up By: Wilankurgab - Thursday, Jun 01, 2006 at 20:15

Thursday, Jun 01, 2006 at 20:15
Thanks for that. Considering the inverter has a 2000w surge should that cover it?
Also if not a trade secret how do the calcs work?
0
FollowupID: 432228

Reply By: Keith_A (Qld) - Thursday, Jun 01, 2006 at 20:20

Thursday, Jun 01, 2006 at 20:20
What cable size are you running from the battery to the inverter?

If it needs 500w to start - then at 12V it draws 41 amps.
If the cable length is say 2.5m to your battery, total cable (neg + pos) = 5m
- max voltage loss = 0.36V
0.36 = length x amps x .017 / (cross section wire conductor)
.36 = 5 x 41 x .017 x wire / (cross-section)
Thus Wire cross section = 10sq mm cable.
This is the copper cross sectional area, NOT the automotive size.
Check this website : caravanandmotorhomebooks.com/articles/wiring_woes.htm

If the wiring from the battery to the inverter is too small, the voltage drop at the inverter (at start up of the fridge) would cause the 'low voltage' error'.
Could this be the problem?
regards.................Keith
AnswerID: 176191

Follow Up By: Wilankurgab - Thursday, Jun 01, 2006 at 20:26

Thursday, Jun 01, 2006 at 20:26
Gday Keith, thats starting to make sense. I have battery type cables connected with a 150amp fuse inline on the positive. The length is only 600mm.
Cheers Wilankurgab
0
FollowupID: 432230

Reply By: Geoff (Newcastle, NSW) - Thursday, Jun 01, 2006 at 20:46

Thursday, Jun 01, 2006 at 20:46
What everyone else has said is fair and reasonable.
Another area to look at,
Will the fridge actually run on any Modified Sine Wave Inverter?
It may not have anything to do with voltage drop, starting or inrush current at all.
There's all sorts of sine wave dependent physics going on when you start a split phase motor.

Are you able to beg borrow or generally obtain a Pure Sine Wave in a similar size?
Or just as good a Kipor, Honda or Yamaha inverter style 1kva generator will soon eliminate the problem of Modified v's Pure Sine Waves.

Geoff.
Geoff,
Landcruiser HDJ78,
Grey hair is hereditary, you get it from children. Baldness is caused by watching the Wallabies.

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 176204

Reply By: Member - Doug T (QLD) - Thursday, Jun 01, 2006 at 22:13

Thursday, Jun 01, 2006 at 22:13
Wilankurgab
You have to have BEER in the fridge mate
still going strong with 836,179 K's

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 176232

Reply By: Member - George (WA) - Thursday, Jun 01, 2006 at 23:01

Thursday, Jun 01, 2006 at 23:01
Wilankurgab
Get the battery tested, the voltage may be OK but it may fail under load. I had the same problem as you explained, purchased a new battery, problem solved
Cheers
AnswerID: 176245

Sponsored Links

Popular Products (13)