Try bad three!
You cant really set them up wrong, inlet outlet gas. That is all that is required. I have spent hours fiddling with the damn things to get them to function every time. But without success
The advantage of the new one is its sensitivity. It fires up very quickly, but more importantly, doesn't allow for a high build up of pressure so shuts off quickly too.
Also it heats my water to 48deg, which is perfect.
Also the L5 doesnt had a flue, so to speak. So you can get condensation in the van, or f you vent it outside, you are suceptable to wind