I'm not familiar with the Lochnivar brand here in North Central Florida. My opinions of gas heaters from a servicability point of view. I look at broken and rotten gas heaters every day.

Raypak makes the best machine, however their cabinet is the weakest link. They seldom breakdown. Lots of old Raypaks out here still chugging away.

Hayward, I repair a great deal of these for various reasons. I wish I could put Raypak's heater in Hayward's cabinet. Haywards are quite popular due to its price point. I've not seen a rotten Hayward cabinet yet. The units are real easy to access and work on.

Jandy, not popular here, I think they're a bit more involved to move through its troubleshooting process. The few I have seen are as old as 9 years and lookin' good and strong. I think they might not be priced as well as the Hayward units.

Sta-rite, easy to work on, easy to troubleshoot. I see a lot of these in my travels. Cabinet comes apart w/ 4 bolts and its fiberglass. The weakest point seems to be its thermistor combined with an out of check pH level in the pool. I'm not convinced the forced air concept is the way to go in terms of longevity for the heater. Overall I think its a great unit. Easy to convert to LPG or Natural as needed too.

Pentair's MinMax units. Only problem I ever see is failed transformers. The cabinet seems a bit weak, but have not experienced a whole lot of cabinet problems. Again, the forced air concept may give this one more servicability issues in the future.

Overall, I believe the Raypaks are the workhorses. They seem to last so much longer than the others. If you want to double the lifespan of your heater, then install it inside with proper venting.

My suggestion...hire a qualified gas professional to make the connection, a mechanical contractor to assure your venting meets code, and keep your pH in check. I'd go for the Raypak everytime, just fewer service issues. Oh and stay away from the milivolts, their a service opportunity every season.

Where are you located? If youre anywhere near the ocean, then forget lifespan, heaters just get killed if your on the coast due to the moisture and salt.

-Jeremy
Tech I APSP
Florida