I was comparing apples to apples. Then I was thrown an orange!
I was assuming the application allowed a CHOICE of either design, and
YOUR main concern was an electrical outage.
You made no mention of these other concerns and desires (utility room installation, limited combustion air, desired side wall venting). Also you stated that you were going to replace
YOUR unit, not one many miles away in a rental.
If you are replacing a unit in a rental apartment then go with the vented design
if you want. You will most likely call a tech on those units anyway, I presume.
You are going to pay more for the unit initially so I assume that the cost to purchase and service the equipment is not the major issue.
Application is the main concern, not a power failure as initially stated. Right?
As far as
YOUR house or unit, since YOU sound like a handy guy
(and you have this forum to guide you too!) I suggest a simpler unit to work on so that
YOU can fix it instead of the tech. In a HWH I don't believe that there would be substantial short term savings in fuel.
If I had that information from the getgo, perhaps I would have responded this way initially. That is why sometimes we like to SEE the installation and make recommendations based on what we hear and see.
Maybe others have contrasting input? How 'bout it fellas????
Good luck,
Charlie
