Originally Posted by Whirlaway
... "enough power" to run the furnace over night in New England in the fall and spring?...
as a user feedback report, with a larger, modern trailer with 2 grp 27 batteries and the factory furnace...
one can usually expect to get 1-2 nights of furnace use in spring/fall IF the batteries start fully charged.
you might find some of the stuff and install info in this thread useful...
and the s/n unit of the wb' has a lot of useful info on these issues...
basics on batteries, solar and stuff...r
there is no reliable way to deal with this larger issue (solar) that doesn't include math...
one needs to know ~ how much juice the gadgets use and how much juice is available,
then work out a plan to replenish the batteries.
here's a member chart that is a good example...
the typical new furnace in these units consumes 7-9 amps with the fan running...
or the equivalent of a 90-100 watt light bulb (keep this in mind)
the owners manual for your furnace size will have the amperage/specs.
depending on how cold, how often the door is opened, leaks and so on...
one can estimate HOW LONG the furnace fan runs per hour and day...
as a simple example, if the fan runs 10 minutes/hour and is only turned on for 12 hours,
thats ~2 hours of fan time...or about 15-20 amps of consumption.
so the furnace would use 30-40 amps over 2 nights.
colder outside, OR longer run times and that goes up.
based on btu size of furnace and trailer size and outside temp one can calculate ~ energy needed to keep warm...
again it's a lot of math, but many do these calculations.
2 grp 27s have approximately 200 amps of stored juice, using 1/2 is considered a healthy approach.
so with 100 amps available the furnace should be useable for 2-4 nights or LESS if really really cold.
does that make sense?
of course most of us will use the other 12v
systems (water pump, lights, fans, outlets) so the furnace is not the only draw.
and batteries performance declines as they get cold, yours are stored partially inside which helps some.
1. adding a 3rd battery is the least expensive way to expand capacity and simple.
2. using a genset to REcharge the batteries every few days (as needed) may be the next step and also easy to do...
(keep in mind it's a little harder to START a genset manually if really really cold)
3. adding a catalytic lp gas heater is probably the next step in price/ease and effectiveness (some larger streams need 2 cats)
4. then comes solar, and the every expanding options for a system.
to maximize REcharging with solar in your region the panels will need to TILT, which isn't part of the factory set up.
the service center CAN do tilting if you request it, but it is not part of the standard install.
there are formulae for calculating how much juice is supplied under ideal conditions
and allowing for panel IN/efficiencies, hours of exposure and so on...
that math should be used in estimating panel size and battery bank.
2x130 is a better option than 2x110 but not a factory option (lots of vendors have 130 w panels)
yes 3x110 will fit on a 27 but the panels will be spread out (which means they could tilt in different directions)
to take FULL advantage of 220 to 260 watts of collection capacity (panels)...
one really needs to increase STORAGE capacity too, in other words more or bigger batteries.
here is an owner article on a diy system install from the s/n unit ...
it will cost ~3000$ to max out your roof space and add the proper accessories gizmos, PLUS the cost of battery additions.
again many of us are capable of 2-3 night of moderate furnace use already.
a 3rd battery is 150$ plus wiring.
a genset is 800-1000$ plus gas.
a safe/reliable (vented) cat heater installed is 500-1000$
many folks diy these things for less $.
it is expensive to have the factory service center do these things, but they have years of experience which is valuable.
so many solar users have highly personalized set ups and power needs and locations that clearly...