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Thermostat for Campingtrailer

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TheSwede73

New Member
Hi!

I have just bought a electronic thermostat and will install it in my camping trailer.
The old one was a non-electronic bimetall one, but this runs on 12v.

The question is:

A campingtrailer battery that gives out 12V, will it destroy a circuitboard that's made for 12v, is the acid battery in the campingtrailer so much more powerful than, let's say a 12 volt normal battery?

I'm not that good with powersources, i mainly use my lab, power unit or regluar batteries.

Thanks!
/Anders
 

3v0

Coop Build Coordinator
Forum Supporter
You are confusing voltage and current. 12 volts DC is always 12 volts DC. Read about current and voltage on the web if you want more information.

A car battery can deliver a lot of current at 12 volts but the thing to remember is that the thermostat will only use the current it requires. So you are OK here.

But there are other problems. The first is that that a 12V car battery should measure about 12.6V. This may or may not be OK with the thermostat.

The second and much more serious problem is what happens if/when the battery is charging. A typical 12V battery needs a charging voltage of about 14V. If the charging current is provided by a running car you can expect to see voltage spikes as high as 60V which would kill the thermostat.
 

TheSwede73

New Member
Ok, i got that a little wrong :) have studied some after this post, so now i know :)

Ok, is there any way to protect the thermostat? resistors? or somekind of electronicfuse that shuts off when/if a spike occurs and then on when its down to 12v again?

12,6 wont be a problem i guess..

Thanks!
 

john1

Active Member
whats wrong with getting another one like the old one ?
 

tcmtech

Banned
Most Helpful Member
Ive never seen a 12 volt digital thermostat. 24 volt AC is standard. All the digital thermostats I have ever seen were either ran with two AA batteries or were loop powered.
Running it off a external system wont work if its not intended to be ran that way. It wont have any input power filtering or voltage spike protection. Plus the internal circuitry likely shares common electrical connections with the internal battery and was intended to work with a isolated power system and not an external system.
 

Dean Huster

Well-Known Member
If you bought the thermostat from an RV supply source, don't worry about it and just install the thing according to the directions. It was made for the RV furnace which runs from the 12v DC system and not directly from the 120 shore power. It's also made to handle the typical spikes, ripple and higher voltage of charging. If it goes up in smoke, take it up with the supplier.

Most RVs use roof-mounted air conditioning units (Coleman, Dometic, etc.) and I've never seen third-party digital thermostats for those.

The massive $200,000+ bus-style motorhomes with 50 amp connections sometimes might use only 120vac devices using either shore power or a big built-in generator. These rigs are normally parked in big commercial campgrounds vs. state parks because the owners want every bit of life's luxuries they can get while on the road. So less and less of their equipment is powered by 12vdc vs. a few while-on-the-road lights.

Dean
 

TheSwede73

New Member
Thanks!

This is a thermostat for "anykind" of use, 12V. no internal battery, but i understand why RV's and campingtrailers use to have mechanical thermostat, not running on electricity, because of the voltage drop when you discharge the battery...

This thermostat has no special kind of use, but i can see the problem if battery getting low and the relay wont close..

There are a lot of thermostats out there, from AAbattery powerer to 12v, i have never seen a 24v... either battery, 12v or 220V...

I guess the mechanical is the best for this purpose...
 

MikeMl

Well-Known Member
Most Helpful Member
...
This thermostat has no special kind of use, but i can see the problem if battery getting low and the relay wont close...
If the battery is so low that the relay won't close, it is too low to hold in the gas valve or to power the 12V fan in your heater :D
 

TheSwede73

New Member
That is true!! :)

But i would be more relaxed with a mechanical thermostat...no worries about powerspikes or anything else power related :)
Maintanance free is the word... :)

And the last one wasn't electronic so...

I could use it for something else, not so important maybe :)
To start fans if it gets to hot or something :) not so important, but automated :)

Or just warn if it gets to cold outside..
 

stevez

Active Member
I own an RV and it has a 12 v thermostat. As Dean suggests, it's made for that application. The original power supply was poorly filtered AC with battery backup and my guess is that the t-stat is relatively immune to normal spikes. I've since replaced the AC to DC convertor with a switched mode supply - what a difference. You certainly could provide some extra protection on the 12 volt line but it might be overkill. I replaced mine - $45 or so and would not want to do that often. I suppose I could have added a TVS crowbar circuit or similar suppressor.
 

TheSwede73

New Member
Our campingtrailer is from the late 70's, its made for mechanic things :) so i'll go with a new mechanic thermostat... but im going for a hightech controlpanel :)

Thanks for all help!

I will be asking more things......

:)

Anders
 

Dean Huster

Well-Known Member
Older trailers made in the 1960s may have had a gas furnace that had no air handler system, just using normal convection to move the heat. They sure could make that top bunk into an oven!

Newer trailers often have forced air and ducting with an air handler, gas fuel, 12vdc control electronics and blower motor. The old system gave you heat whether you had battery or not. The new ones demand that you have a charged 12v system or be hooked to shore power.

Our old 1960s trailer had a gas light over the table. You don't see those in newer ones anymore!

Dean
 

geomade

New Member
If you purchased the thermostat for a RV from a location that sold it for an RV it will work fine. The only thing to look for is if the new thermostat is a two wirw or a three wire unit. If it is a three wire or has a connection for three wires this probably means it require a source voltage if it is a two wire it will use the signaling voltage for the thermostat. A bimetallic thermostat is maybe yhe best for you but in a pinch for a camping trip a mercury type thermostst will work for a parked trailer.
 
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