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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 ?

#### 3v0

##### Coop Build Coordinator
Forum Supporter
John has a point.

But if you want to continue with the electronic unit how low of a voltage do you expect to have on the battery and still have the thermostat work ?

#### tcmtech

##### Banned
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.

#### mrwhitee

##### New Member
battery powered stat would be much better. The batteries last a long time so its not a big deal.

#### 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.

#### 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

##### 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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