Min voltage for gas heater?

gemkam

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May 22, 2024
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Furrion thermostat in our Transcend 231RK had "Lo" error middle of the night (35 degrees outside!) Heater fan kicks on and when the gas ignites it turns off and "Lo" error appears. Battery voltage read 12.53v (and dropping due to the fridge, etc.) Hooked up to the truck and it runs fine. What is the minimum voltage requirement for the heater? Fridge is running fine and specs say it will run down to 10.4v, but can't find minimum for the heater. Seems like it should run down to low 11v. Brand new battery too. Got the battery up to 12.9v and the heater ran fine for the 1st cycle, then repeated the shutdown/error upon 2nd cycle.
 
The voltage you read when the furnace is off will be higher than when the blower fan is on. They don’t publish an operating range, so you just have to guess. 12.53V is in the 70% charge range, but seeing what the voltage drops to when the fan kicks on may be enlightening.

Could also be poor connections in the wiring.

12.9V is an odd number.much to low if the charger is on.
 
I would recommend a couple of 100ah lithium batteries. They hold a much higher voltage as they discharge, plus you can discharge them to a much lower percentage without harming them.
 
New lithium batteries would be nice but with already having new LA batteries it makes sense to understand what is going on. Do you have a smart shunt and it really make sense to get good battery life and trouble-shoot.
 
New lithium batteries would be nice but with already having new LA batteries it makes sense to understand what is going on. Do you have a smart shunt and it really make sense to get good battery life and trouble-shoot.
I do have a smart shunt. I know that it's bad for the deep cycle LA batteries to get below 50%, it can start killing cells. I think 50% is like 12.2volts.
 
I do have a smart shunt. I know that it's bad for the deep cycle LA batteries to get below 50%, it can start killing cells. I think 50% is like 12.2volts.
No truth at all to damaging them below 50%. Any use “damages”, and the rate of cycle life loss is linear from about 20% DoD down. The only inflection point is around 20%.
 
I do have a smart shunt. I know that it's bad for the deep cycle LA batteries to get below 50%, it can start killing cells. I think 50% is like 12.2volts.
Very good on having the smart shunt and thanks for the reply. I was also thinking that you could get current, voltage and history figures from the smart shunt to trouble-shoot. This might answer some of JKWilson's questions.

What batteries are you using (one, two, size?).

In my opinion, with a true deep cycle battery, going to 80% DOD using a smart shunt is fine. Charging it back up right away and storing above 70% SOC is much more important. You could run into low voltage issues though.
 

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The voltage you read when the furnace is off will be higher than when the blower fan is on. They don’t publish an operating range, so you just have to guess. 12.53V is in the 70% charge range, but seeing what the voltage drops to when the fan kicks on may be enlightening.

Could also be poor connections in the wiring.

12.9V is an odd number.much to low if the charger is on.
This sounds like a good option, based on my recent experience. We had voltage drop affecting the furnace motor, as well as hydraulic jacks and slides. Extensive troubleshooting came down to tightening a few loose bolts!
 
........had "Lo" error middle of the night (35 degrees outside!) Heater fan kicks on and when the gas ignites it turns off and "Lo" error appears.......

What makes you think Lo is a voltage issue? Could it mean that although you know the propane is lit, but the controller does not? Maybe the temperature sensor is faulty and the controller thinks there is no flame?

I would confirm your though process is correct first.
 
What makes you think Lo is a voltage issue? Could it mean that although you know the propane is lit, but the controller does not? Maybe the temperature sensor is faulty and the controller thinks there is no flame?

I would confirm your though process is correct first.
Maybe because Lo is the low voltage error on Furrion products.
 
Then if that is the case, I would check the battery voltage at the heater. Checking it everywhere else may test ok. A simple voltage drop test would confirm if the circuit is good or not.

Don't forget that all the juice that goes to the heater, must go back to the battery. A voltage drop test on the ground side is equally as important.
 
The voltage you read when the furnace is off will be higher than when the blower fan is on. They don’t publish an operating range, so you just have to guess. 12.53V is in the 70% charge range, but seeing what the voltage drops to when the fan kicks on may be enlightening.

Could also be poor connections in the wiring.

12.9V is an odd number.much to low if the charger is on.
@12.74v with the blower running, it was dropping at about .01 to .02v every 2 or 3 seconds. The 12.9v was just what I got the battery back up to when running the truck for 20-30 mins. I assume the smart shunt would be installed near the heater to get an accurate reading vs. the factory voltmeter that is near the solar controller? It would be hard to monitor from there without adding some wire to make it more accessible, which would add more connections to be concerned about. I can go and find all the connections and clean/tighten. I wasn't ready to go LiFePO yet, as we don't do much off grid. I would normally just use the generator, but this was a odd situation and I wasn't unhooked from the truck and couldn't get the tailgate down to get it out.
 
You are seeing residual surface charge anytime you see more than 12.65V on a conventional lead-acid battery.12.72V for Trojans.

Using voltage to estimate battery state of charge is only valid when the batteries have been resting. No charging or discharging for several hours.
 

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