Water Heater On or Cycle?

I turn my gas WH off at night so it doesn't wake up neighbors at 3am.

Make it as complicated as you want I guess.

I turn mine on when I arrive at camp, turn it off when I leave. If I'm on a road trip with multiple stops, it gets turn off when it's time to refill the propane, or when I get home.

Thanks for the replies. I have to agree with the "too much time on my hands" comment. I just invented a couple of projects for the next time I get close to a Camping World, so the water heater issue is off my mind for now. It's on and I'll leave it that way until the morning we hit the road for Myrtle.

I have a very simple approach. I turn the water heater on when I leave on a trip and shut it off when I get home. I was camping all but 7 days in October between the hot water and with some time on propane for the fridge and cooking. The tank never got off full. Now add in the furnace and some colder weather and you will use a lot more. If I get low I by more.
Bill

jplante4 wrote:
I would be able to figure this out using my extensive thermodynamics knowledge :B, but I'm missing a piece of information.

Is it better to leave the (propane) water heater on all the time while parked, or shut it off after you're done with the hot water and turn it back on when you'll need hot water again.

As far as cycling goes I figure it uses 4000 BTUs to get back to temp (50° temp rise, 80 pounds of water) and a gallon of propane contains 90,000 BTUs, so I use about .05 gallons for each cycle.

The piece of info I'm missing is what's the duty cycle of the heater in standby? In other words, at what temp does the burner kick on and off?

This is the kind of stuff that enters your head when you're sitting around all day at a campsite.

First off it's a 30*F rise
T-stat recloses at 110*F and opens at 140*F

Duty cycle is roughly 1X per hour

There's your missing pieces.....so figure away


For me............WH goes ON when we set up and stays ON until we tear down to relocate.

I like HOT water when I turn faucet hotside on....that is why I have a water heater.

DrewE wrote:
From a themodynamic point of view, it uses more energy to keep the water hot all the time than to turn the heater on and reheat as needed. This is also true for the furnace for the air inside the RV, for that matter.

This fact is a little clearer if you approach it from the point of view of energy leaving the system (the water heater) which, absent water use, is basically just water radiated to the environment through the tank etc. Since the heat transfer is proportional to the difference in temperature between the water and the outside, the heat is lost fastest when the water is hottest. Keeping the water at a high temperature constantly means more energy is radiated away, and that needs to come from some fuel--propane, in this case, or possibly electricity.

There are a few odd cases where it turns out that maintaining temperature is more efficient because the efficiency of the heating system is quite variable. One example (not likely for an RV) is with many geothermal heat pump systems where attempting to extract a lot of heat at one time from the ground depletes the supply (cools down the ground loop) and lowers the system efficiency considerably. A constant, lower level of heat transfer is much preferred to a sudden burst, and maintaining temperature is more economical than letting it cool and trying to bring it back up. Propane flames and electric elements do not act this way, of course.

Spot on, had problems like this in school! Only thing I would add is the insulation around the water heater will resist the heat transfer to some degree making the difference in propane usage smaller. In the end it comes down to more of a convenience factor. Do you want hot water instantly available whenever, or are you willing to plan a bit? We leave ours off over night, I flip it on in the morning. Off when we leave the RV to sight see and on when we get back.

WyoTraveler wrote:
I run my hot water on electric. Leave it on all the time when in RV parks.

The downside though for those owning a rig running on 30 amp service is it's so easy to exceed the campsite source supply - run A/C, have the WH running on electric, then someone decides to make popcorn in the MW oven and BOOM your breaker trips. Had that happen, turned out to be the main breaker on the campground distribution panel which was located within a fenced off and locked area ... what a PITA having to go to the park office, then wait for park staff to eventually show up to unlock the gate and reset the breaker. :M I now only use the WH electric heat option when I KNOW it won't push me over a 30 amp draw. ;)

Depending on the model BELOW 130 or 140 degrees
If you have a Atwood EXT model---- BELOW 160 degrees.

These are the Tstat temps to cut off. The variable will be HOW long it takes for the interior water temp to drop and how fast that translates thru the Aluminum or Glass lined tank to that tstat.
PS. You have way to much time on your hands to worry about these type things. IMO, IF you worry about the negliable cost of LP for this type item you cannot afford the RV or the LP:B Get another hobby:B Doug

From a themodynamic point of view, it uses more energy to keep the water hot all the time than to turn the heater on and reheat as needed. This is also true for the furnace for the air inside the RV, for that matter.

This fact is a little clearer if you approach it from the point of view of energy leaving the system (the water heater) which, absent water use, is basically just water radiated to the environment through the tank etc. Since the heat transfer is proportional to the difference in temperature between the water and the outside, the heat is lost fastest when the water is hottest. Keeping the water at a high temperature constantly means more energy is radiated away, and that needs to come from some fuel--propane, in this case, or possibly electricity.

There are a few odd cases where it turns out that maintaining temperature is more efficient because the efficiency of the heating system is quite variable. One example (not likely for an RV) is with many geothermal heat pump systems where attempting to extract a lot of heat at one time from the ground depletes the supply (cools down the ground loop) and lowers the system efficiency considerably. A constant, lower level of heat transfer is much preferred to a sudden burst, and maintaining temperature is more economical than letting it cool and trying to bring it back up. Propane flames and electric elements do not act this way, of course.

I run my hot water on electric. Leave it on all the time when in RV parks. Cost is zero. When I am on the road moving I only turn propane on in the morning. Dry camping only on when I need it in the morning.