Can anyone tell me how much propane the hwh will use? The PO told me the fridge uses next to nothing. Just wondering, since i'm living in the RV f/t now, if i should leave it running all night, or just fire it up in the morning for shower/dishes.

Thanks!

The hwh will use lots more propane than the fridge. That blowtorch roar it makes tells you that from the start. The quiet little flame in your fridge only provides heat to circulate a working fluid. The propane flame in the hwh directly heats the water.

FWIW, As a matter of safety & comfort I shut it off at night, & turn it on to shave & shower in the AM. Our hwh roars right under my wife's berth & I witnessed two people die in a fire started by a malfunctioning hwh. A working smoke detector probably would have saved them.

Living aboard, if you stay plugged into shore power, an electric heating element, available in RV supply stores, would be a worthwhile investment.

Thanks so much for the input. The massive flame from the tank heater is a concern, so i will use the same regime, re: heat up before use. Electric heating element, or engine heat conversion, would be excellent.

quote:

Originally posted by MGmobile:
Can anyone tell me how much propane the hwh will use? Just wondering, since i'm living in the RV f/t now, if i should leave it running all night, or just fire it up in the morning for shower/dishes.

Thanks!

Short answer: Run it when you need it.

Long answer:

It depends.

The typical RV gas water heater uses between 8000 and 12000 BTUs per hour. A pound of propane is about 20,000 BTUs.

If you know the rating of your water heater, and time the heating of the water from cold, you will be able to figure out what each tankful uses to heat. Or how much propane a shower uses. For example, a 10,000 BTU heater that takes an hour to heat its tank uses a half pound of propane. I think most heaters have around an hour recovery time.

The amount of propane required to heat your water will vary with the outside temperature and the duration and setting of your shower. But, once you know the rating of your heater, you can time the blowtorch sound and be accurate. Once you do that a couple of times, you will have a decent estimate.

You can also get crazy with how many BTUs it takes to raise how much water how many degrees, but the end result requires accurate numbers, but all that high school physics stuff does not take into account how much heat is not transferred to the water.

Here is a ballpark figure I found in my notes:

If you have a 10 gallon, 10K BTU water heater, it'll take about 7,800 BTU's or .36 lbs or .085 gallon to heat each tank of water from 50 degrees F to 120 degrees F (assuming 75% efficiency)

But timing the burner sound is so simple and should arrive at a more accurate number. So many minutes for your shower, so many minutes for washing dishes, etc.


A hwh that has a constantly-on pilot will keep the water decently warm in hot weather without the burner being needed

just fired up the hwh...took about 15-20 minutes to heat the water. After about 30 minutes, the burner shut off, but the pilot stayed on! I guess this is working well, and safe to leave on, as the fridge is pilot lit as well.

I'd shut the pilot down for the road though.

Danny's advice is good. On our first RV almost 40 years ago, I left the hwh on as we traveled. It lit off, & somehow the flame was drawn backwards to destroy the thermocouple & some other small components. It scorched the paint on hwh door, but shut off before it damaged anything else.

Hopefully, manufacturers have changed things to prevent that occurrence. Our experience might have been a fluke, but electronic ignition might have been developed to prevent it.

I drive with all the gas shut off. If I wrap things up in a ball, I don't need a source of ignition or propane spewing out.

Open flames at gas stops are not good, either. No matter how good your intentions, it is likely that you will forget to shut off the fridge or wh pilot whan pulling into a gas station.

MG's Barth is a 73, so I doubt it has the safeguards in place on todays coaches. I have an 04 fridge which I was told is safe to run down the road on LP by the known pro that installed it. I would never run my HWH on LP on the road. But then I don't have to, as the engine assist system that I didn't even know I had until a couple years ago heats enough water for whatever you need that night.

Will definitely shut off the hwh pilot/gas on the road. Ditto for gas during fillup. However, seems overkill to turn the fridge pilot off during trips. Will it run off the 12v system in between stops?

That's what the 12v feature is for. Usually, 12v won't cool the box down, but it is enough to hold the temp. once it's cool.