Tankless Water heater
We are new to this and just purchased our first class A Motorhome ( a 2000 Damon Intruder). Has anyone ever installed a tankless water heater in their class A?
Forum Discussion
Hi,
I would consider upgrading to a 10 gallon hot water tank instead of a tankless heater. The problems is most do not have enough BTU input to take 2 GPM and warm it from a typical 50F water temp to 110F. While some sophisticated home tankless water heaters have variable opening valves, they run burners from 30,000 to 199,000 Btu's to correctly supply hot water. Most RV burners are not variable gas valves, but rely on the user to vary the flow rate. So basically open the hot valve all the way, and close it slightly if your shower is to cold and open slightly if to warm. Fine unless you are running from a pump that will not supply more water and the tank is say 75F, you can not speed it up anymore. Mixing in cold water is a "Option" however then the water heater will not meet it's minimum flow or might reach 130F and shut off the burner completely for a few seconds to cool down. This makes for a hot-cold shower.
Two solutions. When I was living in my RV and the inlet water was 50F in the winter, I would use a tankless L5 water heater to preheat the water going into my storage tank to about 80F. It was 100 gallons and lasted me about 5 days. Then I would have a very long and hot shower with the 6 gallon tank, because I was mixing in 80F "Cold" water with the 140F hot water, and 80F warm water was not cooling the 140F tank to quickly. Before I would get a max 4 minute shower, after I could shower about 15 minutes without it going to cold.
I bought the L5 at Amazon.com for about $139. The more expensive L10 can heat more water faster. You might consider either one to connect to your fresh water line, then you can run it while the kids are showering. It will not heat the cold water to above about 90F while the flow is in the 2 GPM range, and that will lead to long showers without depleting the hot water tank. However be careful not to run the water to slowly, as it will heat up beyond 120F on the cold water line, leading to possible scalding. If the kids know to turn the shower away from them when it is hot, and hold the shower handle in their hands, it should work out fine.
The L5 only runs for about 20 minutes at a time. If you stop water flow, and restart, it starts the timer again. I ran mine from a 5 gallon propane tank via a 4' long hose adapter, the end looks like the top of a propane 1 pound tank, and goes into the BBQ or L5 heater. I hang the heater from my bicycle rack on the back of my motorhome, near the fresh water tank inlet. It is also close enough to the shore water inlet that a 25' hose from campground to heater and 25' from heater to RV is possible.
I think the L5 is about 35,000 BtuH, while the larger L10 is 50,000 - 55,000 Btus? Both have limited variable valves, manual adjustments. So it is practical to use the L5 as a prewarmer for the water coming into the RV while taking showers, then shut it off during normal water use. By adjusting it to maximum flow, and then adjusting the burner output to make the water line going into the RV feel "Warm" to the touch, (while someone is showering or running a normal amount of water from the shower), you can make the inlet water near 80F.
What is 35,000 Btu's? Really good question. If you where to look at home water heaters in the 40 - 50 gallon size, Natural gas, they typically have a 40,000 Btu input rating and a 40 gallon "First hour" production rating. In other words fill it up with 50F water and it will heat about 40 gallons of water by 90F to 140F. If you are camping in Yellowstone with 40F ground water, expect colder showers. Down south in the summer time, expect longer and warmer showers with ground water well into the 60'5 and low 70's in states bordering Gulf of Mexico. In Phoenix, I did not need to run my water heater for showers on the 110F days, the hot pavement and 75F ground water temp warmed the water plenty.
For reference, there is 95,000 Btu's in a gallon of propane. So the L5 will run about 3 hours per gallon of propane. Your typical 6 gallon water heater has a 8,800 Btu input, and can heat the 6 gallons in about 45 minutes on propane alone, saving about 10 minutes on gas and electric.
A typical 10 gallon heater will have a 10,000 Btu burner, and 1,000 watt (3,400 Btu) heating element. So they will put out about 10 gallons per hour, while the 6 gallon can put out 8 or 9 if you are using some of the water during that hour.
I also considered a tankless electric water heater in the 4 KW size range, however it will not provide enough Btu's to warm 2 GPM (typical flow rate of a shower) - only heating it by about 6 or 10F.
Good luck,
Fred.
I would consider upgrading to a 10 gallon hot water tank instead of a tankless heater. The problems is most do not have enough BTU input to take 2 GPM and warm it from a typical 50F water temp to 110F. While some sophisticated home tankless water heaters have variable opening valves, they run burners from 30,000 to 199,000 Btu's to correctly supply hot water. Most RV burners are not variable gas valves, but rely on the user to vary the flow rate. So basically open the hot valve all the way, and close it slightly if your shower is to cold and open slightly if to warm. Fine unless you are running from a pump that will not supply more water and the tank is say 75F, you can not speed it up anymore. Mixing in cold water is a "Option" however then the water heater will not meet it's minimum flow or might reach 130F and shut off the burner completely for a few seconds to cool down. This makes for a hot-cold shower.
Two solutions. When I was living in my RV and the inlet water was 50F in the winter, I would use a tankless L5 water heater to preheat the water going into my storage tank to about 80F. It was 100 gallons and lasted me about 5 days. Then I would have a very long and hot shower with the 6 gallon tank, because I was mixing in 80F "Cold" water with the 140F hot water, and 80F warm water was not cooling the 140F tank to quickly. Before I would get a max 4 minute shower, after I could shower about 15 minutes without it going to cold.
I bought the L5 at Amazon.com for about $139. The more expensive L10 can heat more water faster. You might consider either one to connect to your fresh water line, then you can run it while the kids are showering. It will not heat the cold water to above about 90F while the flow is in the 2 GPM range, and that will lead to long showers without depleting the hot water tank. However be careful not to run the water to slowly, as it will heat up beyond 120F on the cold water line, leading to possible scalding. If the kids know to turn the shower away from them when it is hot, and hold the shower handle in their hands, it should work out fine.
The L5 only runs for about 20 minutes at a time. If you stop water flow, and restart, it starts the timer again. I ran mine from a 5 gallon propane tank via a 4' long hose adapter, the end looks like the top of a propane 1 pound tank, and goes into the BBQ or L5 heater. I hang the heater from my bicycle rack on the back of my motorhome, near the fresh water tank inlet. It is also close enough to the shore water inlet that a 25' hose from campground to heater and 25' from heater to RV is possible.
I think the L5 is about 35,000 BtuH, while the larger L10 is 50,000 - 55,000 Btus? Both have limited variable valves, manual adjustments. So it is practical to use the L5 as a prewarmer for the water coming into the RV while taking showers, then shut it off during normal water use. By adjusting it to maximum flow, and then adjusting the burner output to make the water line going into the RV feel "Warm" to the touch, (while someone is showering or running a normal amount of water from the shower), you can make the inlet water near 80F.
What is 35,000 Btu's? Really good question. If you where to look at home water heaters in the 40 - 50 gallon size, Natural gas, they typically have a 40,000 Btu input rating and a 40 gallon "First hour" production rating. In other words fill it up with 50F water and it will heat about 40 gallons of water by 90F to 140F. If you are camping in Yellowstone with 40F ground water, expect colder showers. Down south in the summer time, expect longer and warmer showers with ground water well into the 60'5 and low 70's in states bordering Gulf of Mexico. In Phoenix, I did not need to run my water heater for showers on the 110F days, the hot pavement and 75F ground water temp warmed the water plenty.
For reference, there is 95,000 Btu's in a gallon of propane. So the L5 will run about 3 hours per gallon of propane. Your typical 6 gallon water heater has a 8,800 Btu input, and can heat the 6 gallons in about 45 minutes on propane alone, saving about 10 minutes on gas and electric.
A typical 10 gallon heater will have a 10,000 Btu burner, and 1,000 watt (3,400 Btu) heating element. So they will put out about 10 gallons per hour, while the 6 gallon can put out 8 or 9 if you are using some of the water during that hour.
I also considered a tankless electric water heater in the 4 KW size range, however it will not provide enough Btu's to warm 2 GPM (typical flow rate of a shower) - only heating it by about 6 or 10F.
Good luck,
Fred.
