mrgoat
52 main st, Goshen MA
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Joined: 02/02/2012
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Using a LP gas tankless system intended for a house in an RV or Camper trailer
This may seem like a bad idea to a lot of people out there but I am only considering this option. I have spent the last hour searching on the web and have been unable to find anyone who has tried this. I understand installing a a home system in a way that is not intended for use will most likely void a warranty. If you tell them. I have been researching two RV systems, one being the Girard RV system, which is cheaper ($350-$800 on eBay) but has bad reviews. It seems to need 1 gallon per Min (1gpm) before it kicks on, so RV-ING somewhere where water can not be wasted people complain that it is kicking on and off. In an RV the water pumps are not very accurate, when you open the faucet the water pressure tends to fluctuate, especially when its running very slowly. I like to travel across country and often find myself holding down the camp at a truck stop for several days while waiting for a check to clear, so I know the importance of not wasting water and if I'm doing dishes I don’t want 1gpm of water being wasted nor do I want the small stream of water being cold. In my shower I use a household water head on a water saver setting, I would say it sprays at least 1gpm but maybe not if I have the cold water on as well. So that might not work for me in the shower either. Then there is the RV-500 by precision. ($1000 on web, not on eBay right now) It has much better reviews and seems to kick on at 0.4gpm. It also seems to have a higher BTU for better hotter hot water.
Why don’t I just replace my leaking 6 gallon water heater with another one you may ask? For one, when I’m at a campground or plugged in somewhere where I am living and have unlimited water I am sick of only being able to take 7 min showers while turning the water on and off in-between soaps. Two, I run out of hot water when doing a sink full of dishes. Three, I want to sit in the little bath tub filled with hot water while more hot water is spraying down on top of me. Four, I live in an 87 royal diamond 35 ft camper trailer, I have done lots of work and carpentry. I have significantly added weight to the poor trailer, so loosing the 6 gallon water tank would be a nice change and reduce weight substantially. Other then the high price of the RV-500 another issue is that you need to get a winter package ($100) if you often camp somewhere cold. (Right now there is snow outside) This adds a fan to blow against wind gusts and also adds some type of heated wires that go around the water pipes inside the burn area I guess, because the RV models separate the RV from the flame by mounting from the outside. I'm sure the heat package must use at least 200-400 watts and when your running everything off one 120 volt plug that's a lot.
I don’t see why I can't pull the old water heater out, cut the shelf off that it rests on under my counter. Frame in the existing hole and mount a home unit for $200-$300 bucks and drill a hole in the plywood for the vent. If their safe enough to use in your house why cant you use it in a small house / RV. That would also reduce the need for the heat tape and crap. It could also be wired to a switch so it can be shut off when not around. As long as its mounted properly and checked after stopping somewhere, What the big deal? You could even screw a simple cage around it to keep something from falling against it. I do understand that the trailer would have to be pretty level to maintain peek performance, and I doubt being slightly unlevel would really be dangerous for I bet all tankless systems have sensors that shut them off if overheating is detected. Has anyone tried this? What do you think? Thank you!
* This post was
edited 02/02/12 11:40pm by mrgoat *
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Golden_HVAC
Fulltime, CA, USA
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Joined: 08/19/2003
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Hi,
I have run my calculator many times looking for a way to ahvea warmer shower. I might install one of these or it's little brother the L5 to pre-heat the water going into my RV.
http://www.amazon.com/Eccotemp-L10-Capac........or-Tankless/dp/B002JLSH5S/ref=pd_cp_hi_0
The L10 might be large enough to meet your water needs. I don't know what it does when it starts snowing outside, I would have designed in a circuit that turns on the burner when the heat exchanger is 35F and shuts off in 10 seconds or at 85F. This way even if the sensor goes bad, the water heater will not get to hot.
I was thinking of installing the L5 to the inlet to my 6 gallon water heater, so that the water heater is taking in 80 - 100F water, and should last more than 4 - 5 minutes. Funny when taking a shower in a COuntry Coach, with a 10 gallon heater, I did not run out of hot water. THey have a 800 watt electric element (about 2,500 Btu's per hour) and gas burner in the 10,000 BtuH range.
I think the L5 is 35,000 Btuh, or about 500 Btu's per minute, about enough to heat 1 gallon by 45F. So if your inlet hose is sitting in snow, at least the incoming water will exceed 80 while the unit is on. You might be able to use it to heat all the water coming into your RV to about 80, and really be able to take a long shower- even though at 3 GPM your flow might cause it to only put out 70F water with the very cold groundwater in your area.
Personally I am resigned to using the 6 gallon water heater for now. It is impossible to upgrade to a 10 gallon unit in my RV, the furnace is directly above my water heater, and I don't want to give up another basement storage compartment to put in the 10 gallon heater. Though this might be possible, then feed the factory heater with another for longer showers - that might work well.
One option that I have and you don't is installing 20' of 2" PVC and painting this black, it can sit alongside my RV and warm the water to the 80 - 90F range, and will provide 2 GPM for 90 seconds of somewhat pre-heated warm water to start the shower off warmer, yet will only extend the shower time by 2 minutes at the most. Cost is right - about $12 in fittings.
A few people have installed a tankless electric water heater to pre=heat the water going into the hot water heater. This can warm the water a little bit with 120 volts, yet is barely noticable at 2 GPM flow rate. I considered a 30 amp 240 volt heater to prewarm my water at the inlet hose while camped in Portland Oregon, at a RV park, using the 50 amp service to power the heater only when taking showers. Still this will not provide a "Hot" shower, at 3 GP it will only warm the water going into the RV, enough to provide hot long showers, yet the cost of a tankless 6 KW heater is a lot, with very little benefit.
I can use my outside shower to put hot water into the fresh water tank. If that is heated to 80F, then a really long shower is possible. Right now if you are using 35F water and 140F water, to get to 100F you will use about 70% hot and 30% cold water. If warmed to 80, then it becomes about 70% cold and 30% hot, you can stay in for 20 minutes or so.
When I lived in Mesa AZ, the ground water temp coming out of the garden hose was 75 after letting it run to cool off. Then run it across the 110 pavement in the shade, and into the RV, I did not need to use the water heater at all! until October.
I also found that if running my furnace, it seems like the water comes out warmer, probably because the water lines run near the furnace ductwork, or maybe I can stand cooler water temps while the furnace warm air is blowing around.
Anyway , I think you might have a problem with your extreemly cold inlet water, the boilers can condense condensation when the inlet water is to cold, and also the flow must be pretty slow to warm water by 70 - 90 F instantly unless the burner is really large.
This is one big advantage to feeding the factory water heater with the lower capacity $100 L5 water heater. It will provide a really long shower because the water into the hot water heater will exceed 90F and output only needs to be warmed slightly! And if the L5 burner cuts on and off due to low water flow or excess hot water outlet temp for 1 second, then I will not get a rush of bone chilling cold water for a couple of seconds while the heater turns back on.
The L5 is low enough cost ($100 - $120) that I might buy one, then hook it up to my water inlet hose for my RV, and test it out. IF I can set it to heat all the water to 80F, and then flow 3 -4 GPM, even if only heated to 60F, I should have a very long shower, and by slowing the flow to 2.5 GPM, I should be able to take a 15 minute shower at 100F inside, because the cold water going into the shower and water heater will be about 80F, and thus I will have about 30% hot water and 70% 80F water, and the 6 gallons will last a long time.
The only things stopping me is I will also need to buy another portable propane tank, and find a place to hang the water heater all winter. In the summer, the ground temp is high enough that short showers are not a problem.
Fred.
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BarneyS
S.E. Lower Michigan
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Joined: 10/16/2000
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Please do not double post. See any additional posts to your question here.
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