Vented Cabin Tankless Hot Water Heater in an RV

[khantroll]

Hi all, I have a couple of questions regarding tankless hot water heaters. I am in the process of renovating my RV, and one of the things that I'd like to do is upgrade to a tankless hot water heater. Initially, I thought my only choice was the Girard Tankless Hot Water heater, but I have seen several videos of vans, buses, and even fifth wheels using one of the small cabin residential tankless hot water heaters. Example: https://www.amazon.com/Ridgeyard-Tankless-Stainless-Bathroom-Supplies/dp/B01LWSPVBS/ref=sr_1_1?ie=UTF8&qid=1493646000&sr=8-1&keywords=d+batteries+tankless+12L  These are less then half the cost of the Girard., and somewhat smaller.
As a follow up, would it be possible to use a plumbing vent as a flue?
Thanks in advance for your thoughts!

[tmsnyder]

Plumbing vent? As in 'plastic'?


I would think 'no' since the efficiency is only 85%.  This is similar to a gas water heater, so the exhaust will be hot, and will need to go into water heater type ducting.


The modern high efficiency furnaces which vent into PVC are well over 90% efficient, the exhaust temp is low enough that they are safe with PVC which can also handle the condensation that happens after the gases cool.

[khantroll]

Interesting. Hm?  I didn't think the exhaust would be that hot, as people run the unvented kind in enclosed places all the time (I'd prefer vented because I don't trust the carbon monoxide detector that much).

[Rickf1985]

Look at the grammar in the safety description, I think you can tell where this comes from. And you generally get what you pay for.

Safety Tips：
-Must be installed by gasman.
-Must be used under the condition of ventilation,ensuring the normal condition of the flue kit.
-Please use and maintain the heater according to the manual.
-Please check the gas connection regularly to ensure there is no leaking risks.

[Rickf1985]

And just because some people do run unvented gas heaters in a closed in camper does not make it safe. I don't trust detectors either. If it fails yo are dead, No returning it for a refund.

[khantroll]

It seems like most things are made in China these days; even things that are made in the USA are assembled from parts made in China. Perhaps I am just used to it as everything in my field comes from Asia.  That particular unit does seem to be lacking in the support department, but I am curious about all those such units (ecoTemp, campShower, etc).


Here is an example of what many people seem to be doing: https://www.youtube.com/watch?v=srqpldS_H_0


which I am NOT a fan of due to the lack of a forced vent. I was also reading over the manuals for the EcoTemp, and their recommendations might be hard to follow in an RV: place unit 2 inches out from the wall, six inches off the ground, 4 inch vent pipe with preferably no more then a 3 degree slant.


The main reason I am curious are the cost vs performance of the on demand rv water heaters: 


Truma AquaGo: 60000 BTU - 2 gallons per minute flow rate - $1100
Atwood Tankless Hot Water Heater: 50000 BTU - 1.5 gallons per minute - $825
Suburban IW60: 60000 BTU - 1-2 gallons per minute: $610
Precision Temp RV-550:  55000BTU - 1 gallon per minute: $1070
Girard GSWH-2: 42000BTU -  1.6 gallons per minute: $514

Most everyone says the Girard sucks, and the Truma is the best, with the other three being roughly equivalent. Meanwhile, the Ridgeway costs about a third of the Girard, and has twice the performance of any on that list.

[Rickf1985]

At least that is what they claim, there are no reviews to back up that claim from what I see. A couple of people have plumbed the portable units so they can hang them outside and hook the hoses up to run inside. That way there are no worries about gases and no interior heat in the summertime. Winter might be an issue but not too many people other than northern full timers have to worry about that.

[tmsnyder]

^^^ What Rick said  ^^^^   Two water and one gas quick connects and hang it on the outside, or on its own little stand. 


The comments on that video are hysterical.  There are instructions on how to disable the 'low Oxygen' sensor so that the heater keeps running even when it has depleted the oxygen in the room.  WOW!

[khantroll]

Yeah, and in the video the guy acts like it's no big deal whatsoever to disable the CO sensor 


Here's a page of that style of heater with more reviews: https://www.amazon.com/Eccotemp-L10-Portable-Outdoor-Tankless/dp/B002JLSH5S/ref=sr_1_1?s=hi&ie=UTF8&qid=1493727833&sr=1-1&keywords=eccotemp+l10

[khantroll]

I went with a scratch and dent Atwood On-Demand hot water heater. 

[Bashedit]

I installed the Girard last winter and it works fine except when there is low water pressure or flow. At shower time I just shut off the water supply and use the fresh water tank and pump which delivers more than enough hot water for a long shower. I also thought about the smaller portable units but don't want to deal with the exhaust issue.

[khantroll]

Hi Bash,


If I had a different kind of rig, I think I would have gone with one of these. If I had a bus (transit or school bus), where the chassis was metal and it could be stored in a compartment or the flue heat shielded, I think it could have worked great. In an old Winnebago, it would have taken way too much work and I never would have trusted it completely.


My Atwood is actually awesome! It took a little finagling to get it to work because the dimensions were slightly different. I think the 1.5gpm listed below is underselling the unit. It's easily capable of providing a shower and hot water to the sink, which is all I need in an RV anyway.


I looked long and hard at the Girard, and I had convinced myself to pony up the money and buy one. However, I got an awesome deal on this Atwood ($200!!!)


Most of the complaints for Girard seem to be that the temperature isn't constant at a reasonable flow rate. Does yours seem pretty stable?