Tiny House, Tiny Living, The Tiny Life.

Precision Temp RV500 Review – Tankless Hot Water Heater

For a long time I have recommended the RV-500 Tankless Hot Water Heater from Precision Temp, but recently I found myself no longer being able to recommend it.   I don’t normally do product reviews, but the RV500 is one of those appliances that a lot of tiny housers use and people wanting to build are planning on installing.  So I thought I’d share my experience here.

tankless-rv500-review

To be transparent, I owned the RV550, which is very similar to the 500, the only difference is the 550 vents out the bottom via a pipe, where the 500 vents out a side panel.  While there are technical differences, they’re almost identical, save the vent method.  Most people don’t know about the 550 as its just a product variant, it’s fair to say its the same series, hence me reviewing this under the RV500 title because that’s what most people will search.

So to the review.

I purchased the unit in 2013 after doing a lot of research about the unit.  It seemed like my options where this unit or an Atwood variant that honestly didn’t look that great as an option.  I laid down the $1100 for the unit (gulp) and awaited it’s arrival.  In addition to the unit I purchased the 110V to 12V adapter, which let’s you simply plug in the unit to a standard power outlet.

When the unit arrived I was checking it out when I noticed an odd noise when picked the unit up.  At first I thought it was just a check valve or some wires jiggling, but upon further listening I became concerned.  I decided to crack open my brand new unit and I’m very glad I did.  What I found was one of the main vent hoses had come loose and the hose clamp was rattling around in the bottom of the unit.

carbon-monoxide-gas-safety

I realized that this was a pretty serious thing, because if I hadn’t investigate and just installed, it would have mean that the vent would be pushing exhaust into the interior of my house.  Very dangerous.  As a side note I later got a new unit and looking at how firmly that vent host was attached, I’m guessing that it was never connected in the first place, not just wiggled off in shipping.

It was then I asked for a replacement unit because I wasn’t sure I could fix it, plus it was brand new out of the box.  I put it right back in the box, repacking just like they sent it to me.  Called them and they sent me a new one and asked for me to send it back, the customer service was good on that call.

wrong

What wasn’t good, was later on, when they received the unit back; one of their staff sent a snide email telling me how there was nothing wrong with the unit and how scratched the unit was.  He then began telling me how I was wrong because they “test every unit before it goes out.”  The unit would have worked fine even if they test it, it just was not venting out the vent tube.  Keep in mind I sent it in the exact packaging they sent it to me in.

The email was rude, the email was petty, but more concerning was that as a layman I could figure out that the unit was not assembled correctly, but the person working for the company didn’t notice a 4 inch vent hose being so loose it wasn’t seated on the connector at all.  I was annoyed by the person’s unprofessional behavior, but ultimately I realized I had a working unit and that’s all that mattered.

I got my new unit and I immediately opened it up to check the internals, all looked in order.  I then installed the unit in my house a while later.  I had a professional plumber come in and install it because I don’t like messing with gas lines.  The install went smoothly until we had to turn the thing on.  The unit would start working, but the vent fan wouldn’t kick on.  Later on we were able to get the vent fan working, but it wouldn’t light.  Finally I gave Precision Temp a call after going round and round, he told me to un-ground the unit by disconnecting the green wire.  The unit turned on and worked instantly.

wiring

This really frustrated me because as you can see above – this is a screen shot from the install manual – you’re supposed to ground the unit.  The support person said that 12 volt is very sensitive so if it’s grounded, it can cause trouble.  This is all true, but their install guide says green goes to ground.  In the end, I didn’t care too much, I had hot water and it was great to have hot showers.

Later that year winter came and I was finding that even in the mild winters of North Carolina, the unit couldn’t get the water hot enough for my showers.  It would be solidly warm, but never hot.  I really like hot showers, one of the best things on earth, so this was disappointing.  I tempered this with the fact that the unit could only rise the water temperature so much, it was rated at around 55,000 btu and that inherently can only warm cold water so much.

I really did like how efficient the unit was, using a 20lb propane tank (like you have on your grill) I could have hot showers and cook meals on my gas range for around 4 months per tank!  That was really nice, I bought four tanks and that would allow me to shower and cook for an entire year, plus have one extra.  This meant my gas cost was $4.50 per month!

Then it all went to hell.

I was taking a shower about a month ago and once I was done, I stepped out to towel off.  I noticed that the tankless didn’t turn off, but instead kept the burner going.  I turned the water back on to see if I could trigger it to turn off, nothing.  Tried the sink, nothing.  I unplugged it, nothing.

What I didn’t know was that the safety pressure release valve had failed and the unit was building steam pressure, all a sudden the unit tore itself apart.  The unit had built up so much steam pressure that it literally ruptured the wall of one valves and tore the threads out of another.  It scared me half to death, but luckily all the steam and debris was kept within the case when it exploded.

rv500-valve-bad

Water began to pour out of the unit, propane began to bubble through into my house, in a few seconds my floor was covered with water and the air was thick with propane.  I ran outside and turned off the water and the gas.  When I turned back water was dripping out of my house from all corners.

I let the gas vent out and then I got to mopping.  This was the last straw for me, what if I hadn’t been home, the water would have flooded my entire house for hours!  What if I had pulled off the cover to inspect it with my face right there as it ruptured!

I cleaned up and called a plumber and schedule an appointment to have a different brand to be installed, I was done with the Precision Temp tankless hot water heater.  I’ll do a post soon about what I opted for in it’s place.

Final thoughts:

In my opinion the unit is way more expensive than it should be.  I was able to get a new unit for around $600 and it has three times the btu and a similarly compact vent system.

I have personally seen two manufacturing failures on two different units.  One faulty unit might be bad luck, getting two faulty units points to a larger issue in their standards and at $1100 a piece, their standards should be high.  Obviously not.

Having a safety valve fail is a really big deal.

Your Turn!

  • How are you planning to heat your water in your tiny house?
7 Comments
  1. I plan on using a Rheem 20-gal electric water heater under the counter in the kitchen. I am NOT messing with propane for the experience you had. Talk about ka-boom your house to pieces, not to mention it will destroy your lungs in the explosion, and you’re left dying from the butterfly effect on your lungs (people bombed in air-tight buses die the same way), even if nothing else happens to you. Plus I have not had good experiences with in-line heaters. They seem fickle and don’t know when to supply hot water. I’ve had one in someone’s house not deliver hot water when doing a weeks dishes for the owner. No thanks. I’ve NEVER had this experience with a traditional water heater. Go down to a 10-gallon if you need it and use a shower head with a RV-style cut-off valve. I do just fine on an RV 5-gal water heater in my travel trailer, my current house while I’m SLOWLYYY finishing the inside of my tiny cabin.

  2. Whoa, Ryan…scary as heck and much appreciated! I hadn’t yet decided on a brand but this one was on my list so now it’s off. I still like the idea of a tankless but I’m taking Stephanie’s advice to heart and will hook up an electric version. I love TH peeps for their willingness to share their wisdom. Thank you!

  3. Yet again another reason why I ditched the tankless unit I had and bought a Noritz NR501-OD-LP from a local dealer—$626.78 and had a professional plumbing company experienced with tankless water heaters of all kinds install it, test it, set it up, blah, blah, blah. And will come out to service it or repair it if I ever need them to do so.

  4. Are there any other units that vent through the floor like this one?

  5. Best bud is a Master Plumber & Steam Fitter with 40+ years of experience. Also have a friend who’s a dealer for Rinnai, and he doesn’t have one in his own house. Both say the tankless are trouble mainly due to being highly vulnerable to mineralization deposits, even more so than traditional tank versions. Add to that the issues of propane being just as un-green as any other fossil fuel, and the tankless units’ over-pricing and they tend to loose their shine for folks like me. Evacuated tube solar collectors appeal to me far more, particularly the split systems that incorporate a tank. Propane/natural gas/methane, it’s all the same, and regardless of what crap you here from the political whores from both parties, there’s nothing ecological about fracking, so get with the times and go solar or go cold. Still get tax credits, no gas to mess with, so safer AND simpler to DIY, AND you get a unit that actually pays for itself, which no fuel burner can.

    Another option that I’m looking at for our next small house project (I’m a retired contractor who specialized in hyper energy efficient design & build since long before it was cool) is trying to incorporate in-floor hydronics that can be driven by one of these. If I were building a small/tiny home on a fixed slab this is a no brainer, but it also illuminates an area of design that I feel many tiny home enthusiasts are not taking full advantage of, and that is passive solar design (see German & Scandinavian design requirements for new residential construction for a broader view).

    One of my favorite packages is based on using the structure as a giant thermal battery. We do this by insulating UNDER the slab, as well as around its perimeter and footings while providing special thermal breaks and drainage to limit thermal bridging and moisture wicking. Outside walls are dry stacked block that are rodded, filled, and coated with a reinforced cementious structural coating that can be sprayed or troweled on. While probably about a 7 on the DIY 1-10 difficulty scale, the dry stack process is within the skill set of folks not gifted as masons.

    https://www.quikrete.com/athome/video-dry-stack-wall.asp

    To complete the basic shell the entire exterior is insulated with a continuous layer of at least 2″ of rigid Iso foam (R-10 per inch) in two layers to allow a staggered seam lapping, then seam taped and covered with either Dry-Vit/Stowe or strapped with firring strips to attach whatever other exterior finish desired. With Pex tubing running at about 12″ on-center throughout the slab, and carrying relatively low temperature hot water, the heat is simply amazing. Radiant is THE most comfortable, period. Barefoot on a tile floor in the dead of winter sounds nuts, but it is simply awesome with radiant hydronics. The efficiencies are incredible since your walls and floor, once tempered, carry an amazing amount of stored heat. Proper siting is of course also critical, along with using things like insulated shutters, extended south facing overhangs and window awnings, etc. but when done properly the result is a structure that can literally be heated with a candle.

    Built my first “Tiny House” for a neighbor about 20 years ago who wanted a small guest house/office on his property. 16’x24′ with a full loft and a 6’2″ center ceiling height in the loft. Used the thermal mass concept along with numerous passive solar design elements and ended up with a building that maintained 55F. degrees all winter long using no supplemental heat at all. That was due to the residual heat expelled by the small apartment sized frig kept there, along with a few watts of CFL lighting ballasts. The installed hydronics proved to be absolute overkill (domestic H/W and supplemental slab heat was provided by a cheapo conventional 30 gal. electric water heater that he had replaced in his main house). We later built a similar structure as a workshop for him that was earth bermed (the building was actually built into a hillside so that two walls functioned as retaining walls) and finished with a flat living roof. The south facing long wall had a full length Solexx greenhouse/entry way that was separated from the remainder of the shop by a trombe wall that featured stacked black water drums. The property is up in Lancaster County, Pa. and once again, the radiant hydronics proved overkill.

    What I’d like to try is an insulated slab of some sort that could take the pounding of over the road travel without disintegrating, which I’m pretty sure we can do with mix additives, fiber mesh, and some rebar. Problem with the thermal mass of course is that, well it’s friggin MASS, or density I should say, it’s just really heavy, so not exactly suited to OTR hauling. Maybe not a problem for Park Trailers or a Tiny home that may only move every couple of years, but hardly RV worthy. Either way the hydronics can still be used with reflectors even under a traditional wood framed deck, so there’s lots of potential there for solar H/W system integration that can do double duty as both a supplier of domestic H/W as well as THE most comfortable heat.

    If you really wanna burn something try a bio-mass wood gas boiler. Friend has one he built himself up in northern Canada that heats all of his farm buildings and home. He burns sunflower seed hulls that are a waste product near him, so he gets deliveries augered right into a giant grain silo that he fashioned another auger to feed out of the bottom and right into his boiler. My current neighbor has a tree company, so an unending supply of free wood chips, and we’re building a low pressure chip fired boiler that will work the same way to heat our 32’x96′ greenhouse.

  6. I have the 500 in my motorhome right now, installed it in 2014, been a pc of crap since we bought it. I design and build industrial equipment and have a full understanding of a wide range of equipment, the problem i have is the water is always too hot, and when you try to use less hot with the cold the unit shuts off, i have it working with the bypass part open right now but if i hook to shore water with a regulator, the pressure is different and the thing won’t start. I also called the arogant imbeciles at the factory and they told me “they can’t possibly have made a unit that worked so poorly and to stop varying the pressure”. I told him that made no sense and that he needed to change his tone, he then hung up and would no longer return my call. Im going back to a tank style

    please hear this, “ITS DANGEROUS FRUSTRATING GARBAGE,AND THERE IS NO HELP, DO NOT BUY IT!!!!!!!!”

  7. I too have a precision temp water heater and have now replaces almost all the parts and its now out of warranty. we had a problem with the ignition bored, they sent us out a new one right before the warranty was up and the ignition trouble shooting isnt anywhere to be found. i have taken this thing in to be looked at the guy said the same thing. there are no ignition specs to be found. this is great. whats is this new water heater your talking about???

Leave a Reply

[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[class*="-body"]
[class*="-body"]
[class*="-body"]
[class*="-body"]
[class*="-slide-open-holder"]
[class*="-slide-open-holder"]
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet_bg']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[data-image-id='gourmet']
[class*="-body"]
[class*="-body"]
[class*="-body"]
[class*="-body"]
[class*="-slide-open-holder"]
[class*="-slide-open-holder"]