Product Spotlight: Precision Temp RV-500 Tankless Water Heater

Two common concerns with recreation vehicles that are (or should be) familiar to just about every RVer on the road today are weight and resource conservation. Carrying excess weight in any rig has distinct disadvantages. In fact, I’m not sure there are any advantages to running an overweight rig down the road. From tire life to running gear to steering/towing/handling issues, shedding excess weight when possible all rack up on the “plus” side of the column. Likewise, conserving onboard water, battery power and LP gas have to be foremost on the mind of even the most casual RVer, especially when enjoying the adventures of dry camping.

Not often does a single product come along that can do all four; reduce weight, save water, use little battery current and consume almost half the normal amount of propane, especially when found in an appliance such as a water heater. But that’s exactly what the RV-500 tankless water heater produced by Precision Temp accomplishes. I’d heard good things about the RV-500 for a long time. I’ve studied the specs and read all the literature, but never had the opportunity to actually install a brand new unit, until now.

 I’ve known for years that the RV-500 was the logical replacement for any 10-gallon RV water heater, but was surprised to learn that with only a slight modification to the height of the cutout size in the sidewall, it can easily replace all those aging 6-gallon units still out there. But why would anyone choose a tankless water heater in the first place?

Well, less weight being one of major draws. Considering that water weighs 8.35 pounds per gallon, that means you can immediately eliminate almost eighty pounds of unnecessary travel weight when replacing a 10-gallon, DSI (direct spark ignition) Atwood heater and a whopping 90-pounds when replacing a like-size Suburban water heater. Over time, your tires and suspension components will thank you.

For those unfamiliar with how a tankless water heater actually operates, allow me to elaborate. First of all, there’s no tank, duh! There’s also no pilot flame since the RV-500 is a direct spark ignition appliance. The high performance, 12-orifice burner will only ignite when water is flowing. Here’s how it works; when the unit is first powered up by applying 12-volts DC, the integral microprocessor readies the gas valve and puts the operational sequence in stand-by status until a hot faucet is opened somewhere in the coach.

Once water starts to flow, (by either city pressure or onboard pump pressure), a small rotary flow meter is activated and begins monitoring the actual flow of the cold water coming into the RV-500. Once it senses a steady flow approaching one-half gallon per minute, a signal is sent to a modulating LP gas valve, opening the valve and starting the automatic spark igniter. Like most other DSI appliances found on RVs, the control board performs multiple functions; opens the gas valve, creates the spark that ignites the incoming fuel and monitors the flame to ensure the LP is indeed being consumed at the burner.

The microprocessor constantly calculates the amount of water flow as well as the temperature of the incoming water and adjusts (modulates), the LP flow through the gas valve accordingly. This modulating of LP inside the gas control valve makes for a very efficient LP-burning appliance. It only consumes what it needs in order to maintain a set delivery water temperature.

As the incoming water passes through the heat exchanger on its way to your shower or sink faucet, the temperature is monitored by three thermistors positioned at various points along the route. The one pictured here, (the compression nut with the black insulation), is positioned about half way through the heat exchanger. There is another one monitoring the water temperature at the cold inlet and yet a third mounted at the hot outlet.

The processor also interprets this information and recalculates the amount of LP flow needed to maintain a consistent output water temperature within (+ or –) two degrees F. The thermostat, by the way, even though preset by the factory at 115-degrees, is adjustable to any set point between 90 and 135-degrees F. As long as you have that hot faucet open, hot water will continue to flow. The burner shuts down when water flow is stopped. No more running out of hot water just before you rinse the shampoo!

LP appliance safety is always a concern on an RV. The RV-500 is equipped with multiple safety features including two electronically operated over-temperature sensors that will shut the sequence down if exceeded, as well as a thermal ECO (energy cut-off), which is automatically resettable.

A redundant solenoid controls gas flow. The gas valve closes in less than one second if no flame is sensed upon initial ignition of each sequence. The circuit board will try twice for ignition, and then go into lockout. A lockout condition means something is amiss; low or no LP pressure, insufficient voltage, etc.

There is a typical pressure relief valve (P&T) common to all water heaters. And like standard RV water heaters, all combustion takes place outside of the living section, with primary air intake and exhaust gases all sealed from the interior of the RV.

 A covered, 3-amp, in-line fuse accessible through a removable side port protects the internal 12-volt DC wiring. It is recommended to install another fuse in the switch circuit to protect it and the conductors between the voltage source and the RV-500.

The microprocessor and electronic circuitry, including two operational LEDs, are contained in a handy drawer that easily pulls out for maintenance and inspection, accessible from the exterior of the RV-500. About the only maintenance requirement I see is to clean the contacts on the circuit boards once a year.

Replacing an existing tank-type RV water heater is pretty straightforward. After draining the tank, the 12-volt DC wires, hot and cold water lines and LP copper tubing must be disconnected, protected and moved aside. The RV-500 will slip right into the same hole as your current 10-gallon heater. It will likely be necessary to reroute the LP tubing, however. Conveniently, the RV-500 has a rear and a side option for connecting the copper tubing to the inlet flare fitting on the gas control valve.

The 12-volt wires and the hot and cold water lines attach at the rear of the water heater, much like they all do. The only wiring modification may be to reroute the hot wire, either from the existing master switch or run a new conductor from a newly installed switch, plus the negative, ground wire.

If you’re replacing an existing non-wired, pilot-model water heater, be sure to use 18-gauge wires for the hot and ground circuits at a minimum (I recommend 14-gauge). And protect the switch and power circuit with a 3-5-amp fuse or circuit breaker as previously mentioned.

One difference with the water tubing connections on the RV-500, is that the hot and cold are reversed, top and bottom. On a typical RV water heater, cold water enters at the bottom of the tank. On the RV-500, the cold water enters at the top and the hot water emits from the bottom. Of course, if you happen to install it the other way around, you’ll soon find out! Thankfully, I didn’t have that problem since both water connections are clearly labeled! Any RV handyperson should be able to easily replace a standard, tank-type water heater with the RV-500.

The good (quality-wise and customer service-wise), suppliers in the RV Industry freely post their technical literature. And Precision Temp is one of them. Technical specifications, installation manuals, user’s guides, etc., are all available on-line, but are also shipped with each unit. They cover the full spectrum of installation options as well as all the nuances of safety. As with all LP appliances, it is necessary to check all connections for leaks prior to putting the appliance into service. Take the time to read all the paperwork!

I do recommend that the LP system, not just the connection at the heater, but the entire coach be leak-checked by having a certified RV technician perform a timed pressure drop test. Additionally, this appliance, like all RV appliances, must be fed a steady diet of LP delivered at 11.0 water column inches. A manometer and a specific set of procedures are necessary to set the LP delivery pressure and to test the rig for leaks. Rely only on a Certified or Master Certified technician to perform these procedures.

Though the RV-500 was designed initially for use in a recreation vehicle, I chose to install it in what’s called a “tiny house.” There is a distinct “tiny house” movement going on that is quite cool to say the least; basic, simplistic living at its best! Try Googling “tiny house movement” and spend the next few hours (or days) perusing the growing popularity of this social phenomenon.

The installation of the RV-500 in the tiny house is the perfect marriage of sorts. A small dwelling with simple accoutrements simply does not need to house six or ten (or twelve) gallons of water in the water heater. Aside from the RV market, it wouldn’t surprise me to see the RV-500 installed in more of the tiny houses within this growing movement. To read the story about Zoey’s tiny house, go to: http://www.togetherweareone.com/building

As with the tiny house movement, RVers everywhere have long embraced the practicality of sustainable living; that’s exactly what self-contained RVing is, right? Without a doubt, the tankless, instantaneous water heater is here to stay. As a matter of fact, as I type, another product supplier has jumped on the tankless water heater bandwagon, albeit far behind the efforts of Precision Temp. And as more RV manufacturers become more weight conscious, and with eight million (maybe more) RVs on the road in America, I believe Precision Temp just may be busier than ever!

Your homework assignment starts here: http://www.precisiontemp.com/pt_rvmd_main.html

And remember, RVing is more than a hobby, it’s a lifestyle!