PrecisionTemp RV-500 Installation And Operating Instructions Manual

PrecisionTemp – RV-500

Instantaneous Gas Water Heater

Installation and Operating Instructions

The RV-500 is certified as a direct vent automatic instantaneous water heater designed to be
installed in recreational vehicles or mobile homes. This appliance must be installed in accor­dance with local codes or in the absence of local codes the following applies:

Manufactured Home: Standard, Title 24 CFR, Part 3280
Recreational Vehicle: Standard ANSI A119.2/NFPA 501C-1987

Every water heater is inspected and tested before it leaves the factory. In order for this unit
to operate safely and effectively, all installation instructions must be followed. Failure to
comply with all installation and operating instructions will void the warranty. PrecisionTemp,
Inc. will not be responsible for anything that is a result of non-compliance

WHAT TO DO IF YOU SMELL GAS

• Extinguish any open flame.

• Shut off the gas supply at the gas

• Do not touch any electrical switch

• Do not start the vehicle’s engine

• Contact the nearest gas supplier

• If you can not reach a gas sup-

• Do not turn on the gas supply until

Keep this book with the water heater at all times. It contains instructions regarding installa­tion, operation and maintenance of your water heater. If you need further information,
contact your dealer, your nearest service center or PrecisionTemp Inc.

FOR YOUR SAFETY

container or source
or use any phone or radio in the

vehicle.
or electrical generator.
or qualified service technician for

repairs.
plier or qualified service

technician, contact the nearest fire
department.

the gas leak(s) has been repaired.

FOR YOUR SAFETY

DO NOT STORE OR USE GASOLINE
OR OTHER FLAMMABLE VAPORS
AND LIQUIDS IN THE VICINITY OF
THIS OR ANY OTHER APPLIANCE.

WARNING!

Improper installation, adjustment, altera­tion, service or maintenance can cause
property damage, personal injury or loss
of life. Refer to the installation instruc­tions and/or operating instructions
provided with this appliance. A qualified
installer service agency or the gas sup­plier must perform installation and
service.

Rev. 4/07

Please read these instructions thoroughly before starting your installation

Installation Instructions For The RV-500 Water Heater

The RV-500 water heater is designed to be installable and removable from the exterior of the
vehicle. The mounting instructions are for the PrecisionTemp flush mount and surface ac­cess doors. No other door should be used. Doing so will void the warranty and cause the
heater to malfunction and could cause damage or injury.

Please read these instructions before making any modification to the construction of your RV.

Selecting Installation Location

The water heater must not be installed in an area where the vent can be covered when any
door or access panel on the coach is opened. The water heater should be located in an area
where leakage will not result in damage to other items of, or in the structure. If such an area
cannot be avoided, it is recommended that a suitable pan and drain be installed under the
heater.

Install the heater as close to the gas supply as practical to minimize length of the gas line.
There must be a minimum of 8" of clearance between the vent cover and any other surface.

Do not install where the vent is closer than one foot from any window or opening into the
coach.

Although the RV-500 can be mounted with zero clearance around the sides, top and bottom,
be sure that the installation does not interfere with any wiring, plumbing or cabinets inside the
coach. Do not install the water heater or any other appliance where it can vent into an area
covered by an awning, canopy or any other enclosure. For better support and ease of instal­lation, install where the bottom of the heater case rests on a floor.

Installing Heater In The Side Wall Of A Coach

The RV-500 can be installed as a flush mount or a surface mount. The model RV-500 refers
to the heater ordered with the flush mount door kit. The model RV-500-1 refers to the heater
ordered with the surface mount door. The RV-500 flush mount can retrofit an Atwood ten
gallon flush mount water heater without side wall modification regardless of side wall framing.
If the side wall framing is steel or aluminum rather than wood framing and the original water
heater is anything other than an Atwood ten gallon flush mount water heater, it is recom­mended that only the surface mount configuration be used unless done by the RV
manufacturer or dealer.

Surface Mount Installation
Surround the opening on the skin of the coach with four to six inches of masking tape to pro-

tect the skin of the side wall.
The rough opening for the RV-500-1 should be 13.75” wide x 14.625” high. This is about

2.75 inches taller than an Atwood six gallon tank heater. If the opening needs to be enlarged
by cutting the internal side wall structural member, a 2”x2” wood support should be installed.

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Do this on the inside of the side wall so that a screw would go through the screw hole on the
RV-500-1 case flange, through the side wall and into the 2”x2” support sandwiching the side
wall between the flange and the 2”x2” support.

2”x2”

Support

Surface mount, edge view

Side wall of coach

Case Flange

RV500 Case

Attach a 3/4“thick 2 x 2” wide wood spacer to the bottom of the cut out. This will center the
flange of the RV-500 vertically in the opening. This applies if you are installing the RV-500 in
either the flush or surface mount configuration.

3/4” Thick Spacer

Side wall opening

”

Place the bottom of the back of the RV-500-1 on the bottom frame of the opening. Tilt the
water heater back and feed the gas line through the gas line grommet. (Note: If there is no
access from the inside of the coach to the back of the water heater compartment the water
lines and electrical must be connected at this stage. Refer to those sections of this manual).

Push the RV-500-1 into the opening. Center the heater in the opening and start a screw in
the top center hole.

Run the screw down but not tight. Apply silicone or other appropriate sealant under the RV­500 flange.

Push the unit into the opening to bed into the sealant. Now screw in the other three center
screws.

Apply silicone or other appropriate sealant heavily in the corners and on the flange around
the corner holes.

Place the corner pieces in the corner so the holes line up and put four screws in each corner.
Seal where the corner bracket meets the corner of the case. Remove excess sealant.

Flush Mount Installation

• Surround the opening on the skin of the coach with four to six inches of masking tape to
protect the skin of the side wall.

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• You are now going to mark the setback cut-out. Place the door frame over the opening.
Center the frame on the skin. Use the inside edge of frame to draw a corner radius on
each corner. Mark the .5” setback and remove the frame. Now check the markings to
make sure they are 18.5” wide by 18.25” tall and adjust the markings to this dimension.

(Note: Do not cut the setback as a square! The rounded corners of the frame will
not cover the square opening setback corner!)

• Cut 0.5” deep on the lines with a circle skill saw being careful not to cut past the radius.
Use a narrow chisel, a .125” drill bit, or router to cut around the radii.

• Use a wide wood chisel to cut 0.5” from the opening back to the cut you just made with
the saw. Clean the radii out with a smaller chisel. Now place the frame in the opening
and check to see that the flange part of the frame is flush with the skin of the coach. The
side wall opening is now prepared to accept the door frame.

• The rough opening for the RV-500 case should be 13.75” wide x 14.625” high. If the
opening needs to be altered and the internal side wall structural member is cut through, a
2 x 2 wood support should be installed on the inside of the side wall. Do this so that a
screw would go through the screw hole on the RV-500 case flange, through the side wall
and into the 2 x 2 support sandwiching the side wall between the flange and the 2 x 2
support.

Flush mount edge view

2” x 2”

Support

Side of coach

Frame

RV500 case

1/2” cut back

• Place sealant on the back of the door frame and push it into opening.

• Put flush door adapter ring over back of heater and bring forward to the mounting flanges.

• Slide the RV-500 and adapter ring into door frame already mounted into opening.

• Tilt the water heater back and feed the gas line through the gas line grommet. (Note: If

there is no access from the inside of the coach to the back of the water heater
compartment the water lines and electrical must be connected at this stage. Refer
to those sections of this manual).

• Push the RV-500 into the opening. Center the heater in the opening and start a screw in
the top center hole.

• Run the screw down but not tight. Back the screw off enough to put silicone or other ap­propriate sealant on the frame under the RV-500 flange.

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• Put the door onto the frame and adjust the frame so the door screw threads align with the
screw catch.

• Remove the door and tighten the top center screw

• Apply silicone or other appropriate sealant under the RV-500 flange. Push unit into open-

ing to bed into the sealant.

• Now screw in the other three center screws. Apply silicone or other appropriate sealant
heavily in the corners and completely around the flange. Remove excess sealant.

Connecting Gas Supply
The gas line should be of approved type and size with a 3/8" female flare nut. If the gas line

is very long or has numerous bends in it, it should not be less than 5/16" ID or performance of
the water heater will suffer. The maximum inlet gas pressure must not exceed 13 water col­umn inches.

Some standards may require a manual gas shut off valve in the gas line external to the water
heater. The water heater must be isolated from the gas supply system during any pressure
testing of that system at test pressures equal to or in excess of 1/2 PSIG.

To Connect A Gas Line:

1. Remove foil insulation and set aside until gas line connection is complete.

NOTE:

The gas line can be routed into the case through the grommet in the back or through

the side of the case. If the gas line is to be brought into the side of the case, the positions of
the knockout plug in the side of the case and the sealing grommet in the back of the case
should be reversed. Both of these devices will snap in and out.

Never operate heater with either of these holes left open. The gas inlet fitting on the top of
the gas solenoid valve must be repositioned to point to the side of the case. To do so, sup­port the gas valve and back-up with a wrench, turn the gas fitting 1/4 turn clock-wise taking
care not to damage the threads. Caution: Turning the gas-fitting counter clock-wise may
cause the seal to leak.

2. Route gas line through sealing grommet (back or side) of heater case. Take care not to

damage wiring.

3. Screw gas line fitting onto the flare fitting of the gas valve by hand and then tighten with a

basin wrench or crow's foot.

4. Turn on gas supply and check for leaks using a soapy solution on the joint. Never use a

flame to check for leaks. Be sure that sealing grommet is intact. If it became torn or dis­torted through the installation, fill cup on back of grommet with silicone caulk (RTV) to seal
against any possible leaks.

Warning: This flare fitting is a dry seal. Pipe dope should never be used on this fitting.

5. Replace the foil insulation taking care that it is secured to the Velcro attachment points.

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Connecting The Electrical Supply

The water heater is designed for 12 VDC negative ground. Never connect to 115 VAC. The
power leads are on the back of the heater and should be connected directly to the breaker
panel of the coach, extending the wires if necessary. Red is positive (+) and black is nega­tive (-).

If the leads need to be extended or any wiring is extended or replaced inside the heater, use
a minimum of 18 gauge wire with a temperature rating of 105°C. It is suggested that the
heater be connected to a switch or breaker rated at 2 amps.

Never connect heater to a power converter without a battery in line. Doing so could damage
your heater and void the warranty. Be sure that the heater is connected to a "filtered" (pure
DC) circuit of the converter. To test whether the circuit is pure DC, take a voltage reading us­ing a multimeter set on the AC voltage scale. If the reading is more than 1/4 volt, the circuit
is not DC voltage and should not be used. (See the tag on red and black power wire on the
back of heater)

Connecting The Water Supply And Hot Water Outlet

The water connections are on the back of the heater. They are marked "Cold" inlet and "Hot"
outlet. The Hot water is on the bottom and cold water is on the top. This is reverse of most
tank heaters.

The standard fitting is 1/2" NPT. Piping and components connected to the heater shall be
suitable for use with potable water. The heater shall not be connected to any system or
component(s) previously used with a non-potable appliance. When tightening water connec­tions to the water line, be sure to back up the fittings with a wrench as to not damage the
copper water tubing. Re-tighten the compressions nuts on the water fittings.

With the power and gas supply to the heater turned off, pressurize the water system, purge it
of all air and check for leaks. Also, verify that the rotor in the flow meter is rotating counter­clockwise while a water hot water tap is turned on. If it is not rotating counterclockwise the
hot and cold water lines have been installed backwards.

Note: There is no need for a bypass kit when installing the RV-500. It is recommended any
bypass kit be removed. If a bypass kit is installed the valve must be in the off position or the
heater will not operate properly. If the coach is going to be used in freezing conditions, it is
suggested that a drain valve be installed at the hot water outlet connection to drain the heater
while transporting in freezing conditions.

Recommendations For Water System Installation

In order to realize all of the temperature control features of your water heater and to extend
the life of the water system, observe the following recommendations:

• Be sure all water strainers and aerators are removed and cleaned.

• Any water flow restricter located on the inlet of the showerhead should be removed. Fail-

ure to remove this could effect the performance of the temperature control.

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• Keep hot water lines as short as possible and no larger than 1/2" ID to conserve water
and accelerate the delivery of hot water.

• Install a water strainer into the water line preceding the water heater to keep particulate
matter out of the system.

• Always have a water pressure reducer in place when using city pressure water.

• It is strongly recommended that an accumulator tank be installed in the cold water line.

This maintains a constant flow of hot water when using the pump, enhances the operation
of your water heater and extends the pump life.

Operating Instructions

The RV-500 is now ready to operate. Follow this procedure to operate the water heater:

1. Pressurize the water system by turning on pump or city water pressure.

2. Purge all air from system by turning on the taps until a steady stream of water flows from

the taps. Turn off taps.

3. Turn on the 12 VDC power supply. A green LED should now be flashing on the front of the

electronics drawer. (Front cover must be opened to observe LED). This indicates normal
operation. Close front cover.

4. Turn on the propane supply at tank and the manual gas valve if installed in system.

Heater will remain dormant until a water tap is opened and the heater senses a water flow
of at least 0.4 GPM.

5. Turn on hot water tap. The heater will fire up within two seconds and hot water will flow

from the tap in the time that it takes to get through the plumbing from the heater to the tap.
Hot water delivery will continue as long as the water is flowing. (Note: You may have to
turn the water on and off several times to bleed the air from the LPG line before the water
heater fires up.) If the heater fails to light after several ignition attempts, turn the power to
the unit off, wait 5 seconds and turn the power on again.

6. Close the hot water tap and the heater will shut off.

NOTE: When using an "on/off" button on a shower head or an outside wash down box, al­ways turn off the hot and cold water valves when finished. Not doing so will result in cold
water bleeding into the hot water system and causing the water heater not to ignite. Cold wa­ter or alternating warm and cold water will result.

The RV-500 is designed to give a continuous flow of hot water as long as required and main­tain the approximate set temperature through all flow rates within the capacity of the heater
(85°F temperature rise per GPM). The heater will not fire at very low flows; i.e., under 0.4
GPM.

It is recommended that even when dry camping, take a real shower and leave the water run­ning as you would at home. You won't run out of hot water and you won't have to waste
water waiting for the cold water to purge from the water line every time the water is turned

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back on. RV showerheads are designed to drip when turned off and will allow the hot water
line to be filled with cold water.

WARNING: Always turn off the 12-volt power supply to the heater during any fueling opera­tions. Operating this water heater or any other ignition source during fueling could cause a
fire or explosion, which could result in serious injury or death.

NOTE: Should overheating occur or the gas supply fails to shut off, turn off gas valve at the
supply tank. Immediately call a qualified service technician.

Do not use this appliance if any part has been under water. Immediately contact a qualified
service technician to inspect the appliance and replace any part of the control system and
any gas control, which has been under water.

Changing Temperature Setting

The temperature on your water heater has been factory set to approximately 120°F. It is not
recommended that you change this setting. Doing so could result in dangerously hot tem­peratures that could result in severe injury. If it is necessary to change the setting it can be
done as follows:

Open access door of heater. Pull the steel electronic drawer out about one inch. The
adjustment screw is located on a small blue block at the lower right corner of the elec­tronics board (R6), just inside the drawer.

A small blade screwdriver should be used. To decrease temperature, turn screw
counterclockwise. To increase temperature, turn screw clockwise. Check the water
temperature and adjust as necessary.

Use a voltmeter with the black lead in black test point and the red lead in blue test
point adjust the screw in R6 to read 2.0 vdc on the voltmeter. This will set the tem­perature control at 120º F.

Routine Maintenance

All faucet aerators and showerhead screens should be cleaned regularly.
It is recommended that the RV-500 be inspected by a qualified service technician at least

once a year. Particular attention should be paid to the following:

1. Be sure that the air inlet openings and flue area are clear of any debris or obstructions,

(leaves, bug nests, spider webs, etc.)

2. Check that heater mounting is still secure to the coach and there are no areas for potential

water leaks.

3. Open the cover of the heater and inspect for debris or obstructions under the burner or in

flue hood.

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4. Visually inspect wiring. Be sure there is no chafing of the insulation. Be sure that the di-

rect spark ignition cable (yellow) wire is secured to the electrode under the burner and that
the connector is not touching anything.

5. Check seat on front lip of electronics drawer to be sure that it still seals when drawer is

shut. Check that all case sealing grommets are secure and not leaking.

6. Check for soot around the flue. Soot is a sign of incomplete combustion and a qualified

service technician should be notified to correct the problem.

7. The pressure relief valve should be manually activated at least once a year by moving the

lever on the top of the valve 90°. Never perform this operation while the burner is operat­ing. Water will flow freely from the valve and could cause scalding.

Never plug the pressure relief valve. If the valve is actuating too frequently, contact Preci­sionTemp.

Winter Operation and Winterizing Water Heater

It is not recommended that you operate water systems in the winter. Any freezing of the wa­ter heater or other plumbing components can cause severe damage that is not covered by
warranty.

However, if it is necessary to operate the RV- 500 under freezing conditions, the power and
gas supply to the unit should not be turned off. As long as the power and gas are on, the unit
will ignite to protect the heat exchanger as the water temperature approaches freezing.

For extended cold temperature use contact PrecisionTemp regarding our optional
freeze protection kit.

Under no circumstances, however, should you travel under freezing conditions without first
draining water from the unit. To drain the system:

1. Turn off water pump and the power and gas to the heater. Open the pressure relief valve
by lifting the handle to a 90° position from the normal position.

2. Open drain valve that was installed at hot water outlet fitting of heater.

3. Open at least one hot and cold water tap in the coach. This should drain the system.

Before storing the system for the winter, the plumbing system must be winterized. This can
be done by either of the following methods:

1. All water should be drained from the system. To do this, open one tap at a time, using

compressed air to purge the system of all water.

2. Recommendations of your coach manufacturer should be followed. Since the RV-500 has

no storage tank, there is no need for a water heater bypass kit. It holds less than one
pint of anti-freeze. The water system can be filled with RV, non-toxic anti-freeze. When
you see the anti-freeze coming from the hot water tap, the heater is protected.

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Troubleshooting

The RV-500 is equipped with self-diagnostics. In the event the red LED is flashing please re­fer to the Service Codes section.

Most problems are easily remedied by consulting the trouble-shooting guide. If problems still
persist, contact PrecisionTemp or an authorized service center. Only a qualified technician
should do any work involving the gas system.

Heater Does Not Come On When The Water Turns On. Green LED Not Flashing.

1. Be sure all electrical connectors are secure and the polarity is correct. (Red wire to posi­tive terminal) of RV electrical panel.

2. Be sure power is on and panel breaker is not tripped.

3. Check electrical contacts in electronics drawer. Be sure the connector with red and black
power wire is plugged into board. Using a voltmeter, check for 12Volts on this connector.

4. The fusible link in this wire might be blown. Replace power cord.

5. Be sure there is a battery in the system. Never connect the heater directly to a power con-

verter. Some converters have circuits that are not pure DC. (See the tag on red and
black power wire on the back of heater)

Green LED Flashing But Heater Does Not Come On When Water Flows

Be sure that no water-mixing valve has been left in the on position, using the showerhead
as a shut off. This will permit water to bypass the water heater and bleed cold water into
the hot water system. Always turn off both hot and cold water valves after using. Be sure
that the bypass valve at the water connections is in the "off" position.

Heater Does Not Come On When The Water Turns On. Red LED Is flashing a series
of three red Flashes, or a double red flash.

The T-Mid thermister (pair of yellow wires going to heat exchanger) is not connected or de­fective. Be sure wiring harness connectors are secure and that wires are not chaffed. Be
sure connector is secure on electronics board. If these are secure, re-power unit. If the red
LED still flashes, contact factory for replacement thermister probe

Green LED Is Flashing But There Is No Ignition When Water Is On.

1. Be sure the gas valve at the tank is “On” and there is gas in the tank.

2. Be sure that gas is turned on and water flow is at least 0.4 gallon/minute.

3. Check that yellow ignition wire is clipped to the spark electrode terminal and is not touch­ing anything else. Align so that it is not in contact with anything but the terminal.

4. With water running, check that the paddle wheel in the flow meter is turning counter­clockwise. This can be visually observed with the access door open by looking through
the clear window of the flow meter.

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If it is not turning with the water flowing, there is an obstruction in the flow meter. Re­move the clear cover of the flow meter by firmly pushing on the cover and turning
counterclockwise (approximately 1/8” turn) to remove the plastic cover. Remove the
paddle, taking care not to lose the "O" ring seal and the pin that the paddle rotates on.
Remove any debris and re-assemble by reversing the procedure.

To secure the window, line up the guides, firmly push to seat and turn clockwise.

5. Check flame site hole to see if igniter is sparking from the probe to the burner. Bend ig­nition wire to adjust to proper gap or contact PrecisionTemp or your nearest authorized
service representative.

There Is No Ignition. Red LED Is Flashing A Series Of Seven Flashes.

The ignition has locked out. Check for these possible causes:

1. Locate the high temperature switch (two light blue wires) at the upper right hand of the
heat exchanger. Push the reset button in the center of the switch. (Early models only.
Newer models have an auto reset.)

2. Check that the yellow ignition wire is clipped to the spark electrode terminal and is not
touching anything else. Check that there are no cuts or breaks in the yellow wire. Align it
so that it is not in contact with anything but the terminal.

3. Excessively high or turbulent winds way cause the burner to extinguish. Adjust the posi­tion of the vehicle relative to the prevailing wind.

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Heater Turns On But Temperature Fluctuates Erratically.

1. Hot and cold water lines are reversed on back of heater. If the flow meter rotor is not ro­tating counterclockwise, pipes are connected in reverse. Be sure hot water is connected
to bottom fitting and cold to the top fitting.

2. May be caused by excessive restriction at the water outlets, showerheads, aerators or
water strainers. These should be cleaned and the any showerhead flow restrictor re­moved as defined in “Recommendations for Water System Installation”

3. The VariFlame gas modulating valve is out of calibration. Consult PrecisionTemp.

Heater Does Not Ignite When Water Is Turned On

The gas flow may be too low due to an improper gas line diameter (under 3/8 inch outside di­ameter). The gas line may be excessively long (over 20 feet) or the on/off solenoid at the
tank (if you have one) may have an orifice that is too small (under 3/16th of an inch).

Heater Comes On But Rapidly Cycles On And Off.

1. Water flow is too low. Increase flow at a tap. Clean all aerators and shower head screens.

2. Water pump is not functioning properly. Repair or replace pump.

3. If the heater cycles as the pump cycles, a pressure accumulator tank is needed in the wa-

ter system. If you have an accumulator tank, check to see if it has become filled with
water. If it has, drain it so that it contains air only.

4. Air is in the water line. Bleed air by turning on all water taps.

Heater Ignites But Water Temperature Is Too Low

1. Check thermostat setting. See "Changing The Temperature Setting"

2. The water flow may be so high as to exceed the capacity of the heater particularly if your
supply water is very cold. Slow the water flow.

3. The heater may be subjected to excessively strong winds, cutting the efficiency. Shield
from wind or change the location of the unit.

4. The gas pressure may be too low. Check the regulator pressure. The LPG pressure
should be 11 water column inches, (WCI) while the heater is running. A gas-testing
gauge should be installed on the manifold tap so that it may be read while heater is run­ning. If it is too low, turn up the gas regulator to the proper pressure. Be sure the gas
flow control valve is in full “on” position. This should only be done by a qualified techni­cian.

5. The gas flow may be too low due to improper gas line diameter (under 3/8 inch outside
diameter). The gas line may be excessively long (over 20-30 feet) or the on/off solenoid

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at the tank (if you have one) may have an orifice that is too small (under 3/16th of an
inch).

6. Check the heater for an airflow obstruction and clean.

7. Check the two conductors, black and white wire to the modulating valve. It should be se­curely plugged in to the control board terminal.

Water Temperature Is Too Hot Or No Temperature Control.

1. The thermostat is set too high. See "Changing The Temperature setting."

2. Fuel tank regulator is set too high. Have the regulator checked by a qualified technician.

3. Be sure that the hot and cold water lines are not reversed on the heater hook-ups. The
unit will not function properly and water could become extremely hot.

4. If water temperature reaches 165°F, the high temperature limit switch (ECO) will trip,
shutting the heater down. Locate the high temperature switch (two light blue wires) at the
upper right hand of the heat exchanger. Push the reset button in the center of the switch.
(Early models only. Newer models have an auto reset ECO)

Low Heat Rise. Excessive Water Flow Is Required To Trigger Water Heater

If you find that your heater requires excessive flow to activate it (over1/2 gallon per minute), it
is likely that you have cold water bleeding into the hot water side of your water system.
Check that valves and faucets are closed when not in use. If there is an on/off button on your
showerhead, always turn the water valves off after the shower to prevent cold water from
bleeding into the hot water system. This will keep the heater from functioning properly.

If any problem persists, contact an authorized service center or PrecisionTemp.

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