Hayward H-Series Heaters

Hayward H-Series Heaters

Hayward has been producing different gas heater models under the H-Series label. It can be confusing when you have a problem and find information about a Hayward heater but not your specific model.

Universal H-Series

The Universal H-Series comprises the HXXXFDN, HXXXFDP, W3HXXXFDN, and W3XXXFDP models. N denotes Natural Gas, and P denotes propane gas. FD means the heater is forced draft, which uses a blower to create airflow.

The H models are Hayward's EXPERT LINE products, only available through your local pool professional. The W3H models are available through other channels. We believe they are functionally identical; the only difference is Hayward's warranty.

Cupro-nickel is the standard heat exchanger on the Universal H-Series gas heaters. Cupro nickel heat exchangers last longer than standard copper, and their superior corrosion resistance protects them from damage and premature failure caused by unbalanced water chemistry.

The INSTALLATION, OPERATION, & SERVICE MANUAL for the HXXXFD Series is here.

Hayward has this YouTube video - Universal H Series & ASME Gas Heater Installation, Start-up and Troubleshooting

Altitude of Installation—Heaters may be installed at any altitude up to 10,100 ft above sea level, provided the appropriate modification(s) are performed. The altitudes that require modification vary depending on the model. The heater includes parts necessary to convert it for outdoor installation at altitudes up to 7,700 ft (minimum). More information can be found on pages 9 and 10 of the Installation Manual.

Hayward requires the use of a GFCI for their gas heaters. See the 4/14/2021 Technical Updates for Pool Professionals.

HXXXFD Remote Connection

The Hayward HXXXFD Installation Manual shows the connection for the 2-wire remote control in the wiring junction box.

However, you may find the remote connection is not installed where the manual shows.

A wiring kit that includes the Remote Harness should be inside of the heater taped to the side in a plastic bag.

The remote wiring harness must be installed and plugged into the green board above the igniter.

HXXXFD Error Codes

Universal H-Series Diagnostics Guide provides detailed diagnostics for troubleshooting problems and error codes.

bO Code

A bO code is a normal display on the heater when it is controlled by automation. It indicates that the heater is in remote control mode.

To put your heater in bypass you:

1. Press the Mode button to place the heater in Standby Mode
2. Hold the Down Arrow and Mode buttons simultaneously for 3 seconds for Bypass operation. “bO” will be displayed on the screen
3. Heater must then be in the Spa or Pool Mode for operation. The heater will fire when instructed by the external control.

To remove your heater from bypass mode, you:

1. Press and hold the DOWN key and
2. Then press and hold the MODE key
3. Hold down both keys for 3 seconds until the indication ‘‘bO’’ is removed from the display.

LO Code

A Hayward LO code is a limit string open error that occurs when any of the safety circuits on your Hayward pool heater opens. This forces the heater to shut down to protect it from damage.

The usual reason for the LO code is insufficient flow, which prevents the Water Pressure Switch from closing. Low water pressure can also be caused by a filter that needs to be cleaned, low pump RPM if a VS pump is used, an open heater bypass valve, a low skimmer water level, or even a stuck weir door.

The temperature Limit Switch, Exhaust Gas Temperature Limit Switch, and Vent Pressure Switch are also on the limit string.

See pages 40-43 in the Universal H-Series Diagnostics Guide.

IF Fault

IF ignition failure usually means it attempted to light and the flame went out. It will try three times and then give you the IF code. It could be as simple as a bad flame sensor. On the FD units, the flame sensor is a separate sensor, and sometimes, you can use steel wool or a small steel/diamond file to clean it, and it will work.

The flame is sensed in current (microamps or uA) in what is called DC but is a highly dampened AC Sine wave. The AC Sine wave is dampened because of the large difference in the area of the flame sensor (small area) and the grounding area (large area).

The flame sensor should be cleaned with steel wool or a small steel/diamond file because cleaning with sandpaper or emery cloth can leave a residue impeding conductance. On the other side (ground side), all surfaces from the burner back to the case ground must be clean, bare metal (as the flame signal is sensed through the flame). This includes the burners and burner slots, which can be cleaned with a wire brush, and any other metal-to-metal surfaces back to the case ground that may have lost conductance due to dirt/corrosion/oxidation. This would include orifices ( if the burners are hung directly on the orifices ), burner brackets, and any other metal-to-metal breaks between the burners and the case ground.

If the grounding surface is reduced through dirt, corrosion, or oxidation, you are reducing the difference in area between the flame sensor and ground, and the current can no longer be read as DC (highly dampened AC).

If you need to check the flame current, you can use a meter that will read microamps DC by removing the flame sensor from the circuit board and placing the meter in series from the flame sensor wire to the flame sensor post on the circuit board.

CE Code

The CE code on the display indicates a display failure. Water gets in around the display, making the keypad non-responsive. The thread Design Flaw in Hayward Pool Heaters Causing CE Error Codes goes deeper into the problem and its causes. The fix is an expensive replacement of the display boards.

A replacement display board arrived with part of the board having a soft raised area that was bubbled. That’s a conformal coating, and its purpose is to waterproof the components that it applied over. It’s too bad more pool equipment suppliers don’t apply this on their PC boards, as it prevents corrosion damage (due to electrolysis) when water gets on energized electronics. It looks like they coated the microprocessor and nearby components.

That is what a standard conformal coated board should look like.

SF Code

The SF code is a failure of the temperature sensor. Turn off the power to the heater and your pump. Remove the top and bottom side panels and the two front panels.

Check the sensor wiring and connections for kinks or rodent damage. Inspect terminals for breakage or corrosion. Remove the thermistor and examine the wiring.

If the wiring looks good, then replace the temperature sensor. Check that you are getting the correct sensor for your model heater, as there are different sensors for low-NOx and IDL heaters.

Hayward changed the temperature sensor's style. Older heaters use the metal FDXLTER1930 sensor, while newer heaters use the plastic FDXLTER1931 sensor. They are different sizes, so check which one you have.

Failure To Stay Lit

If the heat goes out within a few seconds of coming on, you can have a clogged orifice. Check the left-hand one at the ignition and flame sense area. Spiders seem to like that orifice. Turn the gas off at the external gas valve. Remove the gas pipe to the main valve, remove the four screws holding the manifold in place, and examine all the orifices.

If you see a clog, remove the orifice (3/8" or 7/16" wrench, depending on what Hayward installed) and push the clog backward out of the orifice. The clog will move to another area if you don't remove the orifice.

These are easy manifolds to remove and replace. While removing the wires from the main valve is easier, you don't have to if you are careful. If you do, take a cell phone picture first to put them back where they belong.

Be sure to use a bit of thread sealant when reassembling the gas line EXCEPT on the union. Make that very tight. Do not tighten the pipe into the main valve beyond where the old sealant shows; if you overtighten it, you can crack that valve. Use some soapy water to check for leaks. If you are not comfortable working on gas plumbing, hire a pro.

Hayward HXXXFD Gas Pressure Test Procedure

See page 24 in Hayward UHS INSTALLATION, OPERATION, & SERVICE MANUAL

Transformer

The transformer converts the field supply voltage (240 VAC or 120 VAC) to a 120 VAC output for blower and igniter power and a 24 VAC output for powering the ignition control board, control circuits, and gas valve.

HXXXFD Components

Universal HC Series Heater

Hayward released its HC Series Heaters, including models HDF400 and HDF275, in 2021. The units are 21"x 21" and are currently the smallest 400K BTU heaters available. Everything is accessed from the top, and you can place the HC Series heater right up against the heater's back wall.

Cupronickel heat exchanger tubes are standard, and the HC Series heaters have an integral water bypass to maintain the correct water flow through the heat exchanger. However, we still recommend installing an external Heater Bypass with the heater. The maximum water flow through the heater is 125 GPM.

Plumbing adapters are available to connect HDFXXX heaters to Pentair MasterTemp and Max-E-Therm (UHXWPAK1930) or Jandy (UHXWJAK1930) plumbing with no modifications.

All units are set up for natural gas, and the parts to convert it to propane are included in the customer kit with every unit.

Heaters are factory wired for 240V AC and include a plug to change the voltage to 120V AC.

The Installation Manual describes the required adjustments if the heater is installed more than 3 feet above or below the water surface.

HDF heaters are set at the factory for outdoor installations at a maximum altitude of 2,000 feet.

• The HDF400 models are certified to be used at altitudes up to 10,100 ft but require additional components. Everything needed to convert the HDF400 heater for use at altitudes above 2,000 ft is contained in the HDXFHIALT400 kit.
• Currently, the HDF275 is certified to a maximum altitude of 2,000 ft above sea level, and Hayward says higher altitude certifications are coming soon.

The heater is claimed to be rodent-proof and sealed in all the common rodent entry points.

HC Series Documents

Universal HC Series Owners Manual includes installation instructions.

Hayward HC Series Troubleshooting Manual provides detailed diagnostics for troubleshooting problems and error codes.

HDF400 Gas heater Service Parts contains parts breakdown diagram and part numbers.

Universal HC Series Sell Sheet describes key features of the HC Series heaters.

Universal HC Series Replacement Options lists the differences from a Pentair, Jandy, or Raypak heater.

Condensate Management System

HDF heaters include a condensate management system that allows any moisture in the combustion chamber to drain out of the unit. The condensate formed during combustion will be slightly acidic, about the same pH as a cup of black coffee.

If condensate from the unit needs to be routed off the equipment pad or into a drain, the unit has been supplied with a 6-foot length of rubber hosing and a connection on the bottom of the exhaust side. If a longer length is needed, any 3/8” ID rubber hose can be connected to the unit drain.

An overflow indicator has also been molded into the base of the unit.

If a hose is connected to the drain and water drips from the overflow port, the drain hose is likely clogged and needs to be cleaned out. After the tube is disconnected from the unit, this can be done using a garden hose or compressed air.

If the heater is to be operated in freezing conditions, heat tape should be wrapped around the condensate drain to prevent it from freezing.

HC Series Automation Connection

To connect to a pool automation system, you use the 2-Wire Remote Connection (Fireman's Switch) to connect to the automation panel gas heater relay or LVR in Hayward Omni systems. The HC Series heaters do not have RS-485 heater control.

The heater must be configured for 2-wire remote thermostat control:

• Use the “MODE” key on the heater keypad to put the control into “STANDBY” mode.
• Then simultaneously press and hold the “( - )” and “MODE” keys for 3 seconds until “bo” (bypass operation) is displayed.
• Once in bypass operation, press the ‘MODE’ button until the ‘POOL’ or ‘SPA’ LED is illuminated.

The heater is now ready to operate with a 2-wire remote thermostat control. The thermostat will only limit the return water temperature to a maximum of 104°F.

To switch back to local thermostat control:

• Use the “MODE” button on the keypad to put the control into “STANDBY” mode.
• Then simultaneously press and hold the “( - )” and “MODE” buttons for 3 seconds until “bo” disappears from the display.
• Using the “MODE” button to put the heater in either “POOL” or “SPA” mode will start the heater using the local thermostat.

Diagnostic Codes

HC Series Diagnostic Codes

Code	Description
AC	Blower Vacuum Switch closed
A1	Air switch circuit open before ignitor warm-up
A2	Air switch circuit open after ignitor warm-up
A3	Air switch circuit open after post purge
b1	Ignition control board data error
b2	Gas valve sensed "ON" error
b3	Gas valve sensed "OFF" error
b4	Data retrieval error
bo	Bypass operation mode
CE	Communication Error Between Control Module and Display Interface Assembly
EE	Bad board
HF	Flame present with Gas Valve not energized.
HS	Maximum return water temperature exceeded and / or rapid water temperature rise.
IF	Ignition Failure
IO	Ignitor Circuit Open
LO	Water Pressure Switch, Vent Pressure Switch, or Temperature Limit Switch Fault
PF	Voltage polarity reversed, low voltage detected
SB	Keypad failure
SF	Temperature Sensor (thermistor) input failure

HXXXIDL Models

The HXXIDL heaters are from the early 2000 vintage and were replaced by the Universal H-Series heaters. XXX is the BTU rating of the heater in thousands, and IDL means "Induced Draft Low NOx." The Installation, Operation, & Service Procedures for the H250IDL2, H350IDL2 & H400IDL2 can be found here. Troubleshooting begins on page 36.

The IDL models use an air blower for the induced draft. There are four different blower parts/kits available for the H400IDL2 heater:

• IDXLBWR1930 - Original model w/240V motor, which is listed in the manual
• IDXL2BWR1930 - New model w/120V Jakel motor, used in heaters manufactured after 9/20/04
• IDXL2BWR1931 - upgrade kit with yet another new blower w/120V Fasco motor, along with a new control board & vacuum switch - which was needed to switch from the Jakel to the Fasco motor.
• IDXL2BWR1932 - Newest blower w/120V Fasco motor, does not include new control board & vacuum switch - you would only buy this if your heater already has the 120V Fasco motor in it.

The original blower used in these heaters - model IDXLBWR1930 - was a 240V motor. Then, in 9/2004, they updated it with a 120V Jakel motor. And then sometime after that (after S/N (21)130701100532001, according to several websites), they switched again to a 120V Fasco motor. The 120V Fasco motor is different from the older 120V Jakel model. The 120V Jakel motor pulls 1.3A and has a 9.0 MFD capacitor, and the newer Fasco motor uses 1.6A and has a 7.5 MFD capacitor.

The heater has a Hot Surface Ignition Control System that automatically lights the burners. The control system requires an external power supply.

Sea-level/high-altitude installation—The H-Series IDL heaters may be installed up to 2,000 feet above sea level.

Hayward HXXIDL Ignition Problems

It is important to check for spider nests in the orifices, especially the one on the far left, right at the igniter on an IDL heater. Usually, if that one is blocked, the heater won't light, but it could, but the flame-sense rod won't see a flame, and you could have the problem. The manifold on an IDL heater is easy to remove and replace.

Remove the gas line from the main gas valve. This will require closing the external gas valve, opening any union in the line, and unthreading the pipe from the main gas valve. There will be about six screws that hold the manifold in place. A 5/16" socket or nut driver will easily remove and replace those. You will need either a 3/8" or 7/16" wrench to remove any clogged orifices (Hayward used different sizes occasionally, so have both available). Always remove the clogged orifice and push whatever is blocking it out toward the back. Use a copper wire, a toothpick, or a small twig to not scratch the orifice. You don't want to push the debris into the manifold; it will just move and block somewhere else.

On reassembling, use some pipe sealant specified for gas; a small tube of RectorSeal #5 costs about $4-5. Be sure the union is tight, and no sealant is used. After you assemble it, turn the external valve on and check for leaks with a bit of soapy water at each joint you disturbed. You will see how far the pipes were threaded into the fittings by whatever was used to seal initially. Use that as a guide. It is especially important not to get too tight going into the main gas valve in the heater; it will crack and need to be replaced. Always leave at least three threads showing outside any fitting.

This probably sounds harder than it really is, but if you are not comfortable working on gas plumbing, call a pro. That is the safest way if you are not the DIY type. The tech that checks your gas pressure could most likely do this if the gas pressure is not the issue.

Hayward HXXIDL Yellow Burner Flame

The flame should be blue, not yellow.

A yellow flame indicates too little air or too much gas. It is burning rich, which causes sooting. The likely cause is that the burners are "burned" through, the slots are either too large now, or there are areas where the slots have broken out, and the flame is too large.

Hayward heaters have very thin burner tubes with hundreds of slots in them. When they are burned through you get that yellow flame. The slots near the ends, especially the end closest to the front of the heater cabinet, are usually still a good reference for how large they should be. It's the ones toward the middle and back of the burners that usually wear out the most.<ref?https://www.troublefreepool.com/threads/hayward-h250idl2-overheating.287101/post-2517595</ref>

HXXX Models

The H SERIES MV AND ED2 INSTALLATION, OPERATION, & SERVICE MANUAL for the HXXX Series is here.

The HXXX comes in a millivolt (MV) and an electronic ignition (ED2) model.

The millivolt heater must be lit manually. It has a standing pilot and a thermopile (pilot generator). The pilot generator provides all of the electric current required to operate the controls within the heater. No external wiring or electrical connections are required.

The electronic ignition models are lit automatically on each call for heat. The electronic ignition system is equipped with the same basic controls as the millivolt-operated heater, but a direct spark ignition device (DS) is used to automatically light the main burners on each call for heat. With the DS module, these controls operate on 24 volts, so an external power source is required.

The HXXX models use a natural draft and do not have an air blower.

Sea level/high altitude installation—The early H-Series heaters may be installed up to 2000 feet above sea level. For elevations from 2000 to 4500 feet above sea level, the heater shall be a high-altitude model with the suffix “H” in the heater model designation (Example: Model H400H1). For elevations above 4500 feet, consult Hayward Customer Service.

By now, any of these HXXX series heaters are old and rarely worth repairing. Even in their day, they had consistent problems and poor performance. If you have one of these heaters and it is working, then continue to run it often. Spiders love to lay eggs in the heater orifices, and running it cooks them out and extends the life of the heater.

Lighting Pilot in Millivolt Heater

The normal sequence for lighting the millivolt (MV) pilot would be to turn the gas valve knob to the "pilot" position and push it down to allow gas flow to the pilot. While holding the gas valve knob down, push the piezoelectric " spark generator" button multiple times until you observe a pilot flame.

Keep holding the gas valve knob down for about 2 minutes. At this time ( after 2 minutes ), you can use a multimeter to measure the output of the thermopile in DC millivolts (the part that sits in the pilot flame and has two electrical leads attached to the gas valve ). It should measure 325 MV or above with no load. If it doesn't measure 325 MV or above, replace the thermopile.

Millivolt Heater Pilot Not Staying Starting

A millivolt heater operates on just that, thousandths of a volt. The pilot generator is labeled as a 750mV generator (3/4V DC). A good one, new out of the package, will usually get you up to 700mV, usually around 650mV, after being heated for a while.

It takes at least 100mV to keep the pilot portion of the gas valve open; that's why you have to hold the button so the generator gets hot enough to put out that voltage. Holding the button after that makes no difference.

It then takes about 400-450mV to open and keep the main portion of the gas valve open. Your generator may just be worn out. You need a millivolt meter to test the output, but it may not have enough voltage.

You need a minimum of 600mV to be safe. It takes 100 to hold the pilot open, 400 to open a gas valve, and at least another 100 "just hanging around." Without that 100 reserve, a millivolt heater will not operate properly.

Replacing the pilot assembly should also include replacing the pilot generator if it didn't come with the part. If it did, be sure there are no shorted wires, even a tiny one. Pull the terminals off the gas valve and be sure that there is zero corrosion. With such low voltage, stopping voltage from flowing doesn't take much. Do the same with each item in the control circuit: the pressure switch, limit switches, and thermostat.

How Much Gas Does A Heater Use?

That is a tricky question to answer on an individual basis since it varies from pool to pool based on:

• How big is the pool?
• How warm do you want it?
• Where is it located (both locally and geographically)

What we can answer is how much gas the heater uses per hour of operation. A few facts:

1. Hayward heaters are sized based on the amount of input gas they need per hour in BTUs. Example: An H250FDN needs 250,000 BTUs of natural gas input per hour of operation, and an H250FDP needs 250,000 BTUs of propane gas input per hour of operation.
2. A BTU or British Thermal Unit is the amount of heat necessary to raise the temperature of one pound of water one degree.
3. Natural gas has a BTU rating of 1037 BTUs per cubic foot. Put another way, there are 100,000 BTUs in a Therm of natural gas. This is the way it is sold.
4. Propane has 91,000 BTUs per gallon, which is how it is sold.

Considering these facts, we can calculate how much gas a heater will use per hour of operation.

For the H250FDN mentioned above, the heater will require 2.5 therms of gas per operation hour.

For the H250FDP, the heater will require ~2.75 gallons per hour of operation.

A H500 heater will require twice as much gas per hour but will also deliver twice as much heat per hour, so the cost per BTU is the same.

One last bit of math.... If you have a 18,000-gallon pool and you want to raise the temperature in the pool from 70 to 85, you will need:

• (18,000 gallons X 8.34 pounds per gallon) 150,120 BTUs per degree,
• or 150,120 X 15 degree temperature rise = 2,251,800 BTUs to bring the temperature up to the desired 15 degrees

Hayward heaters are 84% efficient. That means 84% of the BTUs you put into the heater are added to the pool water. So, the H250, with an input of 250,000 BTUs, actually puts 210,000 BTUs into the water per hour.

Discounting heat loss (which there is always some), if you are using a Hayward gas heater to heat the 18,000-gallon pool we have discussed above, you will need:

• 22.58 therms of natural gas
• 24.75 gallons of propane
• To raise the pool water temperature by 15 degrees

No matter which heater size you choose, these numbers will remain the same since the number of BTUs needed does not change.

What will change is how fast the pool is heated!

• For the H250 to heat the pool 15 degrees (again discounting heat loss), it would have to run for 10.71 hours
• If you were using a H400 it would take 6.7 hours

Time to heat would not change between natural gas and propane heaters.