Exhaust Gas limit causing LO on brand new Hayward H250 Heater

[jkoz]

I am replacing all of the old pool equipment at my new house with Hayward equipment. I have tried to install a brand new Hayward heater model W3H250FDP that keeps throwing a LO code. I have checked everything I know to check based on searches on this site and the Hayward diagnostic manual, and I wanted to see if anyone here had any ideas before I call in a pro.

What I know:

1. The heater is brand new

2. I have installed a water flow meter and it reads 90 GPM just before the heater inlet (which is well above the minimum flow rate for the heater)

3. I have connected a multimeter to each of the limit switches and have verified with certainty that it is the exhaust gas limit switch (at least, what I THINK is the gas limit switch: it is the white switch above the inlets pictured below is causing the fault).

4. I have opened up the heater inlet union valves and have looked for any debris that might be blocking water flow to the heat exchanger, and found nothing visible.

The heater runs for about 2 1/2 minutes when cold before the switch trips. I tried to remove the internal bypass service cartridge but could not. Either I don't have the strength to pull it out, or there is some release lever that I am unaware of. I looked inside the outlet valve and did not see anything like a broken part.

I do seem to have a small suction side leak that I can't locate. Little bubbles form in my pump basket after a bit. I bled all the air out of the filter before I tried to engage the pump, but I suppose small air bubbles could be trapped inside the exchanger and its boiling?

Is there any way to test the gas temperature limit switch to see if it is defective? Maybe shoot some area of the heat exchanger with an infra red temperature gun and see if it is REALLY too hot? I am doubting it is a defective switch because the unit is new, but I guess it's always possible.

Any ideas?

 

[1poolman1]

I am replacing all of the old pool equipment at my new house with Hayward equipment. I have tried to install a brand new Hayward heater model W3H250FDP that keeps throwing a LO code. I have checked everything I know to check based on searches on this site and the Hayward diagnostic manual, and I wanted to see if anyone here had any ideas before I call in a pro.

What I know:

1. The heater is brand new

2. I have installed a water flow meter and it reads 90 GPM just before the heater inlet (which is well above the minimum flow rate for the heater)

3. I have connected a multimeter to each of the limit switches and have verified with certainty that it is the exhaust gas limit switch (at least, what I THINK is the gas limit switch: it is the white switch above the inlets pictured below is causing the fault).

4. I have opened up the heater inlet union valves and have looked for any debris that might be blocking water flow to the heat exchanger, and found nothing visible.

The heater runs for about 2 1/2 minutes when cold before the switch trips. I tried to remove the internal bypass service cartridge but could not. Either I don't have the strength to pull it out, or there is some release lever that I am unaware of. I looked inside the outlet valve and did not see anything like a broken part.

I do seem to have a small suction side leak that I can't locate. Little bubbles form in my pump basket after a bit. I bled all the air out of the filter before I tried to engage the pump, but I suppose small air bubbles could be trapped inside the exchanger and its boiling?

Is there any way to test the gas temperature limit switch to see if it is defective? Maybe shoot some area of the heat exchanger with an infra red temperature gun and see if it is REALLY too hot? I am doubting it is a defective switch because the unit is new, but I guess it's always possible.

Any ideas?

According to the manual, there are 15 different problems that can cause that code. The easiest, and usually the most suspect, is the pressure switch. Test for continuity when the pump is running.
Page 50/53/54 of the manual have the various items.

 

[jkoz]

According to the manual, there are 15 different problems that can cause that code. The easiest, and usually the most suspect, is the pressure switch. Test for continuity when the pump is running.
Page 50/53/54 of the manual have the various items.

I am 100% certain it is the exhaust gas temperature limit switch. I disconnected the switch wires, placed a jumper wire across the leads, and then connected my multimeter to the exhaust gas limit switch. I then ran the heater. At the expected time, the multimeter indicated the exhaust gas limit switch had activated (it broke continuity) and the heater continued to run due to my jumper wire. So now that I know it is the switch, I'm trying to figure out how to test the switch, and assuming the switch works (because the heater itself is brand new), what would cause the heat exchanger exhaust heat to run away? The only thing I am aware of is low water flow (which I know the inlet is getting 90 GPM), and/or a blockage. I saw no debris with a visual inspection of the inlet and outlet, but I don't know if there is more that I can do. Is there a good way to test the flow thru the tubes of the exchanger? Could there be some adjustment to the gas flow I missed?

 

[JamesW]

What is the input voltage and is the selection correct?

Note: Do not randomly change the selection to "Try" it.

You need to know for sure.

Putting 240 volts on a heater set to receive 120 volts will cause serious damage.

 

[JamesW]

If you have 120 volt supply and the heater is set to take 240 volts, then the fan will run slow and cause overheating.

Make 100% sure before changing selection.

 

[JamesW]

ELECTRICAL CONNECTIONS:
GENERAL INFORMATION: An external supply of power is required to operate the control system of the heater.

The electrical specifications for this heater are 120 or 240VAC, 60Hz, 1-phase, 5.5A maximum current.

It is recommended that circuit protection for the heater circuit be rated at 15 Amperes.

The heater is shipped from the factory wired for use with 240VAC, 60 Hz field power supply.

To convert the heater to 120VAC, 60 Hz operation remove the 240VAC voltage selector jumper from the ignition control
board and replace it with the 120VAC jumper.

These jumpers are tie-wrapped together and are located on the fuse board.

See Figure23 for location of the fuse board. All wiring connections to the heater must be made in accordance with the latest edition of the National Electrical Code ANSI/NFPA 70, unless local code requirements specify otherwise.

In Canada, follow CSA C22.1 Canadian Electrical Code, Part 1.

The heater must be electrically grounded and bonded in accordance with local codes or, in the absence of local codes, with National Electrical Code, ANSI/NFPA 70.

Wiring connections must be made as shown in the wiring diagram found inside the heater cabinet, and a copy is provided for convenience in the GETTING STARTED section at the beginning of the manual.

The heater must also have an independent ground and bond connection.

There is a ground lug inside the control box adjacent to the power connections per figure22 and a bonding lug on the side of the heater per figure13.

Use a solid copper conductor, size No. 8 AWG (8.4 mm2) solid copper bonding wire or larger for bonding conductor.

Run a continuous wire from external bonding lug to reinforcing rod or mesh. Connect to the grounding lug provided and to all metal parts of swimming pool or spa, and to all electrical equipment, metal piping (except gas piping), and conduit within 5 ft. (1.5 m) of inside walls of swimming pool or spa.

IMPORTANT - Reference NEC codes for all wiring standards including, but not limited to, grounding, bonding and other
general wiring procedures.

https://hayward.com/media/akeneo_connector/asset_files/U/H/UHS_IO_manual_2020_2316.pdf

 

[jkoz]

What is the input voltage and is the selection correct?

Note: Do not randomly change the selection to "Try" it.

You need to know for sure.

Putting 240 volts on a heater set to receive 120 volts will cause serious damage.

It is wired for 120 volts, and I did change the jumper before I fired it up. I will double check the voltage coming in. Thanks for the suggestion.

 

[JamesW]

Any update?

 

[jkoz]

Well, I ordered a new Exhaust Gas Temp sensor from Amazon to try it out "just in case." I figured for $15 I might as well try it, though I had low hopes. After changing out the sensor, the heater ran fine! So, despite the heater being new, the sensor was bad. The "old" sensor did have a little rust on the contacts, so maybe there was some water intrusion from a hard rain shortly after I placed the unit? Go figure.