Hayward Heater LO Code

Check Out These Causes and Fixes For the Hayward Heater LO Code

If you have a Hayward pool heater and have seen the LO code pop up, this can be very frustrating. What can you do about it? We can help. The LO code, the limit string open error code, indicates that the limit string is open. This in turn will shut the heater down and make it go into lockout mode. The automatic restart time is two minutes, provided you fix the error and the limit string closes. For each issue that spurs the Hayward pool heater LO code, there are several possible solutions.

The Hayward heater LO code is meant to signal a fault in one of the following:

• Temperature limit switch
• Vent pressure switch
• Water pressure switch

To make the fix, you will have to make sure the pump is on, wired and connected. You also need to make sure the filters are clean and the water flow is above the required minimum pressure. You will have to replace any broken switches or ask a pro to do it for you.

Hayward Heater LO Code: Common Reasons

You can engage in Hayward pool heater troubleshooting if you have a basic knowledge of your  pool heater. If not, call a professional so you don’t damage the heater.

The LO code can arise from many issues, including:

 

Faulty water pressure switch

The water pressure switch is designed to shut off the heater when the water circulation pump switches off. The premise is simple: it will ensure the water heater is off when there is no water present to heat. This saves on power, but also prevents damage to parts. Read your Hayward pool heater manual to find where the pump is before you try to fix it.

Follow these steps to troubleshoot a faulty water pressure switch. Check:

1. If the pump is running or not.
2. If the water flow is enough for the switch to work.
3. If there is a faulty electrical connection or wiring.
4. To see if the water pressure switch contacts are working.
5. That the low pump pressure isn’t due to dirty filters or improperly positioned valves.
6. For correct settings on the water pressure switch.
7. If the water pressure switch is defective or in good working condition.

These are the most common reasons that the LO code on your Hayward pool heater would be prompted.

Repairs

Here are some solutions.

1. Turn on the pump (LO codes can come on when the pump is off).
2. Make sure the water flow is above the required minimum (20 GPM (H150FD & H200FD), 25 GPM (H250FD & H300FD), and 30 GPM (H350FD & H400FD).
3. Check that the wire harness terminals have been connected to the spade terminals on the water pressure switch.
4. Remove wire leads both from the water pressure switch and the jumper leads. Turn on the heater and measure the continuity across the water pressure switch. If open, the water pressure switch contacts are to blame. If closed, remove the jumper and reconnect the water pressure switch.
5. If you detect low pump pressure, clean the filter and make sure the valves are positioned properly for optimal pressure.
6. If you notice incorrect settings for the water pressure switch, make adjustments as noted in the manual.
7. Replace the water pressure switch if defective.

Faulty temperature limit switch

A defective temperature limit switch could be another reason for the code. This switch makes sure the temperature of the pool heater is safe. Also known as the furnace plenum thermostat, an LO code may display if this switch is to blame.

You can check if it’s a faulty temperature limit by:

1. Checking that the wiring is not faulty.
2. Checking the contacts of the temperature limit switch.
3. Checking for proper water flow.
4. Checking for proper operation of the temperature limit switch.

Repairs

Try these troubleshooting suggestions:

1. Fasten the wire harness terminals to the spade terminals of the temperature limit switch
2. Remove the wire leads both from the jumper leads and the limit switch to check the contacts to the temperature limit switch. Turn on the heater and measure continuity across the limit switches. If open, you have a faulty temperature limit switch. If closed, remove the jumper and reconnect the leads to the switch.
3. Make sure there is an adequate water flow (20 GPM (H150FD & H200FD), 25 GPM (H250FD & H300FD), and 30 GPM (H350FD & H400FD). Lower numbers will trigger the code.
4. Replace the temperature limit switch if defective.

Faulty vent pressure switch

Another reason for the code is a defective vent pressure switch. This safety feature will shut down the heater if any negative pressure from the draft inducer motor has been detected. This backdrafting is comprised of dangerous exhaust fumes that can pose a danger to occupants, a danger that can be prevented by the vent pressure switch. If the pressure switch is open, the exhaust fumes can infiltrate your indoor air.

Here are some troubleshooting tips:

1. Check for wiring and connection problems.
2. Check the security of the vent pressure contacts.
3. Check the flue to see if there are any blockages or restrictions.
4. See if there is a defective vent pressure switch.

You will find the vent pressure switch by checking the manual of your Hayward pool heater.

Repairs

Here are some tips to repair this issue:

1. Check that the wire harness terminals are securely connected to the spade terminals of the vent pressure switch.
2. Remove the wire leads from the jumper leads and the vent pressure switch to see the state of the vent pressure contacts. Switch on the heater and measure the continuity across the vent pressure switch. If open, a fault in the vent pressure switch is to blame. If closed, the cause is something else.
3. Check the pool heater manual to determine the flue’s appropriate vent sizing and make sure there are no blockages.
4. Replace the vent pressure switch if it is faulty.

We hope these tips were helpful in aiding you to restore the proper operation of your Hayward pool heater. If you can’t clear the LO code, call the professionals at Central Jersey Pools. We can come out to troubleshoot the issue in no time!