Hayward H300 Ignition Fail Code

[Kevin_O]

Hi everyone,

I have a 4 season old Hayward H300 that over the last few weeks ignited but timed out after the prescribed 4 seconds on the first attempt but would ignite normally on the second or third. I replaced the flame sensor and it worked great then this week it ignites fine but shuts off after 4 seconds on all three automated attempts and reports IF. Each time it ignites fine and runs the prescribed 4 seconds and times out.

I've done the following.
Verified the proof switch string is working as it should. Failure of any of these would prevent even getting to light off.
Removed and inspected the flame sensor
Checked the inlet gas pressure
Checked the manifold gas pressure
Removed the manifold and verified the orifices were clean
Pulled the heat exchanger to inspect the burners and box. Burners are fine and the box is dry
Vacuumed anything loose from the firebox and made sure the flame sensor was not touching anything

I'm fairly sure the old and new flame sensors were not OEM parts but they looked exactly like the original that was replaced a few years ago. Since they are inexpensive I'm going to hunt down a OEM sensor and try that even though I'm near certain that won't be the culprit.

Starting to lean towards the control board as the problem but having worked for years on a bunch of large industrial heaters whose control philosophy is the same I've not seen a burner control board intermittently fail before a complete failure.

I've seen the troubleshooting guide that's been posted in other threads and it does not address this.

Does anyone know the voltage measurement at the flame sensor terminal that proves ignition and allows the heater to continue running after the 4 second proof period? And what is the reference point?

All input will be appreciated.

Thank you!
Kevin

 

[swamprat69]

It all depends on the design of the flame sensing circuit, but almost all will cut out below 1 microamp. Normal expected range is 1-10 microamps. Normal actual in use range is 2-6 microamps new or clean. What microamp reading are you getting with your meter in series with the flame sensor? The microamp reading is through the sensor to and through the flame and on through the burner to ground. So any dirt on the burner near the sensor or resistance through the burner/ground connection will reduce the reading. If the flame sensor is the exact same configuration and mount as the original there should be no problem with it.

 

[swamprat69]

The reading is in microamps if there is no marked terminal for a voltage reading.

 

[Kevin_O]

Thanks for the feedback!

The flame rod is new today and yesterday when I had the heat exchanger out I ran a small wire brush over the burner tubes and vacuumed out any debris.

I looked the control board over and do not see a test point identified for measuring voltage as a indication of the flame rod signal.

In series with the rod my meter measures 4.05 uA AC while the flame is on. Prior to ignition it reads 2.4uA AC

 

[swamprat69]

Should not read any uA with no flame as there is no completed circuit. If your meter is off by 2.4 uA you should still have 1.65 uA. Check continuity of flame sensor to ground with nothing running. You might want to contact Hayward as to minimum uA flame signal needed. FC+ and FC- can be read as uA, or as voltage with a true RMS meter on Fenwal ignition modules and some oem circuit boards.

 

[Kevin_O]

I verified the meter did zero well and rechecked the uA readings. Definitely 2.4 without flame. Continuity from the flame sensor to ground is wide open. I'll touch base with Hayward to see what they say.

Thanks for getting back to me.