Brand New Max e Therm burning through igniters literally

[Lake Placid]

Brand new Max E Therm 200 wired for 120v. Installed and running, in the first 12 hours the heater had an ignition failure error. Diagnosis, burned out igniter. Installed a second igniter under warranty. Heater fired up and ran fine for 18 hours. Returned to the account for another ignition failure error. Diagnosis - second igniter burned up. The heater seems to be functioning fine otherwise. On diagnosis igniter is receiving 122 volts on call for heat/ignition. At rest (no call for heat) I noticed the plug for the igniter is seeing 3.4 volts. I’m waiting for a callback from my Pentair rep, but thought I’d post here spitballing that the 3.4 volts the igniter is seeing at rest is burning it out over the course of 12-18 hours? Does this seem plausible? Is this errant voltage a possible sign of a bad Ignition Control Board? All thoughts welcome.

 

[ajw22]

Measure the amperage at 3.4 volts. That gives us the watts the igniter is glowing like a light bulb.

Igniter is powered by the Fenwal box through a relay. I don’t see from the wiring diagram how the igniter can get other than 120 volts.

Is the 3.4 volts AC or DC?

 

[ajw22]

 

[ajw22]

Look carefully at both sides of the voltage plug for any abnormality.

 

[JamesW]

Verify the input voltage and verify that the correct plug is installed.

Measure the current before, during and after the ignitor is powered.

Maybe the ignitor is getting continuous voltage after the initial startup keeping the ignitor too hot.

 

[Lake Placid]

Measure the amperage at 3.4 volts. That gives us the watts the igniter is glowing like a light bulb.

Igniter is powered by the Fenwal box through a relay. I don’t see from the wiring diagram how the igniter can get other than 120 volts.

Is the 3.4 volts AC or DC?

3.4 volts is AC
Amperage wise I get two readings, .05A and .13A. .05A is with the heater at rest .13A is when it is turned on a spools up. I did not test the amp draw with a known good Igniter as I don’t currently have one on me. The amperage readings were at the plug. Another mystery…even with the heater in off mode the 3.4V is present at the igniter.

 

[JamesW]

As soon as there is sufficient air flow, the AFS closes, closing the circuit to the hot surface igniter (HSI), which ignites the fuel mixture. On a call for heat, the blower and HSI are energized.

In about 20 seconds, the gas valve opens and ignition occurs.

The HSI then switches to a sensing mode and monitors the flame

The ignitor should receive 120 volts for only 20 seconds.

 

[JamesW]

At the end, with 120Vac it get a bright light in 1 sec with a current of ~3.9Aac.

 

[Lake Placid]

Verify the input voltage and verify that the correct plug is installed.

Measure the current before, during and after the ignitor is powered.

120V on a 15 amp circuit. Verified and I installed the correct 120v plug at installation.

Maybe the ignitor is getting continuous voltage after the initial startup keeping the ignitor too hot.

It’s getting 3.4v AC regardless of the state of the heater (whether calling for heat, not calling for heat, or off).

 

[ajw22]

Sounds like you are seeing the flame sensing circuit voltage. But flame sensing voltage is DC, not AC.

I would pressure Pentair to replace the heater.

 

[InyoRich]

I'm not sure about the constant 3.4 volts but I wouldn't think that would cause them to burn out. Those ignitors are wonderful, but they are also extremely fragile. The original one may have been damaged/cracked and operating it a few times broke the crack. Ditto for the replacement. Shipping these through the mail can be risky if you are far away from the shipping source.

I hope the heater gets working 100% again soon. Following......

 

[Lake Placid]

Got a call from my pentair rep….senior tech will be calling me shortly. Update to follow….

 

[JamesW]

Amperage wise I get two readings, .05A and .13A. .05A is with the heater at rest .13A is when it is turned on a spools up.

The ignitor is about 450 watts, which is about 3.75 amps at 120 volts.

 

[Lake Placid]

Hopefully this update will close out the thread, meaning the issue is corrected. I should know definitively tomorrow.

Was informed by the Pentair Tech that in the fall of 24, a design change was implemented due to a concern of flame leakage from the ignition chamber. The design change called for additional insulation to be placed in the slot/cavity that the ignitor slides in to. This insulation is placed in close tolerance to the heating elements and if it shifts at all during shipping it will cause the insulation to contact the elements of the ignitor - burning them out during operation. The fix is to remove enough of the insulation around the ignitor element to prevent contact and burnout. As of the first of the year (2025) Pentair has already reversed course on this design change due to the issues it has caused, so the effected models are only those manufactured in the fall of 2024.

As for the 3.4 volts I was seeing at the ignitor when the heater is powered off/idle, but still electrically hot at the breaker, he indicated this is normal behavior but couldn’t provide a definitive answer as to why. He did indicate it has nothing to do with flame sensing when I asked him directly if that’s what it may be.

The most frustrating thing about the repair is the time wasted as you have to disassemble a fair amount of the top half of the heater (touchpad, touchpad wiring, brackets, Fenwal case, fenwal support brackets, ground wires, etc), just to gain enough access to the slot the ignitor sits in to cut away the insulation. Just another case of an engineer drawing Crud on paper that they never have to work on creating a cascading effect of problems/trouble.

 

[JamesW]

The relay that powers the ignitor is a DPDT relay and there should be no voltage when the heater is off unless it is the Flame Sense voltage.



Relay: electromagnetic; DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI
Manufacturer part number: SMI-S-224L

SMI-S-224L SANYOU - Relay: electromagnetic | DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI | TME - Electronic components USA

SANYOU SMI-S-224L | Relay: electromagnetic; DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI - This product is available in Transfer Multisort Elektronik. Check out our wide range of products.

www.tme.com

 

[Lake Placid]

The relay that powers the ignitor is a DPDT relay and there should be no voltage when the heater is off unless it is the Flame Sense voltage.

View attachment 629925View attachment 629926

Relay: electromagnetic; DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI
Manufacturer part number: SMI-S-224L

SMI-S-224L SANYOU - Relay: electromagnetic | DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI | TME - Electronic components USA

SANYOU SMI-S-224L | Relay: electromagnetic; DPDT; Ucoil: 24VDC; Icontacts max: 8A; SMI - This product is available in Transfer Multisort Elektronik. Check out our wide range of products.

www.tme.com

@JamesW PM sent…

 

[JamesW]

The Fenwal can detect a Flame Current when No Call for Heat.

It would give a 2 Flash indicator LED red light.

On a call for heat, the blower and HSI are energized.

In about 20 seconds, the gas valve opens and ignition occurs.

The HSI then switches to a sensing mode and monitors the flame

The ignitor should receive 120 volts for only 20 seconds.

I do not know if the Hot Surface Ignitor gets voltage before the Call for Heat.

It still monitors for flame current, so maybe it is sending voltage looking for a flame current.

When it switches to Flame Sense Mode, I do not know what voltage it is using.

I think that it only uses one leg of power to send the AC voltage to the ignitor with no return path except through a flame using ions in the flame to carry DC current through the flame to the burner and then back to the Fenwal through the ground.

This is Flame Rectification because the Voltage goes from AC to DC.

I think that the S2-FS is the Flame Sense terminal that sends voltage to the Hot Surface Ignitor.

The relay is Double Pole Double Throw, so it can connect both legs to two different sets of contacts.

If it was only an On/Off switch, it could be a Double Pole Single Throw Normally Open relay.

A DPDT has to be on one set of contacts or the other.

So, maybe the power is going to the flame sense when no call for heat or when in flame sensing mode.

I think that the red dots are the switch, blue is flame sense and yellow is line power (120 or 240 volts).

So, S1 and S2 are connected to the blue dots (Flame Sense) when the coil is not powered and to the yellow dots (Line Power) when the relay coil is powered for 20 seconds to power the HSI (Hot Surface Ignitor).

 

[Lake Placid]

I do not know if the Hot Surface Ignitor gets voltage before the Call for Heat.

Thanks for your replies both in PM and here, very helpful.

In my testing, the HSI is sitting at 3.4v AC or 1.4v DC when idle. I’m unsure if the actual voltage is ac or dc because the meter is stable at the listed voltages in either mode at idle. When the call for heat is initiated, the blower spools up and about 5 seconds later the ignitor receives 120v AC for 20 seconds. Once ignition has taken place the ignitor drops back down to the lower voltage reading.

ETA I assume the delay between the blower initiating and the ignitor voltage increasing to 120, is to allow the AFS to verify correct airflow prior ignition.

 

[JamesW]

As soon as there is sufficient air flow, the AFS closes, closing the circuit to the hot surface igniter (HSI)

ETA I assume the delay between the blower initiating and the ignitor voltage increasing to 120, is to allow the AFS to verify correct airflow prior ignition.

The Voltage to the ignitor is AC for Flame Sensing.

However, the current mostly goes from the ignitor to the burner due to the difference in surface area.

So, that makes the current mostly DC.

The DC voltage/current travels back to the Fenwal through the ground.

Check AC voltage from S1 to Ground and from S2 to ground before Call for Heat, during ignitor heat-up and during heating when in Flame Sense Mode.

 

[JamesW]

To check the Flame Sense Voltage, you need to check from S2-FS to ground since both wires are not connected and you will not get a good reading from S1 to S2.

A heater flame sensor works by utilizing a phenomenon called "flame rectification," where the flame itself acts as a conductor, allowing a small current to flow in one direction only due to the difference in surface area between the flame sensor electrode and the grounded burner, which is significantly larger; this one-directional current flow indicates the presence of a flame and is detected by the heater's control system.

Surface area difference:
The flame sensor electrode is small compared to the grounded burner surface, causing most of the current to flow towards the larger grounded area.

A typical AC voltage used for flame sensing is between 40 and 80 volts.

Flame rectification is measured in DC micro-amps.

This is symbolic of the extremely low current being flowed from the flame sensor back to the furnace ground.

Generally, the furnace will see a production of 1 to 10 DC micro-amps.

In order to test your furnace for proper flame rectification you will need a digital multimeter that is capable of measuring DC Micro-amps.

The symbol for DC Micro-amps is “μA”.

Upon a call for heat, before the burners ignite, the furnace control board will send AC voltage to the flame sensor. This amount of voltage varies from manufacturer to manufacturer, but it’s usually between 80v – 100v. This voltage goes through a wire from the control board, to the wire that connects to the flame rod.

Even without a call for heat, the board is still checking the flame sensor for safety at all times, so you will always have voltage present at this sensor.

Flame rectification – HVAC Basics

Tech Tips Blog Post: Flame Sense - East Coast Metal Distributors Blog

The flame sensor is a vital part of the modern-day gas furnace. It ensures that we do not allow gas through the furnace unless a flame has been established.

blog.ecmdi.com