smart valve problem help

Glenn Harrison

Is this an armstrong unit? If so, there was a service bulletin about moving the entire pilot assembly over about a 1/4". Let me know and I'll dig up the info.

GW

smart valve problem help

Hi

I lost the first message, I'll try again.

Have a smart valve problem

The pilot comes on, but won't prove flame to the rod, the flame dances around like a candle in the wind. I cranked the pilot screw up as much as it would go.

Now, when I take the inducer out of the loop, the pilot runs like a champ (obvoiusly for testing only), and the burner comes one like normal. One bit of advice I got was to suspect the inducer baffle being rotted out, but thos was all intact.

Other times the pilot won't come on at all. Too much air across the pilot assy from the inducer. Then other times it will start up.

Any ideas?

Thanks,

gary

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Alan R. Mercurio

Gary, I'm the last guy that should be answering questions regarding Gas However I did want to share something with you from my my tech files that a friend shared with me a few year ago on Oil Tech Talk.

The Honeywell Smart Valve
(Remember the Ignition module is built into the gas valve)

1. Notes: The first generation smart valve (SV9500) wasn't too smart, it had some problems that were addressed in subsequent models.



2. Model identification: First generation was the SV9500 which is characterized by (A)-The round, (mechanical on-off) gas control knob on the top off the valve. (B)-One of the Molex connectors, connecting to the top of the valve with the second Molex connector, connecting to the side of the valve.



3. The next generation is the SV9501 and SV9502, with the only difference between these two models being that the 9502 has a prepurge time delay built into the internal module. These valves differ from the earlier 9500 series as follows. (A)-Both the Molex connectors are located on the top of the valve. And (b)-The (round mechanical on-off) gas control knob on the top of the valve is no longer used and has been replaced by a small electrical (on-off) slide switch.



Pilot Assembly

1. The igniter operates on 24 volts AC for all models of the smart valves.


2. The pilot assembly used with the smart valve is the Q3450/Q3480 and should be carried as a troubleshooting tool. By connecting it to the valve outside the unit (with the gas off) the igniter should glow confirming that it is getting power. Remember to make sure the valve is powered during this test.


3.The cold resistance measured, with an Ohmmeter, across the two leads of the igniter should be less than 10 ohms. If the igniter is cracked and has a white powdery substance surrounding the damaged area, it is an indication off high voltage to the igniter. So be sure to check for this. The voltage to the igniter should be between 19.5 - 26 volts AC.


4.On the SV9500 series valves, if the igniter element is broken the pilot valve will not power up. On the later model valves, 9501 & 9502 the pilot valve will power up, and pass gas, even if the igniter is damaged or broken. This is why it’s a good idea to check the igniter resistance early in the troubleshooting sequence.


Flame Rod Voltage

1. The flame sensing rod voltage to ground (valve body) should be as follows, and is measured best from the flame rod itself to ground or it can also be measured from the flame sense terminal at the valve to ground (valve body). The readings for the SV9500 series should be 24 volts AC and for the SV9501 and SV9502 series should be 80 volts AC minimum or higher.



Trial for Ignition

1. The pilot valve on the SV9501 and SV9502 will stay open during the entire 90 second trial for ignition even though the igniter cycles on and off. The internal module will then shut down for five minutes before it goes though another 90-second trial for ignition. This process will repeat indefinitely for these model valves.


2. The SV9500 series valve will not pass pilot gas if the igniter is damaged or broken.



Electrical Testing

1. Electrical testing can be done at the Molex connectors on the smart valve itself. There are two different factory made harness assemblies used for testing purposes. One test harness assembly is used to test for microamps and is Honeywell number 395466-1. The other, and I think more useful, test harness is used to check for input voltages to the Smart Valve, this is called the "Smart valve input voltage test harness" number 396085. It is a very useful tool to have because it allows the user to easily test for voltages while the valve is in the operating mode.



Detailed instructions come with the test harness supplied by Honeywell for testing the smart valve.

Basically the following voltage readings should be present during testing.

1.Constant 24 volts across the common and hot leads. Note: If an appliance is wired so the 24-volt hot lead is controlled with the TSTAT/PSWITCH lead, there is no voltage between the 24-volt hot lead and the 24-volt common lead in step 1.


2.A steady 24 volts should be present between the common and TSTAT/PSWITCH leads on a call for heat, and the igniter should be glowing. This voltage measurement should not be outside the range of 19-26 volts AC.


3.The voltage measured between the EFT (electronic fan timer) lead and common, with the main burner on, should be between 15-28 volts AC.
Note: All these voltage measurements can be made without the test harness but it is MUCH faster and easier to perform these tests with the test harness. The test harness has labels that identify each wire and what the voltage readings should be from each one of the wires.



Grounding

1.The return or ground path for the microamps is by way of the pilot tubing. Make sure the pilot tubing is clean and tight.


2.If the pilot comes on and the main burner doesn't fire you can try connecting a jumper from the pilot assembly to the valve body. If this causes the main burner to come on then you know that the valve is good and the problem is with the ground path for the microamps back to the valve.


3.Always make sure the flame rod is clean and in good condition, if not, replace it.




Your friend in the industry,
Alan R. Mercurio

Oil Tech Talk

GW

Tempstar NTC 5050

I understand the basics with this valve, my only guess is the pilot gas is too wimpy.

Thanks,

Gary

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