pilot relight control or gas valve?

meticulousmike

pilot relight control Wr 5059-23 and gas valve Wr 36C84 type 346.Are there any troubleshooting tests that I can perform on these units to confirm why the pilot keeps going on and off in cycles.Sparks,ignites pilot,stops sparking,runs 30 seconds,pilot goes out.retries until enough heat makes the mercury flame sensor snap on.I replaced the mercury sensor,i bent the electrode into the pilot flame and raised the height off the pilot.thanks.

Empire_2

Pilot

Try cleaning the pilot orifice.  this should solve your problem.





Peace;



Mike T.

meticulousmike

pilot orifice

the pilot orifice has nothing to do with the electronics. I had already tried that.i took the whole assembly out and sandpapered the tips of the sensor and electrode,that's when I bent the sensor previously back to straight - I broke it.had to wait for days for new part.the pilot is fine-it's the electronics that are the problem.

Empire_2

Reply?

OK your pilot has EVERYTHING to do with this circuit.  If it were poor it would not heat the merc to required temps.  Think before you jump on me.  In my opinion, mercury switch are the worst things ever invented.  The cost is outrageous and reliability is poor.  I have often switched the WR you are looking at to spark ignition w/ new GV, Pilot burner and ICM ignition control mod.  oh, there is also a resistor board that attaches to the GV, and if memory serves I believe it it amplifies the signal to GV and also eliminates short cycle if the pilot ever went out during operation.  



Peace;



Mike T.

Tim McElwain

What you are dealing with is called

a Cycle Pilot System from White Rodgers. They have been a problem from day one.



Let me see if I can help you through the system troubleshooting. You should have a little white box which is a pilot relight module # 5059. The plug in mercury sensor is a 3094 plug-in-pilot and like all mercury pilots the flame has to be adjusted from a soft flame to a sharp blue flame and the tip should glow cherry red. Sanding the tip or bending the tip is not recommended it will only make things worse. The gas valve has built in pressure switch, if it has the resistor added it means the switch had problems and the resistor is there to insure a delay in the burner coming on until the pilot safety switch goes over from Common to normally closed over to common to normally open a SPDT switch.



On a call for heat 24 volts is sent to the 5059 control and a spark should occur at the pilot, also at the same time 24 volts is sent to the pilot valve through the "C" to "NC" switch. The spark should light the pilot the flame should cause the mercury sensor to glow "Cherry red", The 3.5" W.C. pressure should be checked at this time on the outlet side of the gas valve. The 3.5" W.C. is necessary to cause the internal pressure switch to close. That is very important because when the mercury switch breaks "C" to "NC" and Makes "C" to "NO" the pressure switch is the path internally for 24 volts to stay applied to the pilot valve in the gas valve. If the pressure switch does not close it will light the pilot but then it will go out when the SPDT switch walks over. If there is a resistor plugged in with the mercury sensor its job is to insure the same function to allow a safe circuit to keep the pilot valve energized. When the mercury switch walks over the main valve is energized and the burner should come on.



It is critical that the pilot is clean so pull the pilot and clean the orifice as a lot of times that is sufficient to get the flame hot enough to boil the mercury in the sensor, it boils at 400 degrees and a real sharp flame is required to get it to do that.



I hope that helps, and by the way parts for these systems are getting scarce.



What is the equipment this is on?

meticulousmike

equipment these controls are on

slant fin galaxy boiler model GG-75E. serial # 4866385.pilot relight control 5059-23.flame sensor wr3049-115 bracket mount-not plug in.i can't do gas pressure testing, I don't have a manometer.i raised the pilot height abit,but can't get it to a sharp point.i had cleaned the orifice from the beginning.i don't know when I left that night it wasn't working as it is supposed too.it would spark a few times inside where the wire enters the electrode ceramic and then spark a few times at the pilot hood where it would ignite the pilot.while the pilot knob on gv was in pilot position and I had the gas main shut off the spark would be concentrated at the hood constantly,but when I turn on the shut off the spark would spark inside the ceramic and sometimes at the hood.after a few tries at turning shut off on and off,and gas valve off,pilot and on,it managed to light the pilot only to keep retrying.so it would spark,light,stop sparking, run 30 seconds,pilot shuts off.repeats in sequence until enough heat has traveled through the flame sensor element to make burners kick on.At just the right time before the piolot would go out again.this sounds a little dangerous to me.i had tried before I got the new sensor part to just jump the wire at the sensor to kick on the main burners everytime the stat called for heat,but since the pilot wasn't consistent at sparking at the hood I decided to not jump it and just shut it all down.i haven't heard nothing from my customers tenant yet for a few days.i think that they are afraid of having no heat at all rather than just having it work when it wants to.i was grateful that they were on the second floor and that the tenants below had heat and that kept the boiler and supply lines,etc from freezing when we had below zero temps. for days in a row.so far so good,lol! thank you for the reply.

Pughie1

W/R resistor

Timmie,

great explanation of the operation of the W/R cycle pilot gas system. Utica used these for some time so we worked on alot of them. Your description brought back many memories. There was an earlier thread (can't find it) that discussed this where you went into the use  of the resistor to go around the defective pressure switch. Could you review your findings on that issue if you have a moment so I can file it away with this thread? I'm aware that this caused some difficulties, can't remember what you said. Thanks

John Pughe

Tim McElwain

The problem was with the pressure switch

on the original 36C White Rodgers gas valve. The pressure switch was installed to insure that the outlet pressure was 3.5" W.C, the problem was they failed and stayed open even though the pressure was found to be okay. White Rodgers came out with the EQSO resistor which was to be placed under the SPDT pressure switch attachment to the gas valve. The EQSO resistor was supposed to offer enough resistance to allow time for the mercury pilot to light, the flame boil the Mercury (400 degrees F or higher) and keep 24 volts still going through the switch to keep the pilot valve energized during the making and breaking of the SPDT switch. The problem with them was if you switched the thermostat on then off and then back on it would cause the system to delay on ignition. I nor the gas company I worked for at the time felt this was safe so we required White Rodgers to replace all the gas valves on equipment in our jurisdiction.



Hope that helps.

Pughie1

Resistor

Timmie,

I know you have been busy, looking at your classes this last week. I appreciate you taking the time to re-explain the W/R Resistor situation. I wanted to get your take on it. I'll file this away along with your explanation of the workings of the cycle pilot system.

John Pughe

Dave_Chapman1

I have this exact setup on a Clare Bros HEHB120s furnace installed in 1987. Pilot light lighting always has been temperamental but all & all a good reliable furnace with simple controls. Planning to replace it this summer due to age & pilot issues and parts availability.

The past week the pilot won't light on 1st call for heat. If it does light everything works exactly as your described sequence. I've done everything you've suggested. I have 3 spare orifices and all have same problem.

For some reason (driving me nuts) when lighting the pilot on initial (cold) startup the pilot won't light when spark is jumping from spark igniter to center end of pilot flame hood. I've taken the entire assembly out several times cleaning it and making slight alignment adjustments on bracket mounting adjustments. Gas is coming out of orifice & flame hood but won't light from spark. Verified good solid ground from pilot assemble to spark control unit.

If I light the pilot with a match or long handled grill lighter it will light. The flame is steady on the mercury switch probe & it turns red hot and the main burner lights. All safeties and sequence of operations work as designed at that point.

After it's been light for a few seconds I can shut it off by tripping safeties, turning off thermostat call for heat, etc. Then return safeties back to normal or returning Tstat call for heat back on, the spark starts jumping to the pilot flame hood. After a couple seconds the pilot valve opens & the pilot lights heating up the mercury switch then lighting the main burner. Spark stops after pilot lights as it's always done since installed in 1987.

I run it thru the complete heating cycle & all works fine. After warmed up I can start & stop burners all I want with safeties and it will go thru normal purges and relight the pilot immediately then light main burner.

If burners have been off for a while and cooled down pilot will NOT light from spark but will light with a match. I've let it run for several minutes trying to light but doesn't. No pilot light fail lock out timer on this old furnace.

After burner running if for any reason the pilot flame fails or doesn't hit the mercury flame sensor the main burner turns off. Then the process starts all over if still a call for heat. Normally will always relight pilot with spark immediately when pilot valve opens.

Long story hope I explained it well enough. This thread is 4 years old but just saw it for 1st time tonight. So valuable & I learned so much about it's operation right down to the resistor mine has had since it was brand new. Pretty much figured out sequence of operation on my own but this thread was a huge help & support.

It has me so stumped that a spark jumping to the flame hood of the pilot thru gas can't light the gas when at normal room temp. Once it lights pilot is stable, mercury switch & tip of igniter probe glow red until shutdown from satisfied Tstat. Opposite from most problems I hear about that pilot won't stay on after lite.

WTH any ideas?? Again planning to replace furnace this summer so don't want put a lot of $$ into it. Parts are hard to find & very expensive for just a few more weeks of winter.

Thanks for any ideas. This has become like starting a wood stove every morning.

Dave Chapman
Midland Michigan

JUGHNE

An 80+ lady had a Rheem/Ruud with the same vintage gas valve.
It failed 3 years ago, I ended up just replacing the valve with a standing pilot set up. The thermocouple fit fine where the mercury sensor used to be. Light off was always good.

Other than that and she just had a new blower motor installed, the furnace was always trouble free (what else is there?) and still solid.
She didn't want to do a complete change out which would have included AC. We reviewed her gas bills for the last 2 years. I could only tell her of 15% savings she could expect. Compared to the complete change out and looking at ROI and she knows her age.
I know many others who would have convinced her to do the change out.

HomerJSmith

Let me throw this out. A spark doesn't necessarily ignite nat gas as you noticed. The spark has to be hot enough to raise the temp to ignition level of the gas. The air around a cold furnace pilot is denser than the warm air after a flame has been operating. Dense air is an impediment to spark and is also an absorb-er of temperature.

Mod/con manufacturers state the gap of the ignitor. HTP says it should be about 1/4". If the gap is 1/8" the spark will not ignite the gas because the spark jumps the gap at a lower voltage, perhaps at 12K, instead at 25K. At 12K the ignition will be erratic and at 25K rock solid.

Think of the gap as a resistor. The spark energy has to build up to the point where the stored energy can jump the resistance. It can be anywhere from 0v (grounded electrode) to infinity (3") depending upon the resistance.

So, how do you get a hotter spark? Increase the voltage of the spark. Most persons think that if ignition isn't happening that they have to move the electrode closer to ground, close the gap. The opposite is true. You have to widen the gap so that the spark generator can build up a high enough voltage to jump the gap to produce a hot spark.

This is my feeble attempt at reasoning.