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Cross reference on Honeywell gas Valve... (6 Posts)
Cross reference on Honeywell gas Valve...After replacing Honeywell valves on boilers after 7 years due to pilot magnets failing to hold, I am switching to White Rodgers for replacements in hopes to getting better service life. A little more cost, but it may be worth it. However, I have not been able to find a replacement valve for the step opening valves that Burnham and New Yorker use. First step is fixed at 0.7 inches and full open is set at 3.5, adjustable 3 to 5 inches. The smaller valve is a Honeywell VR8200C 6008 (1/2 by 1/2) and there is also a 3/4 x3/4 model I need. I use Johnson Controls Husky thermocouples set for 28 to 30 MV open circuit.The Steam Whisperer (Formerly Boilerpro)
Chicago's Steam Heating Expert
Noisy Radiators are a Cry for Help
Dave those are as you knowstep opening valves you are looking for and White Rodgers does not offer much in the way of replacement.
You could try Robertshaw who offer their catalog number 720-472 factory number 7200ERCS-2 valves which will handle up to 150,000 BTU's. They step open to 40% of full flow and then 30 seconds later are open to full flow. This is a little slower than Honeywell who open to full in 10 seconds. These valves are 1/2" x 1/2" only.
I know you had stated in the past you are having problems with Honeywell valves what seems to be wrong with them?
Problems...I installed 5 New Yorker boilers in rather short succesion a few years ago, both SP and EI, also step opening. 4 of them had problems with the regulators holding steady pressure. They would gradually increase manifold pressure and then suddenly drop back to normal. I replaced 3 of them immediately and the fourth finally stablilized and has been fine ever since. The recent failures has been with standing pilot models, both step and standard opening...the pilot magnets simply stop holding after about 7 years of use.
Thanks for the Cross reference. These step opening valves are really nice on the Burnhams and New Yorkers because they give a nearly silent light off, but are very pricey to replace. If I could find a high capacity model for the bigger Burnhams I'd be all set, but I do understand that standard opening valves can be used for replacement.
How well would a slow opening valve work? I have one that I replaced with a slow opener and it lights off very nicely.The Steam Whisperer (Formerly Boilerpro)
Chicago's Steam Heating Expert
Noisy Radiators are a Cry for Help
You may get away withreplacing step opening valves with standard opening (slow opening preferred) on boilers as light off on boilers is usually pretty smooth. Furnaces are a different story as it will definitely affect light off.
On the valves you were having problems with make sure there is nothing caught in the outlet sensing port in the valves (such as Teflon tape). The sensing port can be seen by removing the valve and looking into the outlet opening, it is a small opening which senses down stream demand and positions the servo regulator in the gas valve which in turn controls outlet pressure.
Thermo-cpl magnets replaceable?In '98 I worked for a very experienced service plumber who preferred repair to replacement in certain situations (eg. most hot water dispensers respond to a fuse replacement and the valve at the top also can be serviced easily) . Seems I recall he had a test for those magnets and had a source and a way to replace them. It happened so rarely that he still had parts he'd layed in 10 years ago and IAC I never did it so I don't recall the detail. Perhaps it only worked on older valves.
He also insisted on testing the output of the TC if there was a problem after installing a new one; IIRC in 3 years I found two marginal TC's straight out of the package.
Rufusdisclaimer - I'm a plumber, not a heating pro.
Since 1979you have not been able to replace component parts on gas valves. If any part of the gas valve fails the entire gas valve must be replaced.
Yes there is a complete procedure for checking thermocouples. Here it is:
PROCEDURE FOR TESTING THERMOCOUPLES
I am often asked about troubleshooting a thermocouple on gas systems. This will be a permanent reference that will give a step-by-step procedure.
A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The thermocouple is a device made up of two dissimilar metals. They are joined together at the tip (Hot Junction). When heat is applied to that hot junction a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red". If the flame is adjusted to a sharp flame it will glow "cherry red" this will cause the tip to be welded and eventually the thermocouple will fail. The flame should be adjusted to a soft blue flame, not roaring or lifting. The normal millivolt output is 25 to 35 millivolts, on some you may even get up to 35.
The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE. The electromagnet is made up of a coil of wire and "U" shaped iron core. When the thermocouple is heated and the millivolts generated the coil will be energized and create a magnetic field. The magnetic field will cause the "U" shaped iron core to be magnetized; it in turn will hold open a seat allowing gas to pass through.
When this system malfunctions it typically causes the pilot to go out and the gas will not flow. The first thing that should be done when arriving at a pilot outage situation is to do some visual checks.
1. IS THE PILOT LIT?
2. IS THE PILOT CLEAN? (NOT YELLOW)
3. IS THE PILOT HITTING THE UPPER 1/2 TO 3/8 OF THE THERMOCOUPLE?
4. ARE CONNECTIONS TIGHT?
5. IS TIP DAMAGED?
6. IS THE COLD JUNCTION BEING HEATED BY THE PILOT OR MAIN BURNER FLAME?
Once those things are addressed it is a good idea to take some millivolt readings. It should also be mentioned that many times it is the policy of some to replace the thermocouple on a call and clean the pilot. It is not a bad thing to do, however it is statistically about 85% of the time it is the thermocouple giving the problem. It is the other 15% of the time that taking readings can solve other problems.
You need a multimeter with a DC volt scale, as the millivolts generated are DC volts. There are four readings we are going to take they are
OPEN CIRCUIT - this is taken with the thermocouple disconnected and the meter leads attached to the outside of the thermocouple and the other meter lead attached to the tip of thermocouple. The pilot-on-off knob will have to be held manually to take this reading. This measures the output of T'couple the readings must be above 17 to 18 millivolts.
* CLOSED CIRCUIT - This measures the millivolts used by the coil in the electromagnet. A rule-of-thumb is this reading should be roughly half of the open circuit. It is taken using an adapter screwed into the magnet and the thermocouple screwed into the adapter.
CLOSED CIRCUIT LOAD - This reading is taken the same as the previous reading except the burner is now on. With a proper flame this reading should be about the same as the previous reading. With a lifting main burner flame or excessive drafts or chimney pull, this reading may reduce from previous reading (flame being pulled away from the thermocouple). With the cold junction being heated this reading may increase. If the "cold junction" is heated excessively it will break down.
DROP OUT - This is the final reading. It requires the pilot to be blown out. It measures the ability of the magnet to hold under reduced MV input. A good unit should drop out below 6 MV's - normal is 1 to 2 MV's. The allowable "drop out" time is 180 seconds yes three minutes. It is more likely to be a minute and half to two minutes. There will be an audible "click" when the magnet shuts down.
* THE CLOSED CIRCUIT READING REQUIRES A SPECIAL ADAPTER THAT SCREWS INTO THE MAGNET ASSEMBLY TO ALLOW CONNECTION OF THE METER. AN ADAPTER CAN BE PURCHASED FROM ANY ROBERTSHAW DEALER THE PART NUMBER IS 10-038 THERMOCOUPLE TEST ADAPTER.
A normal set of readings
OC- 30 millivolts
CC- 15 millivolts
CC(load) -15 millivolts
DO- 1 millivolt
The best way to be able to diagnose these readings is to use MILLIVOLT CHARTS these can not be displayed here but I can provide them if you e-mail me.
Thermocouples from different manufacturers vary as to their dependability. The only thermocouples I recommend are made by Johnson Controls. The K15 and K16 series are the best. If you are having durability problems then use the K16RA, which is a nickel-plated high ambient or corrosive environment thermocouple. The Husky (K16) will fit most applications and for those that it does not the Slim Jim (K15) will fit.
To repeat the adjustment of the pilot flame to envelope the upper 1/2 to 3/8 of the thermocouple is important, the flame should be a soft blue flame not roaring which will cause the tip to glow a "dull red" versus "cherry red".
The combustion condition (excessive temperatures) in the chamber is also an issue and this will require a combustion test and draft measurement to insure that excessive temperatures are not being applied to the pilot. In some cases on water heaters it may be necessary to alter the pilot adaptation to get better quality performance. This however should not be done unless you have had proper training.
The possibility of the equipment operating in a depressurization environment will certainly lead to thermocouple failure. In addition if the equipment is flued together with a "fan assisted" furnace or boiler this can lead to problems. There are solutions to this also but training is required.
The thing that I find is often a problem is the environment in which the equipment is operating. Many times corrosive chemicals and airborne contaminants are being drawn into the air gas mix and a chemical reaction takes place. This again requires attendance at a training session by a professional combustion person to help you to see the various affects this will have.
Last of all the failure to put all the doors and covers back in place on equipment. The failure to do this will cause an alteration in combustion air and the flame stability is affected.
The design of some equipment is also a problem. When there is high demand for heat (very cold weather) the temperatures that are created in the chamber have an adverse affect on the pilot and thermocouple system. The addition of the K16RA thermocouple can offer some assistance toward extending the life of the thermocouple in this situation.
Insufficient air for combustion and dryers operating in close proximity to equipment also lead to problems.
Last of all and this is not directed at any one in particular but just plain lack of service personnel and installers knowing what they are doing.
My book "Circuitry and Troubleshooting" Volume II addresses many of the things in question here.