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Old 03-24-2010, 03:21 AM   #1
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gas valve outlet pressure


On a White-Rodgers 36C74 gas valve, type 205, is the testing device used in the outlet labeled
"Press
Tap", shown in the picture below.

And how can the plug be removed? Is it an allen head plug, that's been 'rounded'?
Thanks.


Last edited by leehinkleman; 03-24-2010 at 03:31 AM.
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Old 03-24-2010, 10:13 PM   #2
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gas valve outlet pressure


Yes, that's where you measure your manifold pressure. 3/16" allen key if I remember the size correctly.





Last edited by beenthere; 04-08-2010 at 03:00 PM. Reason: Removed link to another forum
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Old 03-24-2010, 11:10 PM   #3
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gas valve outlet pressure


Thanks, Tech X.
A 4 mm allen key was too small and a 5 mm was too big, and 3/16", I think, is equivalent to 4.7625 mm, so I'll find a 3/16" key, and then proceed with testing.
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Old 03-25-2010, 05:52 PM   #4
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gas valve outlet pressure


One other question I have is: what prevents water, from a column, from entering the other chambers of the valve, when connected to the 'PRESS TAP'
outlet?
Thanks again.
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Old 03-25-2010, 06:26 PM   #5
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gas valve outlet pressure


What are you trying to accomplish?
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Old 03-25-2010, 08:13 PM   #6
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gas valve outlet pressure


Quote:
Originally Posted by NHMaster View Post
What are you trying to accomplish?
In this specific instance, I'm attempting to determine the valve's outlet pressure.
I've been advised, by the technician who installed 4 new brass jets, with smaller diameters for conversion from NG to LPG, and who tested the furnace, that the outlet pressure was 11 W.C.
I also was advised that the spring under the 'cover screw' was not changed, but that 11 W.C. was achieved by tightening the internal adjustment screw, compressing the (apparently unchanged) adjustment spring.
What concerns me is that the black printing on the valve's side specifies the outlet pressure as "3.5 W.C. to 5.5 W.C.", which is only halfway to the goal, as I understand it.
Another issue, possibly related, is that the flame sensor's sense seems 'variable' with its sensing ability ranging from (perceptively) perfect, to zero.
In cases which seem like 'incomplete' flame sensing, the flame of the sparked #2 burner remains lit, but only after mechanical rattling, which I think is from the valve's main solenoid.
A second burner(either #1 or #3) lights, but usually only #2 with #1, or #2 with #3, are lit after 1 minute.
Thanks.
Thanks.
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Old 03-25-2010, 08:30 PM   #7
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gas valve outlet pressure


Quote:
Originally Posted by NHMaster View Post
What are you trying to accomplish?
After reconsidering your question/answer, I've decided to change my answer, after guessing what the technician was trying to describe, by phone, as a homemade manometer.
I think I understand now that the 'homemade manometer' probably is a 'U" shaped tube, partially filled with water, and with either end of the 'U' attached to the "PRESS TAP" outlet.
Please correct me if my guess is wrong.

Last edited by leehinkleman; 03-25-2010 at 08:32 PM.
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Old 03-25-2010, 09:16 PM   #8
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gas valve outlet pressure


Your inlet pressure for natural gas is only 7" of WC and an outlet of 3.5". LP is 12" in and usually 10" out. Call him back out to put the propper spring in since you paid for a LP conversion and that's part of it. Delayed ignition on a burner or two is almost always a dirty crossover.
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Old 03-25-2010, 10:53 PM   #9
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gas valve outlet pressure


Question, why didn't you call the tech back to finish the job properly?
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Old 03-26-2010, 12:44 AM   #10
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gas valve outlet pressure


Quote:
Originally Posted by log_doc_rob View Post
Question, why didn't you call the tech back to finish the job properly?
This furnace was won for NZ$250 on a New Zealand auction website, but was 350 miles north of me in Auckland. The auction seller took it to recommended Auckland gasfitters, who had it for 6 months before saying they "couldn't fix it, but they've given it to a more expert gasfitter".
He had it for another year, before delivering it to me, while taking his daughter on a ski trip. I paid him for the work, long distance delivery, and gave him a 10% tip(and tipping is not 'normal' in New Zealand.
Anyway, more bad news: I just checked the outlet pressure from the outlet(not from the tap) on a homemade manometer, and it's FIVE INCHES WC.
He told me by phone it was 11 WC inches. Obviously, there's no point phoning him again.
I removed the Adjuster cap screw, and tried to remove the smaller screw inside, but it unscrews ~9 turns and then stops. Have White-Rodgers made an adjuster screw which can't be removed?
Thanks again.
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Old 03-26-2010, 05:28 AM   #11
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gas valve outlet pressure


If on a u tube manometer. You see the water column rise 5 inches on one side. Then it also lowered 5" on the other side. Which means it moved a column total of 10"(so you have a 10"wc of pressure,). Which is allowable pressure for LP(presuming your checking on the manifold side of the gas valve, and not i ts inlet side).
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Old 03-26-2010, 06:59 AM   #12
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gas valve outlet pressure


Here's a link to the operating instructions for that valve. I can make a house call if you like. $85 per hour plus travel time. I am coming from Virginia Beach, Virginia USA. Please send directions to your place. :-)

http://www.white-rodgers.com/wrdhom/.../0037-5868.pdf
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Old 03-26-2010, 07:31 AM   #13
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gas valve outlet pressure


Quote:
Originally Posted by beenthere View Post
If on a u tube manometer. You see the water column rise 5 inches on one side. Then it also lowered 5" on the other side. Which means it moved a column total of 10"(so you have a 10"wc of pressure,). Which is allowable pressure for LP(presuming your checking on the manifold side of the gas valve, and not i ts inlet side).
That's a very good answer, and I was checking on the outlet side. I took a photo of the U tube nailed to a board, from which I'd removed a piece of goat skin, with black hair, which had been salted and nailed to that board.
And "5 inches" probably was extravagant, and I could have seen close to 3 1/2"...I just was sure it was well under 5.5 inches, when I saw the water level reach its peak, and I think I still need to get the adjustment screw out of its hole.
Thanks.
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Old 03-26-2010, 07:42 AM   #14
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gas valve outlet pressure


Quote:
Originally Posted by log_doc_rob View Post
Here's a link to the operating instructions for that valve. I can make a house call if you like. $85 per hour plus travel time. I am coming from Virginia Beach, Virginia USA. Please send directions to your place. :-)

http://www.white-rodgers.com/wrdhom/.../0037-5868.pdf
Thanks, and I've been reading the same .pdf file's instructions for the past 5 days.
But it looks, from the drawing that the adjustment screw is in the same thread diamters as the adjusting cap screw, so I can't see why the screw becomes wedged when I try to remove it.
Do you think that screw could be removed?
Regarding your fees + travel time, your fees are very reasonable. I thought US plumbers charged more like $850 per hour.
But it would be best if I travel to Virginia Beach, and to bring the valve to you.
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Old 03-26-2010, 07:46 AM   #15
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gas valve outlet pressure


No, that cap must be in place for normal operation.
Call the tech back, and tell him its not at 11"

The gas pressure is often different with the cap i n place, then when it is removed. Did you check with the cap in place or removed?

Did you check what your inlet pressure is while the burner is on?

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