Pressuretrol wiring does not stop gas

sashas

Hi,
I have steam boiler PENNCO 1604HSID
(https://penncoboilers.com/sites/default/files/16 Series IOM.pdf)

Pressuretrol
https://www.supplyhouse.com/Honeywell-L91A1037-Pressuretrol-Controllers-Modulating-0-psi-to-15-psi

LWCO: GC400

The issue that when pressuretroll cuts off there is noise and I noticed that sometimes gas starts before ignition is on what causes a small exposure.
I think there may be an issue with the wiring.

Video where small exposure visible: https://photos.app.goo.gl/P3HDkLpLo3PCp1gk8
Video with sounds after pressure cut off: https://photos.app.goo.gl/vGPjt1yFvnqCYphM7

I tried to understand the electrical scheme for the builder and think that the Black cable from pressuretrol not connected correctly because it should be connected somewhere to LWCO instead of how it is currently. I added pictures of connections.

Please help me to find out why the issue happens or about the connection.
Thanks in advance!

HVACNUT

@sashas, shut off the emergency switch and the gas valve. 
Go to "Find a contractor in your area" at the top of the page and see if anyone here is within reach. If not, you still NEED a steam pro to check/ repair, and test your system. This is beyond DIY. When things go boom it's time for a pro.

Big Ed_4

I agree it needs to checked out . Seem like from here with the chatter, power is bleeding through . I don't understand why a L91 pressure control is being used . They are used for modulation . Then in back of my mind , Pennco did have a issue with their pilot set up ... I noticed the camera shake when the burner lit off

sashas

@HVACNUT Thank you. I going to call and find someone.

@Big Ed_4 Is L91 not support to be used with this system? May power still be connected because the pressure control not connected to the water cut of ?

EdTheHeaterMan

Agree with @HVACNUT & @Big Ed_4

If I came across that service call, I would recommend a completely new wiring harness. The cost would be based on about 3-4 hours of labor and the needed wiring connectors. The flat rate quote for the repair would include the time and material to search for the manufacturer's wiring diagram if available, or I would provide something that includes all the components including the proper safety limits, LWCO, gas valve ignition control, and (if was there) the vent damper. They are usually available from a manufacturer's website.

The cost might be a little high in the customer's opinion because "Well it is already working" But I would either do it right or walk away. If I walked away the switch would be left off, the supply valve would be closed, and the service ticket would read: "WARNING: OPERAT AT OWN RISK! MECHANIC LEFT SWITCH OFF"

Hearing the gas valve open, and the hiss of the main gas valve with no flame would make me cringe and dart for the emergency switch. then the manual gas shut-off valve.

Respectfully Submitted,
Mr.ED

STEAM DOCTOR

Definitely need a pro. Might not be a wiring issue. Might be a gas valve issue. But only a pro onsite will know for sure. Not really situation where you want to play Russian roulette. 

Big Ed_4

The burner circuit should run though P1 and P2 of that Low water cut off . I am not sure about the L91 it may just be an over kill or the culprit . I never work on one to understand their behavior . They are used for modulation of a burner or motor .

sashas

Thanks, everyone. The issue was pressuretrool because it has rele instead of a simple switch.

sashas

But I interested if anyone can explain what is the difference between L91 and regular pressuretroil?
I know it may be a lot to explain so if there a link where I can read and understand on a simple level I would appreciate it!
@Big Ed_4 @STEAM DOCTOR @EdTheHeaterMan

bburd

The L91 is a modulating control, designed to work with a modulating burner that can vary its firing rate. These are sometimes found on large commercial or industrial boilers.

So far as I know, all residential size steam boilers have burners that are either on or off and are not compatible with modulating controls. The standard pressuretrol acts like an on/off switch and works properly with these burners. 

EBEBRATT-Ed

@sashas

@bburd

Is correct the L91 is a series 90 modulating control used on commercial boilers. It chanhes resistance to operate a mod motor or valve or damper. Its is not an on off control and can't be used on a residential boiler it isn't a limit or operating control.

Jamie Hall

And, perhaps more important, must be backed up by a high limit pressuretrol as a safety -- preferably one which is strictly manual reset.

retiredguy

I won't go into detail here about how an L91 modulating control works, since it was used to control a multi-position motor that controlled the flow of a fluid like steam, water, oil, gas, and etc. If you want to understand how that control worked search for the term "wheatstone bridge circuitry" for a complete explanation. I will tell you this that 1/2 of the circuit is in the L91 control and the other 1/2 is in the motor being controlled.