Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

which one is broken?

Hi Tony,

Thanks for your reply. I kind of thought the inverted "J" might have been intended to provide protection, but I didn't have confidence that such a short stem under each control/gauge could really protect the sensors very well. You're sure this is a good setup, then?

The grey controller on the left is a Honeywell PA404A or 404B. The middle controller is an L604L. The controller on the right is an L91B. The Power Flame burner is a model WJR50A-15C, which has controls for modulation. The gas valve and air intake are clearly set up for modulation, too. The control knob for modulation is currently set at the mid point of its scale. There's more pix posted with a previous question, http://tinyurl.com/2xyvdq.

I've probably messed up the modulation by lowering both the PA404 and the L91B, trying to get the pressure down below 5 pounds. Even though both controls appear to be set at less than 2 pounds, the gauge still reads around 5 psi.

There's a guy coming on Tues. a.m. from Cordell Mechanical (anybody heard of them??), and I hope that when I ask what pressure we should be running, he'll say "2 psi or less". That's my litmus test!

Comments

  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    2 pressuretrols, 1 gauge, no sense

    Still trying to figure out what's going on with my overheated building. There's two pressuretrols, set as shown in the pix. The 'demand' lamp on the Powerflame controller lights up when the gauge says 5 psi. (It drops to about 4 psi by the time the gas ignites.) The burner cuts out when the gauge says 5.5 psi.

    I keep easing the pressuretrols down (I've brought the pressure down from the 7-9 psi range), but I don't understand why both pressuretrols read below 2 psi and the gauge hovers around 5 psi. Is the gauge faulty? Are the pressuretrols faulty? Which one is actually controlling the burner?

    thanks,
    Stuart
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Check the differential adjustment

    which is located inside the Pressuretrols' cases.

    TURN THE POWER OFF BEFORE OPENING THE CASE!

    The differential is probably a white wheel with numbers on it. It also may be a small metal wheel with numbers on it, on older units. Rotate this wheel to 1. Then, the setting on the front of the unit plus 1 becomes the point at which the burner will stop. The burner will restart at the setting on the front.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Timco
    Timco Member Posts: 3,040


    Do these presstrols have pigtails? If so, have you checked them for dirt / crud? I would replace both and the pigtail(s) if any questions...they are cheap enough. Have you checked the gauge's accuracy? You can get a new pressuretrol with a .5lb-5lb scale, and a manual reset type presstrol for the safety high limit...and a new gauge is really cheap as well.

    Tim
    Just a guy running some pipes.
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    no pigtails

    By "pigtails", I think you mean what the manufacturer calls "siphon loops" -- and I don't see any (picture attached). Some effort seems to have been made to separate the water from the controls, but I can't see how they are protected from the steam. I will have all these controls replaced, with proper loops as shown in the Honeywell installation documents.

    I can't tell you how much I appreciate this forum, and the kind people who are taking the time to help! Thank you so much.
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    Thanks!

    Thank you, Frank. I'm going to have these suckers replaced in any case, after discovering the bad installation practice.

    (Love that rehab story of yours on the find-a-pro page!)

    stuart
  • Tony Furst
    Tony Furst Member Posts: 12
    Steam syphon

    The installation detailed in your picture creates a syphon loop for the controls. Basically what happens is that as the steam cools and collapses in the pipe below the controls it becomes the syphon and provides the seperation between the controls and the live steam. Without knowing the actual model numbers of the three Honeywell controls pictured can't tell which one is which but it almost looks as if you have a high limit, low fire and high fire operators. I also thought you mentioned a Power Flame burner, is it on/off or full modulation? This will make a difference in controls setup. Went back and looked closer at controls photos one of the Honeywell controls appears to be a series 90 135 ohm modulating control. I wouldn't replace the controls, however I would have them setup properly. Most likely cut-in, cut-out and proportional band or set incorrectly so the burner is operating at high fire rather than modulating.

    Tony
  • Tony Furst
    Tony Furst Member Posts: 12
    Controls

    Stuart,
    The PA404 is the high limit ad should be set for 5 PSIG or slightly higher. The L604 is your operator, since it is a mercury bulb style switch make absolutely sure the case is perfectly level before trying to get it setup properly. This control should be configured with a subtractive differential so that it opens at setpoint and closes at setpoint minus the differential. As for the L91B this controllers setpoint should be about 1 PSIG based on a 2 PSIG operating pressure. My suspicion is that the burner is ramping to high fire too quickly for the modulating control to work properly. You may have to replace the modulating controller with one that has a much lower range. Not sure how you arrived at the 2 PSIG number because the correct steam pressure setpoint is really defined by what your heating devices are. Is it radiation or air handling unit coils, is the steam going to any converters?

    Tony
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    Controls

    Thanks, Tony. Maybe that's how the p'trols *should* be used, but that's not how they've apparently been installed. The L604L mercury switch is set for 12.5 psi; when I tried cranking it down and the mercury tipped, an alarm sounded and the burner cut out; the high-pressure alarm lamp lit. So that has to be the high limit for safety, right?

    According to what I downloaded from Honeywell, the L91B is a "proportioning" controller, so I'm thinking it has to be controlling the burner modulation. If this is the case, does it have *any* effect on when the boiler cuts in or out, or does it only affect the fuel/air flows while something else controls the burner on/off state?

    That leaves the PA404A (it is an "A", I verified the model number). Honeywell describes it the same as you do, as a high limit. But if the L604L is the high limit and the L91B is the modulator, then I guess the PA404A must be controlling when the burner cuts in and out? (i.e,. the "operator"?)

    Gee, I wish I knew where the wiring diagrams were :-(

    I'm aiming for 2 psig because this is a 1925 building with only standard column radiators, and everything I've read about such systems says 2 pounds or less. (Mr. Holohan says it an awful lot of times in his books ;-)

    Once again, my thanks!
    Stuart
  • Tony Furst
    Tony Furst Member Posts: 12


    Stuart,
    Based on what you have described for the radiation the 2 psig is correct at least as a starting point. What will ultimately drive the final pressure setpoint is radiator condition on the inside and if someone at some point in time did something like install control valves at each radiator. If they have added automatic control valves at the radiators they increased the total pressure drop at each radiator and you now have to overcome that added pressure drop that wasn't there to begin with.

    Basically the wiring needs to be reversed on the two pressure controls so the 404A is wired as the high limit and the L604 wired as the operator. The L91B does nothing more than modulate the burner from low to high fire or anywhere in between and does not turn anything on or off. Basically it is setting up a resistance balance between the motor and the controller to position the mod motor.

    As for the 12.5 PSIG setting of a high limit I would prefer that be set much lower only because of safety. The boiler should be equipped with a 15 PSIG relief valve and having your limit set that close to the relief setting is not good practice. I would recommend setting it around 5 PSIG or slightly more than twice the normal operating pressure.
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    TRVs are in place

    Hi Tony,

    OK, this is making more sense now. I've been told the rad's were removed and cleaned within the last 12 years (not sure if all of them got treated), and I think it's possible some of the supply pipes from riser to rad are partially blocked by corrosion?

    Yes, there are thermostats on most radiators, though many of them are the wrong type (combined sensor/dial/valve within an enclosed cabinet), or installed in the wrong orientation (vertically above the supply pipe), or have failed for one cause or another (sensor and capillary tube resting directly on blazing hot rad, for example). I'm pretty sure almost all the traps are shot, too, so I guess it's premature to try fine-tuning the system pressure. But I didn't realize that the added TRVs would affect the pressure drop.

    I learned yesterday that there were a lot of call-backs after the 2005 boiler installation, with disputes and finger-pointing. Not surprising to learn something fundamental like wiring reversal is involved. I've got someone coming round to the building tomorrow a.m., so we'll see what he has to say. I only hope he really does know old systems!

    thanks again,
    Stuart
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    TRVs are in place

    Hi Tony,

    OK, this is making more sense now. I've been told the rad's were removed and cleaned within the last 12 years (not sure if all of them got treated), and I think it's possible some of the supply pipes from riser to rad are partially blocked by corrosion?

    Yes, there are thermostats on most radiators, though many of them are the wrong type (combined sensor/dial/valve within an enclosed cabinet), or installed in the wrong orientation (vertically above the supply pipe), or have failed for one cause or another (sensor and capillary tube resting directly on blazing hot rad, for example). I'm pretty sure almost all the traps are shot, too, so I guess it's premature to try fine-tuning the system pressure. But I didn't realize that the added TRVs would affect the pressure drop.

    I learned yesterday that there were a lot of call-backs after the 2005 boiler installation, with disputes and finger-pointing. Not surprising to learn something fundamental like wiring reversal is involved. I've got someone coming round to the building tomorrow a.m., so we'll see what he has to say. I only hope he really does know old systems!

    thanks again,
    Stuart
  • Tony Furst
    Tony Furst Member Posts: 12


    Stuart,
    It's good that things were cleaned but if there is serious build-up in the piping that will continue to cause grief for you.

    I'm not a fan of thermostatic radiator valves especially with older low pressure steam systems as they have a pretty significant pressure drop and can actually cause you more problems tha they are worth.

    Before you get too carried away adjusting and rewirig the pressure controls I would test all of the traps and repair or replace those that are defective. That task in and of itself will do you a world of good as well as lower your energy bills.

    If you contact Powerflame directly through their website and give them the model and serial number of the burner they should be able to send PDF copies of the factory diagrams for the burner.

    Not sure where you are located and wish I could offer more assistance. The control setup issue should take a good boiler tech two hours or less to resolve and properly configure the controls.

    Tony
  • Stuart Rogers
    Stuart Rogers Member Posts: 49
    Relief at last!

    Thanks for the reply, Tony.

    The guys we had in to look things over this a.m. seem to be really good -- four generations of family business dealing with steam. They're going to give us a full report with recommendations for a staged renovation of the system and for ongoing maintenance. They want to start by installing a Heat Timer or similar outdoor sensor so the boiler is not maintaining a head 24/7, which it is doing now. Then we'll tackle trap replacements and see whether we still even need TRVs on the rads -- it may be enough to simply get the boiler and returns under proper control.

    I've asked bldg mgmt to scour the files for more documentation -- we don't even have an inspection certificate posted on the wall per local statutes (how did we get insurance?!). If they don't find wiring diagrams, I'll contact PowerFlame as you suggest. Thanks for the tip.

    Thanks again,
    Stuart (in Toronto, btw!)
This discussion has been closed.