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Peerless 211A help with RM7890

My boss went by this morning and turned off the service switch to the old boiler. We let the problem boiler run all day, still connected to the tekmar boiler staging control. It ran fine all day. We will let it run tonight as well and make periodic checks during the night.

I have the Honeywell sheets you are refering to and will do as you suggest. I got stuck on service calls today and didn't get a chance to tear into the Peerless.

I wonder if it could somehow be related to high gas usage during the night?

Tim, thanks again for all your assistance. I have been doing this for many years but the more I get on The Wall, the more I realize how little I know.


  • John McArthur_2
    John McArthur_2 Member Posts: 157

    I have a 211A with the RM7890 burner control that keeps going into lockout. The boiler is a nat. gas unit and I have checked the high and low pressure safety switches on the gas train. The manifold press. is 3.5" w.c. When I test the dc volts at the flame amplifier, I get ~2-4vdc with the pilot lit. None of the safties trip but it keeps intermittantly going into lockout.

    The only odd thing I have noticed is that the power light on the RM7890 blinks on and off at a slow pace. I don't know if this indicats line noise or is normal. I have read through the literature but since I have never witnessed the boiler go into lockout, I don't have any idea what is causing the problem. The problem occurs summer and winter so it is not a temp issue for the control or flame amp. The boiler sits directly in front of a louvered door. I don't think it is a draft blowing the pilot out because I have been in the room for hours with the boiler in operationg w/o issue. The second boiler has ran about 4x as many hours in the past year as the problem one. The second boiler is older and has the 24v control/ignition system.

    Any help would be greatly appreciated. Thinking about getting a display module for the burner control to help troubleshoot.

    I posted the same question in the general forum as well.
  • Have you done a combustion analysis

    on the boiler? It sounds to me like from time to time you may be having a poor flame condition. Doing a combustion test can determine if draft/air/gas etc is set up correctly and get your CO level below 100 PPM.

    How is your ground on the system? Sometimes it is a good idea to actually run a seperate ground wire just to be sure.

    Even though your DC amps are okay I would pull the pilot and make sure you still have a good 4 to 1 ground to rod ratio. On some burners adding some ground area can help.
  • John McArthur_2
    John McArthur_2 Member Posts: 157

    Thanks. Another thing that Barry Engleman brought to my attention was that inadequate gas valve venting may cause some problems too. I noticed today that both gas valves are tied together on each boiler and then tied together with a tee. Both boilers vent on a 1/4" tube all the way outside.

    I'll check the ground as well. The failure is intermittant and difficult to diagnose.

    FWIW, the old boiler is a 211-09 and the problem boiler is a 211-08. Kind of a shame since the heat loss for the entire building is only 485,000 Btu/hr.
  • How long is that

    1/4" tubing. If it is too long it will affect the opening of the valves. I usually run my tubing to a piece of black 1/2" or 3/4" pipe and then run the pipe outdoors. Is the regulator vented seperately? If not it should be, this can also affect operation of the regulator as the regulator vent does not vent gas but is required in the event of a rupture of the regulator diaphragm. It also allows the regulator to "breath".
  • John McArthur_2
    John McArthur_2 Member Posts: 157

    The entire length or 1/4" tube is about 12-15'. The regulator and the gas valve are vented together, I just looked at a PDF of the manual and it specifically states to vent them separately. I had not noticed before and the installer simply matched the old boiler. I will vent them separately tomorrow.

    I went to check on the boiler an it had already locked out. Only ran for about 2 hours. Funny thing is, the old boiler is vented the same and has worked fine for many years. I wonder if the old 24v ignighter is less sensitive than the RM7890?

    Thanks again, I'll also do a combustion test tomorrow.

    Any reason the power light on the RM7890 should flash on and off?
  • I will check on the power

    light thing on the RM7890 and get back to you. Off the top of my head it sounds like it is not making good electrical contact. Check your input voltages with various loads running, you may have a power problem.
  • John McArthur_2
    John McArthur_2 Member Posts: 157

    I'll be in the boiler room most of the day today. I just replaced the heat system circ. pumps and have to wire a tekmar 132 into the system and re-vent the gas valves and regulators.

    I'll do a combustion test and note all of the readings. I'm a noob to combustion testing. I have only used mine a few times on high-efficiency units that tell you what readings you shoud get.

    A former employee did the initial wiring and setup. Still cleaning up the mess. :(

    Some day I'll get a digital camera so I can post before and after pics of jobs. I love to see the fine work that the people on this board do.
  • John McArthur_2
    John McArthur_2 Member Posts: 157

    I decided to go through the previous wiring while I was installing the pump sequencer. I found some loose connections between the boiler staging control and the RM7890. I reconnected and double checked the remaining wiring.

    I also found that the manifold gas pressure was only at ~2.9"wc. I adjusted to 3.5" and re-routed the vent lines. I did not get around to doing a combustion check. It seems to be running fine now. Maybe the poor connections were the culprits.

    Thanks for all the advice.
  • The diagnosis sheet on

    the RM7890 control do not indicate any reason for the power light pulsing on and off. The loose connections could certainly be your problem.
  • John McArthur_2
    John McArthur_2 Member Posts: 157

    Well I thought I had it fixed. Unfortunately, this morning it was in lockout again. The darn thing ran all day without a hitch while I was working in the mech room yesterday. I disabled the old boiler so only the new one would run. It worked great. I'm afraid to let it run with the old one disabled unless I'm there. Don't want a building full of upset people this close to a holiday.

    There must be something I'm missing. I have read nothing but good things about the control. I might end up stripping all the controls off and starting from scratch. I may even change it to a 24v system.

    I bet Barry wishes he never sold me this boiler!
  • Do you have the

    7800 Series Spec Sheet Honeywell # 66-2032-1 and
    7800 Series Checout and Test information Honeywell # 65-0229-1.

    Before you condemn everything I would get those and go through a complete system checkout along with a combustion test.

    To get the spec sheet go to

    look for Literature/Image Search (Lower rh corner) insert literature/image number 65-0229-1 it will come up as a PDF file and you can download it to your printer.

    If you have trouble let me know and I will fax it to you.
This discussion has been closed.