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LWCO demise, is this a replacement I can do?

NiCu Member Posts: 3
Hi all..  First off, thanks everyone for sharing your experience and knowledge. I've learned so much just by searching and browsing this site.

Now on to my question/problem. At some point this evening the LWCO on my steam boiler started buzzing, and the red indicator light on top was lit while the system was still happily boiling along. The LWCO is a McDonnell PS-801-24. The boiler was firing when I found it and there was plenty of water in the system as I topped it off this afternoon. There is only one light on the LWCO, most diagrams I've found by searching the model number show multiple lights. I'm guessing this is a really old example of this model.

I cut of power to the system and used this as an excuse to drain the system dry to make sure the sight glass was reflecting the drain and subsequent refill accurately. The glass seems to have been telling the truth. After a refill to my normal water level I energized the system again and the buzzing stopped, yet the red light is still lit. Also the boiler is firing again as the thermostat dictates.

Am I correct in my belief that the LWCO is hosed and needs to be replaced, and is this a part that someone who is reasonably handy can replace themselves? As I have a manual fill system and it's right next to my work bench, I tend to check the glass daily so I'm not worried about running dry in the immediate future.

Thanks in advance for any insight you may be able to share.


  • Charlie from wmass
    Charlie from wmass Member Posts: 4,285
    It may be the probe

    that is going not the LWCO itself.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,826
    edited February 2012
    A couple o' things...

    1. The 24-volt model is now the PS-802-24. 801s are only 120v.

    2. Like Charlie said, it could be the probe. Have you taken it out and cleaned it? Clean it with a rag and clean water, and when you replace it, use thread sealant, not PTFE tape.

    Since you don't have a second LED, I assume you don't have a test button. Do you still have the manual that came with it?

    Yes, it's an easy thing to replace, but you might want to make sure it's not just the probe, unless you think it's so old it might be a good idea to just replace it anyway. If you're not in too big a hurry you might want to check out their newer PSE-800 series or the RBT-3000.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • NiCu
    NiCu Member Posts: 3
    Reply to a direct contact

    Someone replied to this post directly last night via "Contact the poster", so here's the answer to their query for future Wall searchers.

    In my case the old LWCO was done for and had to be replaced. The PS-802 series was discontinued and replaced with the PSE-802-24 in terms of the comparable model, so I found one at a local plumbing supply house and was off to the races. (Matt from the now lost and sorely missed Triple Crown Plumbing came and muscled the old one out as jumping on the wrench didn't even get the old one to budge for me.)  From watching it was basically a 1 for 1 swap out with the same wiring, but the schematic diagram that came with it was quite good if you get lost.

    Good luck!
  • BobC
    BobC Member Posts: 5,410

    for letting us know how it all turned out. You might want to find out where Matt is working now in case you ever need help.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • NiCu
    NiCu Member Posts: 3
    Still around

    Thankfully I keep in touch with Matt, one of the many benefits of living in the same (small) town
This discussion has been closed.