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McDonnell & Miller RB-122-E (171207) / Series 67 & 750B-24 24VAC Electronic Low Water Cut-Off (LWCO) & Probe Kit Engineering Diagram
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SPECFOUNDRY SKU: SF-HVC-110 · BRAND REF: McDonnell & Miller / Xylem

McDonnell & Miller RB-122-E (171207) / Series 67 & 750B-24 24VAC Electronic Low Water Cut-Off (LWCO) & Probe Kit

Stamped Casting / OEM Numbers: RB-122-E 171207 67 PS-802-24 36C03-300 MM-RB122E

Compatible Units: Residential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)

Critical Dimensions & Spec: 24VAC, 20,000 Ohm sensitivity; 3/4" NPT brass self-cleaning probe; automatic reset with 15-second anti-slosh delay; green/red LEDs

$112.99
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Pre-Order Dimensional Verification Checklist

OEM Cross-Reference & Stamped Casting Number Table

Use this cross-reference table to confirm that the number stamped or printed on your original hardware or circuit board corresponds to SpecFoundry SKU SF-HVC-110:

Stamped / OEM Part Number Manufacturer / System Brand Compatible Models & Years SpecFoundry Replacement SKU
RB-122-EMcDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)
171207McDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)
67McDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)
PS-802-24McDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)
36C03-300McDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)
MM-RB122EMcDonnell & Miller / XylemResidential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin)Direct Match (SF-HVC-110)

Common Failure Symptoms Solved by SF-HVC-110

Technicians and property owners typically replace RB-122-E when experiencing one or more of the following failure modes:

  • Boiler fails to fire even with 15 PSI water pressure because fouled LWCO probe reads dry
  • Red Low-Water LED stays illuminated on RB-122-E control box
  • Weeping boiler water around cracked Teflon insulator on 3/4" brass probe

Step-by-Step Dimensional Verification & Installation Notes

Drain boiler pressure below probe tapping, unscrew brass probe, clean or replace with included self-cleaning probe using non-insulating pipe dope (do NOT cover entire thread with heavy Teflon tape, as the brass body is the ground return path).

Related Technical Guide: Taco 571-2 vs. Honeywell V8043E Zone Valve Powerheads, B&G Couplers & Boiler Cross-Reference →

Frequently Asked Technical Questions (RB-122-E)

Where is the casting or OEM part number (RB-122-E / 171207 / 67) stamped on this part?

On McDonnell & Miller / Xylem assemblies, look for the stamped or die-cast numbers (RB-122-E, 171207, 67, PS-802-24, 36C03-300, MM-RB122E) on the underside of the metal housing, along the link arm, on the stainless hinge track, or printed on the circuit board/valve label. Note that casting numbers identify the housing casting, so always confirm critical dimensions (24VAC, 20,000 Ohm sensitivity; 3/4" NPT brass self-cleaning probe; automatic reset with 15-second anti-slosh delay; green/red LEDs) as well.

Does SpecFoundry SKU SF-HVC-110 directly replace OEM part RB-122-E (RB-122-E, 171207, 67, PS-802-24, 36C03-300, MM-RB122E)?

Yes. SF-HVC-110 is verified to match the mounting footprint, electrical/mechanical ratings, and dimensional envelope of McDonnell & Miller / Xylem RB-122-E, 171207, 67, PS-802-24, 36C03-300, MM-RB122E used on Residential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin).

What measurements should I verify before ordering SF-HVC-110?

Before ordering, verify: (1) Stamped or OEM code matches one of RB-122-E, 171207, 67, PS-802-24, 36C03-300, MM-RB122E; (2) Dimensional spec matches: 24VAC, 20,000 Ohm sensitivity; 3/4" NPT brass self-cleaning probe; automatic reset with 15-second anti-slosh delay; green/red LEDs; and (3) Application matches: Residential & Commercial Hot Water & Steam Boilers (3/4" NPT Tapping — Weil-McLain, Burnham, Peerless, Slant/Fin).

How fast does SF-HVC-110 ship and what payment methods are accepted?

SF-HVC-110 ships within 1–2 business days from our US warehouse network. Flat-rate US Ground shipping is $8.95, or FREE on orders of $150+. You can check out online immediately via PayPal, Venmo, Credit/Debit Card, or request an Instant Card Payment Link / Net-30 Commercial PO Invoice.

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