TECHNICAL ENGINEERING IDENTIFICATION GUIDE · HYDRONIC BOILER & HVAC
Taco 571-2 vs. Honeywell V8043E Zone Valve Powerheads, B&G Series 100 Couplers & Boiler Ignition Cross-Reference
How to replace failed hydronic boiler zone valve actuators (555-050RP and 40003916-026) without draining a single drop of boiler water — plus exact cross-references for Bell & Gossett 118844, Weil-McLain 383-500-095, Watts 1156F, and McDonnell & Miller RB-122-E.
1. Hydronic Boiler & Furnace Master Part Cross-Reference Table
| OEM Part Number | Cross-Ref / Casting Codes | System Application & Electrical Spec | SpecFoundry Replacement SKU | Order |
|---|---|---|---|---|
555-050RP |
571-2, 570-2, 572-2, 573-2 |
Taco 24VAC 3-Terminal Wax-Motor Zone Valve Power Head (Twist-off top, no draining) | SF-HVC-101 (Taco 555-050RP Powerhead) | |
40003916-026 |
V8043E1012, 802360, V8043F1036 |
Honeywell / Resideo 24VAC 4-Wire Zone Valve Replacement Head with End Switch (2-screw body) | SF-HVC-102 (Honeywell 40003916-026) | |
118844 / 189134LF |
118705, P2Z-12291, 189034 |
Bell & Gossett Series 100 1/2" x 1/2" Cast-Iron Spring Coupler & Bearing Assembly Spec | SF-HVC-105 (B&G 118844 Coupler Kit) | |
383-500-095 |
511-330-403, 511-330-148, AG13A020 |
Weil-McLain GV / GV90+ / WM97 / Ultra Silicon Nitride Ignitor, Flame Sensor & Gasket Kit | SF-HVC-104 (Weil-McLain 383-500-095) | |
0067397 / 1156F |
SB1156F, S1156F |
Watts 1/2" Sweat/NPT High-Capacity Feed Water Pressure Regulator (15 PSI Preset) | SF-HVC-107 (Watts 0067397 / SB1156F) | |
070 / 071 |
TEK-070, 10K-NTC-TYPE2 |
Tekmar 070 / 071 10k Ohm @ 77°F Outdoor Reset Thermistor Temperature Sensor | SF-HVC-108 (Tekmar 070 Outdoor Sensor) | |
RB-122-E / 67 |
171207, PS-802-24, 36C03-300 |
McDonnell & Miller 24VAC Electronic Low Water Cut-Off (LWCO) & 3/4" Brass Probe | SF-HVC-110 (M&M RB-122-E LWCO) | |
7000BMVR / 720-400 |
7200ER, 700-506, 710-502 |
Robertshaw 24V / 750mV Millivolt Combination Gas Valve (1/2" & 3/4" NPT) | SF-HVC-106 (Robertshaw 7000BMVR) | |
Q314A4586 / Q340A1090 |
Q314A-4586, BCR-18 |
Honeywell Standing Pilot Burner & 36" 30mV Universal Copper Thermocouple Kit | SF-HVC-109 (Honeywell Q314A4586 Kit) | |
7021-9450 / 7021-10702 |
320725-756, HC21ZE117, A157 |
Fasco / A.O. Smith 115V 3000 RPM Draft Inducer Blower Assembly for Carrier / Bryant 80% | SF-HVC-103 (Fasco 7021-9450 Inducer) |
2. Taco 555-050RP vs. Honeywell 40003916-026: How to Swap Without Draining
Both the Taco 571-2 and post-1988 Honeywell V8043E1012 hydronic zone valves separate the 24VAC actuator head from the sealed brass water body:
- Taco 555-050RP: Label wires on terminals 1, 2, and 3. Rotate the green/gold power head 1/8 turn counter-clockwise and lift straight up off the brass plunger pin.
- Honeywell 40003916-026: Check that your valve body has 2 mounting screws (at diagonal corners) and a small dimple on the brass cover. Lock the manual lever into the
MAN OPENslot, loosen the two captive screws, and lift the head off.
3. Why Bell & Gossett 118844 Couplers Snap (And How to Prevent Repeat Failure)
When a Bell & Gossett Series 100 circulator pump snaps its cast-iron spring coupler (118844 / P2Z-12291), check the two rubber motor isolation rings cradling the 1/12 HP motor. Over-oiling swells and softens the rubber mounts, letting the motor shaft sag 1/8 inch below the bearing assembly (189134LF) centerline.