Send a part number, a photo, or a whole BOM — we supply it and stand behind it. Worldwide shipping to 80+ countries.

3G Electric
RFQ CartGet a QuoteSign inSign up
MCDONNELL RB-122E Low Water Cut-Off, 120V - Replacement HVACR Pumps, Valves & Tubing
MCDONNELLReplacement HVACR Pumps, Valves & Tubing

MCDONNELL RB-122E Low Water Cut-Off, 120V

MCDONNELL Replacement HVACR Pumps, Valves & Tubing. Specifications: Product Type: Low Water Cut-Off.

SKU 3G-OTH-77737

Also listed as: RB122E · RB 122E

Brand
MCDONNELL
Item
RB-122E Low Water Cut-Off, 120V
Category
Replacement HVACR Pumps, Valves & Tubing
Available to Order
Trade pricing by quote — replies within 24h
Qty
WhatsApp an engineerMessage via Telegram
No account needed — your quote request goes straight to our engineers. A free account lets you track quotes and re-order faster.
Worldwide Shipping
Air & sea freight
Datasheet on Request
Technical specs
1-Day Quote
Replies within 24h

Local availability & support — Singapore

Local office
20 Woodlands Link #09-05, Singapore 738733
Phone
+65 8878 8355
Delivery
Same-day or next-business-day delivery within Singapore for in-stock items; 7–14 days for factory-order parts from Europe.
Payment
Invoicing in SGD. PayNow, bank transfer, and corporate PO accepted.
Ships to
Singapore

Technical Specifications

MCDONNELL
Manufacturer Part Number
RB-122E
Product Type
Low Water Cut-Off

Technical Documents

No technical documents available for this product.
Request documentation →
Not sure this is the right part? Get a recommendation.

Need installation or engineering help?

Installation, commissioning, maintenance plans, system design, and bundled product + service quotes — one team handles the full scope.
Talk to an engineer

Ask a question

MCDONNELL Products
3G Electric (S) Pte. Ltd. — Singapore

Product Description

MCDONNELL Replacement HVACR Pumps, Valves & Tubing. Specifications: Product Type: Low Water Cut-Off.

Frequently Asked Questions

What is the MCDONNELL & MILLER RB-122E low water cut-off used for?

The RB-122E is a residential low water cut-off that protects hot water boilers from damage caused by low water conditions. It automatically shuts down the burner when water level drops, preventing overheating and potential system failure in hydronic heating applications.

What are the specifications of the MCDONNELL & MILLER RB-122E?

The RB-122E is a low water cut-off with a 120V power supply, designed for residential hot water boilers. It is manufactured by McDonnell & Miller under part number RB-122E and is a direct replacement for compatible systems requiring float-type level sensing.

Where to buy the MCDONNELL & MILLER RB-122E worldwide?

3G Electric supplies the McDonnell & Miller RB-122E low water cut-off to customers worldwide. As a global industrial sourcing partner, we handle logistics, customs clearance, and delivery to your location. Contact us for a quote and lead time on this replacement part.

How to install the MCDONNELL & MILLER RB-122E low water cut-off?

Installation typically requires mounting the RB-122E on the boiler supply line above the water line, wiring the 120V control circuit to the burner safety circuit, and verifying proper float operation. Always follow the manufacturer's instructions and local codes for safe boiler operation.

Used in

Common applications for MCDONNELL
Steam boiler low-water cutoff — McDonnell & Miller 61 level control
Condensate receiver level monitoring — McDonnell & Miller RS-4-BR-1 4-level sensor
HVACR pump suction filtration — McDonnell & Miller 340700 strainer basket assembly
Flow switch head replacement — McDonnell & Miller 63-HD head mechanism
Boiler control circuit safety — McDonnell & Miller 7-BM electrical switch with manual reset
Field servicing of flow switches — McDonnell & Miller 310452 cartridge kit

MCDONNELL Products

3G Electric supplies MCDONNELL replacement hvacr pumps, valves & tubing. We supply genuine products with in-stock availability on common SKUs, technical documentation, commissioning support, and warranty service — worldwide.

You might also need

Pump Accessories →Valves & Regulation →Motors & Drives →All Products →

Compatible alternatives & equivalents

Cross-referenced by specification & description
This low water cut-off is designed for use in steam and hot water boilers to protect against low-water conditions. It automatically shuts down the burner when the water level drops, preventing dry-fire damage. Suitable for commercial and industrial HVAC systems
MCDONNELL
This low water cut-off is designed for use in steam and hot water boilers to protect against low-water conditions. It automatically shuts down the burner when the water level drops, preventing dry-fire damage. Suitable for commercial and industrial HVAC systems
The MCDONNELL 157S-RL is a low water cut-off with a snap switch, designed to protect boilers and steam heating systems from low water conditions. It automatically interrupts burner operation when water level drops below safe limits, preventing dry-firing and equipment damage. Suitable for HVACR systems requiring water level monitoring and safety shutdown
MCDONNELL
The MCDONNELL 157S-RL is a low water cut-off with a snap switch, designed to protect boilers and steam heating systems from low water conditions. It automatically interrupts burner operation when water level drops below safe limits, preventing dry-firing and equipment damage. Suitable for HVACR systems requiring water level monitoring and safety shutdown
This low water cut-off/pump controller is a replacement component for HVACR systems. It is compatible with manufacturer part number 162300. Used in heating applications to protect boilers and pumps by shutting off the burner or activating a pump when water levels drop
MCDONNELL
This low water cut-off/pump controller is a replacement component for HVACR systems. It is compatible with manufacturer part number 162300. Used in heating applications to protect boilers and pumps by shutting off the burner or activating a pump when water levels drop
Low water cut-off and pump controller for HVACR systems. Protects boilers from low-water conditions and sequences pump operation. Replacement component compatible with manufacturer part number 163000
MCDONNELL
Low water cut-off and pump controller for HVACR systems. Protects boilers from low-water conditions and sequences pump operation. Replacement component compatible with manufacturer part number 163000
The MCDONNELL 93-M-HD is a combination low water cut-off and pump controller for boiler systems. It integrates low water cut-off and pump control functions in a single device, protecting boilers from low-water conditions by shutting down the burner and managing the boiler feed pump
MCDONNELL
The MCDONNELL 93-M-HD is a combination low water cut-off and pump controller for boiler systems. It integrates low water cut-off and pump control functions in a single device, protecting boilers from low-water conditions by shutting down the burner and managing the boiler feed pump
This combination low water cut-off and pump controller integrates two functions into a single device for boiler protection and pump management. It is used in steam or hot-water heating systems to prevent low-water conditions and control condensate or feedwater pump operation. The controller is a replacement part for HVACR pumps, valves, and tubing applications
MCDONNELL
This combination low water cut-off and pump controller integrates two functions into a single device for boiler protection and pump management. It is used in steam or hot-water heating systems to prevent low-water conditions and control condensate or feedwater pump operation. The controller is a replacement part for HVACR pumps, valves, and tubing applications

More from MCDONNELL

View all MCDONNELL parts →
Level control for monitoring and regulating liquid levels in boilers, tanks, and receivers. Used in HVAC and industrial systems to help prevent low-water conditions that can damage equipment
MCDONNELL
Level control for monitoring and regulating liquid levels in boilers, tanks, and receivers. Used in HVAC and industrial systems to help prevent low-water conditions that can damage equipment
Automatic water feeder for low-pressure steam boilers and hydronic heating systems. Maintains water level to prevent dry-firing and boiler damage. Suitable for commercial and industrial HVAC applications
MCDONNELL
Automatic water feeder for low-pressure steam boilers and hydronic heating systems. Maintains water level to prevent dry-firing and boiler damage. Suitable for commercial and industrial HVAC applications
The MCDONNELL 64-B is a level control float block used in HVAC and industrial systems to monitor and regulate liquid levels in boilers, tanks, and receivers. It provides on/off control for pumps, valves, or alarms, helping maintain safe operating conditions in steam and hot water systems
MCDONNELL
The MCDONNELL 64-B is a level control float block used in HVAC and industrial systems to monitor and regulate liquid levels in boilers, tanks, and receivers. It provides on/off control for pumps, valves, or alarms, helping maintain safe operating conditions in steam and hot water systems
Level control tapping for HVAC and boiler systems. Monitors and regulates water or liquid levels to prevent low-water conditions in steam boilers and hot water systems. Used in replacement HVACR pumps, valves, and tubing applications
MCDONNELL
Level control tapping for HVAC and boiler systems. Monitors and regulates water or liquid levels to prevent low-water conditions in steam boilers and hot water systems. Used in replacement HVACR pumps, valves, and tubing applications
Level control for monitoring and regulating liquid levels in boilers, tanks, and receivers. Used in HVAC and industrial systems to help prevent low-water conditions. Product type: Level Control
MCDONNELL
Level control for monitoring and regulating liquid levels in boilers, tanks, and receivers. Used in HVAC and industrial systems to help prevent low-water conditions. Product type: Level Control
Replacement cartridge and strainer kit for HVACR pumps, valves, and tubing. Compatible with manufacturer part number 101A. Used to filter debris and maintain fluid flow in commercial heating and cooling systems
MCDONNELL
Replacement cartridge and strainer kit for HVACR pumps, valves, and tubing. Compatible with manufacturer part number 101A. Used to filter debris and maintain fluid flow in commercial heating and cooling systems
This low water cut-off and pump controller is used in steam and hot water boilers to prevent dry-fire damage. It automatically shuts down the burner and controls the feed pump when water level drops. Suitable for replacement in HVACR pumps, valves, and tubing applications
MCDONNELL
This low water cut-off and pump controller is used in steam and hot water boilers to prevent dry-fire damage. It automatically shuts down the burner and controls the feed pump when water level drops. Suitable for replacement in HVACR pumps, valves, and tubing applications
Replacement casting for HVACR pumps, valves, and tubing systems. Compatible with manufacturer part number 193. Used to restore proper flow and pressure regulation in heating, cooling, and refrigeration applications
MCDONNELL
Replacement casting for HVACR pumps, valves, and tubing systems. Compatible with manufacturer part number 193. Used to restore proper flow and pressure regulation in heating, cooling, and refrigeration applications