Name: Resideo L4081B1047/U Multi-Function Aquastat Controller, High and Low Limit, SPST: High & Circulator
Brand: Resideo
SKU: HONE-L4081B1047/U
Price: 326.24 USD
Availability: InStock

Multi-Function Aquastat Controller, High and Low Limit, SPST: High & Circulator

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Electrical Ratings	0.25 A @ 0.25 to 12 Vdc; At Full Load-- 8A @ 120 Vac: 5.1A @ 240 Vac; At Locked Rotor-- 48A @ 120 Vac: 30.6A @ 240 Vac
Operating Temperature	High Limit-- 130 F to 240 F; Low Limit-- 110 F to 220 F
Operating Humidity	0 to 95% RH, non-condensing
Mounting	Horizontal
Application	High Limit and Circulator
Dimensions	3 7/8 in. high x 4 1/8 in. wide x 2 3/4 in. deep.
UL	UL Listed: File No. MP466, Vol. 12, Sec. 4, Guide No. MBPR2
CSA	Certified: File No. LR95329-1
Hazmat Information	Dangerous Goods in Excepted Quantities
Temperature Range (F)	Maximum--150 F at switches; 265 F at sensing element
Differential Temperature (F)	High limit : 10 F fixed; low limit: 10-25 F adj.
Switching Action	SPST: High Limit & Circulator
Well Spud Size (in.)	3/4 in. - 14 NPT
Insulation Depth (in.)	1 1/2 in.
Electrical Ratings, Ignition	Transformer Load: 360 VA

Specification Sheet PDF ↗

The L4081B1047 is a controller from Resideo (Honeywell Home) that senses boiler water temperature and switches the burner, the circulator, or both. It operates over the range printed on the control, with SPST contacts.

The aquastat is the control that keeps a hydronic boiler inside its working band. It holds the water hot enough to serve a call for heat and shuts the burner down before the boiler reaches a temperature the relief valve would have to handle.

A control that serves as high or low limit covers both jobs depending on how it is wired and where the bulb sits. As a high limit it shuts the burner down at the top of the range; as a low limit it keeps a minimum boiler temperature so a tankless coil or an indirect tank always has hot water to draw from.

When you replace an aquastat, match the temperature range, the switch action and the differential to the control coming out, not to the boiler nameplate. A boiler will happily run on a control with the wrong range — it will simply cycle badly, or trip a limit that was never meant to be the working control.

The sensing bulb belongs in an immersion well, filled with heat conductive compound, threaded into the tapping the boiler manufacturer provided for it. A bulb strapped to the outside of a pipe reads the pipe, not the water, and it reads it late.

Brand: Resideo (Honeywell Home)
Manufacturer Part #: L4081B1047/U
Switch action: SPST
UPC: 085267053433
Category: Aquastats & Wells

Full Specifications

Application	High and Low limit
Approvals and Standards	UL Listed: File No. MP466, Vol. 12, Sec. 4, Guide No. MBPR2, CSA Certified: File No. LR95329-1
Compatible With	Gas Hydronic Heating System, Oil-Fired Hydronic Heating System
Mounting Type	Horizontal Mount
Low Limit Differential Temperature	10 °F to 25 °F Adjustable
Low Limit Set point Temperature (Min)	110 °F, 43 °C
Low Limit Set point Temperature (Max)	220 °F, 104 °C
High Limit Differential Temperature	10 °F Fixed
High Limit Set point Temperature (Min)	130 °F, 54 °C
High Limit Set point Temperature (Max)	240 °F, 116 °C
Electrical Ratings at Full Load	8 A @ 120 V AC, 5.1 A @ 240 V AC
Electrical Ratings at Locked Rotor	48 A @ 120 V AC, 30.6 A @ 240 V AC
Electrical Ratings Millivolt	0.25 A @ 0.25 to 12 V DC
Switch Action	High Limit Switch breaks on temperature rise, Circulator Switch makes on temperature rise
Switch Type	SPST:High Limit & Circulator
Well Spud Size	3/4 in 14 NPT, 19 mm 14 NPT
Insulation Depth	1.5 in, 38 mm
Product Height	3.88 in, 98 mm
Product Width	4.13 in, 108 mm
Ambient Temperature (Max)	150 °F at Switches, 66 °C at Switches, 265 ° F at Sensing Element, 129 °C at Sensing Element
Operating Relative Humidity (Min)	0% RH, Non-condensing
Operating Relative Humidity (Max)	95% RH, Non-condensing
Hazmat Information	Dangerous Goods in Excepted Quantities