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Guide to the aquastat reset button:
Where is the reset button on a heating boiler or water heater aquastat control? How to use the reset button: press it once? Why not twice? What to do if the red plastic reset button itself has been broken off or lost.
Where are all of the reset buttons & switches found on heating boilers & water heaters?
This article series explains how aquastats work and what the different aquastat controls are, what they do, and how they are set. We define various controls on heating boiler aquastats and explain what they do and how they work. We explain the location and use of the heating boiler reset button found on aquastats.
How to Find and Use the Reset Button on the Aquastat Combination Control on a Boiler
Summary of the Functions of a Typical Combination Protectorelay™ Primary Control and Aquastat® Controller
[Click to enlarge any image]
Our photo shows an older aquastat type primary controller on an oil fired heating boiler. You can see the gray box covering the control in the right in our photo and near the top center of that control cover you can see the aquastat's red reset button.
The coiled "wire" leaving the upper right corner of this control is routed to a thermal sensor mounted in a well inserted into the water of the heating boiler.
Unlike the aquastat shown at the top of this page, poking through the upper-center of the cover of this heating system control you'll see a red "reset button" in the center of the upper portion of the gray control box.
If this heating boiler or water heater has turned itself off - SAFETY OFF - you'll see that the red reset button will have popped UP higher out of the control cover.
If the red "reset" button on the this safety control is sticking up and the oil burner has shut down, the homeowner is permitted to try ONCE to "reset" the system by pressing the red reset button. Also see our more detailed instructions for using the reset button on heating equipment at our article: CAD CELL RELAY SWITCH.
Just below I've removed the cover so that you can see the actual reset switch (green arrow).
Depending on wiring hookup choices, this control operates the heating system oil burner, circulator, and zone circulators. An aquastat can also be configured (factory default) to keep the heating boiler hot to provide domestic hot water through a tankless coil even when the building room thermostats are not calling for heat.
The aquastat controller often also includes connections to a flame sensing device, typically a cad-cell (CAD CELL RELAY SWITCH) or on older heating systems a stack relay (STACK RELAY SWITCH) to shut down the boiler if the burner is not operating properly.
Above: I'm pressing the reset button on the actual reset switch inside the aquastat of a heating boiler.
Watch out: there is live electrical voltage inside of heating and water heater controls. Removing the cover risks fire, shock, or death from electrical shock if you touch live wires or live electrical connections or screw terminals.
There is a "reset" button to re-start the heating system if it has shut down for safety. We discuss all of these controls in detail below.
See RESET SWITCH on PRIMARY CONTROL
Watch out: sometimes the red plastic button on older heating equipment primary controls can break off.
At RESET SWITCH, HEATER REPAIR we show how to reset the equipment safely if this happens to you.
Question: We have to hit the reset button on our furnace for it to run.
(Nov 23, 2015) Jackie said:
We have to hit the reset button on our furnace for it to run. It runs for 4-5 heating/hot water cycles,then reset button again. We took the cover off the Aquastat(L8124A) and saw a semi exposed wire and the circuit board looks like it been arced. Not sure if arcing mark is from close proximity to exposed wire or damage to board. Should I replace connector(to correct exposed wire) or aquastat or control box?
(6 March 2016) Kev said:
My overheat button knocks off boiler its a honeywall.is there a suggestion what might cause this
Reply: do NOT keep pressing the heater or water heater reset button
Watch out: repeated use of the re-set button risks a dangerous puffback explosion. That's because the burner that is shutting off on "safety" may leave un-burned fuel in the combustion chamber; it can accumulate until we have an ugly experience.
If you see arcing burns on the circuit board I suspect the problem may be more than the wire - perhaps overheating. I would ask for an inspection by your heating service tech to decide:
1. what's causing the system to go off on re-set
2. what caused the arcing you found
3. based on those steps, repair or replace what's needed.
I understand the appeal of just plugging in a new part - certainly I do that myself. But just swapping in a new control or circuit board without having an idea of what was happening risks having to repeat the repair.
If you are referring to the reset button on an oil fired heating system most likely the problem is with the oil burner: an inadequate or faltering flame. DO NOT keep pressing the reset button as you could cause a dangerous puffback explosion. I'd call for service.
Question: blinking green light on boiler controller
2016/10/27 DD. said:
My heater green light blinks. I tried to set but it back on blinking. What might be reason please?
I can only guess since you haven't said what type of heating system you've got installed nor given me the brand and model ofd the heating system controller. Here's an example that might help:
IF your system is using a Honeywell R7184 aquastat controller, and IF someone pressed the RESET button two times without a successful call for heat, THEN the indicator light will flash at one-second intervals, or as the control manual says at 1HZ 1/2 second off, 1/2 second on.
You can RESET the controller by pressing and holding the RESET BUTTON for at least 30 seconds. That should stop the green blinking.
Watch out: if still your heating system will not start and run normally, do not keep pressing the reset button as you could cause an unsafe condition. Instead, call your heating service company for repair assistance.
If the Honeywell R7184 is what's found on your heating boiler and if you do not already have the instruction manuals fodr this control you can download them from honeywell.com OR free from
Where are all of the Air Conditioner, Cooling, Heating, Heat Pump & Water Heater Reset Buttons Located ?
Above: red reset button on the cad cell relay found on many oil burners used on boilers, furnaces, and water heaters.
If you are looking for the main reset button on heating equipment you'll want to see COOLING & HEATING CONTROL & SWITCH INDEX - master index to all controls for cooling or heating equipment reset buttons, switches, controls, or see the suggested articles below:
A/C - HEAT PUMP CONTROLS & SWITCHES - identifies all of the controls and switches that control or may turn on or off air conditioners and heat pumps. Some of these switches can be tricky to find and use properly. For example a condensate tray overflow switch or a blower compartment door safety switch can leave your air conditioner or furnace off when nothing else is wrong.
AQUASTAT RESET BUTTON - reset button found on aquastats used on heating equipment such as boilers & water heaters.
CAD CELL RELAY SWITCH - hot water boilers and some water heaters that are oil-fired use this switch as a safety control. It turns off the oil burner if the flame is not solid
DISTRIBUTION PANELS - where to find the circuit breaker controlling the equipment that is OFF - check for a tripped circuit breaker or blown fuse. Sometimes you may need to trace an electrical circuit to find which breaker or fuse is powering which device.
See ELECTRIAL CIRCUIT ID, MAP & LABEL
ELECTRIC MOTOR OVERLOAD RESET SWITCH - some electric motors such as at oil burners and well pumps include a user re-settable thermal overload switch or reset switch. Other motors contain an internal thermal overload switch that will reset itself when the motor cools down.
ELECTRIC PANEL INSPECTION - things to look for when examining an electrical panel to find circuit breakers controlling heating equipment
ELECTRICAL POWER SWITCH FOR HEAT - lists the various ON / OFF switches found on cooling & heating equipment. Note that ON/OFF switches for cooling or heating may also be found on some thermostats.
Continue reading at RESET SWITCH, HEATER REPAIR we show how to reset the equipment safely if the plastic button has been broken or lost, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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Thanks to Bottini Fuel service manager Ron Thomas for discussing aquastat functions, low limit controls, oil burner short cycling causes, and boiler maintenance, reliability, and service contracts 4/13/2010. Bottini Fuel is a residential and commercial heating oil distributor and oil heat service company in Wappingers Falls, NY and with offices in other New York locations. Bottini Fuel, 2785 W Main St,
Wappingers Falls NY, 12590-1576
(845) 297-5580 more contact information for Bottini Fuel
Thanks to reader powderfinger5 for careful reading of this text and suggesting clarifications - August 2011
Thanks to reader Gary (Buddy Cat) for careful reading & editing - November 2012
We provide links just below to several aquastat installation, setting, and adjustment documents in response to reader requests and comments that people sometimes have difficulty finding this information. But readers looking for specific aquastat control information should always first try the control manufacturer.
Armstrong 24-hour time and aquastat control accessory: provides on/off pump control according to preset operating times, designed only for use with specified Armstrong Astro series wet roto circulators installed in indoor hot water re circulation applications. Typical timer applications will cycle the pump at preset times, allowing the user to select
operation of the circulating pump during high peak usage periods in order to decrease the
delivery time to outlet fixtures and reduce wasted water, also available at www.honeywell.com
Honeywell Corporation, control installation guides for Honeywell aquastats and other heating and cooling controls: see http://customer.honeywell.com
Honeywell L4008E Aquastat high limit,manual reset, aquastat controller instructions
Honeywell L4006, Manual Reset Strap-On Aquastat (high limit control, 100 to 240 °F) [we consider strap on controls less accurate and reliable than immersion type sensor controls; these were commonly found on older heating boilers including the GE series downfired boilers]
Honeywell L4026B Aquastat control instructions (contact Honeywell Corporation) Here is some basic description of the Honeywell L4026B control, also available at www.honeywell.com
Honeywell L6006 and L6007 Aquastat Controllers, installation instructions for the trained service technician, these controls combine low or high limit and circulator control, with or without an immersion well depending on the control model A,B, C etc., also available at www.honeywell.com
Honeywell L6191 Dual aquastat immersion thermostat, also available at www.honeywell.com
Honeywell L7224 Aquastat Controller, oil electronic controls allowing high limit, high limit differential, low limit, and separate low limit differential settings - set to the specifications of your oil heating equipment manufacturer - 69-1957-1 L7224 Series controls, also available at www.honeywell.com
L7224U1002- is a universal electronic aquastat (replacing over 40 other aquastat models) that provides circulator, burner and boiler temperature control with electronic temperature sensing. The L7224U1002 provides status and diagnostic information through an LED display to enhance the diagnostic process.
In "Run" mode the LED displays the boiler temperature followed by the ambient temperature. Buttons inside the control permit the service tech to scan through the control's settings as well as to change them, much like the functions on a programmable room thermostat. Using the "I" button, the LED display can be cycled through: boiler temperature, high limit, low limit, high differential, low differential, local thermostat status, EnviraCOM thermostat status, Burner status, Circulator status, Zone control, Zone request, Error code, °F/degC.
Five diagnostic LEDs inside the control provide additional diagnostic features, indicating (counterclockwise from upper left) EnviraCOM network active, Thermostat calling for heat, Burner on, Power to zone circulator interrupted (lockout), Circulator powered.
This is a "triple aquastat" providing High, Low, and circulator controls, as well as advanced features permitting electronic configuration and an LED display for diagnostics. This aquastat can provide multiple zone control as well. The L7224U1002 supports Honeywell's EnviraCOM™ communications that permits remote diagnosis as well as OnWatch diagnostics. The low-limit can be disabled for "cold-start" boiler applications such as where no tankless coil is in use.
Eight error codes: 1=sensor fault (check sensor), 2=ECOM fault, check EnviraCOM wiring, 3=Hardware fault, replace the control, 4=B1 fault, check B1 wiring/voltage, 5=Low line voltage, check L1/L2 110VAC, 6=Fuse, check ECOM wires, replace fuse, 7=EEPROM limit and differential settings, restore to desired settings, 8=Repeated B1 fault, (voltage present at B1 when output is turned off); check B1 wiring/voltage
Honeywell link for a powerpoint training session on this aquastat: http://customer.honeywell.com/NR/rdonlyres/5C67D10A-631C-4404-9149-25BA61F5D8BB/4041/L7224UUNIVERSALAQUASTATTrainingModule.ppt
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
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