Honeywell R8182 Aquastat Reset (C) D FriedmanAquastat Reset Button
How to find & use the reset button or switch on a boiler or water heater aquastat control

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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.

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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

Aquastat with reset button (C) Daniel Friedman

[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).

Reset switch on Energy Kinetics Oil Boiler (C) D Friedman

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.

Honeywell R8182 internal reset switch assembly (C) D Friedman

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.

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 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 OR free from

Where are all of the Air Conditioner, Cooling, Heating, Heat Pump & Water Heater Reset Buttons Located ?

Cad cell relay reset button (C) D Friedman

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:


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.


Or see MANUALS for HEATING SYSTEM CONTROLS for a list of aquastat installation & repair guides

Suggested citation for this web page

AQUASTAT RESET BUTTON at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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