AC Flood Guard GraviTrip, home

For HVAC professionals

Install the GraviTrip™ in seven steps.

Step-by-step instructions based on the factory installation insert and the installation video. Read the whole guide before you start, then work through each step and finish with the functional test.

  • Professional installation only
  • Indoor 24 VAC controls only
  • 7 steps + functional test
Start at step 1 Download the insert
A completed GraviTrip installation beside an air handler.
A completed installation in an air-handler closet.

Watch first

Installation video

See every step in about two and a half minutes, then follow the written guide as you work. The chapters match the steps below.

Chapters

  1. Before you begin
  2. 1. Shut off power
  3. 2. Assemble the bottle
  4. 3. Choose placement and mount the switch box
  5. 4. Set the chain and clip
  6. 5. Connect the drain and adaptor
  7. 6. Wire the low-voltage switch
  8. 7. Finish, test the trip weight, and reset
  9. After a water shutdown and maintenance
  10. Installation complete

Read before installing

Safety first

Danger / warning: risk of electric shock

  • Disconnect or shut off power to the HVAC equipment before installation or service.
  • Installation by a qualified HVAC technician or licensed electrician only.
  • For low-voltage HVAC control circuits only. Do not connect to 120/240 VAC line voltage.
  • This device is a supplemental safety device. It is not a leak detector.

  • Qualified installers

    An HVAC technician or licensed electrician must install the kit.

  • 24 VAC controls only

    Low-voltage control circuits only. Never connect to 120/240 VAC.

  • Indoor use only

    Keep the switch box dry and protected from weather.

Follow the HVAC equipment manufacturer's wiring diagram, and confirm the installation meets local code and the equipment manufacturer's requirements before wiring.

Before you begin

Check the kit, tools and site

This kit helps reduce the risk of condensate overflow by tripping a switch when water routed to the collection bottle reaches the set fill level. Where the equipment manufacturer permits it, you can wire the switch to interrupt the HVAC low-voltage control circuit.

Kit contents: verify before installation

The GraviTrip kit in its foam packaging, with each part labeled by letter.
  1. Switch box assembly: UL 61058-rated switch in a UL 94 V-1-rated switch box, with wiring leads
  2. Bottle hanger
  3. Collection bottle
  4. L-type adaptor: antimicrobial, to reduce algae buildup
  5. Chain assembly: full factory length, part of the calibrated trip weight
  6. Chain clip
  7. Mounting screws (2)
  8. Red and black wire leads: one pair, 18 AWG, UL 1007-rated

Also in the box: the instruction and warning insert. Inspect every part, and do not install cracked, bent, corroded, missing or damaged components.

Tools & materials (not included)

  • Voltage tester, to verify power is off
  • Screwdriver or drill/driver for the mounting screws
  • 3/4-inch PVC pipe and fittings, PVC cutter or saw
  • Approved PVC cement (and primer, where local code requires it)
  • Wire nuts or approved low-voltage connectors
  • Wire cutter/stripper
  • Wire ties or clips to secure low-voltage wiring
  • Water for the functional test

Choose a location that…

  • Lets condensate overflow run downhill through PVC to the bottle
  • Stays accessible for inspection and emptying
  • Is clear of walkways, moving parts, heat sources and sharp edges
  • Has a stable support for the switch box that can hold at least 2.2 lb, including water load, vibration and service handling
  • Lets the switch box sit directly above the bottle
  • Is indoors, dry and out of reach of children

What you're building

Installation overview

The switch box mounts above the collection bottle. The full chain hangs straight down to the bottle hanger, and overflow from the condensate drain runs downhill through 3/4-inch PVC into the bottle.

Installer
HVAC technician or licensed electrician
Control circuit
Indoor 24 VAC, in series on R
Drain route
3/4-inch PVC, continuous downward slope
Switch box support
Holds at least 2.2 lb
A completed GraviTrip installation in an air-handler closet, with each part labeled by letter.
  1. Weight-activated switch box, mounted above the bottle
  2. Switch leads to the 24 VAC control circuit
  3. Calibrated chain, full length, hanging straight down
  4. Bottle hanger, with the chain clip at the top
  5. L-type adaptor, bonded to the PVC with its narrow end in the bottle
  6. Collection bottle
  7. Condensate drain connection
  8. Air handler

Installs in three stages

Start by shutting off power in step 1, then work through each stage.

  1. Steps 24Hang the switch

    Assemble the bottle, mount the switch box and set the chain.

    Go to step 2

  2. Step 5Direct the overflow

    Route drain-line overflow to the bottle through the L-adaptor.

    Go to step 5

  3. Steps 67Wire and test

    Wire into the 24 VAC circuit, then run the functional test.

    Go to step 6

Step 1 of 7Shut off power

  1. Turn off power to the HVAC equipment at the service disconnect, breaker or main electrical panel.
  2. Verify that power is off before you open any HVAC panel or make electrical connections.
  3. Keep power off until all wiring is complete.

Power stays off until step 7.

Restore power only after the low-voltage wiring is secured and every cover is back on.

A residential electrical panel with rows of circuit breakers.
Shut off the HVAC circuit, then confirm it's de-energized with a voltage tester.

Step 2 of 7Assemble the bottle

  1. Thread the collection bottle A into the bottom of the bottle hanger B.
  2. Turn it until it's secure.
  3. Keep the bottle A upright.

Seat the bottle fully. Bottle seating is one of the first things to check if the functional test fails.

The collection bottle threaded into the base of the white bottle hanger.
  1. Collection bottle: keep it upright
  2. Threaded connection: the bottle screws into the base of the hanger

Step 3 of 7Choose placement & mount the switch box

3.1 Plan the placement

  1. Choose a position for the bottle A that can receive overflow from the condensate drain line B.
  2. Make sure 3/4-inch PVC C can run downhill from the drain B to the bottle A.
  3. Place the switch box D directly above the bottle A.
  4. Leave room to inspect and empty the bottle A.
The switch box mounted on the wall above the bottle, with the chain hanging straight down and a PVC line running from the drain to the bottle.
  1. Collection bottle, where overflow collects
  2. Condensate drain connection
  3. PVC route, running downhill to the bottle
  4. Switch box, directly above the bottle
  5. Chain, hanging straight down

3.2 Mount the switch box

  1. Fasten the switch box A to a stable support that can hold at least 2.2 lb, using the two supplied mounting screws B.
  2. Let the chain C hang straight down to the bottle hanger.
  3. Keep the box A dry, and keep the hanging assembly clear of other components.

The bottle must hang vertically and move freely.

It must not rub, bind or touch other components.

Close-up of the white switch box screwed to the wall, with the chain and red and black leads hanging below it.
  1. Switch box, kept dry
  2. Mounting screw into a stable support
  3. Chain to the bottle hanger
  4. Low-voltage leads (red and black)

Step 4 of 7Set the chain & clip

Calibration warning: keep the full chain

The control switch is factory calibrated to activate at a specified suspended load, and the full factory-supplied chain is part of that load. Do not cut, shorten, remove links from, replace or otherwise alter the chain. Keep every link attached and fully suspended, and don't let excess chain rest on another surface.

  1. Thread the chain through the hole A at the top of the bottle hanger.
  2. Slide the chain clip B along the chain to set the distance between the switch box and the bottle hanger, so the L-adaptor will sit properly inside the bottle.
  3. When the distance is right, squeeze the ends of the clip B together to secure it.
  4. Adjust the clip B, never the chain length. Do not cut off any excess chain.
Close-up of the chain passing through the top of the bottle hanger, held by the metal chain clip, beside a yellow warning label.
  1. Top hole: the chain threads through here
  2. Chain clip: slide to adjust, then squeeze the ends closed
  3. Warning label: do not cut the chain

Step 5 of 7Connect the drain & adaptor

5.1 Slope the drain pipe

  1. Route condensate overflow from the drain connection A to the collection bottle with 3/4-inch PVC B.
  2. Give the pipe B a slight, continuous downward slope toward the bottle so water flows freely.
  3. Keep the water path clear. Do not kink, crush or obstruct the piping B.

Water must flow freely toward the bottle.

A horizontal PVC line running from the condensate drain tee across to the L-adaptor above the bottle hanger.
  1. Condensate drain connection
  2. 3/4-inch PVC, sloping toward the bottle
  3. L-adaptor, bonded to the PVC
  4. Narrow end, down inside the bottle

5.2 Bond the L-adaptor and check alignment

  1. Bond the L-type adaptor A to the PVC B with approved PVC cement C.
  2. Place the adaptor's narrow end D down inside the bottle.
  3. Check the alignment. The bottle should hang vertically, and the piping and adaptor A must not restrict, rub or bind the hanging assembly.
  4. If needed, reposition the chain clip (step 4) to get the alignment right.

Keep the bottle and hanger free to move.

The adaptor must not restrict the hanging assembly, or the switch may not trip.

Close-up of the white L-adaptor joined to a PVC elbow, with its narrow end dropping into the neck of the bottle.
  1. L-type adaptor
  2. 3/4-inch PVC elbow
  3. PVC cement at this joint
  4. Narrow end inside the bottle

Step 6 of 7Wire the low-voltage switch

Power must still be off.

Before doing any wiring, confirm power to the HVAC system is off at the breaker or main electrical panel.

  1. Locate the low-voltage thermostat cable where it enters the air handler or furnace control area.
  2. Identify the 24 VAC R (red) control wire, using the HVAC equipment wiring diagram.
  3. Cut the R control lead.
  4. Connect one AC Flood Guard switch lead to each cut end with wire nuts or approved low-voltage connectors. This puts the switch in series on R.
  5. Leave the other control wires as they are. Do not connect the switch across R and C.
Wiring diagram: the switch goes in series on the R wire The thermostat cable runs from the left to the R, Y, G and W terminals on the air handler or control board. The red R wire is cut. Each cut end is joined to one of the two AC Flood Guard switch leads with a wire nut, so the switch sits in series on R. The Y, G and W wires are not changed. From thermostat Thermostat cable R cut here AC Flood Guard weight-activated switch Wire nuts or approved low-voltage connectors Air handler or control board R Y G W Y, G and W stay as they are. Wiring diagram: the switch goes in series on the R wire The thermostat cable on the left runs to the R, Y, G and W terminals on the air handler or control board. The red R wire is cut, and each cut end is joined to one of the two AC Flood Guard switch leads with a wire nut. The Y, G and W wires are not changed. AC Flood Guard weight-activated switch Wire nuts R cut here From thermostat Thermostat cable Air handler or control board R Y G W Y, G and W stay as they are.
With the switch in series on R, a full bottle opens the 24 VAC control circuit and the HVAC system shuts off.

All wiring is low voltage (24 VAC).

Use appropriate low-voltage materials and keep wires away from line-voltage components. If the equipment manufacturer calls for a different control or alarm circuit, follow its requirements.

Step 7 of 7Finish, test the trip weight & reset

7.1 Secure, cover and power on

  1. Secure the low-voltage wires and keep them away from line-voltage components.
  2. Reinstall all covers.
  3. Restore power to the HVAC system.

7.2 Test the trip weight

  1. Add water to the bottle A until the switch activates.
  2. Confirm the HVAC system shuts down, or that the selected alarm or control circuit activates.

When the bottle reaches the trip weight, the weight of the water trips the switch.

The installed bottle hanger and collection bottle, with the chain running from the switch box above down through the hanger.
  1. Add water to the bottle to test the trip weight
  2. Gently pull the chain to reset the switch

7.3 Empty, refit and reset

  1. Empty the bottle A and refit it securely.
  2. Gently pull the chain B to reset the switch.
  3. Confirm that normal operation returns.

Emptying the bottle alone does not reset the switch.

Always finish by gently pulling the chain.

7.4 If the test fails

  1. Power off

    Disconnect power before making changes.

  2. Check

    Mounting, chain routing or clip position, bottle seating, adaptor alignment and wiring.

  3. Retest

    Correct the issue, then test the shutoff again.

Do not use the unit until the test passes.

Installation complete. Before you leave, show the homeowner how to reset.

Empty the bottle, refit it, then gently pull the chain. Point them to what to do after a shutdown.

After installation

After a shutdown & ongoing maintenance

After a water shutdown: clear the cause first

  • If the HVAC system shuts off and the bottle contains water, treat it as a drain or overflow condition.
  • Have a qualified technician inspect and clear the condensate drain problem.
  • Empty and refit the bottle, then gently pull the chain to reset the switch.
  • Correct the overflow problem before restarting.

Ongoing maintenance: keep the system ready

  • Test the switch and inspect the entire installation every six months.
  • Inspect the bottle, hanger, chain, clip, adaptor, screws and wiring after any HVAC service.
  • Keep the bottle upright and clean. Clean it with mild soap and water only.
  • Replace the complete unit if any component is damaged, discolored, cracked, corroded, loose or unreliable.

Know the limits

Use restrictions & important limitations

Use restrictions

  • Indoor use only.
  • For low-voltage 24 VAC HVAC control circuits only. Do not use above the approved control voltage.
  • Do not submerge the switch box or expose it to outdoor weather.
  • Do not install in corrosive or explosive atmospheres, or where children can reach the kit.
  • Dispose of electrical and electronic components according to local e-waste rules.

Important limitations

  • This is a supplemental safety device, not a leak detector.
  • It does not detect leaks outside the collection path, internal evaporator-pan overflows that aren't routed to the bottle, freezing, power loss, or improper installation.
  • Activation may come early, late or not at all if the chain is cut, shortened, has links removed, is replaced or is otherwise altered. The switch is calibrated for the weight of the complete factory-supplied chain.

Sign-off

Installer checklist

Run through this list before you leave the job. Your checks are saved in this browser tab only.

Installation, testing, maintenance & warranty insert

The two-page insert that ships in every kit, including the full warranty.

Download PDF

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