No-Heat Emergency Call Response

Purpose

This standing instruction makes a no-heat call a combustion-safety and habitability call before it is a repair call, and it puts the shop's authority to leave an appliance off above the customer's wish to have heat tonight.

The pressure on a winter no-heat visit runs one direction, and it runs against the tech. The house is cold, the family is standing there, and the fastest way to be a hero is to reset a tripped safety and watch the burners light. That reset is how a furnace that opened its limit on a blocked heat exchanger passage goes back into service, and it is how a rollout switch that was doing exactly its job gets defeated by a tech in a hurry. A no-heat SOP that only describes a repair is a no-heat SOP the shop stops following the first cold night.

Safety actions that gate the work

• If the caller reports a gas odor, tell them that everyone leaves the building immediately, touching no switches, no lights, no thermostat and no phone inside, and that they call the gas utility emergency number and 911 from outside or from a neighbor. Do not diagnose over the phone and do not tell them to open windows first. Nobody re-enters until the utility clears it.
• If a carbon monoxide alarm is sounding, everyone goes outside and stays outside, and they call 911. Anyone with headache, nausea, dizziness or confusion goes with them and gets medical attention. That call then follows the carbon monoxide alarm response SOP, not this one.
• Put the personal carbon monoxide monitor on before you enter the mechanical space, not after. Record the ambient reading before any appliance is fired, because a reading taken after startup cannot tell you what the occupants were breathing before you arrived.
• Prove dead before opening any control compartment, using live-dead-live per NFPA 70E-2021, 120.5; work on this utilization equipment is controlled by 29 CFR 1910.333(b)(2). Close the appliance gas shutoff before any work on the gas train.
• Never jumper, tape closed, or reset-and-walk-away from a limit, rollout or pressure switch. Each one is evidence of a condition that is still present.

Scope

Covers residential and light-commercial heating failures dispatched as same-day or after-hours emergencies on gas-fired furnaces, gas package units and heat pumps with auxiliary heat, from the call taker's first question through the end-of-visit outcome.

Does not cover the evidence standard for condemning a heat exchanger or the mechanics of tagging, owned by the cracked heat exchanger condemnation and red-tag SOP; hand off to it the moment a heat exchanger is in question. Does not cover a sounding CO alarm, owned by the carbon monoxide alarm response visit SOP. Does not cover boilers or oil-fired equipment.

Roles and handoffs

Procedure

1. Ask the combustion-safety questions first, before anything about the equipment. Does anyone smell gas, is any CO alarm sounding, does anyone have a headache, nausea or dizziness that improves when they go outside. Acceptance: three explicit answers on the ticket. Stop rule: a yes to any of them means the evacuation or 911 instruction above is given immediately and the call is re-routed, and no tech is dispatched into a building nobody has cleared.

2. Then ask the freeze-risk questions and give the interim instructions on the same call. Indoor temperature now, whether plumbing runs in exterior walls or an unheated crawlspace, and whether anyone in the house is elderly, an infant, or medically vulnerable. Instructions: open sink cabinets on exterior walls, let a faucet drip, close off unused rooms, and never use a cooking appliance for heat. Acceptance: instructions given and noted. Wrong looks like giving only an arrival window while a supply line in an exterior wall drops toward freezing.

3. Take an ambient carbon monoxide reading in the space before the appliance is fired and before you touch a control. Monitor on before you open the door to the basement or the closet. Acceptance: a recorded ppm value and the time. Stop rule: a meaningful ambient reading with the appliance off means occupants out and the space ventilated, and the visit converts to the CO response SOP. Wrong looks like firing the furnace to "see what it does" in a space that was already accumulating.

4. Read the appliance's own diagnostics before you change its state. Record the control board fault code exactly as flashed, then watch a full call from thermostat to lockout and write the sequence you observed: inducer, pressure switch, igniter, gas valve, flame proof, blower, and where it stopped. Acceptance: a written sequence with the point of failure named. Wrong looks like cycling power first, which erases the code that was the cheapest information on the job.

5. Verify gas supply and combustion air before you condemn a component. Inlet pressure with the appliance firing and manifold pressure against the rating plate, and a physical check that the flue and any combustion air intake are clear of nests, snow, ice and rodent packing. Acceptance: manifold pressure at the rating plate value with inlet pressure holding above the minimum while firing. Stop rule: if inlet pressure sags below the minimum when the burner lights, the fault is the gas supply and the appliance stays off until the piping or the meter is corrected. Never adjust the regulator to compensate for a supply that cannot hold.

6. Where a safety device is found open or tripped, establish the physical cause before you treat it as the fault. A limit, rollout or pressure switch that opened is telling you something is still wrong. Acceptance: a named cause, verified corrected, with a measurement that proves it. On a furnace, measure temperature rise (supply minus return, probes out of the line of sight of the exchanger) against the rating plate's stated rise range. Stop rule: no reset without a cause, and where the evidence points at the heat exchanger, the appliance is shut off, tagged, and the red-tag SOP takes over.

7. Decide the outcome and give it in three parts before you pack up. Heat restored, heat restored with a return needed, or appliance off with heat not restored. Acceptance: the customer hears what is fixed, what is not, and what happens tonight. Where the appliance stays off, escalate to the manager for temporary heat and freeze protection: safe electric heat placed with the manufacturer's clearance to combustibles and plugged into a wall receptacle rather than an extension cord, plumbing protection instructions, and a documented recommendation to stay elsewhere where a vulnerable occupant is involved.

8. Write the readings and the outcome before you leave. Acceptance: the ticket carries the ambient CO reading and time, the fault code verbatim, the observed sequence, manifold and inlet pressures, temperature rise against the rating plate range, the cause of any open safety, and post-repair combustion readings. Wrong looks like "reset limit, unit running," which is the note the next tech finds three weeks later on the callback that mattered.

The record this produces

One emergency heating record per call, attached to the equipment:

• The three combustion-safety answers, the freeze-risk answers, indoor temperature at call, instructions given
• Ambient CO in ppm before firing, with the time
• Fault code as flashed, and the observed startup sequence with the stopping point
• Inlet and manifold gas pressures, rating plate manifold value
• Temperature rise measured, and the rating plate rise range it is judged against
• Any safety found open, and the named physical cause
• Post-repair flue CO air-free and the limit it is judged against
• Outcome given, temporary heat provided or declined, and any tag applied with its number

Dispatch reads the triage answers. The next tech reads the sequence and the rise to know whether tonight's fault is the same fault. The manager reads the tags and the ambient CO readings across the book, because a cluster of either in one neighborhood is usually a venting or a supply problem rather than a coincidence.

Worked pass: 12 F night, house at 51 F, induced-draft furnace

Step 1: no gas odor, no CO alarm, nobody symptomatic. Step 2: two children under six, indoor 51 F, kitchen plumbing on an exterior wall. Faucet drip and cabinet doors instructed at 20:05. Dispatched ahead of two unoccupied-property calls.

Step 3, arrival 20:40. Personal monitor on before entering the basement, ambient reads 0 ppm with the furnace off. Recorded.

Step 4: board flashes a limit-circuit fault. Observed sequence: inducer runs, pressure switch closes, igniter glows, gas valve opens, flame proves, blower starts, then burners drop out roughly six minutes in with the inducer and blower still running. That is the limit opening, not a flame-sense failure, and the sequence written down is what distinguishes them.

Step 5: inlet pressure holds above the minimum while firing and manifold pressure matches the rating plate value. Flue and intake clear. Gas supply is not the fault.

Step 6 FAILS on the first pass. The high limit is confirmed opening on temperature, but the filter, while dirty, is not blocked, and a dirty filter alone is not a named cause with a measurement behind it. Stop rule taken: no reset-and-leave. Temperature rise is measured across a full cycle at 92 F against a rating plate rise range of 40 to 70 F, which is 22 F above the top of the range and confirms an airflow restriction rather than a control fault. Continued search finds a supply trunk damper closed to a remodeled room and a collapsed return flex behind the joist. Damper opened, flex replaced and supported, filter replaced. Rise re-measured at 58 F, inside the 40 to 70 F range, and the furnace completes three full cycles without the limit opening.

Post-repair combustion: flue carbon monoxide reads 65 ppm air-free against the 400 ppm air-free limit the ANSI Z21 series sets for listed vented appliances, or the manufacturer's own lower limit where one is stated. Ambient in the basement re-checked at 0 ppm with the appliance firing.

Step 7: heat restored, no temporary heat needed. Customer told what closed the damper and why the room that was remodeled needs a return path.

Checking the pass against the sections above: step 6's acceptance condition is a named cause verified by a measurement, and the first pass is reported as failing that condition rather than as a partial success, because a dirty filter without a rise measurement is a guess. The 92 F and 58 F figures are both supply-minus-return rise on the same probes, judged against the same rating plate range stated in the step, not against each other. The ambient CO in step 3 was taken with the appliance off, which is the condition that step specifies, and the post-repair reading is labeled as taken with it firing rather than compared to the first as if they shared a condition.

References

• ANSI Z21 series listing limits for carbon monoxide in the flue products of listed vented appliances, at 400 ppm air-free, superseded by a lower manufacturer limit where one is stated
• Appliance rating plate for the manifold pressure and the temperature rise range, which are equipment-specific and are the only correct source
• 29 CFR 1910.333(b)(2) and NFPA 70E-2021, 120.5, for de-energizing and proving dead before opening a control compartment
• See related: the cracked heat exchanger condemnation and red-tag SOP, and the carbon monoxide alarm response visit SOP