Multi-Tenant Comfort Complaint Investigation

Purpose

In a strip center or a small multi-tenant office, most comfort complaints are not equipment faults, and the shop that treats them as equipment faults burns two visits and a part before anyone asks the question that solves it. One unit serving two bays, a thermostat hanging in the wrong tenant's stockroom, a bay that added six feet of west glass and a drying station since the unit was sized: none of those show up on gauges, and all of them produce a tenant who is certain the air conditioning is broken.

This procedure fixes the order of work: measure the space before you touch equipment, prove which unit serves it before you diagnose, and classify the finding before you quote. It also keeps the shop out of a dispute it cannot win, by producing numbers instead of opinions for two parties who may not agree about who pays.

Scope

Covers investigation of a comfort complaint in a multi-tenant building served by packaged rooftop units: space measurement, zone-to-space mapping, control location, delivered capacity, load change, and routing the finding to the right party.

Does not cover a unit that is down, owned by the no-cool and no-heat emergency call SOPs. Does not cover economizer repair or minimum ventilation, owned by the economizer SOPs, or a complaint that follows this shop's own recent repair, owned by the 30-day callback investigation.

Roles and responsibilities

Procedure

1. Take the complaint from the person who has it, in full, before the truck moves. Record which space, where in that space, what time of day, which days, how long it has been happening, and what changed in the space recently. Acceptance: all six fields plus a contact who will be on site and access to the complaining space at the complaint time. What wrong looks like: a ticket reading "too hot", which sends a tech at ten in the morning to a problem that only exists at three. Stop rule: a complaint that cannot be tied to a time and a location gets scheduled for the reported time rather than guessed at. Hazard: none physical, a phone call made at the office.

2. Measure the space before you touch any equipment. At the complaint location, read dry bulb and relative humidity at about 4 ft above the floor, away from diffusers, exterior glass and equipment, then take a second point elsewhere in the same space. Acceptance: two space readings, the controlling setpoint, outdoor conditions and the clock time, all recorded before anything is adjusted. What wrong looks like: a reading taken at the return grille, which is a mixed average of the whole space and never matches what the occupant feels. Stop rule: a space already at setpoint at the complaint time means the complaint is about something other than air temperature, so measure again on a second day before quoting anything. Hazard: none physical, though ASHRAE Standard 55 is a consensus standard that binds only where a jurisdiction or a contract adopts it, so treat its comfort ranges as a reference, not a code compliance test.

3. Prove which unit serves this space rather than assuming the nearest one. With the site contact's permission, shut one unit down and walk the space identifying which diffusers stop, then restore it and repeat for the next. Acceptance: a written diffuser map showing which unit feeds which part of which tenancy. What wrong looks like: the unit directly above the bay turning out to serve the bay next door, which is common where tenancies have been subdivided. Stop rule: any unit that also serves refrigeration, a server room, a kitchen makeup air system or a smoke control function is not shut down for a mapping test; identify it another way. Hazard: shutting a unit down is your own command creating a risk in someone else's business, so ask first, keep the shutdown to a few minutes and confirm restart before you leave that unit.

4. Find the controlling sensor and confirm it is in the space it controls. Acceptance: the thermostat or sensor for the serving unit is located in the complaining space, on an interior wall, out of direct sun, not above a heat source and not in a supply air stream. What wrong looks like: the stat for the unit serving two bays hanging in the quieter bay, so the unit satisfies on a space that has no load and starves the space that does. Stop rule: a sensor in a different tenancy is a zoning defect and not a setpoint problem, so you do not adjust it to fix the complaint; it gets written up and routed to whoever owns the equipment. Hazard: none physical, an observation made with the cover off a low-voltage device.

5. Prove the equipment is actually delivering. With authority to do so, force a cooling call, then read return and supply dry bulb at the unit and confirm airflow at every diffuser on the map. Acceptance: a dry-bulb drop across the coil in the range the equipment and entering conditions support, commonly 18 to 22 F at a nominal 400 cfm per ton with typical return conditions, legitimately lower in a high-latent space such as a restaurant and higher when airflow is low. What wrong looks like: judging delivery by hand at a diffuser, which cannot separate cold air from not enough of it. Stop rule: a drop outside the range moves this into an equipment diagnosis and out of this procedure. Hazard: forcing a call drives conditions in an occupied space you may not be the tenant of, so time-box it, tell the occupant, restore the original setpoint before leaving the stat, and never force one on a unit tied to refrigeration.

6. Ask what changed in the space since the equipment was sized. Cooking equipment, display coolers, a partition wall, more staff, new lighting, glass uncovered, diffusers closed off by a tenant chasing a draft. Acceptance: a written list of load changes with the tenant confirming each, and the diffuser positions recorded as found. What wrong looks like: quoting a larger unit against a complaint without ever establishing that the space is now carrying a load nobody sized for. Stop rule: a load change large enough to explain the complaint is reported before any equipment is quoted. Hazard: this walk takes you along cooking lines and behind coolers, so keep clear of open flame and hot surfaces, and any smell of combustion products or an alarm sounding routes immediately to the carbon monoxide alarm response SOP rather than to this one.

7. Classify the finding into one of four before anyone talks about money. Equipment fault, which this shop repairs. Control, setpoint or schedule, which this shop adjusts with the responsible party's permission. Zoning or capacity mismatch, which is a design change and a quote. Building or tenant-side, such as glass, propped doors or added load, which is reported rather than repaired. Acceptance: one classification named on the ticket with the measurements that support it. What wrong looks like: a tech resolving on site who pays, which is a lease question. Stop rule: who bears the cost is decided between the tenant, the landlord and their own advisers on the terms of their lease, so the shop supplies findings and a price and routes the rest to them in writing. Hazard: none physical, a determination made from the recorded numbers.

8. Put the findings to both parties in writing and book the verification. Acceptance: a written summary to the caller and to the account holder carrying the measured space temperatures, the setpoint, the diffuser map, the coil drop and the classification, plus a re-measure scheduled at the same time of day after any change is made. What wrong looks like: a verbal explanation to whoever was standing there, after which the tenant and the landlord each remember a different version. Stop rule: no re-measure booked means the shop has no way to prove the fix worked, and the next complaint starts from zero. Hazard: none physical, an office task.

The record this produces

One complaint block: the six intake fields, both space readings with heights and locations, setpoint, outdoor conditions, clock time, the diffuser map showing which unit serves which part of which tenancy, sensor location, the forced-call coil drop, diffuser positions as found, the list of load changes, the classification, and the date and recipients of the written finding.

The diffuser map outlives the visit. It costs twenty minutes once and permanently answers the question that makes these calls expensive: which equipment is responsible for which floor area. Every later complaint in that building then starts from a map instead of a guess.

Worked pass: three-bay strip center, nail salon warm every afternoon

Two rooftop units serve three bays. Complaint booked for 3 pm on the tenant's report that the front of the salon is unbearable after lunch and fine in the morning.

Step 1 captured all six fields, including that the salon added a six-station drying area last spring. Step 2 at 3:10 pm: front of the space, near the storefront glass, 78.4 F and 47 percent relative humidity at 4 ft; back of the space 74.1 F, a 4.3 F difference across one small bay; controlling setpoint 72 F; outdoor 94 F. Step 3, with the property manager's permission and after confirming neither unit serves refrigeration: shutting RTU-2 stopped both salon diffusers and two diffusers in the neighbouring stockroom bay, so one unit serves two tenancies.

Step 4 FAILED. The controlling thermostat for RTU-2 is mounted in the neighbouring bay's stockroom, an interior room with no glass and almost no load, reading 71.8 F against the 72 F setpoint and therefore satisfied. Under the stop rule the tech did not drop the setpoint to force runtime, because that stat governs another tenant's space and pushing it would take that tenancy out of comfort to fix this one. It was written up as a zoning defect.

Step 5 was still run, with the property manager's authority, by forcing a call for eight minutes and restoring the setpoint afterward: return 76.0 F, supply 56.8 F, so 76.0 minus 56.8 is a 19.2 F drop, inside the 18 to 22 F range, with airflow at all four diffusers and clean filters. The equipment is delivering exactly what it should. Step 6 listed the drying stations, the unshaded west-facing storefront, and two salon diffusers the staff had closed against a draft, recorded as found.

Step 7 classified this as a zoning and capacity mismatch, not an equipment fault: one unit serving a high-load bay and a near-zero-load bay, with its only sensor in the low-load one. Three options were quoted through the service manager, with what each does stated plainly: move the sensor into the salon, which fixes the salon and will make the stockroom cold; split the zones with a second unit for the salon; or reduce the salon's load with shading and a rebalance. Who pays is a lease question between the tenant, the landlord and their own advisers, and the shop said so rather than answering it. Step 8 sent both parties the numbers and booked a 3 pm re-measure after whichever option is approved.

What the failure teaches: every instinct on this call points at the equipment, and the equipment passed. A tech who had started at step 5 would have found a healthy 19.2 F drop, told the tenant the unit is fine, and left a complaint that would return in a week. The finding lived in a thermostat on a wall in a different business.

References

• ASHRAE Standard 55, thermal environmental conditions for human occupancy, in the edition your jurisdiction or contract has adopted; it is a consensus standard and binds only where adopted or specified
• The equipment manufacturer's data for the design temperature drop and airflow of the specific unit, which governs over any range quoted here
• See related: No-Cool Emergency Call Response; No-Heat Emergency Call Response; Callback Within 30 Days Investigation; RTU Economizer Damper Repair