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Response time is the least useful thing in most HVAC contracts
It is also the thing they are sold on. Here is what we think is actually worth paying for on a commercial site, what to ask before you sign anything, and why we do not offer a 24-hour guarantee ourselves.
Downtime is made of four things, and only one of them is how fast somebody arrives
When a unit fails, the clock runs through four stages: how long before anybody notices, how long before a technician is on site, how long to diagnose it, and how long to get the part. On most commercial failures the fourth stage is the longest by a wide margin, and the second is the shortest.
Which means a contract that shortens stage two by four hours, and says nothing about stages one, three or four, has improved the smallest number on the list. Meanwhile a five-dollar contactor held on a shelf can remove three days, and a sensor that tells you a room is drifting at eleven at night can remove a whole morning.
So the useful questions are: what stops when this stops, and what would actually shorten it? Both below.
What stops, and what cover you have now
Nothing is sent anywhere and nothing is recorded. This is what we would ask you at a first meeting.
Response guarantees are the easiest thing in this trade to sell and the hardest to honour. Three things are worth checking in the document you already have, and all three are usually in it.
What counts as a response. In a great many contracts it is a telephone call returned, not a technician on site. If the clause says “respond” rather than “attend”, the guarantee is about answering the phone.
What the remedy is. Usually a credit against the contract fee. If missing the target costs the contractor a small refund and costs you a day of trading, the clause is not protecting you, it is pricing an apology.
What is excluded. Parts not held, equipment past a stated age, refrigerant, anything requiring a crane or roof access outside hours, and periods of exceptional demand — which is to say a heat wave, which is to say precisely when you will need it.
And about us, plainly: we do not offer a 24-hour guarantee, because we could not honour it in August across this valley and we would rather not take money for it. What we will do instead is tell you in writing which units we hold parts for, what our realistic attendance looks like in and out of season, and what a temporary measure is for each critical space. If a guarantee genuinely matters more to you than that, take it — but read the three clauses above first, from whoever is offering it.
Buy spares and a temporary plan, not a faster van
Where a failure empties the room, the money is in never reaching the failure and in having something to do on the day. Both are cheaper than a premium response clause and both work at three in the morning.
What we would do: identify the two or three components on each critical unit that actually fail — contactors, capacitors, motors, control boards — and establish which are held locally and which come from out of state. Hold the out-of-state ones yourself. They are small, they do not perish, and they turn a three-day wait into an afternoon.
And write down the temporary plan before you need it: what portable equipment can be hired locally, from whom, how long it takes, and whether your electrical supply can take it. The worst time to discover the answer is the day you are asking staff to send people home.
Find out whether the space actually becomes unworkable, or only unpleasant
This is the case where honest measurement saves the most money, because the two outcomes look identical in a complaint and cost very different amounts to prevent. A room that reaches an uncomfortable temperature by mid-afternoon is a nuisance. A room that people genuinely cannot work in is a different problem with a different budget.
What we would do: log the space for a fortnight — temperature and humidity, through the working day, including the hot afternoons and the closed weekend. That record settles the argument in both directions, and it is cheap.
Then look at the causes that are not the equipment: west glass with no shading, a zone that was reconfigured for a layout that has since changed, a supply diffuser blowing across one desk and nowhere else, and returns blocked by storage. Balancing and shading fix a striking share of staff comfort complaints for a fraction of a plant replacement.
Separate the process from the comfort system before anything else
If a process slows or halts, the first thing to establish is whether the process actually needs the building conditioned or whether it needs something done at the machine. Those are different jobs, and combining them into one building-wide system is how sites end up conditioning a whole workshop to solve a problem at one bench.
What we would do: measure the heat the process itself produces — it is on the equipment labels, in watts or BTU — and look at extraction at the source before cooling at the room. Removing heat where it is made is almost always cheaper than removing it after it has spread.
What we would not do: guarantee a process condition. If the number comes from a machine manufacturer, a product standard or a customer specification, we will design to it and say honestly whether the building can hold it — but we will not invent it, and we will say so on the first visit rather than in a dispute.
You need monitoring and an alarm long before you need a faster contractor
Where a room has a condition it must hold, the expensive failure is not the equipment stopping. It is nobody knowing for eleven hours. A logger with an alarm that reaches a person overnight costs very little and is the single most valuable thing on this page.
What we would do: get continuous monitoring in place with a threshold set below the limit rather than at it, so there is time to act; agree who the alarm actually reaches and what they are supposed to do; and write down what the temporary measure is for that room specifically.
And be clear about whose number it is. If the condition comes from a regulator, an auditor, an insurer or a product standard, that specification is theirs. We will design to it, measure against it and record it. We will not set it, and any contractor who offers to is guessing with your compliance.
If the room needs redundancy — a second unit that can carry it alone — say so early, because it is a design decision rather than something that can be added conveniently later.
Then do not buy a contract sold on response. Buy one sold on measurement.
This is a perfectly good answer and rather more sites give it than admit it. If a failure is an inconvenience rather than a stoppage, the sensible arrangement is an annual or twice-yearly visit that actually measures things, an agreed hourly rate, and no premium attached to speed you do not need.
What that visit should produce: static pressure, airflow, charge against target, temperature split, amp draw and combustion, dated and comparable with last year. That record is what gives you warning, and warning is worth more here than speed.
Where the money should go instead: filters at a sensible interval, drains kept clear, and coils actually cleaned. Those three prevent most of the failures that would otherwise interrupt you, and they are the three most often skipped on a cheap visit.
About trading specifically
Work out what an hour closed actually costs you, once, and write it down. Every decision on this page becomes easy afterwards, and most of them turn out to be cheaper than the number.
About staff spaces specifically
Ask for the logged data rather than for an opinion. Two weeks of temperature and humidity through the working day costs almost nothing and ends an argument that can otherwise run for years.
About a process specifically
Get the equipment heat load off the labels before anybody sizes anything. A workshop full of machines is a heated building with a known output, which makes this one of the easiest loads in the trade to get right and one of the most often guessed.
About a required condition specifically
Find the document the number came from and keep a copy with the equipment records. Half the specifications we are quoted on site turn out to be somebody’s recollection of a figure nobody can locate.
About sites where nothing stops
Say so out loud when you get quotes. A contractor who keeps steering towards response guarantees after you have told them nothing stops is selling a product rather than listening.
With no cover at all
Perfectly reasonable on a site where nothing stops, and expensive on a site where something does. The cheapest first step is not a contract — it is one survey that establishes what is installed, how old it is and what condition it is in. Until that exists, any contract you are offered has been priced on assumptions about your building.
With an agreed rate and no schedule
Better than nothing and it has one hidden cost: nobody is accumulating readings, so nothing gives you warning. If you keep this arrangement, at least ask for measurements to be recorded on every reactive visit and keep them yourself. Three sets of readings on the same unit will tell you more than any prediction.
With a maintenance contract
Read what a visit is required to include, as a list, and compare it with what you actually receive. If the reports have no numbers in them, you are buying attendance rather than maintenance. Also check the notice period and what the fee renews at, because a low first year attached to a multi-year term is a common structure.
With a 24-hour or same-day promise
Read the note above before anything else on this page. In short: check whether “response” means attendance or a telephone call, check what the remedy for missing it actually is, and check the exclusions — particularly the one covering periods of exceptional demand, which is the week you will need it.
Four questions for anybody quoting you a contract
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What exactly is measured at a visit?
As a list, with units. Without it, two prices are not comparable and the cheaper one is usually a shorter visit rather than a better rate.
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Which parts do you hold for my equipment?
Named. This does more for real downtime than any response clause, and the answer tells you immediately whether they have looked at your units or at a template.
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Does “response” mean attendance, and what happens if you miss it?
If the remedy is a credit against the fee, the clause is priced rather than guaranteed. Worth knowing before it matters, not afterwards.
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Do I get the records, and in what form?
They describe your building. You should hold them, and you should be able to hand them to another contractor without asking permission.