Ask these questions before a repair company goes on your vendor list.

• Ask for a certificate of insurance that names your company.
• Ask for a signed W-9.
• Ask whether their technicians hold the licenses your city or county requires for gas and electrical work.
• Ask whether the technicians who handle refrigerant are EPA Section 608 certified. Federal law requires it.

Watch how long the paperwork takes. A vendor who needs three weeks to send a certificate may need a long time to send a technician, too.

"Fast" is not an answer. Ask for the emergency response time in hours, and ask whether they'll put it in writing. Ask who answers the phone after hours and on holidays, and what happens between your call and the technician's arrival.

Then ask where their technicians are based. A shop two hours from your stores will struggle to reach a down walk-in in time.

Here's why the hours matter. Cold food held above 41°F for more than four hours has to be thrown out. Your vendor's response time decides how much product you lose.

The first visit matters less than whether it's the last one. Ask how often they have to come back out for the same problem. A vendor who tracks it can give you a number. A vendor who doesn't will give you an adjective.

Ask what happens when a repair doesn't hold, and who pays for the second trip. Ask whether the trucks carry common parts. When a part has to be ordered, ask how they'll get you through the night until it comes in.

If you use one company for refrigeration, another for HVAC and a third for the cook line, you have three phone numbers and three sets of paperwork. When a problem crosses two systems, you also have two vendors pointing at each other. Ask what the company covers:

• Walk-ins, reach-ins and ice machines
• Rooftop units, make-up air and kitchen exhaust
• Gas and electric cooking equipment
• Planned maintenance visits

Ask which brands they work on, and which brands they're authorized to do warranty work on. Get that list in writing, and check it against the brands in your kitchens.

Price is rarely what sours a vendor relationship. The surprise on the invoice is. Ask these before the first call:

• Is there a trip charge, and how much is it?
• Is the work billed as time and materials, a flat rate or a quote first?
• Will they agree to a not-to-exceed amount, and call you before they go over it?
• Will each invoice show the hours on site, the parts and what was fixed?
• What are the payment terms?

Ask for references from other multi-unit operators, and call them. Ask how long they've used the vendor, and what happened the last time something broke at a bad hour. Read the Google reviews, and read how the company answers the bad ones. Ask how long the company has been in business and who runs it.