Makeup air units, any experts here?

[hockeyoligist2]

Waiting on a call from tech support. Thought I would run it by Y'all.

We have different brands of MAU's with electric heat strips and some with gas burners in them. I don't have much documentation on them.

Are they supposed to heat the building or just keep the incoming air above freezing? The thermostats in the units are factory set at 40 to 45 degrees. If it is colder or if you turn it up, the burners and/or heat strips will cycle on for about 30 seconds, sometimes longer. Not enough time to actually heat the building.

During our recent cold snap we had some pipes freeze. These buildings have no other heat source. I'm thinking they may be working as designed and we need a different heat source?

 

[LarryFine]

I think they're just "pre-heaters" to reduce the buildings heat load in winter.

 

[One-eyed Jack]

Waiting on a call from tech support. Thought I would run it by Y'all.

We have different brands of MAU's with electric heat strips and some with gas burners in them. I don't have much documentation on them.

Are they supposed to heat the building or just keep the incoming air above freezing? The thermostats in the units are factory set at 40 to 45 degrees. If it is colder or if you turn it up, the burners and/or heat strips will cycle on for about 30 seconds, sometimes longer. Not enough time to actually heat the building.

During our recent cold snap we had some pipes freeze. These buildings have no other heat source. I'm thinking they may be working as designed and we need a different heat source?

MAU's are not intended to be a primary heat source. You are correct in they are doing the job they were designed to do. Alternate heat source will be required for colder days.

 

[hunt4679]

MAUs that are heated and or cooled are designed so in the dead of winter they are not pumping in 20 deg air into a heated space. And the opposite in the summer. Otherwise the heat or air would never keep up.

 

[construct]

I agree with Larry and One-Eye. They are not intended to be primary heat. The only purpose is to temper the outside air.

We had a Bar and Grill Restaurant built about 10 years ago that a very large open solid fuel grill which also required a very large volume exhaust hood. When they first fired up the system, the heat strips in the make up air units didn't get hooked up. It was winter and the temp inside the building dropped 30 deg in 10 minutes.

 

[steve66]

I agree they aren't the primary heat for the building.

But are you are talking about one to make up for the air exhausted through a kitchen hood? I'm not sure, but I would expect it to heat up a lot more than 40 or 45. That air normally blows right on the cook. Again, not 100% sure, but I would expect it to get up to at least 60 deg.

I would also expect the heater in one to be able to run continuous, regardless of the temp. setting. The fan will pull in air continuously, so the heat should be able to run continuously also.

All 4 of them cycle, including electric and gas ones? That sounds really unusual. Could something be wrong with the thermostat or controls?

 

[LarryFine]

. . . I would expect it to heat up a lot more than 40 or 45. That air normally blows right on the cook.

I've been in plenty of restaurant kitchens when they're busy. Believe me, the cook usually appreciates that cold air.

 

[quogueelectric]

Waiting on a call from tech support. Thought I would run it by Y'all.

We have different brands of MAU's with electric heat strips and some with gas burners in them. I don't have much documentation on them.

Are they supposed to heat the building or just keep the incoming air above freezing? The thermostats in the units are factory set at 40 to 45 degrees. If it is colder or if you turn it up, the burners and/or heat strips will cycle on for about 30 seconds, sometimes longer. Not enough time to actually heat the building.

During our recent cold snap we had some pipes freeze. These buildings have no other heat source. I'm thinking they may be working as designed and we need a different heat source?

To protect the pipes you can just use localized heat trace it is very common here up north but people dont generally pay for them until they have some sort of freeze damage occur which inconveniences them.

 

[480sparky]

......But are you are talking about one to make up for the air exhausted through a kitchen hood? I'm not sure, but I would expect it to heat up a lot more than 40 or 45. That air normally blows right on the cook. .........?

It's rare for a fully-functioning commercial kitchen to even need to be heated by an air-handling system. The burners, ovens, stoves, heat ledges, soup toureens, etc. put out enough BTUs along with a hustling staff to more than heat the space. Even in the dead of winter, it's not unusual for the AC to be running.

 

[hockeyoligist2]

I agree they aren't the primary heat for the building.

But are you are talking about one to make up for the air exhausted through a kitchen hood? I'm not sure, but I would expect it to heat up a lot more than 40 or 45. That air normally blows right on the cook. Again, not 100% sure, but I would expect it to get up to at least 60 deg.

I would also expect the heater in one to be able to run continuous, regardless of the temp. setting. The fan will pull in air continuously, so the heat should be able to run continuously also.

All 4 of them cycle, including electric and gas ones? That sounds really unusual. Could something be wrong with the thermostat or controls?

They are for normally unoccupied sewer system buildings. And yes the ones I have been troubleshooting all cycle. Tech support hasn't called back, so I'm still hanging. Thermostats are working correctly. They have 2 circuit boards that control the heating and I have no info on them.

Thanks for the answers!