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Multi-Unit central heating system.


barlyhop
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Yesterday I inspected a condo in an eight story building. The complex is 3 years old. Each floor has one gas fired forced air system that serves every unit on that floor. I had no access to the heating unit, it was locked in a small mechanical room. The thermostat was a programmable model and was not responding the way in which I would expect it to do. I had no instructions on operating the thermostat.

How does a system such as this keep each unit at a desired temperature?

Secondly, I had no rooftop access to observe/inspect the A/C system and no way of operating it as the thermostat was basically non responsive to me. The outdoor temp at the time was also 48 degrees.

In the unit, there are ceiling mounted ducts as well as one hallway wall mounted intake which was electronically controlled and also housed a mechanical air filter.

On another note, there was no water heater in the unit, where the hot water came from, I have no idea? There is no management on site and most all utility areas were locked and inaccessible.

I have never felt so helpless in inspecting HVAC and have no familiarity with a shared system and how it might function through forced air.

Any information or insight would be highly desirable!

Thanks to all.

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For condo units, I request access be provided to the roof, mechanical room, etc. prior to the inspection.

Hot water may have come from a central boiler, but often there are water heaters installed in the mechanical room that provide hot water to individual units.

I can't recall seeing a gas fired forced air furnace that provides heat to more than one unit.

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This was a 8 story unit with 10 units per floor. The listing sheet says gas forced air heating.

I have tried to research the complex and obtain mechanicals info with nothing found. It is advertised to be "High Tek" but not sure what that is referring to.

I looked at some info regarding electronic controlled duct mounted dampers, that would make sense as the return in the hallway was also electronic.

I'm starting to feel vulnerable after the fact, not a good feeling as you probably know.

Thanks Guys!

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Well, right out of the chute, you can't have a single forced air heating plant heat multiple apartments. Contaminants in one apartment could be drawn throughout all the apartments.

This is bedrock stuff. It's got to be some other sort of heating system, or the building has a large problem.

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This was a 8 story unit with 10 units per floor. The listing sheet says gas forced air heating.

I have tried to research the complex and obtain mechanicals info with nothing found. It is advertised to be "High Tek" but not sure what that is referring to.

I looked at some info regarding electronic controlled duct mounted dampers, that would make sense as the return in the hallway was also electronic.

I'm starting to feel vulnerable after the fact, not a good feeling as you probably know.

Thanks Guys!

Kurt is right you could not be drawing return air from another unit. The mechanical system would be unballanced. A 42 story building in Los Angeles that has the problem of smokers in one unit and someone with allergies in an adjacent unit. I am sure you can see the problem.

I assume the building is Type 1 construction?

To get water that high in a building you need booster pumps, which eans a mechanical plant. Most buildings that size have the mechanical plant in an adjacent structure, one of my projects in Reno (a 12 story) have a mechanical room on one of the lower floors (3-5). You will usually be able to see the ventilation louvers on the side of the facade.

At any rate you most likely have hot and chilled water circulating through the building. The water is used to cool or heat through a VAV box which is very similar to a hydronic heating system.

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This was a 8 story unit with 10 units per floor. The listing sheet says gas forced air heating.

I have tried to research the complex and obtain mechanicals info with nothing found. It is advertised to be "High Tek" but not sure what that is referring to.

I looked at some info regarding electronic controlled duct mounted dampers, that would make sense as the return in the hallway was also electronic.

I'm starting to feel vulnerable after the fact, not a good feeling as you probably know.

Thanks Guys!

The hot water part is easy. The building has a mechanical room somewhere with a domestic hot water system for the suites.

With regards to the HVAC. Hallways, in this type of structure, typically have their own makeup air unit(s). More often than not though it's a rooftop MUA that feeds the hallways. This may explain the single unit on each floor.

One HVAC unit, that is a VVT (variable volume, variable temperature) used for multi-zone purposes, is highly unlikely for all the reasons the others have given. The only way it *might* work is if the main unit had some type of air to air heat exchanger for return/fresh air. This way the return air is leaving the suites but is going through this heat exchanger so there is no mixing. The unit would still be a nightmare for temperature controls (the old lady likes it 80 degrees in her suite and someone like me likes it 65 degrees).

Was it a dropped ceiling or a finished ceiling in the suites? How about the hallways?

Ceiling hung water source heat pumps would be one option but all that any of us can do is guess.

Before you send your report out call the citys building department and talk to the folks there about this property. Should be a good chance that someone there knows what's going on. A call to the local fire chief might help shed some light too.

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Yes, type 1 construction. The electronic return was located inside the unit, not in a common hall. There is one standard size supply duct in each room ceiling of the unit. The ceiling is finished drywall.

The two top floors of the complex were unfinished in metal studs (trying to sell for over a million per unit and unsold to date). There was no evidence in the unfinished space of hydronic piping, although this theory makes the most sense.

This project was developed by the area's "Donald Trump" of developers.

The presence of the supply and return ducts are certainly what is baffling me!

Thanks again!

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