commercial univents with pneumatic tt's

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i can use a quick lesson on pneumatic tt's controls for commercial univents with steam and hydronic coils thank you

furnacefigher15

Be more specific

I could write a book on pneumatic controls. What exactly do you want to know.



What brand controls?



Model #'s would be nice too.



what do you mean by tt's? Thermostats?

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univents

yes by tt's i mean thermostats,if you are familiar with this commercial univents,all i need is a cronological flow of the operation. very simple. tt to the valve how it open the flow of heat into the coil how the blower kiks on...... i do not have a specific model.thank you.

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univents

yes by tt's i mean thermostats,if you are familiar with this commercial univents,all i need is a cronological flow of the operation. very simple. tt to the valve how it open the flow of heat into the coil how the blower kiks on...... i do not have a specific model.thank you.

BillW

Pneumatic univents sequence of operation

Here is how a typical system operates.  The time clock sets the pressure reducing valve to the "night" pressure, and all the room stats respond by shutting the outside air vents, modulating the water valves closed, and shutting down the blower.  If an individual room drops below the night set back temperature minimum, the fan will start, and the hot water valve will modulate to keep the room from freezing, or going too cold.  At the start of the "Day" cycle, the time clock will set the pressure reducing valve to the "day" pressure, and the stats will start the blowers, and modulate the hot water valves open, until the  "day" temperature is reached.  The valves will modulate to maintain the day temperature, and the outside air dampers will open to the minimum ventilation position, mixing in fresh air.  Once the heating reqirements are met, the water valves will close, and the outside air dampers will open to the full, 100% outside air position.  In certain systems, chilled water may be used to cool the rooms as well.

Day/night thermostats are TP971's, damper motors are MP516's,  water valves are VP512's, and day/night pressure reducing valves are PP901's, relays are either RP418 or RP818.  These are Honeywell numbers, there are also equivalents from  Johnson Controls,Invensys(Powers) and Barber Coleman.  There may be other accessories needed, depending on the manufacturer of the Univent, but those items are typical of the standard Nesbitt.  You won't find this stuff at a residential distributor, go to a commercial distributor, and as far as I know, you can still get these items.

 It is rare to find a unit vent that hasn't been butchered, usually by disabling or removing the damper controls, in a misguided 1970's attempt to save energy, especially in schools.  Good luck.

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great help

thank you for taking your time and answering my question.it is a great deal of information for me.