40 TON McQUAY SELF CONT. MICRO II

[mrhvacmechanic]

Hi Guys,
Just picked up a new account with two 40 ton McQuats with VSD. One on each floor. Both floors have VAV's on them.
Customer says they run on RA temp??? not discharge? mmmmmmmm?

My question:
Even though they have RA and SA sensors, how can I tell which is controlling the temp of unit. Does the model # tell me or is it in the M II programing to select RA or SA?

Now I know I can look at existing temp setting. Just becasue it's set to 68 doesn't tell me thats what governs the MICRO Tech II. Customer said unit hasn't worked properly in two years?

[Octopus]

:cheers:


http://www.mcquay.com/McQuay/common/pages/literaturelistnew?prodtype=Controls&subprodtype=MicroTech II&maintopic=Products&topic=Controls&subtopic=MicroTech® II Controls

[MUNC]

indeed at least the four i have run off return air. Mquay has a sweet web site that i've down loaded all my books for the micro cont. My big prob is the units i have are wayyyyyyy over sized. they planned for future expansion but when it came they put new units on the expansion

[mrhvacmechanic]

Cris,
Which one will give me my answers?

Munc,
I have four compressors in each unit. Can't you unload down to 10 tons?

[Mcgushvac]

If unit is controlled by return temp. it means that this is your changeover temp{control temp} the unit will either go to heat /cool/ fan only based on your heat & cool set points. Discharge air is still control to a set discharge air temp. May have a reset in it though. Download the OM manual from mcquay.com and it will tell you everything you need to know.

[mrhvacmechanic]

Mc,
I understand that the RA could be used as my change over. Also my warm up if unit is a VAV.

Your're sying my discharge sensor can be set for a min or max eventhought my RA govern's heating or cooling setpoint based on return?

[mrhvacmechanic]

Tried to post this in commercial area, don't see my thread listed??????

[MUNC]

Cris,
Which one will give me my answers?

Munc,
I have four compressors in each unit. Can't you unload down to 10 tons?

i can un load down to 12.5% capacity but unit will still trip out on oil press. my suction gets too low do to wayyyyy over sized. have tried to fine tune econo and fans but still dinkin with it. problem up in the mountians is a hellova solar gain on everything. building schdules each vav individually, with most being unocc supply fan slows wayy down thus no load and at times lead comp says " too low sorry" just gonna have to fine tune these babies