Type: Posts; User: Islander
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no the firemarshall was not attending...i thought they were the ones responsible for fire alarm verifications?..anyhow i found several descrepiancies that needed fixing...
we have commissioned and...
I've done some of the AABC commissioning lately. I've had both the GC and mech tell me to ignore (on 2 seperate jobs)the spec's since it had so many unusual points to cover.
IE..big new specs...
external static pressure = the sum of the ahu suction/return static pressure taken approximinately 6" before the ahu and the dischrage/supply static pressure taken 6" after the ahu.
yep...most likely thats air in the system. bleed it out.
main causes i have seen are..
back of the diffuser not insulated.
building has a negative pressure and outside air is being drawn in..ac unit turns off when temp is satisfied..warm outside...
that would make for too much outside air for the ahu to conditon in the summer..down here on the gulf coast.
the full story is..
3 tons served the 1100 sq'office.
2 tons of the 5 served an adjacent
small warehouse with rolling doors open most of the time.
(2 400 cfm diffusers).
1 return air grill...
the ahu serves a small office space.(1100 sq ft).
i beleive the device was a hotgas bypass controller..
i assume it worked but need to follow up with the people that took the suggestion and used...
I have a 5 ton unit that will have some diffusers
capped off and don't want the coil to freeze up.
a couple years ago had similar problem and came here and got the suggestion to use a device that...
the only time i use static pressure to determine actual cfm is when i already know what the original cfm at the original static pressure is via traverse/balometer/etc.
sp new divided by sp old...
Thanks Sirtab i'll check that out along with the AABC one.
Incontrol.. flake off.
anybody been through the latest commissioning process whereas the test and balance contractor is required to:
*check all the controls and operations of the domestic plumbing system...hot water...
ERV=energy recovery unit.
without the dampers most of the return air will probably pull from the return grills closest to the unit...they are just a way of spreading it out by the balance...
on the question in the first post. the main duct return air damper is used to adjust the outside air to design spec's.
if it's an erv system..i can't fathom the need for a return air damper as...
the srt-10 runs a 13.2 1/4 mile...with a good driver.
Lightnings run high 13's-low 14's on average..stock.
there is already a 4 door version of the srt coming....
iaq complaint form.
IAQ...my former employer canceled adapting it
when they discovered it may lead to sitting
in a courtroom.
my experience with them on the test/balance end...
product is good...technicians good.
Lump them in there with the rest of them...in my area at least.
[QUOTE]Originally posted by deanmech
I was thinking low supply air static to be up to 2"wc; medium to 4" and high over 4". Is this correct?
****yeah. class C to 2".
class B to 4".
tons of links there you should be looking at JBF.
...i test/balance systems with bypass ducts on occasion and can tell you they do ok in general..i have'nt tested for exact accuracy/reponse of the bypass cfm though...mostly i see bypass dampers that...
build and patent it yourself.
Then attend any industrial/hvac
conventions you can find.
you could approach Trane..Carrier...TSI.. etc..
but i would'nt unless you have protected it first.
i'd still get an engineer to do the heat load calcs and test/balance to adjust the boxes.
why spend all that time ballparking it..
you can go as high as the sf# on the name plate.
often 15% higher than rated amps.
not sure how low is good...never had a problem with
low actual amps vs rated.
max cfm usually is about 1.1 x square footage of space served...min cool cfm(if applicable) is about 20% of max...min heat cfm is about 50% of max.
the 1.1 is for a typical room without tall...
single or double sensor enthalpy control along with calibrated outside air temp sensor ought to help nicely
given don't have the the leaky bldg, negative space pressure, too much min o.a., not cold...
on a vfd system i've never had any problems reading motor amperage at the motor itself.
.2 to .4 amps to me means you simply don't have a connection.
One of the rooms you could walk into and on the wall opposite the air conditioning unit if you put your hand on it, your hand is wet. There is water on the vinyl wall coating. The wall itself isn't...
make sure backs of diffusers are insulated from attic heat.
check that space served is not under negative pressure.
space temp not being satisfied indicates to me that space has negative...
thrumming noise...possible warped belt.
return air grill hissing...ra duct possibly too small.
if it was me i'd look into slowing the fan speed down a little...might help both items.
more than likely they are right, sounds like too much airflow...unless there is an unusually large amount of outside air being brought in.
Local trane supplier can give you tonnage...you may want...
If the gpm pd is in the ball park i would
zero in on airflow.
rodger on the pbblaster and brakekleen will have to give it a try.
so what happened when they lowered the economizer temp setpoint from 67 degrees? just curious.
get the manufacturer and model of the circuit setters and have them fax you the pressure drop curves...now days you can usually just download it from their website.
every brand circuit setter has...
in a typical duct/fan system...imo very high humidity would reduce static pressure in the duct.
more moisture on the coil..(wet coil=2-3%cfm loss as compared to dry coil) and damp filters...
loosen allen screw..find it won't move..spray with wd 40..give a couple raps with pliers or something heavier..not on any edge..try hard by hand..if it will budge at all you got it..just keep working...
you need to find why cfm is so low.
static pressure profile of the unit would help.
or have test and balance stop by and check out the cfm problem.
kitchen/restaraunt hvac design is flawed imo for the reasons you stated.
I know that there is a specialized hood that shuts off the exhaust based on temperature in exhaust duct that some...
obvious signs indicate when it is the problem.
it's possible his diffusers were dripping because they were'nt insulated from the attic...but since he said the building was very negative..
imo if the coil is efficient enough to produce 55 degree air (15-20 dt)then it is also removing moisture/lheat from the air.
65-70 degrees outside air temp with a 67 degree economizer setpoint...
you won't remove the humidity problem until the building pressure is no longer negative.
If you have to open the economizers too far to compensate for too much exhaust then..low delta T etc..
if it is verbatim as you explained sounds like someones jerryrigged attempt to increase air flow by bypassing the filter and coil.
if the 12" duct is tied into the supply side of the blower and...
The kitchen hood exhaust might be pulling too much also.
but unless you can verify your maintaining minimum required fpm in exhaust duct you may cause a fire hazard by slowing it down.
evap coil totally caked with slimy kitchen hood cooking grease including a few inches of sludge at the drain tray.
(return air grill was 1' from hood...no filter ever used).
hey tab tec
as of late i have controls contractors who tell me i have to provide my own adapters to hook in to the controls.
how much is that i ask...$1500 is the answer.
It's not in any spec...
is carbon monoxide what you get on an 1973 residential gas heat dx unit that has the front panel cover put on upside down?
if so let me describe what it's like.
the gas collects at the ceiling...