Unico High Velocity System
Hawkmeistr
year old home. The installing company came back this past May and started them
up. One evap is in the attic and supplies the second floor. The other is in
the basement which supplies the basement gameroom and the first floor. The
customer is unhappy with the systems and the installers haven't been able to
fix the problems. So...I was asked by my friend to check out the systems.
Condensing units are 5-ton Tranes. Checking the superheat comes out as 12°,
the suction pressure is rock steady at 50 psi and the head pressure is 240 with
an outdoor ambient of 75° . It is exactly the same for both units. I am not
familiar with this type of cooling system. The Unico website offers some
assistance but not what I need to know. And the people have lost all the
paperwork that came with the evaps. Right now the units are operating on the
freezestats until temperature setpoint is reached. I believe that the evaps
are not matched correctly with the condensing units or the evaps do not have
enough ducts to move more air.
Need some help with this one.
C. Hawk Halterman
Destiny HVAC Company
p...@see_my_sig_for_address.com
wrote:
>Condensing units are 5-ton Tranes. Checking the superheat comes out as 12°,
>the suction pressure is rock steady at 50 psi and the head pressure is 240 with
>an outdoor ambient of 75° . It is exactly the same for both units. I am not
>familiar with this type of cooling system. The Unico website offers some
>assistance but not what I need to know. And the people have lost all the
>paperwork that came with the evaps. Right now the units are operating on the
>freezestats until temperature setpoint is reached. I believe that the evaps
>are not matched correctly with the condensing units or the evaps do not have
>enough ducts to move more air.
I would definitely want to check the equipment sizing as you
suggest. With head that high on a low-ambient day ( assuming this is
22 ? ), and suction that low on *any* day, even though SH isn't
bad.... something real funky ! Is this TXV ? That would explain the
SH staying under control.....
>Need some help with this one.
>
>C. Hawk Halterman
>Destiny HVAC Company
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Bubba
5 ton Unico systems installed. They obviously spent major bucks
because those systems arent cheap. The owner isnt willing to have the
installing company come back out to have the system repaired properly?
You have never installed or maybe even seen a properly installed Unico
system? And now you want to jump with both feet into the middle of
this fire??
You are obviously one very motivated individual. ( or very stupid :-)
Might I suggest that if you really want to figure this one out you:
Find a local Unico equipment rep.
Have one of their people meet you on this job to evaluate the system
install.
I, of course, would opt to let the installing company fumble through
it. Its their mess and they probably already got paid. Let them earn
their money.
Bubba
On 02 Aug 2002 22:32:39 GMT, hawkm...@aol.comnojunk (Hawkmeistr)
wrote:
>Last October some friends of a friend had two Unico systems put in their 80
Hawkmeistr
>SH staying under control.....
Yes they both are.
Hawkmeistr
>installing company come back out to have the system repaired properly?
Apparently four different technicians have just shaken their heads and went
away saying they had to look into it further.
>You are obviously one very motivated individual. ( or very stupid :-)
Retired military...never run from a fight or a challenge.
I have seen these systems before but not to work on any of them. I thought I
would try this one as it is quite a dome scratcher. The local rep is approx.
120 miles away in another state.
p...@see_my_sig_for_address.com
wrote:
>Retired military...never run from a fight or a challenge.
And may I add ( assuming you worked for the USA ! ) - retired
from the best in the world !!!!!!
p...@see_my_sig_for_address.com
wrote:
>>Is this TXV ? That would explain the
>>SH staying under control.....
>
>Yes they both are.
OK, low back and high head with a TXV ( good SH )......
Your post sounds like you already know the things to look for
. I think you have a compound problem here.
hey, compound problem guys - take a shot at this one !!! :-)
My guesses :
- equipment mis-match seeing as this is a new start up
- low airflow ( can you blow some free supply air out somewhere to see
what the back does ? )
- what's the DT across the evap ?
- that high head ( R22 ?? ) bothers me a whole bunch - air in the
pipes ? Recover and evac and recharge clean ????
- let's guess the condensor is clean ( new start-up ) - is airflow
out there good ? Good free air paths in and out, no re-breathe ?
Gary R. Lloyd
wrote:
>>The owner isnt willing to have the
My guess would be not nearly enough airflow, and someone stuffed a lot
of refrigerant in it to try to compensate.
To do a proper analysis, instead of guessing, we would need the
following:
Low side:
Evap air in temp
Evap air out temp
SST (saturated suction temp)
Suction line temp near compressor
High side:
Cond air in temp
Cond air out temp
SCT (saturated condensing temp)
Liquid line temp near condenser
Gary
Bubba
Unico rep go out with them and find out what is right or wrong with
the system. Way too many variables that they could have done
improperly.
.......and I thought Id clarify........"stupid" was not meant
literally :)
You need to at least get a Unico book so you can read up a bit before
you tackle it. Its not That hard but that system does use some
different basic information.
Amount of runs per ton
Cfm per ton is different than a conventional system
Air flow is set by a damper and the amperage of the blower motor
etc. etc.
If your really that set on it, email me or call me and I'll get the
book out and give you some of the info
Bubba
On 02 Aug 2002 23:16:05 GMT, hawkm...@aol.comnojunk (Hawkmeistr)
wrote:
>>The owner isnt willing to have the
Iove doII
Product Catalog. Once you have that, and can figure out which model of Unico
fan coil has been installed for each system, you'll have a lot more
information on the particular problems.
The product catalog is quite intensive, offering not only products, but also
design, installation, & system sizing manuals.
You may also want to consult with the Engineering Support Technician, Richard
Eason (314-481-9000)
Unico, Inc
7401 Alabama Ave
St Louis Mo 63111
>Subject: Unico High Velocity System
>From: hawkm...@aol.comnojunk (Hawkmeistr)
>Date: 8/2/2002 3:32 PM Pacific Daylight Time
>Message-id: <20020802183239...@mb-cr.aol.com>
Bubba
didnt have a clue, Id say that your system is overcharged. Id also
guess you have an airflow problem and a mismatched design I can just
see his face as he kept shoving freon in and the suction just sat
there.
As far as mis-matching: You should have a 4260 attached to those 5
ton units. Additionally, they should have a the modular heating
section attached to them too, whether they are using the heating
module or not. Without the heating module, the 4260 will only be able
to achieve about 800 cfm at 1.5 in of static pressure.
The 5 ton system should be delivering approx 1000 cfm (200 cfm per
ton)
Duct layout: 5 supply ducts MINIMUM per ton. However this will vary
depending on the design and load requirements. A full supply duct is
10 ft without any balancing orifices. Keep it as close to 10 ft and
never less than 6 ft. Ex: 2 runs with 50% balancing orifices would
require 2 runs to equal 1 full run.
I DONT think you have air (non condensables) in the system as this
would cause a fluctuating head pressure.
For best results, check refrigerant charge by the subcooling method.
Do not attempt to change the charge of the unit at outdoor temps below
75 degrees. If the unit is to be operated at temperatures below 80
degrees outside, a low ambient kit is recommended. Generally, the
suction pressure will run 10 to 15 psi lower than a conventional
system. The cooling coil runs a lower temp than a conventional system
and the supply air velocity is much higher so Good Luck doing a temp
drop across the coil.
This is just a bit of the info of the Unico system. Much, Much more
fun can be found in "The Unico System" Book.
Good Luck
Hawkmeistr
>from the best in the world !!!!!!
Damn right!!
MechAcc
there is some recommendation about sometimes necessary for head
pressure control when operating below 80 outdoor temp.
MechAcc
http://www.unicosystem.com/ One thing that I noticed is that they
recommend 6 outlets per ton. That means they should have at 30 supply
outlets for each 5 ton system.
Hawkmeistr
>recommend 6 outlets per ton. That means they should have at 30 supply
>outlets for each 5 ton system.
I printed the Installations Tips and the minimum amopunt of outlets per ton is
five. I didn't count all the outlets but from what I saw, there aren't 25
outlets per each unit.
Hawk
Bubba
minimum per ton and not 6. I wonder who that was?? :-)
Remember too, if you count them and there IS only 5 minimum per ton
make sure that their is no reducing orifices in them or you will need
even more runs. You also need to make sure those runs arent less than
6 feet and should normally be 10 ft.
Then all that other stuff .....................
Bubba
On 03 Aug 2002 17:56:04 GMT, hawkm...@aol.comnojunk (Hawkmeistr)
wrote:
Hawkmeistr
>minimum per ton and not 6.
Yes you did! Having read some of the information on the website it is all
coming together. I will have to count the diffusers and get the information
for the website's calculator. I did two of the rooms that I knew about and it
calculated out to two tons of cooling. With four more rooms to figure in for
the downstairs system...just not enough airflow!!
I am going to call Unico on Monday and get their spin on the problem. Thanks
to all who replied. I'm sure I can get it to work correctly.
Hawk
p...@see_my_sig_for_address.com
wrote:
PS - while Gary makes a good point about someone dumping juice
in to compensate for low back, IE, look for over-charge, also keep in
mind the effect of that TXV throttling down, backing refrigerant up
into the condensor.