knkreb
07-08-2006, 03:43 AM
I have a customer (industrial plant) that has a split system A/C that was never put in properly. Here's the list of what it has against it:
1. It draws return air from the ceiling of the plant. The other day that was 100°F db/ 77°F wb air temp. It then blows this air down into a few offices that have no return air means.
2. Someone along the way has changed the piston to a #75 orifice piston. This looks to be about a 3.5 ton piston and the system is 5 tons.
3. The condensor is located on the roof next to the dust/waste collector system, and is prone to plugging up the condensor coils.
4. The other day (mind you having that #75 piston) the system was running about 400 PSIG head with a 72 PSIG suction. Liquid line was very cool (aka lots of subcooling)
Here's my thoughts... anyone have input?
1. Change the system to an expansion valve system with a receiver.
2. Slow the blower down to a lower speed to reduce the heat load on the evap, and to get the discharge air temperature down to a point that it would actually cool the office space.
3. Possibly add a Crankcase pressure regulating valve to the system to reduce possible compressor overload.
And finally my question about engineering this project: I don't have an engineering degree, but I was wondering this to find out what the best way was to find out how much load is actually on the system? To operate at 2000 cfm at 100°F db/75 °F wb, and reduce the discharge air temperature down to about 60°F (most likely I guess with a 60°F wb too?)
My rough guess is that I need to cut the airflow in half at least (1000 cfm) to have a 5 ton system actually cool the space properly.
Oh, I almost forgot, the cost of ductwork modification is way more than the customer's budget to fix it. That's why I'm looking at just getting the refrigeration side to work properly.
1. It draws return air from the ceiling of the plant. The other day that was 100°F db/ 77°F wb air temp. It then blows this air down into a few offices that have no return air means.
2. Someone along the way has changed the piston to a #75 orifice piston. This looks to be about a 3.5 ton piston and the system is 5 tons.
3. The condensor is located on the roof next to the dust/waste collector system, and is prone to plugging up the condensor coils.
4. The other day (mind you having that #75 piston) the system was running about 400 PSIG head with a 72 PSIG suction. Liquid line was very cool (aka lots of subcooling)
Here's my thoughts... anyone have input?
1. Change the system to an expansion valve system with a receiver.
2. Slow the blower down to a lower speed to reduce the heat load on the evap, and to get the discharge air temperature down to a point that it would actually cool the office space.
3. Possibly add a Crankcase pressure regulating valve to the system to reduce possible compressor overload.
And finally my question about engineering this project: I don't have an engineering degree, but I was wondering this to find out what the best way was to find out how much load is actually on the system? To operate at 2000 cfm at 100°F db/75 °F wb, and reduce the discharge air temperature down to about 60°F (most likely I guess with a 60°F wb too?)
My rough guess is that I need to cut the airflow in half at least (1000 cfm) to have a 5 ton system actually cool the space properly.
Oh, I almost forgot, the cost of ductwork modification is way more than the customer's budget to fix it. That's why I'm looking at just getting the refrigeration side to work properly.