Another newbie question

[ohirider]

I asked a question in the general discussion a couple of days ago and was directed to this forum. I think this is the right place to ask my next questions related to system size.
How do I relate lbs. of refrigerant in a system to system size?
Can the system size be expressed in Tons like an A/C or is it expressed in compressor Horse Power?
If horse power, how does H/P relate to Tons?

Example; what size system holds 90 lbs of refrigerant?

Thanks for your help

[Joe Harper]

http://www.supco.com/images/pdfs/Technical%20data%20114-121.pdf

Here are some tables you can calculate what it is you are exactly trying to figure out.
Refrigerant amounts in the system are determined by different factors, not just tonnage.

[Airmechanical]

Example; what size system holds 90 lbs of refrigerant?Thanks for your help

about;

a 30 ton package unit

or a 40 ton chiller



.

[bob_scheel]

Really depends on the system. Length and size of the liquid line is important. Receivers, head master systems have more. The type of condenser i.e. air cooled, water cooled, or a wet dry cooling tower. Hot gas bypass requires more refrigerant. I recovered 180# out of a 25 ton unit recently. (it was correctly charged but had big filter driers, a wet dry tower, and hot gas bypass.)

The off the cuff rules are usually good for small simple systems.

[Joe Harper]

Really cant use that on small simple systems ethier. A 4 ton trane xl14holds 19 lbs. A 4 ton lennox 14hpx holds 11.

[Airmechanical]

Example; what size system holds 90 lbs of refrigerant?


about;

a 30 ton package unit

or a 40 ton chiller



Really depends on the system. Length and size of the liquid line is important. Receivers, head master systems have more. The type of condenser i.e. air cooled, water cooled, or a wet dry cooling tower. Hot gas bypass requires more refrigerant. I recovered 180# out of a 25 ton unit recently. (it was correctly charged but had big filter driers, a wet dry tower, and hot gas bypass.)The off the cuff rules are usually good for small simple systems.

ok, it was a loaded question

the examples were given to the OP for a baseline 30 ton package unit

it's pretty much the same for all 30 ton package units, as well as chillers:patriot:

the examples i gave, did not include, Receivers, head masters, Lee temp coils, water cooled, or a wet dry cooling towers, Hot gas bypass, or other additional items that are out in there


I recovered 180# out of a 25 ton unit recently. (it was correctly charged but had big filter driers, a wet dry tower, and hot gas bypass.)

hot gas bypass added to a 25 ton system, will not require much extra refigerant

even if it's a hot gas bypass coil next to the evap it may require 5 extra pounds at the given 25 ton system

describe the 25 ton system in your example that used #180 of refrigerant

did it have 500 foot liquid line

or just a huge reciever?

#180, seems a bit excessive


.

[Airmechanical]

Really cant use that on small simple systems ethier.

when comparing different brands of the same tonage and efficiency

residential package units pump about 2-3 pounds per ton, the same as BIG commercial package units


.

[ohirider]

Thanks for the responses. I'll never be a Pro but I am fairly mechanical and I understand basics. It sounds like you're talking about air conditioners or maybe the terminology is similar.
I'm guessing that the same statements apply to refrigeration systems and a lot depends on the actual physical set up.
I'm trying to establish the size of 17 identical cooling/gassing chambers at a tomato packing plant.
The OM knows that they hold 90 lbs of refrigerant.
Do I read HP on the compressors for an acurate size? Or??

[icemeister]

I'm trying to establish the size of 17 identical cooling/gassing chambers at a tomato packing plant.
The OM knows that they hold 90 lbs of refrigerant.
Do I read HP on the compressors for an acurate size? Or??

Tomato ripening rooms are rather specialized applications. According to ASHRAE green tomatoes are held in a controlled atmosphere for ripening at relatively high temperatures between 55ºF-70ºF. Ripe red tomatoes are usually at about 50ºF.

The refrigeration systems' condensing units are typically designated by their nominal horsepower. Their compressor model numbers may indicate either horsepower or nominal Btu/hr. To get the best estimate of size, get the unit manufacturer and model number, go to their website and look for the catalog performance data for that unit at the operating conditions for your application.

The evaporator temperature for ripening rooms is usually selected at a 10ºF TD (TD = Room Temp - Evap temp) so for 50ºF room the evap temp would be approximately 40ºF. At that evap temp, the HP/Ton relationship would be about 1 HP/Ton. At lower evaporator temps, that ratio will increase...ie, at +20F ET it's approx. 2 HP/Ton and at -25ºF, 3 HP/Ton.

[ohirider]

"The refrigeration systems' condensing units are typically designated by their nominal horsepower. Their compressor model numbers may indicate either horsepower or nominal Btu/hr. To get the best estimate of size, get the unit manufacturer and model number, go to their website and look for the catalog performance data for that unit at the operating conditions for your application."

This is the information I'm trying to get.

"The evaporator temperature for ripening rooms is usually selected at a 10ºF TD (TD = Room Temp - Evap temp) so for 50ºF room the evap temp would be approximately 40ºF. At that evap temp, the HP/Ton relationship would be about 1 HP/Ton. At lower evaporator temps, that ratio will increase...ie, at +20F ET it's approx. 2 HP/Ton and at -25ºF, 3 HP/Ton."

Very helpful

Thanks for ithe info.

[ohirider]

http://www.supco.com/images/pdfs/Technical%20data%20114-121.pdf

Here are some tables you can calculate what it is you are exactly trying to figure out.
Refrigerant amounts in the system are determined by different factors, not just tonnage.

Thanks Joe - I'll print those and laminate them for my notebook

[Joe Harper]

Tomato ripening rooms are rather specialized applications. According to ASHRAE green tomatoes are held in a controlled atmosphere for ripening at relatively high temperatures between 55ºF-70ºF. Ripe red tomatoes are usually at about 50ºF.

The refrigeration systems' condensing units are typically designated by their nominal horsepower. Their compressor model numbers may indicate either horsepower or nominal Btu/hr. To get the best estimate of size, get the unit manufacturer and model number, go to their website and look for the catalog performance data for that unit at the operating conditions for your application.

The evaporator temperature for ripening rooms is usually selected at a 10ºF TD (TD = Room Temp - Evap temp) so for 50ºF room the evap temp would be approximately 40ºF. At that evap temp, the HP/Ton relationship would be about 1 HP/Ton. At lower evaporator temps, that ratio will increase...ie, at +20F ET it's approx. 2 HP/Ton and at -25ºF, 3 HP/Ton.

Is there anything that you dont know??

[icemeister]

Is there anything that you dont know??

I used to have a life...and this is what it has become. :)