how to fix over sized unit with banging customer

[will173]

I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
I have three years in the trade one in school. Mostly walk ins and reach in units in time
The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.

[CraziFuzzy]

Is it actually causing a problem? I'm thinking an oversized condenser shouldn't really be a problem.. Perhaps you may have to get more water flow through it, but I'd doubt even that.

[flange]

compressor is probably moving more gas out of the evap than necessary, causing low pressure condition in low load? there are ways to skin that cat none of which is easy.

[Iamclayman2000]

Hot Gas by-pass valve with 3ton txv

[air2spare]

If you polish a turd, at the end of the day you end up with a polished turd


...do it right

[just_opinion]

I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
I have three years in the trade one in school. Mostly walk ins and reach in units in time
The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.

If the building load is 3 tons then change OD unit to 3 tons.

If building load is 5 tons then make sure the ducts can handler at least 1800 CFM, and power is large enough, then change the ID unit to 5 tons.

If the owner said he does not want to change any equipment, then tell him "I ain't no miracle worker and good luck"

[chatenever]

The problem with the "marriage" of a 5T compressor to a 3T evaporator is that the evap cannot produce as much vapor as the compressor can pull, resulting in a lower-than-normal suction temp. A compressor operating at a low suction pressure will consume more kw/ton. If the mis-match is severe, the suction pressure can be so that the saturation temp that corresponds to the evap pressure is below freezing, which can cause the condensate on the evap to freeze up, blocking airflow completely. You can fix that problem by installing an EPR (evaporator pressure regulator) between the evap and the compressor. It will sense the upstream pressure, and modulate closed (creating a pressure drop) to prevent the evap from getting below freezing temp. But you will still be stuck with an inefficient compressor because of the low suction pressure after the EPR.

[Octopus]

So which is sized improperly the evap or the condenser?
Who makes the equipment?
How many cfm's are you moving? Fan in evap set to hi.
If the evap is the correct size and the condenser is the improperly sized component I would pick up the extra sub-cooling/ efficiency and install a smaller compressor in the existing condensing unit.

[HvAckid82]

Sometimes this is done on purpose i.e. dehumidification. What is the reason you got called to the job? What part of the country do you live in? 5 ton with a 3 ton is a bit different compared to what I have run across.

[stevrock]

I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
I have three years in the trade one in school. Mostly walk ins and reach in units in time
The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.

Measure pressure drop across and entering liquid temp of the TXV. Work backwards from there to size a TXV for 3 ton capacity.

You can also bring up the liquid temp entering TXV to decrease capacity. Sometimes that's insulating the liquid line, sometimes it involves blocking off some of the condenser.

HTH

[rlpayne]

If the building load is 3 tons then change OD unit to 3 tons.

If building load is 5 tons then make sure the ducts can handler at least 1800 CFM, and power is large enough, then change the ID unit to 5 tons.

If the owner said he does not want to change any equipment, then tell him "I ain't no miracle worker and good luck"

This only correct 3and 3, 5and 5 it's the only and right way it's always best not to half step...

[BACnet]

Technically I don't see why an oversized condenser is all that terrible.

As long as the compressor, evaporator and TXV all match, the oversized condenser is simply going to be able to shed more heat more easily or at a lower fan speed. You will of course need more refrigerant to fill the larger circuit but in the end you could probably run the condenser fans at a lower speed thus reducing both noise and cost.

What type of compressor(s) are involved? Any issues with keeping enough oil in the system?

[doubleduece]

how to fix over sized unit with banging customer

So this customer is hot!!!!!!!

Or is she
BANGING

[pairman]

is this for HVAC or refrigeration - and is there an actual problem or any symptoms?

[3rdgenhvac]

you can get away w/ a slightly larger evap or txv... condensing unit... sorry got to re-do something.

[will173]

Sorry guys 16 hour days latly. I think I like the covering the condenser Idea sounds very inexspensive idea

[ctcont]

You need to do a load calc on the conditioned space first, if the load is 3 tons get a 3 ton condenser afterall hopefully you did not do it wrong the first time it will help them with humidity control and electric bills , age of equipment? Consider replacing condenser and air handler matched system keeps warrantys

[Greend88]

If the building only needs 3 tons of cooling then just replace the compressor with a 3 ton. Will be more energy efficient anyways, my teacher said he used to do it all the time on residential back before they came up with higher seer units.