Converting a 340 ton Trane RTAA to a 400 ton

[rnr07]

Hey guys,

I know this forum is filled with a lot of knowledge, so I wanted to post this question here.

I have a Trane RTAA 340 ton chiller. This uses (2) 100 ton rotary screw compressors and (2) 70 ton rotary screw compressors. It also has 24 fans mounted on the top.

I also have a Trane RTAA 400 ton chiller. This uses (4) 100 ton rotary screw compressors. It also has 28 fans mounted on the top.

I have some spare 100 ton RTAA compressors and several spare RTAA fans. The coil panels measure the same length both inside and out on the 340 ton and the 400 ton.

What would happen if I were to replace the (2) 70 ton compressors on the 340 ton with (2) spare 100 ton compressors and wire in four more fans into the existing fan areas that are currently capped? Could I get 400 tons of capacity out of it? I understand that the expansion valves might not match up, but they can be replaced.

What would be the major hold-up in doing this?

[servicetrane]

would have to change the evaporator, EXV, oil separator

[Healey Nut]

Just coz you change the engine for a bigger one does'nt mean you will get more power ,
Its all about the package then engines no good if you dont feed it enough air and fuel !!!!!!

[servicetrane]

is not possible to make that conversion, obviously the machine is manufactured to a building, imagine a volvo powered wv

[rnr07]

Just coz you change the engine for a bigger one does'nt mean you will get more power ,
Its all about the package then engines no good if you dont feed it enough air and fuel !!!!!!

graham - That makes sense. If the coils are the same size and same number of passes, and the compressors are the same size, and line sizes are the same, that leaves variability to the evaporator, correct? Trane does seem to use modular parts in their chillers that can be used across similar models but different (yet relatively close) capacities. Would you agree? I'm definitely new to this which is why I came here to get professional input on this.

servicetrane - Thanks

[rnr07]

is not possible to make that conversion, obviously the machine is manufactured to a building, imagine a volvo powered wv

If a direct conversion to exactly 400 tons is not possible, do you think a compressor upgrade along with an EXV change and fan additions would net any increase in capacity at all?

[Healey Nut]

The compressors you have are the same 70/100 ton the difference in capacity is acheived by the length of stroke of the slide valve .

[jayguy]

do you need 400 tons?

the 340 and the 400 are the same frame. but they are not the same condensor so you will have to buy a larger condensor as well. and don't forget to upgrade your electrical breakers and wiring from the power source to the chiller as well as from the contactor(s) to the compressor. the oil separator is probably the same. you will need to buy more contactors and wire them up.

seems like a lot of work for a maybe...if you need more tonnage...maybe look at buying another chiller. if you don't have room for another chiller, it would probably work but it wouldn't be a weekend project!

i like the idea and if you can handle it in-house and if you can't get another chiller...it might be cheaper to 'upgrade' than a buy a new chiller...but then again...you are talking about all of this to gain another 60 tons...i would imagine that you can get a lot of 60 ton chillers cheaper than this upgrade.

[flange]

No manufacturer will sanction this move, however, last year we did do a mcquay. remove two smaller compressors and added two larger ones, new expansion valve, and new hot gas valve. This was done with carefull consideration, a liability waiver signed off by the client, the general contractor, and the equipment supplier. In our case, wiring sizes were okay as well as starters. head went up slightly but not nutso. We didnt have a choice, it was pharma and they screwed up their own load calcs. had to run now. not reccommended at all, but it can possibly work. no guarantees. By the way, I was VEEERRRY hesitant on even trying. damn thing runs like a champ.

There may be a better way for you. There is a company that sells a mister system that uses deionized water at a high pressure to wet the condenser coils to reduce head pressure. This is typically sold as energy savings, but could give you the additional capacity you need. I know that guys will not like this, but it does work, and does not hurt the coils since the minerals are gone. not cheap though.

[Tech Rob]

There may be a better way for you. There is a company that sells a mister system that uses deionized water at a high pressure to wet the condenser coils to reduce head pressure. This is typically sold as energy savings, but could give you the additional capacity you need. I know that guys will not like this, but it does work, and does not hurt the coils since the minerals are gone. not cheap though.

I was thinking similarly. If he was feeling ambitious, he could probably gain a little capacity/efficiency just by adding a couple more condenser fans and giving the condenser coil a thorough cleaning. It'd be less expensive, for sure. How to control them, though?

If there is a 340 ton chiller there, someone probably selected a 340 ton chiller for a reason. My guess is that a system problem is making you believe you need more capacity, when in fact you just need to make better use of the capacity you have.