piston size

[craigbhvac]

I just installed a new 2 1/2 ton condensor to an exsisting 3 ton coil. The three ton coil has a number 63 piston.new cond says to use a 68 piston with a three ton coil.what will happen if i do not change piston will it not cool and will my suction be higher than normal?Basicaly unit runs all day was 85 out the other day never got inside under 78 old unit cooled nice before cond replaced.(the orig cond was a 2 1/2 ton) thanks craig

[Chill]

With all things being equal........no, to both questions

[hvaccolo]

I always oversize the evap coil like that (in Denver) due to altitude and extremely dry indoor air...works much better mis-matched like that. Always use the piston from the smaller condensing unit.

[appltech1]

Originally posted by Chill
With all things being equal........no, to both questions

Da noes have it all things being equal.

[mdman]

Toss the piston in the trash and install a TXV so it will work. Unless you live in a world where the outdoot DB is constant over the course of the day and the evaporating coil heat load never changes (i.e. Entering WB constant, TESP constant,...)

mdman
The fight against fixed metering on all variable lift refrigeration applications.

[turtle]

Originally posted by craigbhvac
I just installed a new 2 1/2 ton condensor to an exsisting 3 ton coil. The three ton coil has a number 63 piston.new cond says to use a 68 piston with a three ton coil.what will happen if i do not change piston will it not cool and will my suction be higher than normal?Basicaly unit runs all day was 85 out the other day never got inside under 78 old unit cooled nice before cond replaced.(the orig cond was a 2 1/2 ton) thanks craig

this is Turtle.

Story time.

i had this chevy truck that run good till one day i was driving down the freeway and the engine just exploxed and went all to pieces. I got a new long block and replaced the engine , but I got a little better long block which should give me a little more Horse power and burn less gas. i think they called it a 13 series or something and my old engine was a called a 10 series something. I installed the new engine and everthing went well but when I started to change the fuel injectors out which was 63 type injectors to put the new 68 series type injectors in it for the fuel to be spraied into the each cyclinders . They were stuck and I just left the old ones in there. I just left the 63 type injector in it and did not think it would hurt anything at all to not change the injectors to the new 68 type injectors that come with the engine which was called for by the maker of the engine.

Then got it a going and took it out on the freeway and run it up to 70 mph and found it would just have lack of power at that speed and when the engine heated up to normal temperature it got worst. I took it back to my shop and have done everything to it to try to make it stop having this lack of power at 70 mph and when it warm up to normal temperature it got worst. i'm at my witts end and just give up.

So i took it to the mechneic shop and left it for him to fix it. he called me back and told me it would $500.00 to fix it and i never ask him what it was but I just told him to fix the damn thing. then when i when to pick it up and paid him for it. I took it out on the freeway and hey that thing run like lightening. I think it had way more horse power and get up and go. i rode for hours getting down on it to see it haul A** . then i went home to eat supper.

Then that nite I was sitting watch TV and seen the bill for the work from the Shop on the TV stand and a description of the work done. It said we change the old type series 63 series jets out and put the 68 series jets like it was suppose to have in it and said cost me $500.00.

Holy Moses , i should have change the jets out like the maker of the engine told me to do but I did not think it would matter at all .

Does this story have any likeness to the problem your having with your hvac system right now ? Naw , it can't be any help here , them #63 jets will work fine and make no difference at all.

TURTLE

[BaldLoonie]

The new condenser may say to use a #68 but that is with their coil. Whoevers coil it is may want a different piston for the same size outdoor unit. So no idea what is right. Who knows what capacity & SEER you're ending up with.