2.5 ton coil, 5 ton condenser

John Mills_4

I wonder where I got the notion the original was a Lennox. Must be seeing things :(

Johnson did have a horizontal discharge back in the day. 5 ton probably would have had 2 fans.

John Starcher_4

That's what we....

...found the other day. The coil was frozen. We thawed it and restarted the system, but I can not for the life of me understand how it EVER worked. I believe the outdoor unit is a 1973 vintage, and the coil was installed with a new furnace around 2001. I will be doing a heat loss and quoting the proper equipment, but I'm just curious how the installer got this thing to function at all. It was a reputable local firm who did this, too!

don_207

Sounds like

Sound like to me you are giving him more credit then he deserve.

Unless acourse he design the system for more latent and less sensible.Even then he would had to install a balance port txv and adjust it to maintain superheat to save the compressor.

Then you always have people that luck seem to shine down on them where ever they go.

John Mills_4

WOW

Of course a Lennox of 1973 vintage used a liquid line to function as its metering device. So, unless the installer was sorta smart, he didn't change it and when he replaced the coil, put a 2nd meter in the system!

John Starcher_4

As far as I can tell...

...the metering device is an orifice at the coil. I'm still scratching my head!

Empire_2

System was poorly designed in the first place!!!

The first thing you would notice is an almost pmpdown looking situation since the indoor coil cannot handle the amount of liquid being delivered to the metering device, no matter what kind it was. Also the suction pressure should also must have been lo since the recip. compressor ratio is greater that what the A coil can deliver on the back side. Perform your heat gain on the structure and go from there. Ever hear the saying, " You cant put 5 lbs or crud into a 2.5 lb bag"? Same principle applies here. There was no method to his madness, just uneducation at worst. Determine what the blower drive can handle and then if you choose to keep it, design your A/C around that. AS far a latent or sensible goes. throw that right out the window since the 2 components are so far off it would be erroneous readings no matter how you slice it. Sub cooling, Super heat is all irrelevant due to the grossly mismatched coils.

ALso just currious, was the condenser an HS 6 or HS 9? Both were upward discharge on the cond fan motor.

MIke T.

John Starcher_4

Hi Mike,

It's not a Lennox unit. I don't even know for sure what brand it is. The building owner found a bill from 1973 for the installation of a "johnson furnace BTL160 with 5 ton AC unit." It's a horizontal discharge, and the name plate doesn't list a manufacturer, but does have a weird little logo that looks like a J and an F written together, so perhaps it is a Johnson brand. I was able to find some info on the furnace, and it appears that the blower MIGHT be able to handle 4 tons (but this would be a real stretch) if esp is below .3. Not much of a duct system, so that actually might be achievable.

don_207

Live and learn

John.I'm with you..this thing been working for 8 years now.
How? Its time like these when you put on the detective hat and asked the customer is this your first issue with freezing?How has the power bills been? Has it been cooling find up to now.

Often time I do check airflow,superheat and subcool on a system like this.Its the perfect time to find out just how this thing has work over the years.

You would be surpise to find that some guys can do thing way beyond what is discuss in the class and assumed to be the only way to skin a cat.

Example..You come to a condenser and you find it has a bad fan motor.You also find that its a three wire motor.However you only have a four wire motor in the truck.
Could you make it work on a system with a dual capacitor?

John Starcher_4

Oh really?

This unit has a single fan, not two. Maybe it's not 5 ton after all?? The nameplate was very hard to read, but I THINK the model number is CB57PR1-C. Next to that is F37-312797.

John Mills_4

CB57

Sounds like an old Johnson Air Ease condenser. I know the model, newer than the one with twin fans. Just had 1 BIG fan on the front.