I recently installed a brazed plate chiller system using 8 15ton 06D compressors. The discharge line size from the manufacturer was 1 1/8". Manufacturer guidelines called for an increase in line size to 1 3/8" if line distance was more than 50 ft. I used a coupling to make the increase in line size at the discharge service valve. Upon completion the customer asked me if line size really mattered since there was still 6 inches of 1 1/8" line off the discharge valve. I would like to know if this is a problem. Been running for few months with no problems yet.
You'll be fine. As long as you follow the manufacturers' suggestions the worst that can happen is THERE fault. They're rarely wrong.
The fact is that you increased the line size to accomodate VOLUME, not pressure. You did what they told you to do, so you won't have problems with that.
Yes, you probably could have gotten an 1-3/8 service valve, but I would've done the same thing in your case. The only thing a bigger service valve would've done for you was to shut up the customer.
Yes, the line size matters, but remember, the hole on that O6D that you bolted the service valve to isn't 1-3/8, nor is it even 1-1/8. More like 3/4. The long run of pipe, in 1-1/8 cannot carry the volume that an 1-3/8 can, so the pressure drop in that run would've increased with the smaller pipe.
Increase the pressure drop in a discharge line, and you increase the discharge pressure, right?
Now, when you increase the discharge pressure, what else do you increase?
The discharge temperature.
What happens when the discharge temperature is over 350 degrees?
Yes! That's correct.
You break down the oil.
What happens when your oil breaks down?
You got it!
It turns to acid.
What does acid do to the motor windings in that expensive compressor?
Yessir, it wrecks them.
Feel free to print this out and show that customer that doesn't think the 1/4" line size difference matters.
You saved them a $4000.00 breakdown.