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jzsteal14
07-21-2016, 11:53 AM
Just have a question if the suction line size is a little too small would that make suction pressure go up or down?

TACKERDOWN
07-21-2016, 12:47 PM
Restriction, poor oil return

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jzsteal14
07-21-2016, 01:04 PM
Yeah I understand that part but what effect does it have on your pressure ?

TACKERDOWN
07-21-2016, 01:19 PM
On a short line set it don't think it will effect much going from 7/8 to 3/4. But if it's long on a txv it's going to mess with you SC. You suction pressure will be slightly lower and not correspond with the temperature of the txv properly. I'm not positive but I'd think it would effect your amps as well.

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lytning
07-21-2016, 04:06 PM
And increase the HP.

On a short line set it don't think it will effect much going from 7/8 to 3/4. But if it's long on a txv it's going to mess with you SC. You suction pressure will be slightly lower and not correspond with the temperature of the txv properly. I'm not positive but I'd think it would effect your amps as well.

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TACKERDOWN
07-27-2016, 09:06 PM
Well I hope that helped?

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buttwheat
07-27-2016, 11:49 PM
Restriction, poor oil return

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I will disagree with the poor oil retturn. Smaller suction line increased velocity and better oil return

NETWizz
07-28-2016, 12:59 AM
It should reduce the suction pressure having a restricted suction line... Having a restricted liquid line would increase the head pressure.

By the way, you are assumed to be a Tech posting here. You might want to apply for pro membership.

TechmanTerry
07-28-2016, 05:15 AM
In the Rheem/Rudd install instructions. There was a chart that showed the % of lost capacity for the different suction line sizes. I think they still do.

beenthere
07-28-2016, 05:56 AM
Just have a question if the suction line size is a little too small would that make suction pressure go up or down?

Suction pressure will go down, SH will increase. But you'll have pretty good oil return due to the high velocity of the smaller line.

EG: 4 ton R410A.
1-1/8" vapor line has a velocity of 818FPM with a .7PSIG PD, and 259 BTUs of capacity loss per 100'.
7/8" vapor line has a velocity of 1395FPM with a 2.6PSIG PD, and 936 BTUs of capacity loss per 100'.
3/4" vapor line has a velocity of 1939FPM with a 5.7PSIG PD, and 2074 BTUs of capacity loss per 100'.

That is from a York piping guide.

TACKERDOWN
07-28-2016, 08:06 AM
Yes it would be good to disagree with my statement. I kinda got hung up on just a lower suction pressure and not the fact that the smaller line was the root cause.

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