Temperature drop across filter drier

charliechicago

Hello to all,
What is the acceptable temperature difference across a liquid line filter drier?
Thanks

SuperTech

I'm pretty sure you have a problem if you have 2 degrees or greater.

EBEBRATT-Ed

any td probably means the drier is plugged

pecmsg

> @EBEBRATT-Ed said:
> any td probably means the drier is plugged
Or plugging

Big Ed_4

If you see frost after the filter dryer it's time to change ....

JUGHNE

If feasible, is it seem good sense to keep the old drier in the line to pick up as much as possible, then change the drier out?
This would put most of the nasties in the old one and preserve the new one somewhat.

GW

J, you don’t want a restriction

SuperTech

Always remove the old filter drier. Usually if its located outside or in the condenser I'll replace the original drier with 3/8" copper and relocate the new drier at the indoor unit, as close to the metering device as possible.

JUGHNE

Yes, I know no restrictions and to change it before it becomes detrimental to the operation of the system.
But if it is filtering with little pressure drop incurred would it not be best to let it do it's job as long as possible before changing.

Isn't it normal for suction line filters to have a 1-2 PSI drop before change out. And that is for only about 1/3 of LL pressure.

We would not replace the $30 air filter if only slightly dirty.

But I am thinking small town where the service call may be only 5 minutes away. I understand the nature of larger cities where you want to have no call backs.

pecmsg

If done properly a filter drier is not needed. With that said it is cheap insurance. Suction filters are a different deal all together.
$30 air filter?

ChrisJ

pecmsg said:

If done properly a filter drier is not needed. With that said it is cheap insurance. Suction filters are a different deal all together.

$30 air filter?

It's allegedly impossible to get all of the moisture out of a system and the desiccant in the drier removes the little that is left after vacuuming. This is said to be a huge issue with systems running POE oil.

That being said, 1920s-30s Monitor Top refrigerators did not have a drier and I believe the SO2 ones would self destruct if moisture was present and most are still running fine. So, I don't know. Believe half of what you see and none of what you hear?

My 20x25x5" AirBear runs me about $30 shipped.

mattmia2

A tiny amount of moisture in a monitor top would find something to make a sulfate with and stay out of the way. More than a little and it would become a problem.

JUGHNE

I agree LLFD not needed with perfect system.
I install one with every system 99% of the time, because I know I'm not perfect.
But not cheap to change an existing one......my point is to milk it for all it is worth as it could be picking up scale from brazing without N2 flowing (by others, of course) if feasible.....again the call back situation is not a major concern for me.

I do charge 25 for the air bears. Good mark up. I buy at least 6 at a time. Try to include them with a truck shipment so the freight is not an issue. They take up a lot of shelf space. I even deliver them and sometimes change them for certain people. Usually last 1 year.

ratio

Some of the big VRF systems don't have filter/dryers, just screens. & that's with 100+ lbs charges. IIRC even the Mitsubishi Mr Slim (mini split) doesn't have a filter/dryer. I was scrambling once, looking for it on a warranty outdoor coil change out!

ChrisJ

Every system should have a filter drier and not a cheap bead type, a solid core.

ratio

I've installed $50-100k VRF systems without them, & the mfgr blessed them with extended warrantys. Part of it is a 4-600# pressure test, part is holding under 500µ for hours; part, I think, is the oil. But filter/dryers are not permitted.

pecmsg

> @ratio said:
> I've installed $50-100k VRF systems without them, & the mfgr blessed them with extended warrantys. Part of it is a 4-600# pressure test, part is holding under 500µ for hours; part, I think, is the oil. But filter/dryers are not permitted.

Or required

Or allowed
!

unclejohn

he was not talking about VRF units. Just your good old split system. So Any temp drop is not good and no you should not wait for the dryer to restrict flow to the point of frosting the liquid line on the outlet side. If you have a wet system use flare dryers and change them out every 24 hr's untill you get a dry sight glass.

GW

On a new install (new copper), we are installing the dryer outside, don't care what the instructions say. Aint hauling a torch into the home if we need to open the system down the road.

ChrisJ

> @GW said:
> On a new install (new copper), we are installing the dryer outside, don't care what the instructions say. Aint hauling a torch into the home if we need to open the system down the road.

We put mine up in the attic just before the sight glass when we cut the OEM one out of the outdoor unit but honestly as long as you work clean I'm sure it doesn't matter.

The 5 ton unit I just did has the OEM one outside.

Big Ed_4

The problem with installing them outside in the North East , they are made out of iron and rust out ... I understand the fear of a torch up in the attic but the torch will be up there anyway. Any of my jobs get plywood to work on and to service if filed or not ...

EBEBRATT-Ed

My thinking with driers is if they are plugging they need to be changed. Whatever is plugging them is stuff you want to remove from the system and get it gone.

Driers can break down and release stuff. I have seen Alco pellet driers break down had a liquid line full of pellets

unclejohn

In front of the metering device is where they belong. And I have seen lots of dryers rust through and leak. I'm sure @GW is anything but lazy but thats what I attribute dryers outside too.

JUGHNE

I use a lot of flare LLFD. Inside or out, the logic being is not getting torch out.
The little commercial refr I do all has flare fittings.
You can usually isolate them with valves. Then change them with a little vapor charge flowing to purge any air.

I watch a lot of Utube's of refrigeration, most use flare fitting LLFD and sight glass's on the roof to avoid the torch returning up there.

Big Ed_4

It sucks bringing anything up to Tar Beach ... We have to carry the most tools on and off the jobsite then every other trade ...

EBEBRATT-Ed

@Big Ed_4

LOL Lot's of buckets and a rope, use the bucket handle as a pulley on the way down with the rope doubled up top,

Going up, a hook on the rope and try and get all the buckets at the bottom of the ladder with the handles sticking up.

But, I am sure you know that. Still, it's a lot of climbing. Then you get to trek across miles of mall roofs.

Some won't let you use a hand truck with pneumatic tires on the roof which I think is crazy. Some long hard days when you work alone and it's 95 out

Tar Beach........Love it But Tar beach is better than Rock Beach

mattmia2

Big Ed_4 said:

The problem with installing them outside in the North East , they are made out of iron and rust out ... I understand the fear of a torch up in the attic but the torch will be up there anyway. Any of my jobs get plywood to work on and to service if filed or not ...

It seems like if the environment is harsh enough for a painted filer/dryer to rust enough to be a problem it is going to be even more of a problem for the cabinet of the condenser.