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Latte
28-10-2004, 07:53 PM
Hi Guys,

When does a/c become refrigeration and vice versa :confused:
Why do i ask :confused:

Today i got called to a celler cooler in Norwich which turned out to have a seized compressor

The condensing unit is a Eaton Williams, J 97643-02 S/N Q08591 2003 :confused:

Now the compressor is a L'unite Hermatec RK5515C R407c 240v which according to the NRS book is an a/c pot

Now the system is much like an a/c system, boxed indoor and outdoor unit. all that has to be done is pipe and wire between them. No drier.

Which brings me to another question, why do a/c units never have driers on them. Bi-Directional one's readily available from all stockists.

I have asked the office to quote for a pot, liquid & Suction driers as the unit is cool only and the reclaim and use fresh gas.

So many questions, too slow typing speed

Regards

Fatboy

Brian_UK
28-10-2004, 08:04 PM
A lot of packaged a/c condensing units already have driers built into them - they're not big but are there - more like a cap line drier size.

Latte
28-10-2004, 08:13 PM
Hi Marc,

Remember, it is me you are talking to


AC compressor viscosities of 62 centistokes is fine for saturated evaporating temps around the 0C mark.

Warmer refrigerant temperatures tollerate higher moisture PPM's.


Can you translate this from technical director level to basic engineers level :D

Thanks

Ray

rbartlett
28-10-2004, 08:58 PM
eaton williams bought the remains of qualitair (my first employer)

their cellar cooler (used to be QKK -err 'qualitair keller kooler')
was basically an air conditioning condenser with a different (noisy) evaparator..

anyway all a/c's have a drier but it's a tiny copper spun one..

I remember when the japanese first came over and we used to see loads with a drier -plus a sightglass- fitted in the expansion line

cheers

richard

Latte
28-10-2004, 10:56 PM
Hi Guys,

Thanks for the replies, so what is the consensous of opinion on the drier front.

I am tempted to fit one with a sightglass on the liquid line, anyone disagree with this

Regards

Raymond

frank
29-10-2004, 01:19 PM
Which brings me to another question, why do a/c units never have driers on them.

On most (recent) A/C units the expansion device is on the outdoor unit to save space on the indoor unit and the liquid line between the outdoor shutoff valve and the indoor unit is part of the evaporator. Therefore it should not have a drier or sight glass installed in it. ;) This is another reason why you will see both the liquid and suction lines insulated on air conditioning split systems.

Does your outdoor unit have an EEV or capillary? If not then you can safely fit both a drier and sight glass. A sight glass fitted after the metering device is just a waste of 's. :D

chemi-cool
29-10-2004, 02:12 PM
Hi Raymond.

In the manufacturer catalogue, you will see for each compressor model, the minimum evaporating temp. This one can go as low as -10C (evap. temp.)

It is not important if you call it refrigeration or AC, its the working conditions that count.

According to the manufacturer, this is an AC compressor and its the firs time I've heard that it is used for refrigeration.
AJ 5515C or AJ5518C will do a better job depending on your evap. temp.

Chemi :)

Brian_UK
29-10-2004, 06:56 PM
I am tempted to fit one with a sightglass on the liquid line, anyone disagree with this

I don't know this unit but it all depends on where the expansion device is. If it is at the evaporator then by all means go ahead with your plan - if it is at the condensing unit then your sight glass will never be full and some idiot, at a later date, may try and charge to a flooded sight glass :eek:

Latte
29-10-2004, 09:23 PM
Hi Guys,

I cannot remember see a metering device on the outdoor unit.

I will get a drier and sightglass just in case and will also check the evap just to make sure there is either cap tube or an expandion valve inside.

regards

Fatboy

chemi-cool
29-10-2004, 10:37 PM
Hi Raymond,

I do not believe that a manufacturer will not put as a standard equipment, a drier and sight glass.

What I do believe, is that the person who installed it at the first place, didn't.

If there is a cap tube, you will see the drier just before it.

In AC splits, there is no drier and many people, by mistake, think that what they see before the cap tube is a small drier. It is not. What it is, is a very fine filter to keep the cup tube clean.

Chemi :)

frank
30-10-2004, 05:36 PM
Not quite true Chemi. See this link http://www.spincometal.com/mp_driers.htm :)

chemi-cool
30-10-2004, 06:13 PM
Thanks Frank.

I have learnt something today.
The local manufacturers do not use them.
I have this practice that when a cap tub is blocked, the first thing I check is that filter. Never saw anything else but the fine mash inside.

Every day you learn something new! :)

Chemi :)

P.S. Isn't it CELLAR?

Abe
30-10-2004, 06:45 PM
Marc

Next time God is dishing out the brains............please dont be selfish, leave a little for " us" as well !!!!

Peter_1
30-10-2004, 08:33 PM
Not quite true, Chemi. I am one of those who was born knowing all, forgetting a little bit more every day.
Then we're two. :D

norcool
30-10-2004, 09:49 PM
Hey folks,interesting discussion ,if you have a cap tube and
and increase volume after the condenser you will move the
balance point for the amount of refrigerant you should put
there,its important to have the right condition to inlet of the
cap tube,because of the two-phase flow calculated by the
factory.If this is an old secondhand compressor you better
check for acids by oiltesting and choose a small laying filter
which take care of acid/water.I dont try to learn you something you know, I am only interested in subjects like this.
Have nice day! norcool

eggs
30-10-2004, 11:31 PM
when God was giving out brains, i thought he said "trains" and i said "give me a slow one, that goes chug chug."

cheers


eggs

eggs
30-10-2004, 11:43 PM
you got it, tiger.

Brian_UK
30-10-2004, 11:48 PM
Then we're two. :DListening to you two reminds me of the old poem:-

There's none so queer as folk dear
except thee and me,
But you're a little bit funny yourself. ;)

eggs
30-10-2004, 11:59 PM
i'd watch it if i were you, cos i know a poem aswell.
Roses are red
Violets are blue
i used to be schizophrenic
so did i.

cheers

eggs

frank
31-10-2004, 04:54 PM
Every day you learn something new!

If only the young lads (and Marc :D :p ) would accept this. Instead, they think they know it all. Come out of college with the NVQ2 and think they know everything. Won't listen, get co*ky and give you an ear full if you try to help. :(


P.S. Isn't it CELLAR?

Quite right Chemi :)

chemi-cool
31-10-2004, 05:19 PM
Hi Frank,

It takes years to understand that to say you do not know something and asking for explanation is the best and quickest way to learn!

We all was different when we were young.

The biggest task of us grown ups is to try and help those young ones who "knows it all" to learn how to take one step at a time. That is, if they are keen to learn.

Chemi

Latte
05-11-2004, 06:56 PM
Hi Guy's

Just to report back on the original job. Went back today, checked the indoor unit and it was a Qualitair/Eaton Williams unit with cap tube in the indoor unit so i changed the pot, cut the pipes coming out of the condensing unit and fitted a liquid drier and sightglass and also i suction drier. Vac'd and charged all OK. Original unit charge 1.1kg but a very long pipe run and it ended up taking 1.8kg. Sightglass clear & pressures spot on.


Regards

Fatboy

Brian_UK
05-11-2004, 11:25 PM
Oh oh! :)

I hope the outdoor unit has an accumulator :)Now don't do that Marc you'll be getting him all worried.

He's using the liquid line drier as a receiver and the suction line drier is propably oversized to act as the accumulator;)

Latte
06-11-2004, 12:09 AM
Hi Guys,


Now don't do that Marc you'll be getting him all worried.

He's using the liquid line drier as a receiver and the suction line drier is propably oversized to act as the accumulator;)

You must be confusing me with someone who gives a #### :D

For the record, at 1.1 kg the unit was going out on LP due to one of them stupid solder in preset things hence i added an extra 0.7kg.

The unit is in a large hotel, the outdoor unit one end, the cellar the other. 3/8 discharge, used 083s drier as system smelled burned and wanted to put a fairly big one on and a 165 suction drier (Sporlan of course :D )

regards

Raymond

Gary
06-11-2004, 11:23 AM
A clear sightglass on a cap tube system is cause for concern. It probably means the system is overchanged.

This is why cap tube systems should not have a sightglass. When service techs see a sightglass, they want to clear it.

Latte
07-11-2004, 05:59 PM
Hi Guys,

Popped back in today to check unit now it's had time to get the temp down in the cellar.

Pressures still spot on but sightglass only 1/2 full. didn't put any more gas in following garys post.

can someone tell me why you shouldn't put a sightglass in a cap tube system

Cheers

Raymond

frank
07-11-2004, 09:50 PM
Hi Raymond

The cap tube is a fixed expansion device and does not meter the refrigerant as you would get with a tev as the load changes. The whole point of a sight glass on a system with a tev or eev is that you can check the quality of the liquid refrigerant feeding the expansion device. What you don't want is bubbles ( a mixture of liquid and vapour) as this will lead the valve seat to wear prematurely, and make it difficult to fill the evaporator correctly.

With the cap tube the refrigerant can only feed the evaporator at a set level no matter what the load is. You should charge a cap tube system based on the superheat only. At different stages of the cycle when the system is charged correctly you will get varying levels of refrigerant quality feeding the cap tube and with a sightglass you will see different things at different times of the cycle. If you charged the system to a full sight glass at, say, pull down, then at low loads you will be overcharged and this will put extreme pressure on the compressor. As cap tube systems are small this will lead quickly to compressor failure. :eek:

coolkev
08-11-2004, 05:35 AM
:cool: i somtimes wonder wether some people went to trade school maybe they forgot or wagged that day. Cap system is critical charge it will starve a hot coil and definetly not show full glass s/g on cap system waste of money either start from scratch and add manufactures quantity or ref. This will only be problem if system has been altered in some way. Most usual prob occurrs with comp change if not exactly the same comp if is diff brand but capacities add up exact or nearly exact it still can b prob as the dont all rate them quite the same. If in doubt u have to spend the time to check operation at or very near to cycling temps by checking super heat or frost line or sweat back depending on system. due to these generally smaller herm comps u dont want flood back and if that horrible R22 u dont want too much superheat.this is y most mech much perfer auto type expansion devices quicker and easier to charge. Those who did apprenticships doing domestics know which is the easyer by far to work on commercial much easier

coolkev
08-11-2004, 05:50 AM
:cool: IN REGARDS to drier or strainer in spun cu ive seen both u have to ask manufacturer or cut it open.