One of the ways to start your leak check process – and I highly recommend this – is to start the PGM beforehand, let it warm up, and get
it ready before you walk into the building. One of the processes for leak checking would
be checking the open-front cases. And the best way I’ve found to do that is what I call
the “drop and stroll” method. And here’s an example of open-front cases.
What I’ll do is, is I’ll stick the probe down inside the case and it takes about 5 seconds
for the information to get to the leak detector. I’ll walk down a couple of feet and probe
again. If it would go off here, I would go back to
where I was 5 seconds ago, and start checking in earnest. So basically it is a very quick
process. Don’t stick it all the way in to the bottom in case there’s water or debris
in there. But you move about 4 or 5 feet ahead of time probing into the case and see if you
have any errors. If you encounter any significant gas – 2 PPM or more – I would strongly suggest
that you start looking in earnest for what
might be a major leak in the case.
Always keep in mind that leaks are going to
be at dispersion. So, 2 parts per million in the front of this case could be a much
greater leak as the air mixes and disperses throughout the unit. So any gas at all is
an indicator that you have some kind of leak in process. More leaks occur in these meat cases than
anywhere else in the store – it has been my experience. And it’s a very simple and easy
way to check these. Essentially, what I do is – if I have to I’ll
set this down and then just open the front edge a little bit and let it get a good whiff
inside that case. If there’s any leak at all, it’s going to be at dispersion inside these
cases, and you’ll find it very quickly this way. If you find any leak at all, it’s best to
go a couple of feet at a time. And you can watch the PPM value increase as you get closer
to the leak. So, any hits? I start looking in very close
detail — a couple feet at a time, and I can detect within two feet where this leak would
be and what pans I have to pull in order to get down inside of it to find whether it’s
a cracked coil, or brazed joint, or something like that. As I move down the cases, I just probe in
the front panel here to see if there’s any leaks. Keeping in mind that it takes five
seconds for the leak to get to the instrument, so when I get a hit, I’ve got to go back where
I was 5 seconds ago. Same thing here. Dunk it in. Walk down a few
feet. Use a verification process by checking the
supply air also. Any refrigerant is going to be mixed in there in dispersion and come
out through the supply and you can verify your lower checking periodically checking
that supply air. The drop and stroll method also applies to
these cased freezers. And, what I’ll typically do is open every third or fourth door, drop
it in the grill in the front, and one of the things you’ll notice – nice feature about the
PGM is it does not go off to hot – it does not go off to cold – it only goes off when
it senses refrigerant. So, I’m gonna do the drop and stroll and we’ll
see if we have anything in these cases. So, I’ll usually start with the first door
and then move down to the third or fourth. That’s all the longer it takes. And, I just got a hit on refrigerant. You
can see how quickly the unit responded. A maximum PPM value of 287, which indicates
there’s a pretty good size leak in these cases. So, you can see when I came out into the ambient
air, the detection dropped. I’m gonna walk down a couple more case doors and see if I
get any closer to the leak. Okay, that value is a little, tiny bit lower. Okay, that’s about the same. Okay, I’m up to 390 now. So I’m getting a
little bit higher. 478. Okay, now I’m down to 378. So the leak has
got to be in this area right here. This is where my highest value was as my readings
increased from starting at the other end. At this point, I recommend that you shut the
fans down and put this unit in defrost. The fans right now are mixing that air and it’s
dispersing the refrigerant. Even though I can tell I have a higher concentration level
here, I can’t pinpoint it as long as the fans are running. So once we shut the fans down and put it into
defrost, we’ll be able to isolate and be able to detect within a couple of feet of where
we need to pull the pans to start looking for that cracked fitting, brazed joint, or
whatever is leaking inside these cases. One of the tips you want to take notice of
is if you look up above me here, this is where the line sets are coming down, and the
propensity for leaks are multiplied by where all the lines come in and come in to the back
of these cases. So, it maybe just a coincidence, but this
is one area you want to check very closely when you start getting leaks picked up in
these cases. Testing on coffin cases actually needs to
be done in two places. Since these are fed by a pit underneath of the unit, one of the
best ways to start is to just kind of troll around the outside of it with your probe. And try not to get it too full of dirt. But
just kind of go around the outside of it and if you find anything leaking from underneath,
you’ll be able to pick it up pretty quick. The other way to test these cases is pretty
much like the drop and stroll method. I’m gonna check the front here, and I’m also gonna
check the supply air in the back. I’m going to zig-zag my way down this case. See
if we have anything pooling in the front or coming out of the supply in the back. Once again, any hit at all is a bad thing
because we shouldn’t have any gas in there. And this case is nice and tight. Testing in the walk-in freezer is pretty simple.
We’re just gonna walk in and we’re gonna check both low and high for any leaks. Once I enter the freezer, I’m gonna let the
probe down near the floor and also reach up into the air circulation and in the higher
places you may want to get a ladder to get closer to these. But, either one of these
is gonna tell me very quickly if I have gas in this room. It’s gonna pool low and be stirred
up by the fans at the higher levels. Well, we walked in and immediately got a hit.
So, we have a leak somewhere in there. The same thing pertains as does to the other cases
– you’ve got to shut the fans off if you’re really gonna be able to pinpoint it, so let’s
walk back in again and see what we have going on. Now, keeping in mind that this only responds
to refrigerant, so it didn’t go off false alarm from the cold, it’s picked up actual
refrigerant in this freezer. The higher concentrations are gonna be near
the floor again, and you can see the readout as our beep increases we have about twelve
PPM background in here. And we can also check the air flow from above, but to be able to
check this thing correctly, you would need a ladder to be able to get up and probe all
around these cases, the expansion valve, and entry tubing, and things like that. The detection level in the freezer was constant
– all the way up and down – which means it’s just been in dispersion – those fans are stirring
it up pretty good in there. So you really do have to shut the fans down and put it in
defrost to check with that high pressure refrigerant exactly where those things are gonna be. This freezer is clear. I can get a good sense
by, once again, by placing the probe near the floor. If there’s any refrigerant it’d
be pooling in here. And also I like to get
up into the air flow to see if there’s anything
floating around. Once again, a ladder would
be helpful to get closer to these – especially
if you do detect refrigerant. Alright, we’re in the bakery department doing
leak checking, and one of the things you want to keep in mind is some of the release agents
that are used on the baking trays have a propellant in it which is very very similar to 134A.
Right now I’m reading just a little tiny bit background. And I’m gonna spray some in the
sink and show you what can happen so that you know that this could actually set off
anybody’s leak detector because it is a refrigerant-based propellant. So I put a little bit of propellant in that
sink. I’m gonna stick my leak detector down in here. Take a good whiff, and then we’ll
watch our leak detector as it responds. I got
actually got four parts per million, now it’s going back down as soon as I can out of the
sink. So you can get a false positive – well it’s
not really a false positive, because it is refrigerant. So, keep in mind that your leak
– your pan release could be giving you a leak signal. I’m gonna check the bakery freezer since we’re
in here, to see if we have anything going on in there. I check both high and low, and, not to our
surprise, we got the same background we got from the pan release because we’re storing
baking pans in there and they have that same refrigerant in it. So, that’s not a false positive, once again
we have refrigerant, but it’s actually come from our baking spray and it doesn’t indicate
that that’s a leak since we had the same level of refrigerant detection. Ambient and in that
room. Just to be on the safe side, once a year,
you ought to verify that there isn’t any leak in there by pulling everything out, cleaning
the baking pans out, and checking for leaks in this room.