electronic sight glass

[Kevin S]

I'm trying to find a system for a typical supermarket multiplex system that will generate an alarm when a gas leak has occurred. I have thought about electronic sight glasses, but I think these will give a false reading when the condenser fans cycle on and off and the liquid level changes slightly. Ideally I want a system that will detect a fairly small loss of gas and link automatically to the remote alarm system. Any ideas or experience with such systems?

[Gary]

This can be extremely difficult. The liquid level in rack systems can fluctuate considerably, and various problems can have the appearance of undercharge.

Insufficient airflow through evaporators (fan motors out, incomplete defrost, etc.) can cause extra liquid to be held in the coil(s).

A burnt out SORIT valve coil can block the suction flow, causing the effected coil to fill with liquid.

Heavy load will use more refrigerant.

Blocking valves (flowcon, et. al.) change the liquid level.

Faulty equalization can hold liquid in the condenser.

Probably the most reliable measure is pumpdown level, but even this can fool you.

[botrous]

Never heard of such device , i'll do a search after i come back from a friends wedding and the c_o_k_t_a_i_l after it ,
ps:c_o_k_t.... was written like that because of the word sensoring policy of the forum , the word contains no offense but when written attached like this (c.o.c.k.tail) all waht will appear is ****tail
c ya
best regards

[frank]

I'm trying to find a system for a typical supermarket multiplex system that will generate an alarm when a gas leak has occurred. I have thought about electronic sight glasses, but I think these will give a false reading when the condenser fans cycle on and off and the liquid level changes slightly. Ideally I want a system that will detect a fairly small loss of gas and link automatically to the remote alarm system. Any ideas or experience with such systems?

A static monitoring system is quite common. Have a look at a few of these
http://www.aquilar.co.uk/refrigerant.php
http://www.parasense.co.uk/parasense...detection.html
http://www.tqplc.com/main.php?nav=50...ZWK1MSU4OKI71T
http://www.bacharach-europe.com/prod...rigeration.htm

[Kevin S]

Thanks a mil guys. I will check out the sites shortly. Gary I think you are right about the variations. I have also considered programming the rack controller to do a a pump down at regular intervals (say every 8 hours) and check the receiver level with an infrared sensor (Henry/Ac&R type). later..

[botrous]

Thanks frank , you spared me from the search and here are the links i was searching for . . . . thank you

best regards

[botrous]

Hi again Frank ,,,,, how are you doing ?
I've seen those websites , really thanks those were useful at least for me .
I'm interrested in the bacharach and the aquilar one , as i understood from their explanations sensors should be installed near where the refrigerant leaks are expected as tubes joints etc , my question is , did you ever used those products ... is it accurate ? and how much it coasts ?

[vaidas_78]

I work with "parasense" leak detection systems and they are really usefull.
It will not replace your hanheld leak detector, but will show you whereabouts it is leaking.

[botrous]

vaidas , welcome to the forum , can you post more details about the parasense , because using their website , i couldn't find any useful info , maybe it's because of me because i was stressed , i had a friends wedding and you know drinking and dancing . . . i will look at the parasense website again tomorrow to see what i can find

c ya

[Peter_1]

We always install Murco from the UK and are very satisfied with their products.
Not that expensive to.

But we installed also in the past a small vertical brass cylinder with a glass tube in it and a float inside the glass. On the outside was a reed switch. As long as their was plain liquid, the float floated on the upside of the liquid level. When bubbles appeared, the float felt down.
You must be sure that there is always enough subcooling, otherwise it will generate false alarms
As soon as I'm back at this client, I will take a picture of it.

[Kevin S]

Hello Peter. A pic will be great. Does the glass tube fit onto the receiver or onto the liquid line?
Tks, Kevin.

[malik55]

Kevin
Electronic sight glass will not work as what you was thinking because it is a field instrument to detect the refrigerant flow in the lines externally and is not a refrigerant leak detector, What you need is a continuous duty refrigerant leak detector.

[Kevin S]

Hello Peter, A pic will be great thanks. Does the glass tube fit onto the receiver or onto the liquid line? Thanks Kevin.

[Kevin S]

Thanks Malik, do you mean an electronic gas sensor, as those on the suggested websites above?

[Peter_1]

This can be extremely difficult. The liquid level in rack systems can fluctuate considerably, and various problems can have the appearance of undercharge.

Probably the most reliable measure is pumpdown level, but even this can fool you.

On a pack, we pump down the whole system each night just above atmospheric pressure.
After the 1st pump down, we let the pressure rise again till 1 bar and pump down again.
We repeat this cycle 3 times.
The last time we wait 1 minute and pump down the last time.
We then wait 1 minute and measure then the level in the vertical Bitzer receiver with a special Bitzer sensing device which is mounted above on the receiver.
We store this value in the memory of the PLC.
If we see a progressive descending level after some days, we trigger an alarm.
On 4 crucial places is also a Murco gas sensor installed.

Have a look at http://www.bitzer.de/_doc/d/dp-300-6.pdf on page 9.
We after wards open all the magnetic valves for 7 minutes so that the main line has at least once per day full velocity as calculated to ensure oil return.

[botrous]

Peter , you are pushing my curuosity to the edge . . . . . i can't stop reading anymore . . . i went to store that sells electronic compenents and asked for parallax , remember the one you adviced . . . they will be able to deliver me printed books in a week . . .
Now you are pushing me to a lot more different field . . . i like that

Best regards

[malik55]

Yes Kevin,
Also vist these site you will get some more information on ref.leak detection systems
www.sentechcorp.com
www.toxalest.com
www.automatedbuildings.com
www.murco.com

[Peter_1]

..........;

[botrous]

the post was transfered to the "what's the problem threat"

Best regards

[Gary]

On a pack, we pump down the whole system each night just above atmospheric pressure.
After the 1st pump down, we let the pressure rise again till 1 bar and pump down again.
We repeat this cycle 3 times.
The last time we wait 1 minute and pump down the last time.
We then wait 1 minute and measure then the level in the vertical Bitzer receiver with a special Bitzer sensing device which is mounted above on the receiver.
We store this value in the memory of the PLC.
If we see a progressive descending level after some days, we trigger an alarm.
On 4 crucial places is also a Murco gas sensor installed.

Have a look at http://www.bitzer.de/_doc/d/dp-300-6.pdf on page 9.
We after wards open all the magnetic valves for 7 minutes so that the main line has at least once per day full velocity as calculated to ensure oil return.

That sounds like an excellent procedeure, Peter. I assume a time is chosen when no systems are in defrost?

[frank]

Hi Botrous

Yes we have used these types of static gas leak detectors. We have a couple of R407C chillers with multiple sensors fixed all around the unit by the manufacturer (Dunham Bush) and these stop the machine on alarm.

We also have them installed on VRV jobs to comply with BS4434 (EN378) http://www.aquilar.co.uk/at_rga.php.

I attended an alarm situation once at a customers and spent a couple of hours with a "sniffer" looking for the leak before I noticed that the whole office had just been re-carpeted. It was the fumes from the carpet glue that set the alarm off !

[botrous]

Hi Frank , how are you doing ?
Thanks for the informations . . . this leak detection thing interrested me , because i have a big potential applications for it , we recently installed an air conditioning system for a hospital and the hospital technical department is asking for the highest technology so , i will let them see that and maybe they want to implement that system in their newly installed air conditioning system , sure i have a lot more of research about this subject to do , to get more familiar about it , but the journey start with one step

[Kevin S]

On a pack, we pump down the whole system each night just above atmospheric pressure.
After the 1st pump down, we let the pressure rise again till 1 bar and pump down again.
We repeat this cycle 3 times.
The last time we wait 1 minute and pump down the last time.
We then wait 1 minute and measure then the level in the vertical Bitzer receiver with a special Bitzer sensing device which is mounted above on the receiver.
We store this value in the memory of the PLC.
If we see a progressive descending level after some days, we trigger an alarm.
On 4 crucial places is also a Murco gas sensor installed.

Have a look at http://www.bitzer.de/_doc/d/dp-300-6.pdf on page 9.
We after wards open all the magnetic valves for 7 minutes so that the main line has at least once per day full velocity as calculated to ensure oil return.

Hello Peter, this an excellent suggestion. I must tell all of the members of this forum that I only stumbled onto this Ref Eng web site on Friday last week and I am really blown away by it. The advice and experience shared is amazing! Thanks to all - Kevin S.

[frank]

Thanks to all - Kevin S.

You are welcome Kevin.

I hope that you also will be able to share your experiences with us.

[Peter_1]

Sorry Gary, just saw now your post.

Well, we only do this with pack systems. But even if they're defrosting, all the liquid will be out of the lines when performing this test.

We pump down several times to be sure that all the lines are empty, so that's the reason why we let it rise again till 1 bar and pump again.
The last time, we don't wait till 1 bar because it don't raise that much anymore. We programmed this cycle with a practical trial on site.
Perhaps an ever better technique should be that we install just after the receiver a main liquid valve. We then even can pump down the liquid lines as well. But no,..after re-opening it, it will give an enormous shock on the liquid lines, unless installing a small SV for equalizing firstly.
But you understand the working principle.

The normal working pressure (R404a) is maintained at an evaporating temperature of -5°C (VFD controlled compressors)

We had a program in the PLC - removed it afterwards - that when only one or more rooms which had to be maintained at 10°C needed cooling, we raised the evaporating temperature to +4° C to increase the COP temporarily.
As soon there was a call from a '0°C room', we lowered the evaporating setpoint to -5°C again.
But we encountered 2 problems: humidity rose too much in the '10°C rooms' and it are mainly the '0°C rooms' which asks for cooling, so the compressors were running mainly at -5°C.

Kevin, I was back Friday at my client and I took some pictures. Found on the body that they’re made from Watco but see on their website that these units aren’t available anymore.
Units are now +/- 15 years old.