Converting walk-in compressor to digital controls

[Pandelerium1138]

Let me do some research.

So basically send the BAS the alarm.


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Exactly. Dry contacts would be enough. Thanks!

[WT70]

Yes, all of the above. Off cycle defrost for the medium temp walk-ins, electric defrost for the low temp walk-ins. We can use BACnet or LonWorks, but I would rather the alarms were integral to the system, not generated by the BAS system, since I would have to have our controls guys and/or Staefa BAS contractor figure out the logarithm, and that could get messy. I don't know if there is enough need out there for this kind of system to make it commercially feasible, but there's got to be some, especially morgues. Our morgue uses a MorTech system for lead/lag and alarming that is far less than adequate, and it's only just over a year old. Even the installer hated it. I have looked far and wide, there just isn't anything "plug and play" out there. Some have taken Pelican HVAC systems and modified it to work on a walk-in, but it's far from perfect, and highly experimental. Not something I would use on a morgue. Master-Bilt came up with a controller along these lines, but they are problematic. I know, I have one in another building, it's rather finicky. It needs to be robust, and able to function independently even when the BAS goes down. An option for cloud monitoring with a wireless gateway would be great for customers that do not use any kind of BAS, that would increase the customer base dramatically. Maybe just a standard dry contact for any alarm system and a separate add-on interface for those that want one.

Let me do some research.

So basically send the BAS the alarm.


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[pecmsg]

Hell you can put pressure sensors on everything, the BMS will monitor it all!

[TheReefer]

The condensers came with Copeland High/Low pressure controls and those have separate contacts for High and low pressure, those will work. The ones that have been replaced with Johnson Controls pressure controls do not, I would have to replace them back to the Copeland controls, which seem to have a high failure rate. I agree, simpler is better in some cases. I can have the relay tied into our Staefa BAS, I'm thinking all the relays in series so there's only one alarm, and idiot lights to tell the building operators which one, so when they call me at 2 am, I can tell them if it's redundant, send me a work order and I'll deal with it in the morning -or- have to drive in.

Someone should come up with a digital compressor control system that talks wirelessly to a remote pump down thermostat that controls a solenoid or LEV, uses transducers and thermistors along with a logarithm to determine if and when there's a problem, put the whole thing online with alerting and drag the refrigeration industry kicking and screaming into the 21st century. Online temperature monitoring in the box is useless at telling when system A is down when system B is running fine on a redundant system. Until system B also fails, then you have an emergency that was supposed to be avoided with redundancy. Yes, this is much more complicated, but in some instances a needed option. The reason I bring this up, if a kitchen walk-in goes down, some food might be lost. If our morgue walk-in goes down, it's a whole different story (especially during a pandemic). Yep, I got called in at 9 PM once on just such a call and it sucked. Especially since a contractor that was working on system A under warranty screwed up and turned off the wrong disconnect outside. With this kind of system I would probably have been alerted before I got to the parking lot, not 3 hours later when the box temp went into alarm.

what exactly is the point of this. Are you trying to be alerted of a specific component failure or just being alerted of a system failure sooner. I think everyone gets all gung hoe on controls but remember it doesn't make the system anymore reliable and it makes it that much harder for another guy to come by and figure what its doing when it does fail. I would imagine a box temp alarm along with regular inspection of an up to date system would have a fairly low failure rate.

[pecmsg]

I have several water cooled walk-in compressors for walk-ins on a rack for our kitchen and cafeteria. They are all Copeland, a couple Discus, the rest regular semi-hermetic. They currently have mechanical controls, the standard high/low pressure switch and the overload on the compressor. The issue is, there's no way to tell if they are tripped on high head (other than our online temperature monitoring in the box itself). I was looking onto converting to a digital system like the Emerson EUC or something similar. I cannot find a retrofit anywhere. Any ideas? Thanks!

Water cooled equipment gets Manual Resets.

Problem solved!

[Pandelerium1138]

what exactly is the point of this. Are you trying to be alerted of a specific component failure or just being alerted of a system failure sooner. I think everyone gets all gung hoe on controls but remember it doesn't make the system anymore reliable and it makes it that much harder for another guy to come by and figure what its doing when it does fail. I would imagine a box temp alarm along with regular inspection of an up to date system would have a fairly low failure rate.

You are right, it doesn't increase reliability. However, if you have a very critical system that has redundant systems, you need to know when one of them goes down, preferably before the other one does. Sometimes getting all gung ho on controls and trending/alerting has a purpose. Yes, I am trying to get alerted when specifically one of the redundant systems go down, or has a trending pattern indicating an imminent failure. We perform scheduled maintenance on these every quarter. However, everything man makes will break eventually. Especially the new crap on the market today.

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[Pandelerium1138]

Water cooled equipment gets Manual Resets.

Problem solved!

Has manual resets. Problem not solved, redundant system takes over, no one knows.

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[pecmsg]

Several controls have a SPDT Switch, wire the second contact to BMS, horn, light.

Simple is better!

[WT70]

Has manual resets. Problem not solved, redundant system takes over, no one knows.

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So here is what I have come up with.

Each unit will monitor suction and discharge, lock out and alarm on high pressure.

One temp sensor will be discharge temp, one will be case temp.

Will alarm if either sensor is above setpoint for a set amount of time.

Alarming out: each controller will have an alarm out. You can tie an individual controller alarm out relay to its own alarm input for the BAS, this would alert whoever “unit #” was down.

Or you could have a single alarm to BAS that just says “refrigeration alarm”, wired through NC relays.


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[Pandelerium1138]

So here is what I have come up with.

Each unit will monitor suction and discharge, lock out and alarm on high pressure.

One temp sensor will be discharge temp, one will be case temp.

Will alarm if either sensor is above setpoint for a set amount of time.

Alarming out: each controller will have an alarm out. You can tie an individual controller alarm out relay to its own alarm input for the BAS, this would alert whoever “unit #” was down.

Or you could have a single alarm to BAS that just says “refrigeration alarm”, wired through NC relays.


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WT70, sorry, I got busy with other projects and haven't addressed this one since apparently July. So, what exactly did you come up with? Is this an controls system I can purchase? Something you can custom make?

[WT70]

WT70, sorry, I got busy with other projects and haven't addressed this one since apparently July. So, what exactly did you come up with? Is this an controls system I can purchase? Something you can custom make?

PM me if you get a chance.


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[Pandelerium1138]

PM me if you get a chance.


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Ok, call me an idiot, but I don't know how to PM on this site. I sent a friend request, not sure if that's necessary. I tried Tapatalk, couldn't figure it out there, either.

[VTP99]

Non Pro members can't PM
Use his email in his profile.

[pecmsg]

Ok, call me an idiot, but I don't know how to PM on this site. I sent a friend request, not sure if that's necessary. I tried Tapatalk, couldn't figure it out there, either.

Non Pro members can't PM
Use his email in his profile.

And apply for Professional Member.

[TPARSONS64]

I would install a manual reset HP cutout switch. No need to get technical in my opinion

[Pandelerium1138]

I would install a manual reset HP cutout switch. No need to get technical in my opinion

Sorry, but this is unhelpful. Please read the thread before offering opinions that are irrelevant.

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[pecmsg]

Sorry, but this is unhelpful. Please read the thread before offering opinions that are irrelevant.

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You asked for advice and it was given. Helpful unhelpful is up to you

[Pandelerium1138]

You asked for advice and it was given. Helpful unhelpful is up to you

You are absolutely correct, it is advice. Since they already have manual reset HP cutouts, as indicated a few posts up, I will take it for what value there is.

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[Pandelerium1138]

One down, 11 to go. This is the prototype, hopefully the rest will go quicker



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[TPARSONS64]

Install a dual pressure control with a manual HP cutout. Buy sone Tattletales and wire them across the overload. I would not replace mechanical controls with digital controls unless it is a thermostat reading box temp. Just my opinion. Good luck