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WIF Condensing Unit Time Delay
I installed an RDI R-404A condensing unit during Thanksgiving week to replace an existing condensing unit. Other than a defective factory installed low pressure control on start-up, it has been running great, even in the extreme weather we had last week
Lately, though, I've been getting freezer high temperature alarms through our Building Automation System. Being it's in a public school kitchen, I initially thought it was the kitchen ladies or the delivery guy leaving the door open because every time I would show up, the temperature would be in the single digits and dropping. Eventually, it would cycle off at temperature and work fine...until the next alarm.
So, yesterday, I show up and the freezer is at 8ΊF and the condensing unit isn't running. I checked the unit and it's not in defrost. What I found was the 4-wire ICM delay-on-break time-delay-relay was open, even though it should have been closed. I jumped out the control and the unit started.
My thought, when I first installed the unit, was why is there a time delay? I thought, since it has a Copeland scroll compressor, that was why. I know I've seen time delays on single-phase scroll compressors and I know if a single-phase "short-cycles", that could cause it to run backwards. However, I didn't think that would be possible on a 3-phase compressor.
Right now, I have the control jumped out, but since the unit is still under warranty, I think I need to install a new time delay. BTW, the 4-wire ICM 207 has been discontinued and replaced with the 2-wire ICM 203.
Forgetting the warranty, does the unit really need a time delay?
With your chrome heart shining in the sun, long may you run.
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As long as it seems to work ok without any noticeable short cycling, I'd skip the time delay. What sometimes happens with scroll compressors, is after pump-down there is sometimes a "burp" or something weird that happens with the check valve that's built into the discharge port. The compressor will pump down, shut off, burp out some refrigerant, start back up, pump down, shut off, burp, over and over and over again. Basically after pump down it will shut off for about 10 seconds, start up and run for 10 seconds, shut off, start up, shut off. You get the idea.
A time delay relay is an effective band-aid to keep this from happening. If your compressor doesn't have this burping problem, then you are probably fine without it.
One word of caution for anyone reading this... Some evaps that have an electronic expansion valve, such as Heatcraft's QRC system, do not play nice with those time delay relays. If you have a fancy evaporator like one of those you should get rid of the time delay. They really seem to mess with the EXV's when they open up and expect to see the refrigerant flowing, but it doesn't flow for a few minutes. If you do experience the compressor burping problem I was talking about and you have one of these fancy EXV units, you can sometimes get the compressor to settle down by widening the differential on the low pressure control.
If at First You Don't Succeed, Skydiving Is Not for You.
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Great information on the burping issues. Based on that, Im going to go ahead and install a new time delay.
Thanks!
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Originally Posted by
ammoniadog
As long as it seems to work ok without any noticeable short cycling, I'd skip the time delay. What sometimes happens with scroll compressors, is after pump-down there is sometimes a "burp" or something weird that happens with the check valve that's built into the discharge port. The compressor will pump down, shut off, burp out some refrigerant, start back up, pump down, shut off, burp, over and over and over again. Basically after pump down it will shut off for about 10 seconds, start up and run for 10 seconds, shut off, start up, shut off. You get the idea.
A time delay relay is an effective band-aid to keep this from happening. If your compressor doesn't have this burping problem, then you are probably fine without it.
One word of caution for anyone reading this... Some evaps that have an electronic expansion valve, such as Heatcraft's QRC system, do not play nice with those time delay relays. If you have a fancy evaporator like one of those you should get rid of the time delay. They really seem to mess with the EXV's when they open up and expect to see the refrigerant flowing, but it doesn't flow for a few minutes. If you do experience the compressor burping problem I was talking about and you have one of these fancy EXV units, you can sometimes get the compressor to settle down by widening the differential on the low pressure control.
The solution to the electronic systems that monitor low side pressure is exactly the kind of time delay the OP has. Installing a "delay on break" timer will alleviate any of those problems since the unit will start immediately on a call but the delay will only time out on the off cycle. Also one of Heatcraft's Beacon II varieties monitors compressor current draw and will alarm if it doesn't detect current when the system is supposed to come out of pumpdown. We've had some issues with the low pressure switches not cutting in fast enough for the control to acknowledge it - which would also happen if a delay on make timer was used. By the way, most if not all scroll units with adjustable pressure switches MUST BE CHECKED/ADJUSTED at first startup. The differential is often too narrow or cut out too high.
From my experience, I'd leave the time delay in place, those Copeland scroll check valves take their sweet time to close once in awhile. Just make sure it's the right one for the job.
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Originally Posted by
Out in the cold
The solution to the electronic systems that monitor low side pressure is exactly the kind of time delay the OP has. Installing a "delay on break" timer will alleviate any of those problems since the unit will start immediately on a call but the delay will only time out on the off cycle. Also one of Heatcraft's Beacon II varieties monitors compressor current draw and will alarm if it doesn't detect current when the system is supposed to come out of pumpdown. We've had some issues with the low pressure switches not cutting in fast enough for the control to acknowledge it - which would also happen if a delay on make timer was used. By the way, most if not all scroll units with adjustable pressure switches MUST BE CHECKED/ADJUSTED at first startup. The differential is often too narrow or cut out too high.
From my experience, I'd leave the time delay in place, those Copeland scroll check valves take their sweet time to close once in awhile. Just make sure it's the right one for the job.
Just to be safe, I called RDI technical support and they told me that Copeland requires that they install delay-on-break time-delays on their low temp condensing units with scroll compressors.
The WIF temperatures have been much more consistent with no alarms since I jumped out the TDR, but I've got a new TDR on order.
Thanks for your reply!
With your chrome heart shining in the sun, long may you run.
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Originally Posted by
SandShark
I installed an RDI R-404A condensing unit during Thanksgiving week to replace an existing condensing unit. Other than a defective factory installed low pressure control on start-up, it has been running great, even in the extreme weather we had last week
Lately, though, I've been getting freezer high temperature alarms through our Building Automation System. Being it's in a public school kitchen, I initially thought it was the kitchen ladies or the delivery guy leaving the door open because every time I would show up, the temperature would be in the single digits and dropping. Eventually, it would cycle off at temperature and work fine...until the next alarm.
So, yesterday, I show up and the freezer is at 8ΊF and the condensing unit isn't running. I checked the unit and it's not in defrost. What I found was the 4-wire ICM delay-on-break time-delay-relay was open, even though it should have been closed. I jumped out the control and the unit started.
My thought, when I first installed the unit, was why is there a time delay? I thought, since it has a Copeland scroll compressor, that was why. I know I've seen time delays on single-phase scroll compressors and I know if a single-phase "short-cycles", that could cause it to run backwards. However, I didn't think that would be possible on a 3-phase compressor.
Right now, I have the control jumped out, but since the unit is still under warranty, I think I need to install a new time delay. BTW, the 4-wire ICM 207 has been discontinued and replaced with the 2-wire ICM 203.
Forgetting the warranty, does the unit really need a time delay?
Is this D O B in series with the LP Control? Some of there units delay the LP opening in low ambient to give the system time to build head pressure and stabilize
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Yes, the LPC is in series with the HPC and the Discharge Line Thermostat, but this system does not operate that way, if I am understanding you correctly.
With your chrome heart shining in the sun, long may you run.
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Originally Posted by
SandShark
Yes, the LPC is in series with the HPC and the Discharge Line Thermostat, but this system does not operate that way, if I am understanding you correctly.
OK
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I know this is an old post but have a similar Issue I ran into this week. Installed a new Low Temp Condenser on a evaporator with EEV and Beacon II Controller. After starting up and charging it ran fine till it got down to temp but then overnight started warming back up some. Checked it back out and found it cycling on Time Delay with the EEV only open about 25 steps. Tried resetting the power and it started back up and was running normal again. Well, it did it again; so, did some searching online and found this video from Heatcraft, pretty much describes what ammoniadog said in his post.
https://www.heatcraftrpd.com/resourc...ronic-controls
Bypassed the time delay for the weekend because it was fixed 3-minute time delay and not adjustable. The Beacon II Manual recommends a maximum of 1 Minute Time Delay, and the video says you can bypass it. Will check back in on it Monday to see if that fixes the problem. I wasn't too worried about the time delay because when it pumps down it seems to hold pressure pretty good and not rise any while in Pump down mode on the controller.
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Originally Posted by
Greend88
I know this is an old post but have a similar Issue I ran into this week. Installed a new Low Temp Condenser on a evaporator with EEV and Beacon II Controller. After starting up and charging it ran fine till it got down to temp but then overnight started warming back up some. Checked it back out and found it cycling on Time Delay with the EEV only open about 25 steps. Tried resetting the power and it started back up and was running normal again. Well, it did it again; so, did some searching online and found this video from Heatcraft, pretty much describes what ammoniadog said in his post.
https://www.heatcraftrpd.com/resourc...ronic-controls
Bypassed the time delay for the weekend because it was fixed 3-minute time delay and not adjustable. The Beacon II Manual recommends a maximum of 1 Minute Time Delay, and the video says you can bypass it. Will check back in on it Monday to see if that fixes the problem. I wasn't too worried about the time delay because when it pumps down it seems to hold pressure pretty good and not rise any while in Pump down mode on the controller.
So where was the research and development that allows it to go into the field with issues?
I'm not really happy with intelgen!
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Copeland should just admit there's an issue with the check valve.
I've seen it now on several and yeah the time delay is a bandaid but not the solution.
Everytime I've replaced the compressor the problem went away
until the replacement starts doing the same thing. 
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I actually had two fail on the same unit.
One under warranty the second out of warranty.
When the last one took a chit I installed a CS reciprocating and haven't been back since.
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Sure there is a TDR in the CU. Sure Copeland stipulates one. Sure Cope Scrolls have a discharge check valve problem.
I accept that there is a Scroll discharge valve problem and Cope came up w/ a 'this will do' solution(TDR) and I agree. Problem gone as in covered over. So, so what? Sometimes ,I install a suction line in-line check valve. And I also put in a wrot(suction line size) Schrader T on the evap side of the ck valve. I relocate the PumpDown/LP switch location to that Schrader T access fitting. So, I do not care that the comp body and some of the suction line back to the new SL/Ck Valve get pressurized. And I do not care about that easy path for migration to take place due to the CCH.
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But why should we have to jump thru hoops because Copeland won't address the problem ?
Remember when they added an oil substitute and the industry was flipped upside down trying to clean up txvs.
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Originally Posted by
VTP99
But why should we have to jump thru hoops because Copeland won't address the problem ?
Remember when they added an oil substitute and the industry was flipped upside down trying to clean up txvs.
Because our job is literally to fix other people's mistakes and screw ups.
Use a shitty contractor before me?
Got your back, jack.
Misapplied equipment but you can't afford new?
Hold my beer.
Can't figure out why you're replacing compressors on a yearly basis?
Allow me.
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