Using a low pressure control to control box temp
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- เผยแพร่เมื่อ 7 ต.ค. 2024
- Using a low pressure control to control box temp, this was a service call on a Delfield reach in that was freezing the product. I found that the low pressure control was not set properly and this was allowing the unit to get to cold.
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Evaporator pressure control was once very common, on very early mechanical refrigeration equipment. Neat to see it still being used. With the cut in pressure being above freezing, you have a cycle defrost system, with no other defrosting means necessary. You know, when it’s actually working right. ;)
Chris I ran across this exact same setup the other day and was a bit unsure how to fine tune the pressure control then I found this video you posted. It helped me so much. Got the unit running well and the customer is happy. Thank you so much for posting this video, you are an excellent technician and an excellent teacher. You also have been a great help to me on Lennox rooftop units. Love your channel and keep up the great work you do.
Pressure control is best way to control temp on a static evap case. Nicely done
Nice video.
One additional note:
Set the cut in pressure to match the refrigerant's saturation pressure at the desired cut in temperature.
Rough set the cut out temperature at the saturation pressure matching 10° colder than your desired cut out temperature and you should be fairly close. A few cycles and you should be dead on your marks.
The 10 degree difference allows for an evaporator coil on a running circuit to reach about the air temp you are looking for as the split between the coil temp and the air temp on a mid temp box is around 10°.
Hope this is helpful.
great tips! thanks for watching, I am going live a little early today 12/24/18 at 12:00pm pacific standard time come on over if you can and check it out th-cam.com/video/rDd469JwYww/w-d-xo.html
Thank you doing a video for low pressure control. Excellent video and explained how it works in real life.
Love the recaps at the end. Great job!
You explain things very well. Detailed and precise. Thank you!
Thanks for watching, I will be going live on TH-cam this evening 5/13/19 @ 5:PM (west coast time) to discuss my most recent uploads and answer questions from the chat. Come check it out if you can th-cam.com/video/tQb9QK9LnH4/w-d-xo.html
Nice video, once I figured out how to set a pressure control as a temp control, everything else fell right in place.
On a side note I'm going live on my channel tonight at 6:00 PM Pacific come on over and check it out
th-cam.com/video/4mrNXiCvid4/w-d-xo.html
I would jump at that opportunity to work for you if i lived in your country.
Loving your videos from Australia!
The reason they run liquid line and suction line together is to make sure no liquid enters into the compressor.
I’ve seen many cattle coolers done with those controllers using a residential air conditioning unit. I’m from Iowa they use them for show cattle.
U r doing what no can do God bless u thank you
Love your videos I have been learned from it. Thanks.... show more videos for low pressure control cut in ,cut out. For walk in freezer and coolers....
Nice job, old school temperature controlling. Well done
Great explanation on the topic. I have a couple display cases where I work that use the low pressure switch to control temp. It was a serious learning curve for me on the first attempt at it. I also had one that the contacts stuck/welded together. The unit ran until the coil was a solid block of ice.
It seems that the pressure designation on the scales aren't 100% accurate either. You have to set it where you think it should be and then tweak it from there. It can be very time consuming.
On a side note I'm going live on my channel tonight at 6:00 PM Pacific come on over and check it out
th-cam.com/video/4mrNXiCvid4/w-d-xo.html
Lol I'm working on the exact same system. I set the switch to cut out at 45 and cut in at 65. Its been cooling good I just wanted to make sure its been cycling off for enough time. Thanks for the video!!
I would like to make the point that 39 degrees cut in is a little high. I am dealing with health inspectors that are looking for below 40 degrees internal product temperature. If they catch it during an off cycle, I'm worried that they'll flag the equipment as not operating properly. I ended up setting the cut in for 33 degrees.
you need a wide enough differential to prevent short cycling. especially if you're dealing with a scroll compressor
Very good video I Learned more about those low controls ..Thanks for sharing Your skills
Thanks for watching
AAAAAHHHHHHHHHHH HELL!!!!!!! I HAVE MISSED THE OPPORTUNITY TO BE YOUR TECHNICIAN!!!!!!!! 😭 😭 😭 😭 😭 😭 😭 😭 😭
Phenomenal information thank you
Old school, low temp control for a stat I dig it
Thank you so much for all this great information,
Nice adjustment of PC..37* is what I set mine. Different refers in old days..
Very good video In older system in refrigerant system they use low pressure control to control temperature even rack system back then was R12 /R502 /R22 .Anytime l have a temperature by pressure control having problems with controlling the temperature wirer in electrical thermostat & use low pressure control as a low pressure when using all the new refrigerant essential the blend really can't control temperature inside the box essential in a kitchen that has a heath inspection nowadays .
Very true, thanks for watching!
Blended refrigerants that demonstrate any glide make pressure based controls a little more twitchy to set up and a trace leak in the system changes the Temperature/Pressure relationship, making the problem worse. The manufacturers almost always use mechanical pressure-stats only on azeotropic refrigerants.
Very, very good video.....thanks
I remember doing this and people kept opening the door while i was trying to let cycle. Frustrated. I learned as long as everything else is properly working you can just set to cut out at 20 and cut in at 39.if charge is proper it shoud never ice up .it is the best way as long as everything else is good
Love it, now it works automagicly😁
Thank you for sharing ..it really helps
Good vid Chris ... very knowledgeable and much appreciated ...
Thanks for watching
Thanks for the work you put into this!
Thanks for watching bud
Wow, dejavu from the seventies, , spent the first two years of my apprenticeship building those things, except we mounted the evaps on the roof of the cabinet, then the last two years on the road servicing them. R12, capillary systems, Penn low-pressure controls, Muller Pcquay evaps with Kelvinator condensing units, bulletproof. lol
Muller Mcquay evaps.
Well explain .
Great video Chris! Thank you!
I didn't read all the comments but the reason for a low pressure control and solenoid controlled by a stat, was to allow a pump down cycle. The compressor on the off cycle would have low pressure in its crankcase, thus the seal wouldn't have to hold high pressure on the old belt driven compressors.
great video
Thank you thank you Chris!
You are the man, here is a big question
Can you please make a video adjusting these low and high pressure controls with nitrogen down at the van instead of while its installed on the unit ?
If this is not possible let me know.
Thank you.
Bro great video dude I’m about to move to Cali to work with you this is what I want to do commercial refrigerators and air conditioner work
Good stuff
The only problem whit the pressure control. Would be affected whit the temperature ambient. I used the pressure control como safety if my temperature coil fail. Would be stop for ny pressure that is the flaw and small unit always a tell friend make sure u condenser is clean. So u can see the real pressure on the system. Is great video that unit was modified the reason can be to charge more to the customer pressure control is cheap vs danfoss control
Love it learned something new thank you
You do a good job....👌👌👌👌👍👍👍👍
Great job
wow... I liked this a lot.
Great info! Thanks!
I control about 90% of our refrigeration with pressure controls only. I've been doing it this way for about 20 years now. I have much better temp contr with out freeze up issues.
I should clarify, that is for medium temp, txv fed systems only. I have converted a lot of R22 systems to R407C. Setting up the pressure control to maintain proper temp with out freezing up was interesting, but i realized something very interesting with the p.t. chart, and had to set up the pressure control differently.
@@mikec.2746 Hi Mike,
I know this was 2 years ago for you, but what was your trick setting up R407C LP for temp control? I know due to high glide, during off cycle, you cannot rely on dew point for the range, but don't believe it will be bubble point either. I'm thinking of putting a temp probe on a return bend in the middle of the coil and call that "off cycle refrigerant/ box temp". And use the dew point for differential Thoughts? Am I close to the money? I've done this plenty of times with single or low glide refrigerants without problem, can be fiddly sometimes but works well.
Reason I ask, I've been asked to set this up as a second opinion. Another tech has had troubles setting up to maintain temp without freezing the coil.
Cheers, Morgan.
@@James-vf5gs Hi James. Yes, your on the right track. Looking at your pt chart, you'll need to set up cut out according to dew and set up cut in to bubble. I set up temp probes in the evap coil and for box temp. That way I knew exactly what the coil temp was along with the box temp, along with freon pressures. All you'll need to know is what temp you want the coil at cut out and what temp you want the coil at cut in.
I do chain restaurants and have a couple dozen boxes set up this way, and never had a restaurant fail a health inspection due to temperature, and no frozen coils.
Now, I found that when tried that with R422B, I could get box temp, and maintain it, but eventually would freeze up, so I had to run a defrost time clock. So I converted those systems to R407C and removed the defrost clock.
Let me know how you make out.
Regards,
Mike.
Can you go into more detail of the low pressure control. Like can you explain what does temperature differential mean? And how to adjust it. Thanks
Amazing job!
Thanks bud
Great channel
Recaps are great.... thnx
Yeah just the low pressure control is a great way n very simple. Kinda. You go off pressure not temperature really. Have to watch though because they can be intermittent
You are the best!!!!@@!👏👏👏👏👏👏
Thanks
Thanks for watching!
Thank you
Next time Install an electronic controller and a relay (or solenoid depending on the type of equipment) advise the customer it’s an upgrade. I’ve been doing it for years here in Australia. Great videos mate keep it up!
Unless you set the pressure switch for freeze protection or coil mount the temperature sensor or add a freezestat, you are doing your customers a disservice by disabling the freeze protection functions that the pressure-stat also provides. This is the same idea on the True brand small refrigeration units that use the cold control with the sensor capillary that slides down into the tube that runs through the evaporator coil body, as this control senses ice buildup on the coil as a drop in coil temperature and shuts off the refrigeration. All it takes is a piece of cling wrap or a plastic bag to block the fan intake and your customer is paying for a needless service call.
I have about 500 of these units in service that are exactly the same as this unit, even the same model number. Doing the "upgrade" you suggest is unnecessary IMO.I feel like you're trying to do the right thing and your heart is in the right place but I disagree with you on this issue. This unit is designed to be simple, cheap and effective. Adding a bunch of extra parts is not going to benefit the customer.
Great video thanks
What we think about all this ???? We think that you’re really good person and we learn allot from your teaching. Thank you very much God Bless you always
Measure super heat at the evaporator using the SH66A Atkins Cooper Kit and its pipe strap.
Awsum infor
I will be going live on TH-cam this evening 11/11/19 @ 5:PM (pacific time) to discuss my most recent uploads and answer questions from emails, the Livechat, and TH-cam comments. Come on over and check it out if you can th-cam.com/video/Rm3XGBDxpOQ/w-d-xo.html
Freaking nice!
Cool stuff
Thanks bud
Please share about air blast freezer as well. Thank you.
Good Stuff Bro.
I’d think you should be a teacher at a college or a teacher at a technical school
Love the vids
Thanks
Excellent 👍👍👍
So with singal and dual pressure controls you need gauges on the system to determine correct cut in and cot out pressure the controls are not exact psi all the times .
thats awesome,.
A pressure control used as the temperature control works ok/good when the condensing unit is indoors a controlled enviroment. But on systems where the condensing unit is out doors the pressures fluctuate with temperature effecting the low pressure switch settings. You constantly have to go back to re-tweak the control. Also you can not use a pressure control as a temp control on a capillary system.
You are correct! I cover those points on the HVAC school podcast
On a side note I'm going live on my channel tonight at 6:00 PM Pacific come on over and check it out
th-cam.com/video/4mrNXiCvid4/w-d-xo.html
Outdoor condenser is partially true; with variable head pressure, you must use a TXV on the evaporator and the head master must be fully operable. This system does not like fan cycling condenser pressure controls.
As to cap tube, this is incorrect as long as the box is self contained. The pressure control is sensing the evaporator coil temperature based on suction pressure and as long as the system is not seeing varying head pressures, the "milk box" control configuration, as the old timers used to call it, works quite well.
I worked on a unit where a pressure control controlled temp. I was tripping so much cuz I took everything off the unit to find the temp control.
There are heat pumps with 2 compressors and a sensor to switch between them.
Thank you, good job as always. Would love to work with you but you are not in Houston 😥😥
On a side note I'm going live on my channel tonight at 6:00 PM Pacific come on over and check it out
th-cam.com/video/4mrNXiCvid4/w-d-xo.html
Hey mate what Fieldpiece app/fool are you using? That looks great - I’ve changed a solid state LP to a manual Ranco LP and I’ve got no idea what I’m doing as the unit has 2x solenoids which Control two cabinets on the one condensing unit
I want it to cut out at 2 degrees Celsius in the box 404a) and back in at 5 degrees I’ve set the cut in at 300kpa and differential at 150kpa so cut out is 150 diff (20psi) it’s cutting the IR33 controller compressor symbol off and the temp rises right up to 10 degrees without cutting the comp out - I’m assuming the solenoids close, lowering the gas pressure and eventually cutting out but hell!, it’s taking forever to cut out 😂 I’m just hoping for the best as I’ve already spent 3.5hrs on site
Question. cut in pressure, So if pressure isn’t up to what the cut in pressure is set to the txv won’t feed refrigerant?
When you adjust the pressure according to temperature. Where do you measure the temperature? At coil or box temperature?
Jason
Hey can you film some ice machine service calls I’ve always done residential heating and cooling and want to start doing some refrigeration stuff and need to learn the controls and so on thanks good video
Sure I just uploaded an ice machine video yesterday, I will be going Live on TH-cam this evening 10/28/19 @ 5:PM (pacific time) to discuss my most recent uploads and answer questions from the live chat, Facebook, emails, and TH-cam comments come on over and check it out if you can. th-cam.com/video/wavAI7IcaQ8/w-d-xo.html
Friendly Question. Why would you need to wait for the box to come down to temp, 34 degrees, in order to note the pressure and make adjustments. Why would you not just use your pt chart from the beginning for both your cut in and out temp?
Often times the controls are not accurate, so you want to adjust the control to the actual pressure on your gauges for the correct cut in, or cut out
Hi there I've just finished installing a new lp/hp switch a danfoss but after setting it up corresponding cut in and diff 17 pressure in psi on a walk in freezer on 404a at -18 to -20 the compressor keeps short cycling is it because of the ambient temp (which was about 4 degrees Celsius) or was my settings not right
I never installed solenoid w/temp controller simply to avoid nuisance calls because someone jacked the temp down.
On most of the reach in coolers they are setup as a pump down system so that would be the purpose of the solenoid valve.
Understood
Here's my concern. There is no load in the cooler and you made your adjustment to the low pressure control under that condition. I would think you would want to adjust that control with some load because load inside the case is a normal temp condition and your expansion valve is closed off more to maintain superheat with no load. Once load is inside the case, your valve will be open more than with no load, thus changing your normal suction pressure range. Or at least go higher on your cut in to like 90 psig
It takes longer for product temp to raise than air temp in the case. Surprised no little receiver to help maintain solid column of liquid to exp valve.
Another huge problem with low pressure control only is head pressure fluctuations with ambient and starting plug up with debris will cause temp to pressure issues causing ice ups
Also the blends of refrigerant with leaks may give you a different pressure temp relation, and glide will screw with you too
Federal open air cases were heavy on low pressure controls and now rely on temp controls cutting on and off with evaporator supply temperature.
Electronic temp control with scheduled defrost control is my preferred choice to prevent ice and temp issues.
Nice video.
Not sure if I’m thinking about this right, will this cycle the compressor or the condenser fan? Is this wired same as a relay/contractor, in series on the hot leg? Not sure if I’m mixing this up with a low ambient control. Thanks
Thank you to u explained that very well. does pressure control take the place of the thermostat can you do videos on head master valves
Yes I will try and do a formal video on headmasters. Until than check this video out that explains them a bit and how to charge the system when they are installed.th-cam.com/video/Uzz9o3adkmc/w-d-xo.html
@@HVACRVIDEOS does the pressure stat take the place of the thermostat
Is it common for those controls to go out of calibration and what is the cause? Great video.
No someone messed with it and turned the dials
It is more common for a thermostat or cold control to fail than the pressure switch due to configuration.
Only a pressure control ?
I didn't hear what kind of refrigerant was in the system but I'm assuming 404A
Chris, I work for a commercial refrigeration company as a lab technician. I have been doing it for 4 months now. I am new to the field , I can read a wiring diagram but struggle bringing what I see in the diagram to what I am actually seeing in the wrong in the unit.. any suggestions
Hey great video! What state do you work in?
California
Had a cold pack walk-in freezer running below thermostat set point way below to -27 and it’s set for 0. Started troubleshooting and it shut off cycled several times and it worked properly. Any ideas 💡 what would cause this
👍
What would the feasibility of adding a solenoid valve and t-stat measuring box temp?
It's not needed. The pressure control is as or more accurate and is using an average of the entire evaporator coil temperature. This configuration also acts as freeze protection for the system, all in one package.
Where do you get the product temp from? Lettuce was stored in there. How do you know what temp before it starts freezing?
Most of the operators I deal with are not as worried about their lettuce as the sliced tomatoes. Tomatoes get mushy when cycled near freezing, however lettuce handles slight frosting much better. Set your cut out air temp around 34-35° F.
Hi Chris . Would that scenario be also called an Off cycle defrost ? Just started doing my level 1 for rerigeration at school . even though I have all my hours to do all 3 levels , Im just finally doing my schooling after almost 7 years doing HVAC .
How come the TD was so high for a TXV. It was around 23°F I heard you say. Would you prefer to see 15°F TD for a cooler?
Hello Chris. Was the refrigerant charge ok and do like liquid line sight glasses as a quick reference. I worked for a company awhile back and installed remote condensers for walk ins. My boss never checked superheat but just charged the system till there was no gas bubbles on the liquid line. What’s your thoughts on that ??
Would be easier to use a 1609-101 all range temp control and drill a hole for the bulb to get in the box to control temp and not the pressure control
Gamez516 i have moved away from the mechanical stats and went to the A421-abD. Digital stat with built in defrost control for these boxes.
Chingon
Hi sir can I apply in your good company, i am currently working here in bermuda as a refrigeration and hvac technician
Thank you for a great video,,, how did you decide on that temperature range, I know most region refrigerators have a box temp of 40 but how did you decide on descending to the temperature of 34 as your cut out temp. Many thanks
Is this not the norm anymore? I've never seen one with digital controls.
This is not the norm in 2019. Most systems use a mechanical temp control along with a low pressure switch. The thermostat is just used as a fail safe/defrost method
I find that this type of temp controlling is not accurate enough for me. Maybe you're ok with it.
I notice no one does any video on how to charge for these services you don’t have to tell us how you do it just how it should be done ✅