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    Help cutting open 40ft reefer, we now have problems



    First time on this forum so please bear with me if i dont speak to lingo.

    I have designed a freezer cold room assembly using the following.

    We have 2 x 40ft reefer containers which we have cut open the sides. There is a 3rd 20ft reefer on top of one of the 40's. We have spaced the 40ft reefers apart and enclosed the space in between with KingSpan insulation walls and ceiling.

    We have cut open one 40ft reefer and hung down a plastic curtain.

    We are having problems with the freezer we have cut open in that its condenser is not freezing over?

    I have briefly spoken to the reefer supplier and they have indicated that the refrigeration units will not work properly if we have no air seal? Is this correct? And if so is there anything we can do to get around this?

    Ideally we wanted the space in the actual containers to be approc -5C and the area in between the containers (Cold Store) to be -2 to +5C?

    I would really appreciate some help on this?

    Thanks Adrian



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    Re: Help cutting open 40ft reefer, we now have problems

    So,

    You have grossly increased the heat load and are now asking why the units doesn't cope.....

    Each of your refrigeration units have been carefully designed to cope with the enclosed space within the container it serves.
    Any alterations to this space, like draughts or increased volume, will affect the refrigeration units.
    i.e. they will not cope.

    The only solution to your problem would be to get someone to design replacement/additional plant to serve your new chilled area.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17
    And if so is there anything we can do to get around this?
    Start over. You need some help from a professional. Mr Viking is correct!

    The air infiltration into the space can greatly increase the cooling load, which means the reffer units cannot maintain the temperatures you thought you would get.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    Not a very well managed project after all.

    This type of work requires expert assistance before you start not afterwards when it won't work.
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    Re: Help cutting open 40ft reefer, we now have problems

    Probably would have been better to put them end to end so the first was the chiller and you walk through to the freezer with a box in between.

    But thinking about it where are you going to put a 100 ft long reefer unit?
    If it ain't broke, it doesn't have enough features yet.


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    Re: Help cutting open 40ft reefer, we now have problems

    You are all right...... However i did do some calculations etc for heat flow etc.

    So the 40ft reefers have approx 74m3 of space, we used to freeze these down to -24C

    We now have 3 x reefers which are able to chill 225m3 down to -24C.

    We have added an enclosed area in between which is 300m3.

    So we now have a total of 523m3 and 3 x Reefer compressors.

    We no longer want the reefer boxes to go down to -24C we can live with -4 to -5C and the cool area in between can live at 0C approx.

    We do have plastic curtains covering the sides of the reefer we have currently opened, i was hoping that the poor insulation properties of the curtains will allow the cool room space to absorb some of the cold from the reefers?

    We do have another reefer compressor unit that we could attach so i guess my question really is?

    Can we use reefer refrigeration/compressor units as standlone units? Are the reefer compressors special in any way? Would we be better to get a more specific refrigeration unit?

    I really hope i get a slightly more positive reply

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    Re: Help cutting open 40ft reefer, we now have problems

    This is a reply we have received from the reefer supplier?

    "Engineer has stated that now the freezer has lost its airtight seal, the unit will not operate as designed. The condenser will freeze up and the temperature will rise.
    the fact that the unit will not work correctly unless an airtight seal is maintained."

    Does that make sense?

    Why would the condenser freeze up? Do they require really low humidity?

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    We are having problems with the freezer we have cut open in that its condenser is not freezing over?
    Quote Originally Posted by adrian_uk17 View Post
    This is a reply we have received from the reefer supplier?

    "Engineer has stated that now the freezer has lost its airtight seal, the unit will not operate as designed. The condenser will freeze up and the temperature will rise.
    the fact that the unit will not work correctly unless an airtight seal is maintained."

    Does that make sense?

    Why would the condenser freeze up? Do they require really low humidity?
    The coil inside the box is called an "evaporator", not a "condenser". condensers don't freeze, evaporators do.

    In your original post you state that it is not freezing over. In your last post you state that it is freezing over. Is the evaporator freezing over or not freezing over?

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    Re: Help cutting open 40ft reefer, we now have problems

    Firstly, it is the EVAPORATOR that is inside and takes in heat (gets cold).

    Have you ever tried leaving your freezer door open? ....it will soon develop frost on its cold surface which builds up into ice.....now think what happens when you blow air through the coils and fins of a commercial evaporator...it will ice up quickly and will require defrosting regularly. When iced up it quickly looses the ability to cool as designed.

    A reefer, like your chest freezer is an enclosed space and the air inside is trapped (very few air changes)....so the moisture will stay at a low level once it has 'dried out'. It requires quite a lot of cooling to remove moisture from air.

    I believe a reefer is also probably only designed to hold items that have been already frozen at low temperature....it is not designed to freeze items from scratch. Consequently, the refrigerating capacity of the unit is sized to do just that...with a little spare capacity so that it does not run 24/7 and is able to cope with defrosts.
    The heat load of a low temperature unit is less that that of a higher temperature unit that has lots of air changes, lots of product changes and is trying to cool products brought in to the cold space from higher temperatures.
    The capacity of your refrigeration systems is therefore most likely undersized for what you are trying to achieve.

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    Re: Help cutting open 40ft reefer, we now have problems

    I don't mean to offend, but you simply haven't done your homework. You haven't bothered to learn enough about refrigeration to be able to ask questions that make sense.

    Do your homework and then let's talk:

    http://www.europe.honeywell.com/70_r...07%20R0505.pdf

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17
    "Engineer has stated that now the freezer has lost its airtight seal, the unit will not operate as designed. The condenser will freeze up and the temperature will rise.
    the fact that the unit will not work correctly unless an airtight seal is maintained."

    Does that make sense?
    Yes it does. That is what we have been saying. If any air is allowed to leak into the boxes the units do not have the capacity to cool outside air and freeze the water that is contained in the air.

    If they have to do this, then they cannot keep the box cold.

    BTW, when did the "engineer" tell you this would not work? Before you tried it or after?

    Condenser have hot air blowing out of them, evaporators have cold air.

    Quote Originally Posted by adrian_uk17
    I really hope i get a slightly more positive reply
    You are getting a lot of help, unfortunatley you are not getting the answer I think you expected to get.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    What is the difference between a reefer refrigeration unit and a refrigeration unit that is used in large drive in buildings?

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    Re: Help cutting open 40ft reefer, we now have problems

    unfortunately after, the engineer is only one that services reefers and sold us them before he indicated that and airtight seal is imperative.

    I am proposing the following, does this make sense?

    It will be the evaporator that will be freezing up, when the air changes considerably or the unit is worked too hard the evaporator will freeze up with the moisture in the air, it requires regular defrosting.

    Can we please get all the reefers set to cool to -4 C only, the fact that we still have them set on -24C they will be continuously working trying to reach these temperatures and hence freezing over.

    Can we also get the plastic curtains overlapping (They are currently butted) as we need to minimize the air movements inside the freezer, also can we investigate hanging a lead bar or light steel from the bottom of the curtains in order to stretch them out as last time I was up there, they were curled up, allowing excessive air to move around inside the container.

    At present we are asking a single refrigeration unit to cool/chill 375m3 of volume when it is only designed to chill 75m3. We need to cut open the remaining 2 x containers and get them contributing to the overall cooling of the volume etc.

    We also need to add another refrigeration unit to the side/top of the central area in order to have the 523m3 being cooled by 4 x refrigeration units.

    If we are still having problems by this point then we will need to buy an additional refrigeration unit.

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    Re: Help cutting open 40ft reefer, we now have problems

    To clear a couple of things up:

    The evaporator is freezing over, the engineer told us after

    Thank you all for your help, i think i am getting a sight of the bigger picture now?

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    unfortunately after, the engineer is only one that services reefers and sold us them before he indicated that and airtight seal is imperative.

    I am proposing the following, does this make sense?

    It will be the evaporator that will be freezing up, when the air changes considerably or the unit is worked too hard the evaporator will freeze up with the moisture in the air, it requires regular defrosting.

    Can we please get all the reefers set to cool to -4 C only, the fact that we still have them set on -24C they will be continuously working trying to reach these temperatures and hence freezing over.

    Can we also get the plastic curtains overlapping (They are currently butted) as we need to minimize the air movements inside the freezer, also can we investigate hanging a lead bar or light steel from the bottom of the curtains in order to stretch them out as last time I was up there, they were curled up, allowing excessive air to move around inside the container.

    At present we are asking a single refrigeration unit to cool/chill 375m3 of volume when it is only designed to chill 75m3. We need to cut open the remaining 2 x containers and get them contributing to the overall cooling of the volume etc.

    We also need to add another refrigeration unit to the side/top of the central area in order to have the 523m3 being cooled by 4 x refrigeration units.

    If we are still having problems by this point then we will need to buy an additional refrigeration unit.
    These would be good starting points, but remember anything you do or try is an attempt to reach a point of minimal aggrevation. You may never be satisfied with the results, but you may be able to get it to work with on-going maintenance issues.

    A refrigeration unit is a refrigeration unit. The difference is the system/unit is designed for it's intended operating conditions. If something changes the operating conditions then you see problems begin to surface.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    What are the likely consequences of working a refrigeration unit working too hard?

    What are the likely maintanence issues that might arrise?

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    unfortunately after, the engineer is only one that services reefers and sold us them before he indicated that and airtight seal is imperative.

    I am proposing the following, does this make sense?

    It will be the evaporator that will be freezing up, when the air changes considerably or the unit is worked too hard the evaporator will freeze up with the moisture in the air, it requires regular defrosting.

    Can we please get all the reefers set to cool to -4 C only, the fact that we still have them set on -24C they will be continuously working trying to reach these temperatures and hence freezing over.

    Can we also get the plastic curtains overlapping (They are currently butted) as we need to minimize the air movements inside the freezer, also can we investigate hanging a lead bar or light steel from the bottom of the curtains in order to stretch them out as last time I was up there, they were curled up, allowing excessive air to move around inside the container.

    At present we are asking a single refrigeration unit to cool/chill 375m3 of volume when it is only designed to chill 75m3. We need to cut open the remaining 2 x containers and get them contributing to the overall cooling of the volume etc.

    We also need to add another refrigeration unit to the side/top of the central area in order to have the 523m3 being cooled by 4 x refrigeration units.

    If we are still having problems by this point then we will need to buy an additional refrigeration unit.
    Before you cut open any more containers, start by adding the 4th refrigeration unit to the cold store area. This will take some of the load off the problem freezer and give you a means of controlling the temperature in the cold store area.
    Last edited by Gary; 05-03-2008 at 06:57 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Frequent defrosts or lack of defrost could cause loss of product quality.

    The more something runs under conditions for which it was not designed increases the likelihood something will break.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    Thanks gary i will do that ASAP.

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    Re: Help cutting open 40ft reefer, we now have problems

    do these reefer refrigerators have auto-defrost? or to they just freeze over and stay that way?

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    do these reefer refrigerators have auto-defrost? or to they just freeze over and stay that way?
    A freezer with a fan/coil evaporator MUST have automatic defrost.

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    Re: Help cutting open 40ft reefer, we now have problems

    The controller will set the frequency of the defrosts, and control the length of defrost.

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    Re: Help cutting open 40ft reefer, we now have problems

    Why not get a professional design engineer or an engineer experienced in commercial freezers, in before you change anything else?

    There isn't only the loadings, air throw and flows also has to be considered as well as produce in/out and people.

    It's only so much we can sort out without ever been to site.

    What you have got is a Vauxhall Astra, what you have done is attached a tow-bar and now you expect it to pull a 40ft/20 tonne trailer......

    Sorry,
    But you will need advice from a professional that have actually seen the design.
    Last edited by The Viking; 05-03-2008 at 09:45 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Also getting something designed to do the job will be cheaper to run than bodging old reefer units together.
    This could cost you more in electricity to run than you save by not doin it properly to start with.

    A lot of the reffer units i've seen have been running on R12/R413A/R134a type of refrigerant, i don't know what yours are running on, but these are not the best refrigerants for a freezer. A new system would be on R404A or R507 which would be more efficient.

    Jon

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    Re: Help cutting open 40ft reefer, we now have problems

    Just a small question..

    Why have you done this and what products are you hoping to store in it.
    Brian - Newton Abbot, Devon, UK
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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by monkey spanners View Post
    Also getting something designed to do the job will be cheaper to run than bodging old reefer units together.
    This could cost you more in electricity to run than you save by not doin it properly to start with.
    This is probably true, but a little late. He already has the equipment and most of the construction has been completed. At this point, it's about making it work.

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    Re: Help cutting open 40ft reefer, we now have problems

    Thanks Gary, you are right, we are probably too far through the build phase to start over.

    We do need to try and work with what we have got.

    We are storing pre/preg composite material in the freezers it has a 30 day outlife at ambient temperatures but if you can cool it to -4C it can last for up to a year.

    I have tried to attached some pics of the design, hopefully you can see them.
    Attached Images Attached Images

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    Re: Help cutting open 40ft reefer, we now have problems

    My first thought on seeing the thumbnails is why haven't you put the refrigerated containers on the top....hot air rises and cold air falls.

    Your current design means that you will have a huge temperature variation through the height of the storage area. You will need fans to mix and circulate the air....more power to run and more heat to get rid of!!

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    Re: Help cutting open 40ft reefer, we now have problems

    The idea is that the 2 40 footers at the bottom house racks with spindles that our rolls of material are forklifted onto, the 20ft on the right is used for storing light material when needed.

    The area in the middle is purely for unloading materials from trucks etc before we have time to trace materials in and it is also for storing material over the weekend instead of the shop floor where it begins to stage and use up its 30day outlife.

    We will rarely go much higher than the 1st set of containers but we needed the additional height for the forklift etc to lift up to the second height.

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    Re: Help cutting open 40ft reefer, we now have problems

    Hi Adrian!
    Could you describe a little activities in that storage. Loading and unloading quantities, frequency, number of peoples, type of equipment for load manipulation etc....
    Also, what are acceptable humidity range for that product. Then if you could provide data (manufacturer, model NO, etc...) of existing evaporators and condensers on that site.
    Last edited by nike123; 06-03-2008 at 01:18 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by nike123 View Post
    Hi Adrian!
    Could you describe a little activities in that storage. Loading and unloading quantities, frequency, number of peoples, type of equipment for load manipulation etc....
    Also, what are acceptable humidity range for that product. Then if you could provide data (manufacturer, model NO, etc...) of existing evaporators and condensers on that site.

    Hi Nike123, i would expect the doors to be opened max once or twice a day, to load/unload min 2 rolls max 5 rolls, main doors could be open for 5-10min tops. Load manipulation would be standard forklift with a custom spindle lifting extension.

    Humidity is not a problem as the material is sealed/wrapped before going into the cooler?

    Existing refrigerators are all using the 134A refrigerant which apparently is not very efficient, the model number of a particular reefer is: ? Will find out.....

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    Re: Help cutting open 40ft reefer, we now have problems

    Is the space above the 40ft containers empty/isolated/insulated or does this space need to be refrigerated also?

    Is the entire structure outdoors or within a building?

    Can you show us the positions of the evaporators, as well as the condensing units (compressor, condenser coil, etc.)?

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    Re: Help cutting open 40ft reefer, we now have problems

    Every time those Kingspan doors are opened, even momentarily, a large amount of cold dry air is going to come pouring out, to be replaced by an equally large inrush of warm moist air.

    You will need plastic curtains behind those doors... or perhaps an air curtain.

    And by all means, overlap all of the plastic curtains.
    Last edited by Gary; 06-03-2008 at 04:13 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    In retrospect, I would have placed the 20ft container at the back, forming a U-shape with the containers and then elevated all as needed, minimizing the height. I would also minimize the width/opening of the Kingspan doors.
    Last edited by Gary; 06-03-2008 at 04:35 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Gary all the condensers are at the back of the containers at present 3 in total 1 in each of the 40's and one in the 20. We will be adding an additional one in the cool space.

    The doors are not actually that high, we have since lowered them to approx half the height shown on the sketch.

    I agree abour the U-shape, this is what i started with originally but someone decided to change this. the 40foot storage container is an insulated 40ft container just used to help raise the height of the cool space.

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    Re: Help cutting open 40ft reefer, we now have problems

    What is the cost for all the free design help? This should have been a billable project for some refrigeration firm in your area.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    Hi IceMan, i am not sure I have changed the design at all from what was originally done, we are just trying to make my rather poor design work

    You are right about getting someone in to do the design, but the company i work for are not very good at shelling out money for design, in fact we are very good and getting things to half work Its usually me that ends up with the job of trying to design stuff, i am actually a Naval Architect and this is as far away as you can get..... Although i have done quite a bit of furnace design for a particular project i did at University/.....

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    Re: Help cutting open 40ft reefer, we now have problems

    Gary we are also only ever intending to open one door at a time.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    Gary all the condensers are at the back of the containers at present 3 in total 1 in each of the 40's and one in the 20.
    By "the back" I assume you mean the end of the container furthest from the Kingspan doors. Is this correct?

    Quote Originally Posted by adrian_uk17 View Post
    We will be adding an additional one in the cool space.
    This should also be placed at the back, up high, away from those doors. As noted previously by Electrocoolman, hot air rises and cold air falls... and we don't want to blow cold air out the door.

    Quote Originally Posted by adrian_uk17 View Post
    The doors are not actually that high, we have since lowered them to approx half the height shown on the sketch.
    You may also want to limit how wide they open.

    Quote Originally Posted by adrian_uk17 View Post
    I agree about the U-shape, this is what i started with originally but someone decided to change this. the 40foot storage container is an insulated 40ft container just used to help raise the height of the cool space.
    A place to store Xmas decorations.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by US Iceman View Post
    What is the cost for all the free design help? This should have been a billable project for some refrigeration firm in your area.
    Which would no doubt have been well worth the expense. Proper engineering could have saved on initial construction costs, running expense, maintenance outlays and future headaches.

    If we manage to make this work, it will be second rate at best.
    Last edited by Gary; 06-03-2008 at 05:44 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    We are storing pre/preg composite material in the freezers it has a 30 day outlife at ambient temperatures but if you can cool it to -4C it can last for up to a year.
    Does the product arrive at your location pre-frozen? If not, this represents additional heat load, pulling it down from ambient temperature.

    Is the extension of shelf life linear in regards to temperature (the lower the temperature, the longer it lasts)... or does it only last longer when frozen?
    Last edited by Gary; 06-03-2008 at 06:16 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17 View Post
    You are all right...... However i did do some calculations etc for heat flow etc.

    So the 40ft reefers have approx 74m3 of space, we used to freeze these down to -24C

    We now have 3 x reefers which are able to chill 225m3 down to -24C.

    We have added an enclosed area in between which is 300m3.

    So we now have a total of 523m3 and 3 x Reefer compressors.

    We no longer want the reefer boxes to go down to -24C we can live with -4 to -5C and the cool area in between can live at 0C approx.
    It is a mistake to assume spillage from the freezers in your calculations. The refrigeration system for the cold store area should be capable of handling its own load. You need to minimize spillage in order for the freezers to work as designed.

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    Re: Help cutting open 40ft reefer, we now have problems

    There is little doubt that you are going to need additional cooling for the cold store area, and this is where you can profit greatly from professional help.

    Ideally, this main cold store unit would be a system designed specifically for a cold store (medium temperature) application as opposed to a freezer (low temperature) application.

    This unit should be sized to handle the entire cold store load under normal conditions. Its temperature control would be set to maintain 0-3C.

    The temperature control for unit#4 would then be set to maintain 3-5C, thus acting as a back-up unit, assisting in handling heavier than normal loads.

    This way, assuming spillage from the freezers is minimized, you can have all units professionally designed/sized for their particular areas.

    And at this point, that's as close as you can get to doing this right.
    Last edited by Gary; 06-03-2008 at 08:26 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by adrian_uk17
    ...the company i work for are not very good at shelling out money for design, in fact we are very good and getting things to half work...
    This is an all too common issue. I have been involved in several projects like this where the owner decided he would save a few dollars and do it himself. Then after a year or so of constant problems and lost product they finally ask for help and then complain about all the money that has to be spent to fix the installation.

    There is nothing like being in the position of being the messenger and getting yelled at for previous mistakes made (by someone who shall remain nameless, of course)

    In the long run, if you added all the costs spent on an "alternative arrangement" to one designed specifically for the application requirements the owner would be money ahead. But hey, they saved some money initially, right?

    As you might have guessed, I am more than a little sensitive to giving away too much information in these conditions, because some firm should have made some money from this.

    This is not directed at you personally as it is at the situation Adrian, so don't take my comments to heart.
    If all else fails, ask for help.


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    Re: Help cutting open 40ft reefer, we now have problems

    Quote Originally Posted by US Iceman View Post
    This is an all too common issue. I have been involved in several projects like this where the owner decided he would save a few dollars and do it himself. Then after a year or so of constant problems and lost product they finally ask for help and then complain about all the money that has to be spent to fix the installation.

    There is nothing like being in the position of being the messenger and getting yelled at for previous mistakes made (by someone who shall remain nameless, of course)
    Been there, done that, cried all the way to the bank where I deposited a big fat check.
    Last edited by Gary; 06-03-2008 at 09:10 PM.

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    Re: Help cutting open 40ft reefer, we now have problems

    There are DIYers and there are Hacks.

    Those who invest the time and effort to educate themselves and do the job right have my respect and even admiration.

    Those who do a hack job get no sympathy and get no price breaks. They are an insult to myself and my profession, believing that what I do for a living requires no particular expertise.

    They reap what they sow. Stick it in and break it off.

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    Re: Help cutting open 40ft reefer, we now have problems

    This is a classic case of "should have". A very definite case of should have hired a professional design engineer to do it right in the first place.

    At this point, you need to STOP ALL WORK until an experienced engineer can see what you have and most important, see what you want. He can then address the solution(s) and how to best to salvage what you have. You are at the point of throwing good money after bad unless you get it engineered.

    Ken
    Last edited by TXiceman; 07-03-2008 at 06:51 AM.

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    Re: Help cutting open 40ft reefer, we now have problems

    if you have as i think cut the sides out of the trailer why dont you fit insulated curtains like curtain side trailers and you have no problem with -4 temps

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    Re: Help cutting open 40ft reefer, we now have problems

    Guys:
    There seems to be alot of beating up and very little problem solving here, Lets be professional about what we want in a forum, help and exchange of ideas....

    Okay, I have a very similar setup I use quite sucessfully for a 30x40x16 cold storage in the seafood business. I have nearly constant ingress/egress of product and forklifts, and maintain -5 to -10 F with 4 carrier transicold units. SO HOW DO I DO IT?

    First there was a learning curve I will admit. There are peculiarities about van units that have to be overcome.......If yours are anything like Carrier units, the defrost can be initiated either by time, manual, or will automatically initiate initiate based on lack of differential temp air/coil. The unit then goes into defrost until a thermister above the coil reaches a whopping 78degrees f or 30 min elapses. Works great in a small enclosed area (van full of product with very little air volume) but doesn't ever terminate from temperature (read incomplete defrost) in an open room with several other units sucking the heat away (and the resulting moisture, causing them to ice up) This was the case our trial run, frozen evaps, no cooling

    First step was to attempt to fool the thermister, but the units are too smart and fault out,( so much for parallel resistoring).

    Next step was to enclose the unit air to "isolate" it for defrost. A simple foam box in front of it with a curtain (read blue tarp) door for air inlet and outlet (dont forget a horizontal bulkhead between the two. This allows a small space to get up to temp and the defrost to work "normally" When the fan resumes operation, the flaps are blown in/out without significant penalty of air transfer hp. make sure the box is 2' or so away from the unit so the flaps dont get sucked in, and its important for the inside wall of the unit to defrost, as drain channels are part of it, and it must warm up or it resembles a frozen waterfall soon.

    Secondly, defrosting all units at the same time manually helps, as the other units aren't attempting to blow cold air around your warm moist pocket. when we have heavy traffic, we defrost every 3 hours.....

    Lastly, if your coils are really frozen up, you may need 2 or 3 or more sequential defrosts to deice them to start with.

    If this works out on your units let me know, dglaab@gmail.com

    One other note, until recently, all van units were 12, then 134a, and many still are 134a. They work fine, albeight less energy efficiently than current ones, but that is mostly due to compressor design advances. If our esteemed friend is able to make this work, he will have likely spent about 10-20% over building a purpose built system, and the cost of the electricity to run the long duty cycle will be insignificant compared to the original capital outlay, which would be a good management technique had it been properly executed from the get go.

    Dan

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    Re: Help cutting open 40ft reefer, we now have problems

    where are u from adrian?

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