Author Topic: BD35 Performance with VD 15 Fan Air Evaporator  (Read 7298 times)

Richard

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BD35 Performance with VD 15 Fan Air Evaporator
« on: May 15, 2012, 07:37:03 pm »
BD35 Performance with VD 15 Fan Air Evaporator

First of all well done on your new site and thanks for the continued service to the boating community.

I have a similar set up as mentioned here in this thread. I have a BD35 compressor with a Waeco VD-15 air assisted evaporator.

I have installed a Carel digital thermostat but have opted to sense box temperature rather than evaporator temperature. The sensing probe is installed mid way left to right and mid way top to bottom on the front side of the box - away from the evaporator.

I am presently testing / adjusting my setup so as to have a cool box without overworking the compressor and could do with some of your guidance.

Questions:

How long should i leave the system ON before i can start performing adjustments ? Some people have suggested 24 hours. Is this correct ?

My initial test was conducted over 3 hours. BD35 is set to run at fixed speed of 3000rpm. I started with an ambient temperature of 25C. After 3 hours box temperature at the bottom went down to 4C whilst mid way up at temperature probe it was 11C.

At this point i adjusted set point temperature to 11C, compressor cut out and normally cycling commenced.

My questions at this point are how many hours should one expect it to take for box temperature to stabilise and what target set poing temperature should i start with - considering the temperature probe is mid way up inside the box ?

Thanks
Tyrone


ANSWER:

Tyrone, Thermostat box temperature control on fan cooling evaporators such as VD15 normally control box temperature while conduction heat absorbing plate evaporator control evaporator temperatures. In a standard refrigerator evaporator temperatures are normally controlled not box temperatures by thermostat’s probe attached to evaporator and set to around 12 (11 C) degrees or lower for freezers.

Your Carel thermostat will be used a cooler box zone thermostat set to a point where it will keep fan inlet temperatures warm enough to prevent fan evaporator coil from freezing over. From the WAECO book I am looking at box temperature interring fan chamber of 41 (5 C) degrees for the separate box temperature probe location midway up the box.

Compressor run time on your unit is going to depend on actual box temperature thermostat setting and good efficient air flow over evaporator coil heat transfer fins.

I hope you are aware that fan evaporators do not function well in marine environments except as 41 degree coolers because they freeze up at temperatures below 33 degrees. I did a Q and A research of my records and listed some of the items below regarding the VD 14,15, and 16 fan evaporators. 


VD Fan Evaporator Q and A

I am making a freezer at the moment for my boat and was wondering if anyone has tried the forced air lamellar type evaporators. Waeco makes these and calls them a VD-16 here in Oz, details can be found here WAECO mobile solutions

The main concern I have is with the unit frosting up in a short while, looks like a pain to defrost.

Regards

ANSWER:

 The VD15 and 16 Fan evaporator is functionally designed for cooler boxes where evaporator temperatures stay above 33 (1 C)degrees F when compressor is not running. ALL refrigerator and Freezer fan cooled fin evaporators require off cycle defrosting. The VD15 and16 are not self defrosting and there is no way in tropical climates to prevent moist air or moist food from depositing moisture on a cold evaporator.  About the time WAECO got a hold of Adler Barbour the tech specialist on Adler Barbour’s refrigeration forum answered questions from unhappy customers about the fan evaporator. This AB forum appears to have been deleted from internet. Twenty years ago I produced a line of fan cooled evaporators to use with engine driven icebox conversion refrigeration systems. On an engine driven system the compressor runs once a day to freeze holding plates and my Freeze Blaster was designed to be located in the warmest area of box where it would be defrosted during the twenty three hours a day when compressor was not running. 

Common complaints on Waeco Fan Evaporators

It appears our evaporator is not working properly and we keep getting ice & frost buildup at the bottom of the unit. We have a VD-15 circulating air evaporator for Series 80. Has anyone had a similar problem or is able to make a suggestion?

While not cover with ice , I have a Waeco/danfoss 12V unit on my sailboat . lately , 2 months ,the cooling unit in the box( the one that looks like a car radiator..) is gradually covered with ice , the temp in the fridge getting higher. In 10-14 days , it is so totally covered in ice-and uneffective- that I have to defreeze and dry ( manually). unit worke fine (reg the temp level). what might be the problem?



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Jim Nelson
Road Town, Tortola, BVI
08/07 at 09:06AM
RE: Bavaria 39
343 views
3 replies    Refrigeration
Hello All,
We have a Bavaria 39 Cruiser built in 2006. Our refrigeration seemed to be working perfectly until recently. It appears our evaporator is not working properly and we keep getting ice & frost buildup at the bottom of the unit. We have a VD-15 circulating air evaporator for Series 80. Has anyone had a similar problem or is able to make a suggestion?

Thanks to all!
Jim Nelson

ANSWER:

The VD 15 Fan evaporator is functionally for cooler boxes where evaporator temperatures stay above 33 degrees F.  Refrigerator and Freezer fan cooled fin evaporators require off cycle defrosting. The VD15 is not self defrosting and there is no way in tropical climates to prevent moist air or moist food from interring a refrigerated box.

Freeze of cooling unit..
While not cover with ice , the I have a Waeco/danfoss 12V unit on my sailboat . lately , 2 months ,the cooling unit in the box( the one that looks like a car radiator..) is gradually covered with ice , the temp in the fridge getting higher. In 10-14 days , it is so totally covered in ice-and uneffective- that I have to defreeze and dry ( manually). unit worke fine (reg the temp level). what might be the problem ?


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Alex

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My guess is you have the VD-16 forced air evaporator which has a fan that draws air through the coils. Excessive frost build up is caused by air (with it moisture) leaking into the box through the lid gaskets or any unpluged holes (drain, tube set exit etc). Inspect the gaskets and replace them if worn. Purchase a plug for the drain if it does not have one and fill any holes that you may have in the box.
« Last Edit: May 15, 2012, 07:56:57 pm by Richard »

smonc

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Re: BD35 Performance with VD 15 Fan Air Evaporator
« Reply #1 on: May 31, 2012, 08:24:27 pm »
I have a typical ice box in a 30' sailboat with only 2 90 degree corners, slopes on all other sides.  Box is a little less than 4 cubic feet, 2" polystyrene max, 1" or less on 2 sides, typical drop in lid. I think the box is fairly air tight, but not like a factory frig.  I am drawn to the VD-15 because I can get it into the box through the 10" X 10" opening, without tearing out the counter and it should provide even temps in the box.  Willing to go without any freezer space.  Your comment is concerning:

"I hope you are aware that fan evaporators do not function well in marine environments except as 41 degree coolers because they freeze up at temperatures below 33 degrees. I did a Q and A research of my records and listed some of the items below regarding the VD 14,15, and 16 fan evaporators."

My home frig runs 36 to 37 degrees.  To make the wife happy my installation needs to match that.  It does not have to exceed it, but it must match.  Given that the vd-15/BD35 is rated for up to 8 cu feet, is there a good chance that in my installation the unit will cycle off enough of the time that evaporator will be able to defrost between cycles?  Or, is this just a bad idea, and I should figure out a way to get plenty of plate into the box?

Richard

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Re: BD35 Performance with VD 15 Fan Air Evaporator
« Reply #2 on: June 01, 2012, 07:59:49 am »
You have made a good choice for a high temperature refrigerator and 36º temperatures are possible with out excessive frost formation on evaporator. The BD 35 has more than enough capacity to handle a four cu ft box and fan evaporator will be more efficient in removing heat from product at temperatures above freezing than a standard evaporator. The drawback to fan fin coil evaporators is they must be defrosted frequently in order to allow fan air to pass through coil.

I have no way to predict how often or even if you will need to defrost evaporator coils. If daily amp-hrs are high or box thermometer indicates warmer temperatures than normal it is time to check for frost blocking of coils. To reduce moist air infiltration from interring box a tight lid or door seal is about all you can do to reduce frost formation.