kollmann-marine.com

[joesailor]

Last year I had an issue with a Tundra T80 using BD50 not cooling, running too much. The mfg. gave me a brand new unit and for 5 months last winter it was OK. This summer we ran only a few times, maybe 3 daysa at a time, but very hot outside in Virginia so I did not worry about run time.
Now in 70 degree boat and outside temp unit is running almost 100% of the time ( on AC power ) . Box temp seems OK and evap has frost on whole surface - I have T state at highest setting and still will not shut off, where should I start to look. I am very frustrated with these issues being now on my second unit.

[joesailor]

I do not have temp gauge with me, but even with compressor running all of the time refrigerator section not over cooling. Evaporator is U shape in freezer, frost on top section in freezer, no frost on floor of freezer, frost on all of section facing fridge section.

[kollmann]

ANSWER:

I have never seen a Tundra T80 refrigerator except on their web site. All I can tell you is if there is frost covering all of the evaporator’s surface area and there is no frost on the line returning to compressor it does no appear to be a refrigerant problem. If the evaporator is not forming frost over its complete surface the refrigerant volume is low or compressor speed/capacity is too low or there is poor condenser cooling. Frost on return line can indicate too much refrigerant. The number one problem with any cabinet refrigerators designed for RV’s is when they are installed in a boat added condenser cooling is normally required. With the second unit having the same problems as the first this would indicate it is not designed for your application, or there is a boat problem in disposing of the refrigeration process heat.

I searched my files and found our discussions in 2005 on the old unit sound like the same problem as before:

POSTED SEPT. 2005

DB 50 in Cabinet refrigerator with poor cooling #776

joesailor
Post subject: Tundra T80 Low Cooling

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I have a two year old Tundra T80 with BD50 compressor installed on my trawler. The condenser is clean and ventilation is adequate. System can run on eith DC or AC. This weekend system started to run all the time and not cool well. The evaporator is the thin white type, box has top freezer, bottom fridge. The lower part of evaporator that also cools fridge has frost on the bottom ( in fridge ) but no frost in freezer. Measurements with IR thermometer show that lower plate inside freezer reads 17 deg on left side but 28 deg on righ side.
Am I low on charge. Is that a leak, especially since unit was running OK prior. Amp draw is normal or low ( 3-5 amps running ), evap fan is runnign, not bad noises. What should my next steps be? I have some ice packs in freezer and jugs of water in fridge, trying to see if system will stabalize or just keep running, outside temp righ now is 65-80 degs.

joesailor
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A little more information , I have a Frigoboat SSC also installed.
Wiht 4 leds I have 5 amp draw, with 6 leds I have 6 amp draw; I am running with 4 leds in manual mode to try and see if box will stabalize over next day or so.
Could SSC have messed up my unit?

ANSWER:

You said 3 to 5 amps is normal operation for this unit, I would have believed it to be close 7 amps in warm weather with a warm freezer at 3500 rpm, (6 LED’s ).

I do not have any experience with Tundra refrigerators but if the forced fan air across the condenser is adequate then a small amount of refrigerant has leaked out. You can add additional air cooling as a test by placing any fan near the air intake to increase condenser cooling.

I do not see how the SSC could be involved in this problem. It the compressor were running a 2000 rpm ( one LED )and box did not get cold then it would be caused by the SSC unit.

As much as I dislike anyone connecting servicing gauges to one of these small systems it may be the only way to correctly to identify the trouble. If it does prove to be low refrigerant level then finding and repairing the leak is the problem. Hopefully if there is a leak it will be the seal of the servicing port cap.

joesailor
Joined: 05 Sep 2005
Posts: 4 Posted: 06 Sep 2005 12:56 am Post subject:

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Thank you for the prompt reply. I checked box again tonight, its still not cycling, and with 6 leds on ssc current draw is 6 amps. Freezer is now at about zero and fridge is just about 40 degrees, but for most of day it was at 42, its cooler tonight ( 65 degrees ).
I plan to call Tundra tomorrow and see what they say. I am not original purchaser, but unit was only purchased in April '04 and has had maybe 7 months of use, who knows maybe they will make it right for good will?
If not, how do I find a tech who will do job right? The charge for unit is 2.95 oz, so what are we talking about, a leak of a couple of 1/10's of an oz?

joesailor

Joined: 05 Sep 2005
Posts: 4 Posted: 06 Sep 2005 01:14 am Post subject: Self service Tundra & BD50

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Can I service this myself, assume I would need leak detector and correct gauge set? Location of leak determines if unit can be fixed?


ANSWER:

A current draw of 6 amps and a freezer that almost reaches a temperature of zero would indicate there is enough refrigerant but why does the compressor run continuously? An eight cubic foot box with less than three inches of insulation could require more than the maximum output of a BD50 compressor at ambient temperatures above 75 degrees.

Could it be that when you installed the SSC that the Tundra installed speed resister was not removed and now the compressor is over speeding the maximum speed of 3500 rpm effecting Performance. Tundra would need a resistor as 2000 rpm would have been too slow a speed for an eight cu ft box. You indicated the unit did perform OK before installing the SSC, so what else has changed? On other company’s cabinet refrigerators using the BD compressor that is AC/DC powered the thermostat circuit interrupts the DC power and not the module thermostat terminals. Did your unit have a jumper wire between terminals C and T instead of the thermostat wires?

Is the Door seal in contact all the way around the door? Is the cabin of the boat much warmer than before?

I prefer to avoid suggesting connecting servicing gauges do to the problems that can result even if done by refrigeration technicians. My advice is, avoid servicing now based on what is known and stay with non destructive testing until you have a stronger indications that refrigerant level is low. Field servicing a system that contains less than four ounces of refrigerant is tricky but it can be done.


Posted: 06 Sep 2005 03:10 am Post subject: Re: BD 50 large box poor performance

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kollmann wrote:

Could it be that when you installed the SSC that the Tundra installed speed resister was not removed and now the compressor is over speeding the maximum speed of 3500 rpm effecting Performance. Tundra would need a resistor as 2000 rpm would have been too slow a speed for an eight cu ft box. You indicated the unit did perform OK before installing the SSC, so what else has changed? On other company’s cabinet refrigerators using the BD compressor that are AC/DC powered the thermostat circuit interrupts the DC power and not the module thermostat terminals. Did your unit have a jumper wire between terminals C and T instead of the thermostat wires?

---> The tundra had a speed selection board which I removed. It does not have a resistor in the t-stat wires. Actually, unit was OK after I installed SSC in July, did one trip over 4 days and it cycled correctly in auto mode of the SSC. T-state was connected to C&T terminals before I added SSC. As far as I know nothing has changed between July when I last used unit and this weekend.

Is the Door seal in contact all the way around the door? Is the cabin of the boat much warmer than before?

-----> door seal looks good, boat temperature has not changed.

I prefer to avoid suggesting connecting servicing gauges do to the problems that can result even if done by refrigeration technicians. My advice is, avoid servicing now based on what is known and stay with non destructive testing until you have a stronger indications that refrigerant level is low. Field servicing a system that contains less than four ounces of refrigerant is tricky but it can be done.

-----> what would be a stonger indication of low refrigerant? I am heading south in about 4 weeks and need a reliable unit. Once I hit North Carolina I do not want to be trying to find service on the ICW so any other hints appreciated. We anchor out and I need the unit to cycle correctly and not overdraw down my batteries.

kollmann
Site Admin

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The first sign of some refrigerant loss is that frost does not form over 100% of the evaporator's surface and the compressor runs longer than normal. It is very unusual for one of these solid tube connected cabinet systems to leak. There are two exceptions, a hole is created in evaporator when defrosting or the unit is old and the aluminum evaporator corrodes through. A sudden loss of refrigerant on a two year old sealed unit and still drawing six amps makes me wonder about condenser cooling, compressor speed and heat infiltration into the box.
_________________
R.L. Kollmann


joesailor



Joined: 05 Sep 2005
Posts: 10 Posted: 06 Sep 2005 04:56 pm Post subject: Update on Tundra cooling/running

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I spoke to Tundra today. They asked me to defrost unit ( done ) and also to remove the drain pan that sits below the evaporator in the fridge portion. I did that and will see what unit is doing after 24 hours.
They told me that the factory setting for compressor speed on this unit is 3000 rpm.

kollmann


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My question still is, Did you remove Tundra's Speed resistor before installing the SSC?
_________________
R.L. Kollmann


joesailor
Joined: 05 Sep 2005
Posts: 10 Posted: 06 Sep 2005 11:55 pm Post subject: SSC Install on Tundra T80

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I removed the speed selection resistor board that was attached to the controller before I installed the SSC.
Today I tried forcing more air over the condenser with a fan, did not seem to change anything. Unit was defrosted at 9 am, all items inside were cold as defrost was quick, its now 8 pm and unit has not yet cycled - I will check box at 24 hrs before I call Tundra again.


joesailor
Joined: 05 Sep 2005
Posts: 10 Posted: 07 Sep 2005 02:42 pm Post subject: Update on Tundra Low Cool Runs all time

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Twenty four hours after defrosting and leaving unit without opening doors here is status.
The unit is cycling and running 60% of the time each hour at an ambient of 72 degrees. Inside the freezer is 0 to 7 degrees and the bottom of the fridge is 34 degrees. There is very little frost on the bottom evaporator plate and no frost at all on the right side where it heads back to the compressor suction. I opened doors maybe 10 seconds to take temps with IR thermometer and box needed full hour of running to recover.
I think unit is a little down on charge and causing longer recover/run times. I am not confident that it will handle 90 deg ambient without running all the time.
Plan to talk to Tundra again. The unit may have always been this way. I say that because prior owner of baot never ran unit on batteries, only on shore power or genset so would not have noticed it running all the time. When I used it in July ambients were lower, also I had some battery issues so also ran on genset some of the time. This past weekend was hotter etc.
What should I do next. Tundra factory indicated they do not fool with recharging, guess that leaves swaping out unit?


ANSWER:

I think you now have established the design base line for that refrigerator. The performance is now reasonable on a 72 degree day, good freezer and refrigerator temperatures and only a 60% run time. In my 12/24 volt book I warn about using a single BD 50 compressor system for boxes larger the six cubic feet in the warm tropical climates. RV refrigerators are not designed for environments in a cruising boat, they lack enough insulation, condenser cooling is generally inadequate and the front doors are not sealed adequately.


Because of your unit’s present performance and six amp current draw I see no reason to worry about refrigerant charge. Nor do I believe buying any equivalent refrigerator type, same size, with same amount if insulation, could be expected to perform any better.

When the ambient temperature is increased by one degree my rule is the run time is increased by four percent. By increasing the boats cabin temperature from 72 to 97 degrees the compressor run time would double and because this can’t happen the box would warm up during the day. It would seem that when anchored out in tropical conditions the daily refrigeration power consumption will be 144 amp-hrs.

The only things I can suggest to improve this units performance is to replace the condenser cooling fan with a high output shrouded fan. Do a ribbon test of the door seal and maybe add a door closed latch at both top and bottom to better load the door seals.

joesailor
Joined: 05 Sep 2005
Posts: 13 Posted: 08 Sep 2005 01:51 am Post subject: More Data on Tundra T80

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Here is some more data.
Freezer 0-7 degrees, fridge bottom 34 degrees.
7 am ambient temp 72 deg, max today was 83 degrees. Box was opened 3 times just to verify temperatures.
Over a period of 13 hours total AH used was 43. I belive that at 3000 rpm compressor draws average of 5.6 to 6 amps running, so that is again about 57-60 % run time.

I appreciate your feedback.
How does one do a ribbon test of door seals?


joesailor
Joined: 05 Sep 2005
Posts: 13 Posted: 09 Sep 2005 12:00 am Post subject: Will SSC help Tundra T80?


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Richard,
In light of the operating characteristics of my Tundra is it worth using the auto feature of the SSC? or should I run it in manual mode? or just take it off and go back to 3000 rpm resistor?
Thanks for any insight.

joesailor
Joined: 05 Sep 2005
Posts: 13 Posted: 09 Sep 2005 03:35 am Post subject: Tundra T80 advertised power use


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How does Tundra advertise that at 90 deg outside, 40 deg box temperature that it uses only 28 watts per hour? see here: http://69.37.153.114/Artwork/Dometic/Literature/Tundra%20Brochure/L-2007G%20Tundrabroc.pdf

My measurements showed 36 watts per hour at 83 deg outside?


ANSWER:

How does one do a ribbon test of door seals?
To test the door seal contact all the way around the door a thin ribbon is closed in the door. If there is no resistance when the ribbon is pulled out that area of the seal will leak.

Should the SSC be removed? You know that 3600 rpm is going to be required in tropical weather conditions. and in cool temperatures their may be a small energy advantage by having the SSC. If you were to set the thermostat higher, then the SSC will reduce power consumption.

How does Tundra advertise that at 90 deg outside, 40 deg box temperature that it uses only 28 watts per hour?
Without having all the condition and parameters of their test I have to assume it is creative advertising. Should anyone believe a eight cu. ft. combination refrigerator/freezer box with less than six inches of insulation could consume only 2.3 amps per hour in a 90 degree environment? Not in my book.

[joesailor]

I plan to check the condenser fan next week by pulling out the box. I have no way to tell its running over the sound of the compressor.
If I decide to add fans I assume using a relay off the danfoss compressor is safer? than trying to add to the existing fan lead that is limited to 1/2 amp. Do you have a specific recommendation for relay spec?

[froinlavin]

tom discussed this in the unmoderated topic forum yesterday...

[kollmann]

froinlavin, Thanks, but you forgot to list the un-moderated topic answer or at least the forum's address.
joesailor has a problem and would appreciate any help you can offer, thanks again for your help.

[kollmann]

joesailor, Yes you will need a relay when adding a second fan to a BD50 condensing unit.
A 12 volt automobile 30 or 40 amp plug in relay with either 4 or 5 spade connectors is the normal relay used for adding a second fan.. They cost from $5 to $8 at auto parts stores. They also come with a wiring digram on one side.

[joesailor]

OK,
I plan to add another vent and additional cooling fan.
A question concerning second fan - is it better pulling air into lower vent or pushing air out of upper vent.
Concening the fan on the BD50 already installed - is it possible that after 6 months of use that fan has slowed down like computer fans often do?
Is there a generic replacement or should I go to mfg to get fan?

[CSY Mon]

For what it is worth:

I added two fans to my BD-35 unit: Two 3" computer case fans that blows straight into the big fan, and also ventilates the box.

To make them run, I had to solder in a relay, also from Radio Shack.
Forgot the model number, small black cube with 5 "pronges"

Works great.

[kollmann]

joesailor. I prefer the 12 volt four inch 80 CFM muffin fans available from many suppliers; WW Granger or www.mouser.com phone 800 346-6873 has the ball bearing replacement fan for $13 but I think they have a $30 minimum. Stock number 433-BP1202512L cat. 619 Page 1164

As to airflow heat rises naturaly so fan should be in that direction.

[joesailor]

I am underway crusiing on my boat. Before I left I added 25 sq inches of vent and a 5 inch computer fan to force more air past the condenser. Venting now exceeds mfg spech of 75 sq inches clear vents. Adding vent and fan does not seem to have impacted colling inside of box or run time.
Right now it is 73 deg ambient in boat - fridge section reads about 34-37 deg, freezer reads 14-16 degrees, tstat is set on 2 out of 5 ( 5 being coolest ) - system is running about 75 percent of the time when not opened ( as in overnight ).
Not sure what to do next. How do I check out the tstat? I did check and it is correctly mounted on the evap. Can the compressor be running at the wrong speed even if resistor is set OK? The factory setting for this unit is 3000 rpm.

[kollmann]

Because you reported earlier that there is frost covering all of the evaporator and none returning to the compressor, and this is the same model refrigerator as the previous one with the same problem, it must be a poorly designed unit for your application.

Add a little more insulation between the refrigerator and freezer to increase the temperature difference. This will lower the freezer temp without lowering the refrigerator temp and set the thermostat to a higher number.

This may not be an efficient solution but you own the unit and it will work as a refrigerator/freezer even if it means the compressor runs 24 hours per day. Sorry but not every product lives up to its advertised claims.