Norcold Refrigerator Test

[davlin]

As promised. I'm sure that there will be better ideas for future testing, but I gotta tell you that I may be saving up my lunch money for a Dometic CR-1110.

Dave

[Redtail Cruiser]

Dave, nicely done, easily understandable with good photos and graphs. Even though your results may have been disappointing, you definitely get an "Atta-Boy" for your effort.

Padgett (Rambling Rose) sure could learn a few things from you.

[ThePair]

Nicely done, and I certainly appreciate the hat tip, although I can't take all the credit -- others before me taught me what I know, etc.

I would make a humble suggestion, and that would be to repeat some of these with a different coil-fan arrangement. The idea of the convection flow of air through the back of the fridge coils favors air coming in from below, up through the fins, and then out the top/side vents. The way you have the coil fan set up may not be drawing in sufficient lower, cooler air, then circulating the air around the top of the compartment, and then the stock TM fan, which is essentially sucking in the air at the top (which could be drawn in through the top/side vent rather than the bottom and across the fins). Blowing the air around the top of the compartment could push some down on the fins, which will slow (or even potentially reverse) the natural air convection flow through the fins. I fear this set up could potentially be working against itself, and may be the reason you didn't see much difference in your testing results.

As I said, I mounted my fans onto the upper vent panel itself, blowing out. Much like a computer case fan, the air that is being blown out must come in from the other vent, in this case the lower side vent and/or the floor vent. The air then has no choice but to flow up across the fins, increasing the convection current, and then out the top. There is no way for my set up to slow or reverse that convection flow, and I can definitely feel warm air coming out the top vent when I have it on. I don't use the stock fan at all when the shells are up, doing this with my aux fans only.

I hope this explanation is understandable. I can try to draw a picture if it will help. Edit: crappy drawing attached.

[davlin]

Originally Posted by ThePair

Nicely done, and I certainly appreciate the hat tip, although I can't take all the credit -- others before me taught me what I know, etc.

I would make a humble suggestion, and that would be to repeat some of these with a different coil-fan arrangement. The idea of the convection flow of air through the back of the fridge coils favors air coming in from below, up through the fins, and then out the top/side vents. The way you have the coil fan set up may not be drawing in sufficient lower, cooler air, then circulating the air around the top of the compartment, and then the stock TM fan, which is essentially sucking in the air at the top (which could be drawn in through the top/side vent rather than the bottom and across the fins). Blowing the air around the top of the compartment could push some down on the fins, which will slow (or even potentially reverse) the natural air convection flow through the fins. I fear this set up could potentially be working against itself, and may be the reason you didn't see much difference in your testing results.

As I said, I mounted my fans onto the upper vent panel itself, blowing out. Much like a computer case fan, the air that is being blown out must come in from the other vent, in this case the lower side vent and/or the floor vent. The air then has no choice but to flow up across the fins, increasing the convection current, and then out the top. There is no way for my set up to slow or reverse that convection flow, and I can definitely feel warm air coming out the top vent when I have it on. I don't use the stock fan at all when the shells are up, doing this with my aux fans only.

I hope this explanation is understandable. I can try to draw a picture if it will help. Edit: crappy drawing attached.

Excellent drawing and easily understandable. If I stay with my absorption refrigerator, I can measure input and output air temps and see if one circulation idea is more effective than the other. Even in the most optimal air circulation pattern, however, when you're pulling 100 degree "cold" air in, I fear you're just not going to get good performance from the condenser.

Dave

[Padgett]

Just a thought but when camping with the AC on, is there a way to duct cool inside air over the fins rather than hot outside air ?

[davlin]

Originally Posted by Padgett

Just a thought but when camping with the AC on, is there a way to duct cool inside air over the fins rather than hot outside air ?

Not impossible. Would require fans, ducting, and some new holes in the interior cabinetry. Some large commercial absorption chillers actually have small, refrigerated coolers that can place air on the evaporator/condensers when the ambient air gets too warm. Those big chillers operate differently than our single-stage RV units, but the principle is the same. Before I would want to undertake such a major, messy, project in my TM, however, I think I would just look to replace the Norcold with a compressor driven unit.

Dave

[TrailManorMan]

That is an extremely well organized test, great information. I may consider the compressor model for inside. I have a compressor model portable and it is great.
Not any problem on 95 plus degree days so I'm confident it would be the same results with a built in.
Again your test, graphics etc. we're very informative , thank you

[ShrimpBurrito]

Very nicely done, Dave. To echo ThePair's comments, I too think you may have inadequate cooling from the fan because a) it appears that it is simply recirculating the hot air in that area, and not bringing in any cooler air; and b) not exhausting the hot air from the top of that compartment.

Could you -- pretty please -- mount it on the top vent blowing outward and do another test?

If you wanted to go crazy, I guess one could ALSO install one or two fans on the bottom vent panel blowing IN, being careful not to affect the burner.

You're right, blowing 95 degree air doesn't seem helpful, but I bet/guess the air temp in the compartment where your new fan currently sits is hotter than that. Let's say it's 120 degrees up there --- if you can bring it down to 100 (in 95 degree ambient), that would seem quite significant in increasing cooling capacity.

I think we need to run more tests, Doctor.

Dave

[davlin]

Originally Posted by ShrimpBurrito

Very nicely done, Dave. To echo ThePair's comments, I too think you may have inadequate cooling from the fan because a) it appears that it is simply recirculating the hot air in that area, and not bringing in any cooler air; and b) not exhausting the hot air from the top of that compartment.

Could you -- pretty please -- mount it on the top vent blowing outward and do another test?

If you wanted to go crazy, I guess one could ALSO install one or two fans on the bottom vent panel blowing IN, being careful not to affect the burner.

You're right, blowing 95 degree air doesn't seem helpful, but I bet/guess the air temp in the compartment where your new fan currently sits is hotter than that. Let's say it's 120 degrees up there --- if you can bring it down to 100 (in 95 degree ambient), that would seem quite significant in increasing cooling capacity.

I think we need to run more tests, Doctor.

Dave

Thanks for volunteering me, Dave!

[ShrimpBurrito]

Originally Posted by davlin

Thanks for volunteering me, Dave!

It is an honor and a privilege.

Dave