Hot refrigerator coils...(Fun Finder)

[cannesdo]

I'm posting for a neighbor. She has a little "Fun Finder" travel trailer. There are two vent panels for the fridge and coils in the lower area feel warm but not too warm but the ones at the top are quite hot. Hot enough that you want to take your finger off it in a few seconds. That doesn't seem right. It's a Dometic. Thanks...

[happycamper002]

I'm referring to those who are advising installing fans. Of course you need to remove heat in the condenser portion of any cooling system. This heat that is absorbed at the evaporator end needs to be removed by fans but they are not located in the vents.

Go back and reread the other posts.

[OldSmokey]

happycamper002 wrote:
Bad advice and even irresponsible.

Installing fans and wires in either end of heat vent violates fire safety codes. You can't (well you can but you shouldn't) run electric wires inside heat vents and duct works.

If wire insulation catches fire, and blower is running, you are creating a blow torch.

Unless you use specially insulated wires which are fire retardant/fire rated.

This item is not even available for the general consumer, let alone RVs.
They are mostly available for fabricating furnaces, stoves and jet engines.

fire safety codes.. hmm.. well I doubt the rv was even inspected let alone build to any codes.. LOL

[ttommyy48]

happycamper002 wrote:
Bad advice and even irresponsible.

Installing fans and wires in either end of heat vent violates fire safety codes. You can't (well you can but you shouldn't) run electric wires inside heat vents and duct works.

If wire insulation catches fire, and blower is running, you are creating a blow torch.

Unless you use specially insulated wires which are fire retardant/fire rated.

This item is not even available for the general consumer, let alone RVs.
They are mostly available for fabricating furnaces, stoves and jet engines.

We're not talking about heating ducts here, this discussion is about the refrigerator cooling system that is vented to the outside. A LOT of units come from the factory with cooling fans to help circulate cooling air behind the refrigerators.

[BFL13]

The installation instructions for the Dometic 7401L (smaller sort of RV fridge) include using a baffle below the upper fins so the cool air from the lower vent will pass through the fins on the way up to go out the upper vent.

In some RVs you have a wide space behind the fridge so the cooler air rises up right past the fins and out the roof vent without going through the fins. The baffle stops that.

In some cases a fan can help push/pull the cooler air up. Goodness knows how it can all work down there in Arizona right now! 😞 What "cool air" coming in the bottom vent?

[happycamper002]

Bad advice and even irresponsible.

Installing fans and wires in either end of heat vent violates fire safety codes. You can't (well you can but you shouldn't) run electric wires inside heat vents and duct works.

If wire insulation catches fire, and blower is running, you are creating a blow torch.

Unless you use specially insulated wires which are fire retardant/fire rated.

This item is not even available for the general consumer, let alone RVs.
They are mostly available for fabricating furnaces, stoves and jet engines.

[Old-Biscuit]

Fans use a t-stat that is attached to the condenser fins.
Based in fin temp the t-stat closes to start fan(s) and opens to stop fan(s)

Typical temps used are 130*F (close) and 115*F (open)----that is HOT

Other temp range t-stats are available.

As Chris stated........the more 'heat' that can be removed the more ammonia vapor can be condensed into liquid ......more liquid ammonia the colder the freezer and then more heat absorption left for food section.

Airflow.......its all about airflow (and how/where that airflow is directed)

[Chris_Bryant]

FWIW, what is happening in the top, condenser coil is condensing pure liquid ammonia- the cooler you can make the coil, the more ammonia is produced. From here the ammonia goes down to the freezer, which contains the hydrogen (or Helium). Due to Dalton's law, which basically states that in a mixture of gasses, the total pressure is the sum of each gasses partial pressure, and hydrogen has a very low partial pressure, lower than ammonia, so the liquid ammonia evaporates, which takes requires heat, which comes from the inside of the box.

So, the evaporator coil will be the hottest, but it is where the most heat needs to be removed (other than inside the box 🙂 )

[Searching_Ut]

As mentioned, the refrigerator runs off heaters. Sounds kind of backwards but it's a simple concept when you get into the physics behind it. When not on propane, the two electric heating elements in my Norcold 18cf side by side fridge draw 600 watts of electric heat so there is actually quite a bit of heat that ends up being dissipated by the cooling fins at the end of the process. Those coils are heat exchangers and rely on convection airflow for cooling for the system to work right. As others have mentioned, adding fans to aid the airflow can improve the functioning of the refrigerator.

The option I went with to improve cooling was to add a device called an ARP. It has a couple of temp sensors to kick on cooling fans to help out with the heat when needed, and a sensor it uses to shut off the heating system when it overheats due to being off level, or should you have other issues.

[wa8yxm]

time2roll wrote:
I thought the top coils were the hottest? If the fridge is working I call normal.

Second: Even on electric.. Believe it or not this fridge (Absorption cooling unit is the formal name) runs on HEAT, Yes it has heaters in it.

How it works
Heat, be it from a propane burner or an electric heat element, causes some chemicals to seperate. they then travel via different paths through the outside heat exchanger giving off heat, then they come together again inside the Cold box.. When they come together the term is "Endothermic Reaction" means they Absorb heat, Hence the name "Absorption cooling unit) then the mixture travels down to the boiler where the burners (Gas or electric) cause it to seperate again and round and round we go.

If it is that hot perhaps a fan or 2 will help.. I added a pair of 4" computer fans I got cheap (less than a buck) blowing up and it does seem to help. You can also put 'em in the top vent sucking up and blowing OUT.

[suprz]

No matter if its normal to be that hot, with a side vent for the hot air of the frig coils, i would advise to put in a small 12V computer fan on the top vent blowing outward to promote the natural convection effect of the hot air. Hot air does not like to rise and then have to take a 90 degree turn to go out ;). My first camper was a pop up and i put a thin sheet of aluminum in the top vent to help make a curve to the outside for the hot air and added a smal computer fan to push the hot air out. It made a huge difference.

[Chris_Bryant]

With 2 sidewall vents, it requires fans.

[SoundGuy]

WNYBob wrote:
Sounds love she has a refer in a slide, and therefore the two vents. A non slide unit has one side (lower intake) vent and the exhaust vent on the roof.

Not always. A fridge will have an exhaust vent out the roof if it's positioned in an elevated location in the trailer, which most are. However, in those cases where the fridge may be located closer to the floor with an open space above the fridge - as was the case with my own non-slide KZ Spree 240BH - the fridge exhaust will be located on the sidewall of the trailer above the intake below it. Obviously any fridge that's located in a slide will exhaust through the sidewall as it can't be vented out the slide roof which when stored is within the trailer body itself. :R

[brulaz]

How is the frig's inside temp doing? If it can't keep up with the heat there are a couple of things you can try.

In hot weather I always popped off the top vent to help the hot air escape and improve air flow.

Or you can add a computer fan.

Or park in the shade, or at least keep the frig in the shade. If it's in a slide, get a slide awning.

[SCVJeff]

cannesdo wrote:
She's on electric.

it still gets hot, that's the point of its operation.
It can be, and should be the same temp in the boiler regardless of the heat source

[cannesdo]

She's on electric.