Re-insulating the fridge – chasing my tail

After running for a year with my modified refrigerator compartment venting and insulation, the Nova Kool compressor fridge is still barely keeping up on a hot day. I had to pull the fridge again anyway (to replace the insulation that I pulled when fixing the drip) so I figured I’d try to add a bit more insulation between the back of the fridge and the outside of the camper. I now have 1/2″ poly-iso against the van wall, a bunch more mineral wool stuffed into various nooks and crannies, and no remaining gaps between the OEM insulation sheets and the fridge compartment. I also added mineral wool and a layer of reflective insulation in the microwave compartment, hoping to keep that a bit cooler also.

On suggestion from a family member , I spaced the fridge out into the isle by adding a 3/4″ frame where the fridge mounts. This frees up space between the back of the fridge and the interior of the van chassis.

So far, it looks like the additional insulation has helped keep the compartment cooler when the van is in the sun, but has not made a difference in the fridges ability to keep cool on a hot day, either with or without the fans that pull air from behind the fridge and push it out above the microwave.

I’ve done a few obvious things, such as checking the door seals with a thin strip of paper & measuring the compressor amperage. I’m sure that I’m getting good temperature data – I have a SensorPush Bluetooth recording fridge temp and humidity. When the fridge is running, there is an obvious draft from bottom to top. The coils are warm, not hot.

I’m out of ideas. Either the compressor itself is bad, cold air is leaking out somewhere, or … I have no idea. I’m stumped.

Refrigerator cross-section. Air enters under fridge and exhausts above microwave. Fans boost airflow.

Update 9/1/2020: Nova Kool decided that it was low on freon and replaced it under warranty with a refurbished fridge.

4 Comments

  1. Ole Login says:

    Is coolant full?

    1. Janke says:

      I’m not sure, and there is no way to check the freon level or pressure. AFAIK its sealed. No fittings.

  2. Sam says:

    My first guess would also be low charge. My next step would be to take the intake and exhaust temp when it’s running to see how much heat it’s trying to kick out and get a feel for what kind of heat you’re rejecting (BTU = 1.08*CFM*dT – Fan BTU (Watts/1000/3412))

    Your fans are down stream so the heat they’re dumping in is after the condenser which is great. The insulation helps with radiant heat, but when your cabinet temp > ambient you’re trapping that heat in your van and you’ve got to reject it later through your A/C, but an economizer is soooo not worth installing.

    Is the fan bank totally separating the chambers? If not you could be building a high pressure behind the microwave which is actually STALLING air flow! You should’ve left the drip, the water vaporization lowers the dry bulb down towards the wet bulb temp and actually decreases your air temp across the condenser 😀 (I have to be a smart ass somewhere).

    Once you prove out your airflow isn’t stalling and just recirculating and that you’re getting a good delta T across your inlet/exhaust when the unit is running, then I’d put a thermo probe in the condenser area on a hot day and take readings when the fridge is both not running and running.

    That all proves you’re effectively moving air and CAN reject heat. If you’re NOT rejecting heat, the refrigeration circuit needs service – likely a small leak and a low charge preventing it from building up condensing pressure and rejecting the heat. That gets into service gauges and tools you need buy/rent.

    Good luck!

  3. Sam Sather says:

    Follow up:

    Send me the make/model of the fridge. I’m guessing it uses a capillary tube, but if it’s got a tiny TXV it’s possible the sensing bulb fell off from vibration, or that you’re evap fan isn’t able to adsorb the heat (I’m guessing there’s no internal fan on that thing) due to ice build up or some internal issue.

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