Quote Originally Posted by waterlaz View Post
I have given up on my attempts to fix the DeVilbiss 525. Maybe some day I will try to replace the sieves.
All the years of using a semi-working concentrator ...].
Since you already have a working alternative, hence nothing to lose by giving your "DeVi" one more chance, consider the following*;

* Excerpt from DeVilbiss 525 Service Manual (p.15, COMPRESSOR Note #1 )
https://www.manualslib.com/manual/12...page=15#manual

" NOTE – A built-in thermal cutoff switch will shut the compressor off if it becomes overheated. This protects the compressor from damage caused by heat build-up. (Some models have an auxiliary thermostat mounted within the compressor compartment.)"

1. The "semi-working" of the compressor maybe due to the 'thermal cutoff switch' mentioned above, and the noise dampening foam maybe causing overheating of the compressor. I'd try removing as much of the internal foam as possible.
* My DeVi (515 series) is OLD so it does not have such fancy thermal sensor controlled throttle for the compressor, and when I first opened the housing the internal foam & adhesive were falling/crumbling/cooking on the compressor (which gets as hot as around 70 deg.C / 158 deg.F, clogging the exhaust fan underneath/compounding the thermal stress, and looked like a fudge/brownie batch exploded in an oven!

[ DeVilbiss 515 Foam Meltdown ]

DeVilbiss 515 Foam Meltdown.jpg

This explains why my DeVi took a little 'crap' of foam out of its lower exhausts(causing a brief nervous breakdown of the seller) when I was testing it on the day of purchase. I was more interested in the O2 analyser reading of 94% by 20 minutes of operation at 2~3lpm.

[ DeVilbiss 515 Foam Removed ]

DeVilbiss 515 Foam Removed .jpg
*The marshmallow-shaped compressor exhaust filter is temporarily removed in this photo.

2. Removing the noise dampening foam (ALL in my case, with the help of alcohol & some sticker remover spray for tough spots) would increase the internal 'air volume' (possibly cool air intake as well) around the compressor and may reduce the throttling of the compressor by the thermal sensor, allowing more consistent O2 supply.

The 'older' DeVilbiss units are built tough, but lack a heat exchanger & dedicated fan which most others (like your Nidek Nuvo 8) have. Even the newer DeVilbiss units only have a small aluminum heatsink block (10lpm unit) or an extended silicone hose connection from the compressor to the sieves/valves (5lpm units), which really are not enough considering how HOT the compressed air gets between the compressor and sieves.

My DIY (1m aluminum HVAC pipe) heat exchanger's intake brass coupling hovers around 65 deg.C/ 149 deg.F and its exhaust coupling hovers around 55 deg.C/ 131 deg.F, without a dedicated fan (only the beefy main fan under the compressor). The added moisture separator made of aluminum, and added brass nipples likely drop the temperature a bit further as well.

The noise level is not too bad, even with ALL the foam removed, with the front & back housing(covers) both on.