Yep, if you want it to remain as cold as it was before, only option is to upgrade the compressor.
Shame too. It's hard to find anything really quiet over 1/3hp. There's a few that are pretty good, but nothing is quiet like the Danfoss.
Hey SD, ever used the NF11's at all? Same format and I would think pretty good noise levels too. Just haven't had the pleasure of trying one.
Though if quiet doesn't matter, then it may be ideal to just pick up a new one and sell this, or see if there's anyone building that has a 'trade in' option.
I'm way down here in Canada, though I use a US post box just on the other side of the border it still get's pricey to send that far.
If it works for you, I can give your email to Ron. You can get him at XS but if you're not active there, I could try to hook you guys up. He's in Texas but that's still closer than me I think.
Oh, was going to add that if this is just a 'benching cooler' and you're at a point where you're looking to move up to high load and lower temps then a new cooler wouldn't be a bad idea.
Those cooler express based units that SD makes are great for that. Still not bad for noise, just won't be as quiet as what you have. Nothing is as quiet as what you have
the NL9's have always been pretty famous for it.
But if you want something that's already made for the kind of load and temps you'd probably like, give SD a shout on a price for one. I think you'd be surprised how reasonable they are for what you're getting
At least you could sell this one to get a bit of the cost back too.
Just to give you an idea, I've just finished up the 'guts' of the cooler that's basically identical to what you have.
It's a Danfoss NF9, with a Chilly1 head. I'm using 290 on it, since it's ideal for a high load unit with smaller condensors. Not as cold as some gasses, but very easy to maintain a low condensing temp. Seems to balance out the temperature difference.
So it's the same as that other pic. All I've done with it that's different to yours is add a condensor, and rework the captube. The solid suction return is quite long, with the captube soldered to the line back to the compressor, around 16" of captube is acting as a heat exchanger to improve capacity by ensuring vapor return.
I don't know what head you have there, but pretty much any high end evap will do around the same as this with the mods I'm doing.
I maxed out the charge (just charged it so that the frost is at, but not into, the compressor with no load to ensure no floodback) and haven't changed it. I'm not 100% sure of it's max, but I've tested to 375w so far.
If you wanted to know what to expect (approx.) from a mod to your cooler, that's about it.
I'll get some pics of the load testing either tonight or tomorrow. It's mayhem in the shop right now, way too messy for pics. But a bit of cleaning and I'll get that posted.
I was pretty surprised, but it's colder than the other unit, even though I'm 3-4 degrees above ambient condensing temp.
Downside is that it's noisier now.
I've used the NL11's over in the UK, and they were always quiet, but I never tuned anything higher than around 250w. No reason to back then.
Now it's needed and this is the first NF9 I've had to play with since I got back.
FYI the NL11 and NF9 are approximate equals due to the difference in frequency of power. NL11 runs at 50hz and NF9 runs 60hz.
It's very quiet to around 250w or so, then the noise does come up. Not offensive, but no longer a very
quiet cooler to my ears.
So comparing the 2 coolers, the other one with better condensors is warmer by around 5c, but is still what I would call in the 'very quiet' range of 24/7 unit.
The Danfoss 1/3hp setup is reasonable, but only in the 'quiet' range.
I've made a cooler with a 1/5hp compressor for CPU and at 375w it falls into the 'ultra quiet', but is only running -10c at 350w.
So that should give you an idea of what you'd be looking at. Something like -30 evap temp to no warmer than around -25c if the mod is done right. Possibly better, if someone's got a better tuning method, or is using a colder gas and still able to maintain ambient or close condensing temp at high load (375w)
If that sounds good to you, then you may want to consider the mod.
If it's too warm, and you want more from the cooler, then it's time to look at a new one, something like SD's would be ideal.
Hope that helps and like I said, I'll get some pics of the load testing up soon as I can