Many years ago I bought the HERM-IT coil from onlinebrewingsupplies. It's been a simple and effective unit that outclasses all the other options and setups I've seen for a small home brew system. The only thing I've not been too stoked with was the flow rate, but I haven't heard anyone else complain about this. On the contrary some have said it was quite good. With no other basis for comparison, I accepted it was probably resistance in one of the bends that was slowing the rate down. Recently my element blew and the whole HERMs unit was warped and stuffed from the PVC getting too hot (my fault, left the sensor out twice). I removed the compression fittings which is a lot harder that it sounds. I blew through the coil to see if it was dry and to my surprise there was bugger-all resistance. I checked the tee and near slapped myself. The thermowell was blocking the hole in the compression fitting which was the cause of the problem all along.
This is how it's arranged loosely screwed together -
Note the size of the thermowell -
A very snug fit, like a proverbial in a proverbial. Which means when screwed up, there isn't interference and hence no indication of a problem -
So if you have any flow issues with your HERMs this could well be the cause.
Last Edit: Jun 14, 2020 21:12:32 GMT 10 by Wiggers
Thanks mate, will check mine (bought second hand so not sure if the genuine thermowell) which is in the top of a cross (to direct two ways out of the HERMS - a feature I don't use I normally just block one side with a ball valve). Will report back.
Kegs: T1 Rice Lager, T2 Schwarzbier, T3 Jedi Juice, T4 LCBA Fermenting: Altbier Cubed/Planned: Hoppy Lager, Teninch Dampfbier, Old Melb Ale, Hightail Ale, APA
Your thermowell looks bigger than mine. I'll check the spares box see if can reproduce what you've got going on. OBS does have hermit thermowells in stock and the entire coil kit, currently at discount.
OT Besides the twins I bring to swap I have a spare (original) coil kit not in use, if anyone is in the market.
Last Edit: Jun 15, 2020 7:42:42 GMT 10 by maltjunkie
Interesting, I've never noticed any flow problems with mine. I agree with maltjunkie, pretty sure that thermowell looks bigger than the one that came in the kit, but I haven't opened it up in a looong time so maybe I'm misremembering. On that note maybe I should be opening it up occasionally? Now I'm worried!
I removed the compression fittings which is a lot harder that it sounds.
They've probably galled. Stainless is a bastard for that. For anyone looking to pull theirs apart, be careful. Only do it if you have an issue as you run the risk of stripping the thread. If you do get them apart, apply some anti sieze compound to the threads before reinstalling. There are food grade versions out there.
From a pure flow rate point of view, if it fits, you might be better off putting the thermowell in the side of the tee, and having the wort pass straight through the tee. One less bend for it to negotiate.
I'll measure it tonight and report back. I actually have a second one I got from someone else and it's the same length.
Galling is a cold welding process in stainless (and some other metals). If you have a thread that galled, then those fittings are done for and both go in the bin. In this instance though there are no issues with the threads, it was removing the ferrules from the coil that were the problem. They leave an ever-so-slight raised edge on the back ferrule where it compresses on the tube, and actually deform the tube slightly. Taking them off is a complete menace and involved 3 different pliers, vice, WD40, sandpaper, tiny file and a lot of patience. It's the only problem with the PVC threaded cap design, because as soon as that cap is warped or stuffed these compression fittings really aren't designed to be removed.
Re: the thermowell, it can't be installed on the side as the tip fouls on the tee. This would otherwise definitely be better, save for the hose sticking out the top and being annoying.
I think I'll be moving to a stainless housing in the future, which unfortunately Ned isn't stocking any more.
Here are some possible causes. Note how small the hole in the compression fitting is compared to a cheapo 1/2" from Keg K**g -
My fitting came from work I'm pretty sure, and is robustly built. It's possible other fittings have a larger hole near the thread OR the thread isn't as long OR my tapered threads happen to screw in further than others.
Also, the OD of the thermowell is 10mm. The HERMs is for 12mm pipe. 12mm pipe with a 1mm wall thickness corresponds to a 10mm ID, which the thermowell fits very snugly into. Hmm. I was thinking of drilling out the ID slightly to fix it, but I don't really want any solvents in there. Damn I wish I had a lathe.
I think I'll be moving to a stainless housing in the future, which unfortunately Ned isn't stocking any more
I know I've seen 4" tc caps with 1" bsp thread, then all you need is a spool and a blank to drill some holes in.
Was going to say, Sorekara or someone would have the bits you needed. Those end caps take some drilling though, not impossible but it ain't sheet metal. You could probably just get away with the one on the bottom with the element pointing vertically, and leave the top open. You'd just need a 4" spool long enough to submerge your element.
Found the paperwork. Bought the fittings from Craftbrewer, they're actually 1/2" not 12mm. Paid $30 each too, they're half that price now. I remember now I went to Pirtek and bought some 12mm ferrules to suit it. They were $11 EACH PAIR. When I handed over $22 (all I had in my wallet) he said that was before GST. After I scrounged out another 40c or so he said all good, merry Christmas. What a saint. Thermowell was bought from OBS and is 32mm.
I checked by blowing through it and it takes SFA difference from being almost touching it and sticking in to create a notable restriction. Like, 1mm. I think a few extra runs of thread tape and less bundi when I screw it up should be the difference. Or drill out out a touch with a 12.5mm bit.
Last Edit: Jun 15, 2020 21:15:32 GMT 10 by Wiggers
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