HERMS loop Vs counter flow

[Cain Harland]

I'm looking at putting together a HERMS rig. It will probably be single tier so have 2 pumps. Given that during mash 1 pump will just be recirculating the HLT water I have been thinking why not do away with the HERMS loop and use a counter flow chiller instead, an all metal one. With the HLT water in the outer loop and mash in the inner. There is probably very little in it in terms of price by the time you buy the extra valves, bulkheads and compression fittings for the HERMS.

Can anyone give me a reason why this is a bad idea and a traditional HERMS loop would be better? Eg is the outer loop going to have toxic shit in it because the cooling water usually goes down the drain so I wont be able to use it for sparge.

I would probably find a suitable old pot or something and set the chiller in it in expanding foam to stop it acting like a heat sync in the air. Will probably insulate mash tun too either with wooden slats like a barrel or by placing inside a slightly larger pot (the cheapest thinnest one I can find) and filling the gap with foam.

Also I  go the HERMS loop way then for cooling how much less efficient is cooling by running the wort back through the HERMS loop while running the garden hose into the bottom of the HLT and out the top. Rather than cold in, hot out like counter flow or immersion, its cold in mix out so clearly less efficient, but would it make any real difference or do I just waste a little more water?

[Cain Harland]

Another HERMS related question. Why is the standard for a HERMS coil so long? 50' seems like a lot when the greatest temperature increase one is ever likely to want is from a low mash at say 63c to mash out at 75c so 12c difference. The cheapest way to make one would be to get a cheap immersion chiller and some compressions fittings but their usually 25' to 30'

[Scott H]

Time is prob the biggest factor in coil size you don't want the temp increase time to take forever.

As for the counter flow HERMS it may not be terribly efficient but Maybe try it and check google someone else is bound to have tried it.

[Cain Harland]

Thanks Scott I'm a bit perplexed by this obviously there is a reason for the 50' standard but my instinct tells me that the heat exchange required for the relatively small heat steps involved in HERMS should happen in a very short length of pipe. Maybe its when the temperature difference is small (when maintaining mast temp) so is the exchange of heat.

I'm interested to hear why you think the counter flow would be less efficient.

And where does one purchase a 50' coil? There seem to be plenty of 25' ones around but no 50's that I can find. One of these would be the business but I hate to think how much shipping will be.

I saw a cool set up on you tube where the guy was using a modified gas infinity hot water unit as his HTL. It was recirculating through the outer loop (back into the water heater) of his large homemade counter flow (by large I mean fat pipes it was maybe 5m long in a big U shape 2m tall <1m wide) and he used the inner loop for HERMS recirculation and to heat sparge water. It seemed to heat sparge water from ambient to 75 in one cycle through. He also had 3 way valves at the in and out of the outer loop so he turned the heater off and ran tap water through the outer to use it as a chiller. It looked like a great solution particularly that sparge water was being created on the fly so rather than figuring out how much you needed in advance you could just sparge until the kettle was full.

[Scott H]

If your going to make your own copper coil contact [e-mail] and ask for some prices of the soft copper, I bought my 20M of 1/2in from him for about $100 delivered.

All the research I did for my HERMS coil pointed in the direction that 50ft (15m) of 1/2in Diameter was optimal for desired heat transfer.

The whole heating and mash steps time issue. If you going to do a lot of step mashing then a RIMS is more suited to your needs.  That infinity setup above, is using a $2000 ish (not an approx price but a ball park) appliance just to heat 3-4L of water for the coil, talk about overkill. While no doubt effective not exactly cost effective. While it would also heat water to 75c in one pass through he's doesn't state how long it takes for that heat to get transferred to the mash.

On my system, it takes around 15-20min to go from mash temp to 75c for mash out, which is inline with www.theelectricbrewery.com from which its based.

Also

http://www.homebrewtalk.com/f51/herms-vs-counterflow-herms-349332/

Appears the idea works and has some merit, just maybe requires and extra pump or stirrer.

Go for it man and keep us updated on how it works.

[Cain Harland]

Thats a great price on the coppe,r plenty left over for whirlpool arms etc. I would rather have a pre shaped one after my last attempt at making a chiller, it works but its wonky as and would be a pain to clean if it was stuck inside a pot, but maybe I could try again.

I agree the infinity is total overkill but its cool and say you were or knew a gas fitter and got one cheap that was being decommissioned somewhere it could be a go. And you can spend a lot on an automated HLT if you get flash stuff say 57L Blichmann BoilerMaker $550 + Blichmann Floor Standing Burner $250 + Honeywell Furnace Gas Valve $200ish + assorted gas pipes, valves, regulators and electronics the price is getting up there. Not that I will be buying a Blichmann pot or burner but I might get the Honeywell Valve. It will be a old keg or cheap Chinese pot on my old 3 ring burner.

[Barry]

Exactly how I've set my system up. Can't tell you how effective it is as I haven't had it running yet. Hopefully within a month.
I did enough research online to suggest that the thing should work.

[Cain Harland]

Barry so your saying you used a counter flow rather than a HERMS loop? Let us know how that goes, I really like the idea.

[Barry]

Yep, saves on having 2 coils eh. From what I've read it can be completely adequate.

[Richard Jack]

How are you going to manage the control? Where are you sensing, and what are you controlling, pump or HLT?

[Barry]

Against popular advice (yours) I'm sensing at the outlets (as Kal's design does).

One pump will pump wort through the inside of the CFC back into the top of the mash tun. The other pump will pump water from the HLT through the outside of the CFC, in the opposite direction to the wort, then back into the HLT. The HLT will be switched by PID on the water temp, again measured at the outlet. If the mash temp reading is too low I'll nudge up the HLT temp.

I'm sure there will be greater than 1deg differential, because the CFC sits out in the air and is far shorter than a normal HERMS coil. But I reckon it will be easy to compensate degree by degree with my PID controlled HLT. I don't step mash, but I am curious to see what ramp times will be like even if just for mash out.

We'll see.

[DMAC]

I think the electric brewery system relies on high flow to get temperature control-even without insulation on the mash tun!

The march pumps do 20l minute unloaded and kal says to run them fully open. So maybe you get 10l a minute? So if you are doing a 50l batch the entire volume probably goes through the exchanger in a few minutes. To me it sounds like you don't need a very good heat exchanger given the volume through it. If all else fails you could set the hlt slightly above mash temp with a poor heat exchanger and get the same result.

From what I can tell the people who have trouble with mash temp are the ones who have low flow through the tun. (Based on forum reading - I'm an arm chair electric brewer until my system is running )

[Cain Harland]

Interesting point there about flow rate, I was thinking about having a grant or timer relay to avoid running the mash pump full time and get wort thrashing and suction on the grain bed, it would bring the flow rate down. From what I've read the pump should be off or unthrottled as putting back pressure on to reduce the rate just makes thrashing and cavitation worse. So the timer or grant is preferable to restricting flow but still could reduce flow to the point where the wort may not be passing through the HEX often enough.