Dedicated Herms Guide, Problems And Solution Thread

[TheWiggman]

Your post Burt shows that while the concept of HERMS is [relatively] simple, there are so many different ways the same problem can be attacked. You've got an awesome setup and good on you for detailing it and doing something completely different (though most of us don't have mates willing to part with a gas how water heater ).
I'm a huge fan of the HERMS. I'll bet it'll work a treat.

Only query is how do you intend to maintain the temp of the hot water? My concerns reflect QldKev's - all's good while ramping up, but once the ideal temp's hit the hot water would need to turn off. If the water recirculated I can see a gas water system having issues with hot water being fed into it. Though I'm not sure of the mechanics inside them.

Having a gas HWS at home, and having worked with industrial coolers, I reckon the go would be to have a separate insulated holding tank which stores the hot water. Bear with me...

• Water is pumped
  from the tank
• through the hot water system
• into the HERMS (hottest, say set at 75°C on the HWS)

[*]Water comes out of the HERMS (where it's cooled by the wort) into the tank
[*]An automated ball/solenoid valve is installed AFTER the HERMS before returning to tank
When you have reached control temp (i.e. 67°C) the ball/solenoid valve will stop flow and the hot water system will do its shutdown thing when it detects low flow. Once the temp gets below your hysteresis setpoint, the valve will open up and the heater will go back to heating the water. The pump would need to run full time so a centrifugal pump is required. A mag drive or similar would be ideal. There are ways to address the dead-heading issue.

Oh, and :beerbang:

 

[Burt de Ernie]

Your post Burt shows that while the concept of HERMS is [relatively] simple, there are so many different ways the same problem can be attacked. You've got an awesome setup and good on you for detailing it and doing something completely different (though most of us don't have mates willing to part with a gas how water heater ).
I'm a huge fan of the HERMS. I'll bet it'll work a treat.

Only query is how do you intend to maintain the temp of the hot water? My concerns reflect QldKev's - all's good while ramping up, but once the ideal temp's hit the hot water would need to turn off. If the water recirculated I can see a gas water system having issues with hot water being fed into it. Though I'm not sure of the mechanics inside them.

Having a gas HWS at home, and having worked with industrial coolers, I reckon the go would be to have a separate insulated holding tank which stores the hot water. Bear with me...

• Water is pumped
  from the tank
• through the hot water system
• into the HERMS (hottest, say set at 75°C on the HWS)

[*]Water comes out of the HERMS (where it's cooled by the wort) into the tank
[*]An automated ball/solenoid valve is installed AFTER the HERMS before returning to tank
When you have reached control temp (i.e. 67°C) the ball/solenoid valve will stop flow and the hot water system will do its shutdown thing when it detects low flow. Once the temp gets below your hysteresis setpoint, the valve will open up and the heater will go back to heating the water. The pump would need to run full time so a centrifugal pump is required. A mag drive or similar would be ideal. There are ways to address the dead-heading issue.

Oh, and :beerbang:

Thanks Wiggleman!

Your concept is exactly how the Rinnai operates.

There are thermostatic controls built in to every Rinnai. EG. my commercial Rinnai can be set to either 55, 60, 65, 75 and 85 degrees. Once the set temperature is hit in the hot water loop, the Rinnai throttles the gas.

The STC will control the flow and return pump. EG when wort temp drops the circulating pump operates and moves the cooler water through the Rinnai to heat it again.

 

[Burt de Ernie]

Ok,

Taking on board the advice from Kev above I have reworked my system.

I now have a HERMS system with a total volume of 1.9 litres and 4 metres of coil. Basically the wort will circulate through the center of the Rinnai flow and return pipework.

One of the good things about this system is after the boil I use the same HERMS coil as the chill just by turning the heater off and opening up a discharge valve.

I have also converted a new mash tun that draws off the base of the mash which will increase mash efficiency. One of the things I was most stoked about was the $5.00 stainless false bottom I got from woolies.

The only thing I am not sure of yet is the best position for the probe. Like Kev said the pump may not like the probe being on the return line into the keg as per a regular HERMs setup. Based on this I have installed 3 thermowells into the system two of which are home made. 1 on the wort return, another on the wort flow line and the last one straight into the mash tun. Time will tell.

Below are 2 you tube links demonstrating the system.





Happy to hear all feedback good and bad!

OK, I`m looking for honest feedback good or bad from others using Herms.

So I ran a my first test today to see how well the system would ramp. I started with 40 litres of 17.5 degree water and set the Herms to 75 degrees.

Below is the test result. Anyone care to comment??

 

[dent]

Seems to level off pretty early. Your setpoint is 75 degrees or that is just the HX temperature? Doesn't look like it will ever get there if it is the former.

 

[Burt de Ernie]

Dent,

The test started 17.5 degrees to with an end goal of 67.

The wort coil runs through the center of Rinnai flow and return loop which in this case was set at 75 degrees.

There is always the option to increase the temp in the flow and return loop.

 

[dent]

Sure, that looks great then.

 

[QldKev]

I like the idea of using a liebig condenser for the heat exchanger, as you mentioned it doubles as a chiller. I even thought about a shotgun style condenser/heat exchanger would work well.

It would be interesting to see how the temperature stabilizes once it hits the target temperature.

 

[Burt de Ernie]

I must admit that the Rinnai ran constant because of the amount of heat rejection occurring up until around the 63 degree mark. Because the heat rejection was so low the heater would shut down and fire up every degree above 63.

 

[Burt de Ernie]

I like the idea of using a liebig condenser for the heat exchanger, as you mentioned it doubles as a chiller. I even thought about a shotgun style condenser/heat exchanger would work well.

It would be interesting to see how the temperature stabilizes once it hits the target temperature.

Kev,

This will be tomorrows test which definitely the more relevant test. The other thing I haven't played with yet is the probe positioning.

 

[QldKev]

I think the probe mount you have on the return line is in a pretty good position. I would prefer it as soon as it exits the heat exchanger. Also get all those lines insulated up.

 

[Burt de Ernie]

OK, I`m looking for honest feedback good or bad from others using Herms.

So I ran a my first test today to see how well the system would ramp. I started with 40 litres of 17.5 degree water and set the Herms to 75 degrees.

Below is the test result. Anyone care to comment??

OK,

Have now updated the system curve and added 20 minutes of maintaining 67 degrees.

In short the maintenance section of the curve shows that at a set point of 67 C the temperature ranged from a low point of 66.7 (minimum STC 1000 differential) to 67.4 (0.4 degree overshoot). See below.

Kev....FYI this test was with the probe in the return line which didn't seem to affect the pumps or heater much at all.

 

[mb-squared]

50 degrees in ~50minutes, and holding nice and stable at the target temp. looks to me like you've got it nailed.

 

[Burt de Ernie]

50 degrees in ~50minutes, and holding nice and stable at the target temp. looks to me like you've got it nailed.

50 degrees in 34 minutes..;-)

The challenge of this project has been to try equal the performance of an electric HERMS (not sure how close I am yet). What I have come to realise during this process, is that anyone with standard household gas instantaneous hot water system could incorporate this style of HERMS into a brewery or.....the brewery into your household... The process now is to hone and engineer the system down to a minimum.

I guess what I am not sure of is the 0.4 degree over shoot.

Currently there is approximately 4 meters of coil in a 1.9 litre Herms HEX. The 1.9 litres is directly connected to the overshoot.

Without too much trouble I have the opportunity to halve the size of the HEX and coil down to approximately 2 meters. this means a 0.95 litre HERMS which would presumably result in reducing the over shoot to 0.2 degrees.

Or....am I being too pedantic?

 

[mb-squared]

.4 degrees? RDWHAHB. IMO

 

[QldKev]

50 degrees in 34 minutes..;-)

The challenge of this project has been to try equal the performance of an electric HERMS (not sure how close I am yet). What I have come to realise during this process, is that anyone with standard household gas instantaneous hot water system could incorporate this style of HERMS into a brewery or.....the brewery into your household... The process now is to hone and engineer the system down to a minimum.

I guess what I am not sure of is the 0.4 degree over shoot.

Currently there is approximately 4 meters of coil in a 1.9 litre Herms HEX. The 1.9 litres is directly connected to the overshoot.

Without too much trouble I have the opportunity to halve the size of the HEX and coil down to approximately 2 meters. this means a 0.95 litre HERMS which would presumably result in reducing the over shoot to 0.2 degrees.

Or....am I being too pedantic?

1c per 1min is kind of the norm, so you have got good numbers for the ramp rate. How much thermal mass was that compared to a full run?
An overshoot of 0.4c is great.

Both numbers look good to me

 

[Burt de Ernie]

1c per 1min is kind of the norm, so you have got good numbers for the ramp rate. How much thermal mass was that compared to a full run?
An overshoot of 0.4c is great.

Both numbers look good to me

So on both tests the mash tun had 40 litres of water which is probably more thermal mass than a 10 gallon batch.

It will be interesting to see what happens to the overshoot on brew day.

Oh and Kev....your information has been instrumental in me getting this this right so thank you.

 

[RustyT]

Hi guys,

I am trying to design my new brew stand and HERMS System, I have drawn up a rough system setup. Just want to confirm I am on the right track.

 

[mb-squared]

looks right to me. good luck!

 

[QldKev]

Why do you need 2 pumps for that design, and why have the kettle on another level if you have a pump?

 

[TheWiggman]

Agreed, 2nd pump (if required) should recirculate HLT water only.

Having the STC-1000 control the HLT might require some thinking. I can see overshoot being a potential issue. By the time the mash liquor has reached your setpoint +0.3°C* the urn water will be a fair bit hotter. The temp mash will continue to rise. Then the opposite will occur at your setpoint - 0.3°C.
Sub STC for a PID unit and problem can be solved.

* assumes your STC-1000 is like mine where the minimum hysterisis is 0.3°C