This page is an effort at 'myth-busting' or de-mystifying what each of these brewing systems is, and the advantages and disadvantages of them.
HERMS: Is an acronym for 'Heat Exchange Recirculating Mash System'. You might find this referred to as RHEMS in some places.
RIMS: Is an acronym for 'Recirculating Infusion Mash System'. RIMS is generally attibuted to Keith Royster.
Both systems regulate mash temperatures by taking liquor from the mash tun, heating this liquor if necessary and returning it back into the tun in a closed loop. Two basic items are needed for this: a pump (usually a food grade one such as the March series of magnetic drive pumps), and a method of heating the mash liquor.
It is the method of heating mash liquor that makes these two systems different. A RIMS system uses a form of inline heater to directly heat liquor, whereas a HERMS uses some kind of heat exchanger to indirectly heat the liquor. Each system has its benefits which are outlined below (assumimg a 40-50 litre brewery):
|
Feature |
RIMS |
HERMS |
|
Estimated Heating Power required |
1200 Watts maximum |
3600 Watts minimum |
|
Risk of de-naturing enzymes |
Increased |
Decreased |
|
Ease of construction |
A little more complex |
Simple |
|
Risk of heater burnout |
Increased |
Decreased |
|
Independence of Hot Liquor Tun |
Yes |
No* |
|
Control requirements |
Reliability is critical |
Possibly more complex |
*In a basic HERMS configuration, the heat exchanger is sited inside the Hot Liquor Tun. This means an extra heater is not required, but the liquor temperature is set to regulate mash liquor, rather than for sparging. If you desire a mash out temperature of 75C, a sparge liquor temperature of 80C, and there is a 5 degree loss in the system, then this may not be an issue.
A variation of the basic HERMS has a separate tun dedicated to the heat exchange. This gives full independence but adds to complexity.
** PID is a system of control designed to minimise an overshoot in reaching a target temperature. These systems are 'learning' systems, compensating until regulation is very accurate. They tend to be expensive as they are an 'industrial strength' solution. While many people swear they are necessary, I do not believe so for a couple of reasons. While it might be nice for a home-brewer to be able to set a mash temperature with great accuracy, I defy any home-brewer to tell the difference in a degree of variation of the mash. It is also possible to regulate temperatures to an adequate level without the need for PID.
It is often stated on HERMS sites (justifying a decision against making a RIMS) that there is a significant risk of scorching mash liquor in a RIMS system. It seems to me that this may be a combination of urban myth or poor design practise. Most RIMS systems seem to have astonishingly large heaters installed. From my own experience (well over 100 HERMS brewing sessions on several different systems - but none with RIMS), it seems illogical to have even 1000 watts of heating in a direct system. Let me explain: HERMAN has for a long time been heating 20 litres of water in a heat exchanger in a HERMS machine. The heater in this exchanger is rated at 3600 watts, and does an adequate job (I would not want a smaller heater, but I don't need a larger one either). Now if a directly heated chamber holds 1 litre of mash liquor, then to have the same amount of heating capacity we would need to de-rate the heater by a factor of 20. This assumes that the heat exchanger is 100% efficient (which it is not), so the factor of reduction would actually be greater. An equivalent RIMS heater of 180 watts would be 'large' by comparison.
Assuming we want to increase the power of the machine by a reasonable factor, the heating element still would not need to be larger than say 360 watts.
With an appropriately sized heater, I would suggest it becomes difficult to scorch mash liquor.
If anyone has there own experiences, especially in the field of RIMS heaters, I would be delighted to hear from you to continue the process of busting myths around these systems.
Both systems will do the job in a very capable way. Most people have individual preferences, but I would construct the one that fitted best the equipment available, the confidence level in what I'm making, the skills to carry it out and the like.
