First time home-brewery building questions (mostly HERMS, PID/electrics stuff)

[Spoon]

Jumping straight from brewing kits to a HERMS system, probably a bad idea, but I had some spare copper lying around after the immersion chiller (and it was only a few £ extra right................nope). Vessels are 33l Polypropylene fermenting bins, and the original plan was a 2.5 tier system with the HLT on the worktop, MT on a coffee table, kettle on the floor to sparge via gravity and a valentine arm copper so only needs to be a few inches below the MT), then will probably have to lift the cooled wort back onto the worktop to drain into the FV or buy another pump.

So to regain some budgetary control the electrical side of things is going to have to be on a shoestring rather than the full one electric brewery. So far I've bought 3x morrisons kettles, and an appropriate amount of junction boxes, cables etc.

So the questions are:

1) Where would 2x elements be better, the HLT or the copper? Or should I just buy a 4th and be done with it? 3 came form an idea that a spare one in the copper was a good idea in case one burnt out? But 2 would make sense in the HLT in case I wanted to do stepped mashes. Is 4.5kW just greedy in 30l vessels (so batches of nearer 15-20l)?

2) Assuming I have no practical restriction on amps (setting up in the garage next to the consumer unit with a 100A feed, so diversity gives me at least 50A, I can't cook, shower and brew at the same time). Is the mechanical relay after the SSR in the electric brewery necessary?

My plan was to simply put the PID, SSR and heatsink in a box, with either a 13A or 20A feed for one or two elements, and power each element through a separate IEC cable in parallel if more than 1.

3) HERMS coil. How much water would you have in the HLT and how long a coil? Stands to reason that you could make quicker steps if the element is only heating a few litres of water, but there a lower limit where the PID shouldn't allow the temperature to overshoot, so the HLT cant go above the target by very much, which means the difference in temperature must be pretty small therefore requiring lots of coils?

I was thinking of actually making a flat coil (snail rather than spring), and resting that on something to keep it off the element(s) without ever needing more than ~4" of water?

 

[Spoon]

Muchos googling:

1) May as well go all out and put spare elements in both vessels and build identical controllers. Seems pointless when the kit to make them is going to come to about �£70 and an added element is only �£10 or so.

2) The SSR doesn't go off completely, the residual current could be a problem. How much of a problem I've no idea, but found a few people who do it this way so obviously isn't the end of the world. I think it might be because the electric brewery is controlling 20A elements, on a 10A circuit a rotary switch would suffice to turn the element on/off. [edit] sat down and had another read of the guide and there's a paragraph explaining why there there, it is to do with the current leakage and safety issues when cleaning out the mash whilst the wort is boiling.

3)Simplify the build and put it in a kettle! http://www.thehomebrewforum.co.uk/showthread.php?t=36542 Although that removes control of HLT temp. Now thinking 2 elements at 180deg to each other, and the coil split into 2 across the HLT to minimize the water level and maximize surface area.

 

[Birkin]

I only really read through half of this but I'm confused.. Just heat the HLT with elements, and use the wort chiller coil as a heat exchanger for the mlt, then the temp of the mlt is dictated by the hlt temp. Once you mashout your hlt temp will be just right for sparge, then all you need to do is connect the pump inlet to the hlt outlet and run the sparge water through the smaprge arm, which I'd have used for recirculating the wort anyway..

You could incorporate a level control to fully automated it if you want, but it's probably a bit unnecessary!

 

[Spoon]

There's quite a potential for heat loss in the piping between HLT and MLT and in the sparge arm if you have it 'sprinkling'.

Work (or rather lack of) issues mean I've scaled back the plan to make a more universal controller with a sensor in the sparge arm, and one loose, so it'll control HLT temp at the start, mash temp (by firing the HLT elements), then HLT temp by opening the valve between HLT and the outlet of the HERMS coil, then I can use the same controller to keep the boiled wort at 80C for the steep additions with the original loose sensor probe.

 

[sponge_]

4.5kW is pretty overkill in my books, but you'd also rather have too much power than not enough.

You can purchase voltage regulators fairly cheaply and can use one to dial back the elements if need be. I have 11kW (2 x 5.5kW) in a 130L pot and smashes through the boil. I normally use both elements to ramp up quickly then just use 1 to maintain the boil (depending upon batch size, I sometimes use both elements).

With the PID, I have two SSRs in parallel off the one PID with a switch before each SSR. That way I can control which element I have on if I'm only doing a 50L batch for example and only need 1 element and is only switching the 24VDC side rather than 240VAC.

When I had my HERMS system I used one of these coils in a 2L kettle, and had a PID controlling the kettle. Worked perfectly for my 40L system and got ramp times of ~1'C/min. I'd rather have a smaller coil and volume of water to maintain temps as larger coils and volumes can lead to overshooting your set point and takes a longer time to settle if it does overshoot.