Nick’s Grainfather G40 Review – Part 2

Part 2 – Sea Trials

I maintained discipline for all of about 18 hours after unboxing, before I started playing, first filling with water at various levels in order to determine various dead spaces, and to check the accuracy of the sight gauge that is built in to the recirculation pipe, before heating up to see how quickly it raised the temperature and to also check the accuracy of the temperature probes.

Using water, measured out by weight, I initially determined that the recoverable dead space below the malt pipe, was 7.4L. This value needs to be added to the base liquor calculation when determining the total volume of mash liquor required. So, if you add water at a rate of 2.5Litres per Kg and you have 6kg of grain then you will actually need to fill the G40 with 22.4L of water. Continuing filling the G40 with known volumes of water, I checked the sight glass at various levels. At 8,15 and 20 litres the level of the water was within a meniscus width of the of the line marked on the sight gauge – low, spot on and slightly high in each case respectively. As the volume increased so the water level showed as being higher in the sight glass…so at 30 litres, the level was 2mm above the line…at 46L (which is the practical limit of what can be boiled…even though the vessel can take 55L to the brim) I would estimate the error to be around 4 or 5mm so which roughly equates to 2/3rds of a litre…a discrepancy that is perfectly liveable with.

Next test was to turn the heater and pump on and observe how quickly the G40 could get water up to mash temperatures….at this stage I did not have a jacket or insulation for the G40, and the test was conducted in the arctic conditions of my garage at an ambient temperature of around 5 degrees!!

Theory states that with the specific heat of water being 4200 Joules/Kg/C it should take 4200*10*30 (1,290,000 Joules) to heat 30 litres of water by ten degrees. With the G40 element being 2900W this means it should take 1,290,000 / 2900 = 445 seconds, or 7 minutes 25 seconds to do the job. My observations showed that in fact it took spot on 8 minutes to heat the 30L of water by ten degrees. Not a bad effort considering the cold environment of my garage.

The G40’s controller has a built in PID algorithm that controls the power delivered to the element as the temperature nears the desired setting. The effect of this is that once the temperature reaches to within 3 degrees of the target, the G40 starts dialling back the power and continues to do so as you get closer to the target temperature. The effect of this is that, in my test, the G40 took a full 12.5 minutes to raise the temperature from 55 to 60 degrees. This is slow, but it does mean that you will not overshoot your desired doughing in/mash temperature. Of course you can get round this by setting a target temperature a few degrees higher than what you really want, and then reducing the target setting once you reach the desired temperature. Once at temperature, it was held at the target, using 10% of maximum power, occasionally dropping for short periods by half a degree.

When ramping up to boiling temperatures however, there is no restriction by the PID on the power delivered by the element and even as it nears 100 degrees the element still operates at 100% according to the display on the controller.

One of the things I was keen to check was the accuracy of the temperature probes, though the G40 does have a calibration feature (albeit one that warns you to be very careful in using it) so you can apply an offset if needed. Once the temperature had been stable for 10 minutes, I measured the water temperature (which was being constantly recirculated to ensure even temperature distribution) and found it to be a mere 58.8 degrees (target was 60). I dialled in the appropriate offset, left the G40 for a while and when I came back the measured temperature had increased to 60.1. I then proceeded to heat the water to boiling point and let it bubble away for an hour.

The boil itself was…well, not as vigorous as I had expected with the bigger element….more of a lively simmer and the measured temperature, using my trusted thermometer, when boiling was only 97 degrees!! I cooled the wort down and remeasured the temperature when the display showed 65 degrees….my trusted thermometer displayed 65.1 degrees so at least the calibration was still doing its thing. Once cooled to 20 degrees I checked the sight gauge and it showed 26L….so 4 litres of water lost in an hour’s boil…pretty normal and despite the boil seemingly being weak, i guess it really was boiling!!

The only thing left to do was to pump all of the cooled wort out of the G40 into a bucket on my scales…after a short time the pump started wheezingly telling me it was running dry….the water on the scales weighed 25.25L. Upending the G40 (no meant feat given its size and weight) allowed me to decant maybe a little less than half a litre more water into the bucket….virtually getting me up to the 26L showed on the sight gauge.

So….all in all, a few useful experiments that at least allow me to modify the G40 equipment profile in BeerSmith that I had downloaded.

back to  Part 1: Purchase Rationale and Unboxing or move on to Part 3 – First Brew

2 thoughts on “Nick’s Grainfather G40 Review – Part 2

  1. Re water calculation and dead space. Brewfather calculates this accurately if you specify your equipment as G40

  2. The trouble is that the default values in Brewfather for the G40 are not accurate. The default mash tun dead space for example is 6.9L….accurate volume measurement by weight of water shows it to be closer to 7.4-7.6L depending on device. Likewise the boil off rate is set at 3.5L per hour….most users are experiencing significantly higher boil off rates than the standard 3.5L/hour….I’m closer to 4.1L/hour and I’ve seen some people reporting close to 5L/hour.

    Like all recipe software, equipment profiles need to be checked to ensure they match your particular system.

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