Mash tun - Thermal retention

[marengo]

Evening Chaps

I am shortly to start my virgin AG experience and have acquired various bits n bobs of equipment. Prior to actually getting stuck in I have been testing and trialling the various equipment. Good job too as I have learned a considerable amount about it and have made various mods to calcs and placing of equipment at various stages. (the temp controller on the Brupaks boiler bears little resemblance to the actual temp!)

One thing, however, that is puzzling me is the heat retention of the mash tun which is the 'deluxe insulated mash tun' (aka cooler box). Now I know that i have only used water i.e. no grain but over 1 hour the heat loss was 8-10 degrees C. This was with a quilt and some ersatz top insulation in the form of thick styrene. Given that I wasn't particularly good at physics I maybe missing the point and a 'porridge' of water and grain will hold its temp much better.

I wonder if anyone experienced with this type of mash tun can give me some reassurance or point me in the direction of better insulaton. I will try placing styrene underneath and to the sides as well, but am I being paranoid?

I did pre heat the box, but I didn't allow time before taking a reading for the temp to equalise after adding the water (~76 deg) though I would think this might have only made a degree or so difference in the actual.

thanks
John

 

[PD]

You will find the lid is probably empty with no insulation inside ( not needed for cold use ) so buy a can of expanded foam and fill the void.
also when you come to use it. completely fill the coolbox with hot water the night before and let it stand overnight before emptying prior to use.
Mine use to loose lots in temp but now doing the above it looses less than 1 degree in a 2 hour mash.

 

[TRXnMe]

If your lid is empty, that's definitely the problem.

I was losing up to 8 degrees during a 90 minute mash, I filled the lid with expanding foam and, for good measure, added some of the foil bubble wrap around the sides and base. Having made the mods and pre-heated the tun I got did my third brew and held temperature for the whole 90 minutes

 

[marengo]

thanks guys, will do.

Obliged

John

 

[Springer]

Yes its like Pid says, these boxes are really made for keeping thing cold and as cold air falls they don't bother insulating the lid usually. I used to use a nice thermos box and it performed well even without the added insulation.
I never went as far as leaving it to "warm" over night, but it is essential to put some water in at 70 ish whilst weighting out etc to get it up to 66 degrees ish.
Don't worry, if you have a reasonable quality box, it will be fine, there were some naste types :shock: at a bargin price :hmm: ,about over the summer.
S

 

[PD]

as an aside. an insulated thermo pot used as a mash tun, does it generally need extra insulation on the outside ?

 

[pittsy]

as an aside. an insulated thermo pot used as a mash tun, does it generally need extra insulation on the outside ?

if you mean the s/s ones then no extra insulation needed i may lose around .5 c if that :thumb:

 

[PD]

cheers pitsy

 

[Dr Mike]

How much water do you put in which dropped so much ? Rate of temp drop depends on how much 'thermal mass' you have on there. A full test would need about 15 to 20 litres of water to represent the quantity of material you would have when mashing.

 

[marengo]

Hi Dr Mike :)

Good point. I only had 10ltrs in the coolbox. I will do as the chaps suggested with the foam/additional insulation and then retest with 20 ltrs of hot water after pre heating the box beforehand. I'll try it on Sunday assuming I can do the mods on saturday and see what difference it all makes.

Cheers
John

 

[Springer]

The Doc hit it spot on, not enough heat input, nothing to hold the heat......................don't worry..........as they say, it will be fine.
S

 

[Dr Mike]

Another source of heat loss can be the outlet pipe and valve (usually copper or brass so a very good conductor). Tying a bit of pipe insulation around that might make an improvement.

 

[jimp2003]

Another source of heat loss can be the outlet pipe and valve (usually copper or brass so a very good conductor). Tying a bit of pipe insulation around that might make an improvement.

This is a good point. I find that my mash tun, which is a 45l coleman cooler, has a greater temperature loss at the end with the tap. I now wrap the tap a few times with a bit of fleece material.

 

[marengo]

Hi all,

well I have insulated with everything, pre heated and re tested with just water and am still losing about 3.5 degrees C over 90 minutes. So a big improvement, though strangely still not as good as others are finding. It has been tested only with water, my virgin AG is this weekend so it will be interesting to see how it holds the temp in comparison. I guess 3.5 ish is not too bad?

Anyway, I have tested it to death so now for the main event :party:

John