Rubbermaid Thermal Efficiency?

[WitWonder]

To those using a Rubbermaid 40L cooler as a mash tun, what temp does your mash drop to over the course of an hour? I don't know if I've got a dud or my thermometer is not accurate however today I began a mash as per the following;

-heated water to 76deg for 8.3kg of grain 21L of water (per promash),
-resulted in about 68deg in the mash (after a bit of stirring),
-over the course of an hour i was down to about 63deg


Does this sound right? I have a MM temp controller for my HLT so I assume that temp is pretty accurate, and I have a MM weldless thermometer on my mash tun to measure mash temp.

**Edit - no I did not heat the vessel beforehand.

 

[mickoz]

The Rubbermaid lids are not great I have found. They are not filled with anything which I guess doesn't really matter when you're talking about keeping liquids cold. This unfortunately sucks for the homebrewer as we want to keep our liquids hot and the heat rises and goes straight out through a badly insulated lid. I have toyed with the idea of filling my lid with space invader foam to see if this helps. Anyone else any thoughts on this?

I usually add around 500 - 1000mls of boiling water over an hour to keep my mash on target temps.

Mick

 

[Sammus]

I've heard of people doing that with good success, getting that expanda foam crap and filling the hollow lid with it.

A lot of people also cut out a section of polystyrene or camping mate foam and float it on top of the mash. I dont like the sound of that though, polystyrene or foam dye in my beer...

 

[redbeard]

I have expanded foamed my lid & the temp drop is now only a couple degrees over an hour. be careful, as too much expanda foam can warp your lid, so it doesnt close properly & thus cause grief. Hi Trev !

the foam needs water to react with. i drilled several holes in the lid, put some water in to wet the inside plastic surface, then foamed it.

 

[Trev]

I have expanded foamed my lid & the temp drop is now only a couple degrees over an hour. be careful, as too much expanda foam can warp your lid, so it doesnt close properly & thus cause grief. Hi Trev !

the foam needs water to react with. i drilled several holes in the lid, put some water in to wet the inside plastic surface, then foamed it.

Hmmm.... I have a bent and twisted lid available afyer trying this. Mind you, I also have a new larger mash tun now because I threw the old one out

Just be careful with how much foam you squirt in at a time, follow RB's advice about multiple holes and water.

Trev

 

[ozpowell]

Interesting - I also have a rubbermaid style cooler for my mash tun (it's actually a 36L Cosmoplast Keep Cold). Never see more than about 1^oC drop over 60mins. My mash usually fills 2/3 to 3/4 of the tun. The lid is pretty solid, but I'm fairly sure it isn't insulated... :huh:

 

[kevnlis]

I float foam on my mash and never lose more than half a degree (at most) over the course of a 90min mash. Also have never gotten any dye's or off flavours from it.

 

[WitWonder]

Thanks for the comments. Don't really like the idea of foam on the beer so will try and pre heat the vessel beforehand and maybe put some tin foil on top of the mash.

I'm a bit disappointed with having to do this as the reason i bought the Rubbermaid was because I thought it was best for the job i.e. best thermal properties for a cooler type tun. What would work better other than a direct heated vessel?

 

[Cortez The Killer]

I used polystyrene for a while and it worked well except for soaking up wort and making it a bugger to clean

I have since switched over to camping mat and it works a treat - and it is easy to clean - I hang it on the clothes line to dry after use

Negligible change in mash temp over 1 hour plus - with a willow 44L esky

Cheers

 

[andreic]

I have since switched over to camping mat and it works a treat - and it is easy to clean - I hang it on the clothes line to dry after use

Negligible change in mash temp over 1 hour plus - with a willow 44L esky

Exactly what I do - including the 44L Willow esky and hanging the mat on the clothes line!

However, I lose around 1-1.5 degrees. I bought a cheap round cooler for $40 (definitely not a rubbermaid) and will be making a few mods before brining it into action for my next brew in a few weeks.

 

[mfdes]

How much chemical leaching would come from cling wrap?
It is designed to be heated in the microwave, so perhaps a good quality cling wrap might do the trick, laid on the mash.
I can see potential problems though: it would sink, and you'd need to throw the old bit away and put a new one in every time.

Another thought: Instead of polyurethane foam, one could drill a slightly larger hole and use beanbag beans. They have excellent insulation properties. You'd just need to fill up the lid space and seal up the hole. In fact, I think I might try this. I'm currently just adding boiling water to the mash.

MFS.

 

[afromaiko]

How much chemical leaching would come from cling wrap?
It is designed to be heated in the microwave, so perhaps a good quality cling wrap might do the trick, laid on the mash.
I can see potential problems though: it would sink, and you'd need to throw the old bit away and put a new one in every time.

Another thought: Instead of polyurethane foam, one could drill a slightly larger hole and use beanbag beans. They have excellent insulation properties. You'd just need to fill up the lid space and seal up the hole. In fact, I think I might try this. I'm currently just adding boiling water to the mash.

MFS.

Or even cut a piece of foam to fit the underside of your lid and either glue, silicone or screw it on. Perhaps try velcro tabs so you can easily remove it to clean underneath.

 

[sinkas]

what value do you guys use for the thermal mass for one of these tuns in Promash?

 

[Steve Lacey]

what value do you guys use for the thermal mass for one of these tuns in Promash?

There is a tool for working this out at this site housing a series of mash calculators.

 

[rwmingis]

To those using a Rubbermaid 40L cooler as a mash tun, what temp does your mash drop to over the course of an hour? I don't know if I've got a dud or my thermometer is not accurate however today I began a mash as per the following;

-heated water to 76deg for 8.3kg of grain 21L of water (per promash),
-resulted in about 68deg in the mash (after a bit of stirring),
-over the course of an hour i was down to about 63deg


Does this sound right? I have a MM temp controller for my HLT so I assume that temp is pretty accurate, and I have a MM weldless thermometer on my mash tun to measure mash temp.

**Edit - no I did not heat the vessel beforehand.

Hi WitWonder,

Hope my input is not too late in the game. I've just bought one of those Rubbermaid 40L drink coolers, having done 3 mashes with it and am completely satisfied. Mine typically looses less than half of a degree per hour, and in some strange cases looses absolutely no heat at all (to the tenth of a degree). I think this must be because of where I put my temperature probe; in the middle of the grain bed probably no heat loss, near the edge, maybe an degree or less an hour.

A plot of temperature versus time can be seen in the graph below. The jagged bits are where i stirred the mash, lost heat, and then topped it back up. The first jagged bit is the dough-in, and it takes awhile for the temperature to stabilise. A large amount of heat is lost during stirring, much more than the heat transfer through the walls an lid of the mash tun. In this case, it's about half a degree per hour. My computer was down when I did the mash that lost no heat, so i have no proof, bugger!

As for the lid loosing heat, a good way to see if you are loosing heat is to feel the top surface with your hand. If it is getting warm, then yes, heat is being transferred (lost) from the inside to the outside, heating up the outer surface. I don't personally think that filling the lid with foam would make a big difference, as the thermal conductivity of still air (no convection) is about 0.024 W/m*K, and for polyurethane foam about 0.022 W/mK. So yes, the foam is better than air, but only by about 10%. It's alot of work and risk of warpage for 10%.

Another thing to remember is that heat is also lost through the bottom too (although the insulation is quite thick there) so putting it on a towel may help.

Oh yea, i don't preheat the mash tun as the thermal mass is so low, but i do take it into account with the calcs

I hope this is of help

Cheers,

Rob

 

[lobo]

i have a 36l cosmoplast keep cold, have used it once on sunday (1st ag) and have a mash master temp probe fitted. i lost .5 of a degree in an hour.

but i also 3/4 filled my tun with 65deg water for 15mins prior.

Lobo

 

[Kai]

To those using a Rubbermaid 40L cooler as a mash tun, what temp does your mash drop to over the course of an hour? I don't know if I've got a dud or my thermometer is not accurate however today I began a mash as per the following;

-heated water to 76deg for 8.3kg of grain 21L of water (per promash),
-resulted in about 68deg in the mash (after a bit of stirring),
-over the course of an hour i was down to about 63deg


Does this sound right? I have a MM temp controller for my HLT so I assume that temp is pretty accurate, and I have a MM weldless thermometer on my mash tun to measure mash temp.

**Edit - no I did not heat the vessel beforehand.

How much stirring is "a bit"? I find mash temps don't really stabilise till i've given the esky a stir, a rest for 5 minutes and another stir. Since your thermometer is fixed you're also only getting a temperature reading from one point of the mash; the temperature can vary quite a bit depending on where you take the reading, especially early on in the mash.

Since you only mention one mash, I'd be inclined to run a few more through before worrying about further insulation.

PS what's the ambient temp?

 

[WitWonder]

I was just doing a search for Promash and stumbled over this old post and thought I should update it. The problem, I believe, is largely due to the MM thermometer and not the Rubbermaid. I found the MM was not calibrated correctly (out by several degrees) and I don't think I was allowing enough time for temps to stabilise before taking my reading. I'm also stirring the mash much more than I used to which helps to get an accurate temp more quickly.

I've also been floating some alfoil over the mash and over the hour my temp remains pretty stable.