Strike temp problem with NO thermoboxes

[Jolum]

I'm having problems trying to get the correct temperature using NO thermobox mash tuns.
I've followed Andy's Strike Temperature calculator. For example my last brew was a London Pride, I stuck in all the details and it stated for 66C mash temp I would need a strike temp of 74.9C. So I set the HLT to 75C poured in the required amount of water inot the mash tun but when I mix in the grains I find that the temperature's dropped to around 62C and then I'm messing around jugging boiling water into it and basically messing up my batch sparge calculations. I even tried pre-warming the mash tun with a couple of litres of boiling water for about 5 minutes. So my question to others that use thermoboxes as mash tuns is...what's the secret?
I suspect that I'm not pre-warming it enough, how many litres of boiling water do others use and for how long?

Any info would be great as it's really the only issue I have since moving away from my a plastic picnic box mash tun to the SS pots.

[Scooby]

I used a thermo box and would bring it in from the garage the night before a brew along with the grain, this ensures they are at room temp. while heating the HLT to 80c I boiled a kettle full of water to rinse the dust etc from the tun and warm it a bit. Then fill the tun with 80c water and put the lid on for 5-10mins. Check the temp and if it's over what you require (I used 72-73c) then swirl and splosh it around the tun a bit until you register the right temp, dough in. I think you are right in thinking pre heating is the cause.

[Jolum]

Cheers Scooby.

I was 99% sure that was the prob, nice to be reassured. Can I ask what size thermobox you've got? As I'm assuming that the size difference between a 38.5ltr and an 80ltr means more metal that needs to be warmed up and consequently more boiling water required for the pre-warming.

I must say to anyone thinking of getting one, they are excellent at holding their temp...just getting there is the trick

[beermonsta]

Hi Jolum I used my 50ltr thermobox yesterday to make a 66 litre brew length (28 litres strike liqour). As I fly sparge my method is preheat the strike liqour to at least 80'C and dump in to the box - this lets it preheat (don't forget the lid too!) and it drops about 3-5'C. So at about 74-75'C it's time to add the grain which drops the temp to mash temp at about 66-68'C.

Preheating is very important - I just find it easier to over heat the strike liqour and if it's a little too hot, leave the lid off until the temp drops. Yesterday I brewed outside and it was about 5'C (brrrrr) and the thermobox lost less than 1'C which is awsome. Helps doing a big brew too as the more liqour and therefore grain means a bigger heat mass which looses heat slower.

Cheers, Ben

[Jolum]

Thanks beermonsta. Brrrrrewing outside in this weather, blimey you're brave
Is that due to gas boiler?

I brew either in the garage or (when the missus isn't looking) in the kitchen. But I must admit I'm getting fed up as both places are too small or too busy. I think this year, I'm going to put some money aside and erect a purpose built brewshed in the garden. Anyway, that's my New Years resolution...stop steaming the wife's kitchen

[beermonsta]

gas boiler...correct - just upgraded from 'lecci and loving it. Good results with boiling 80+ litres of wort - even with it being frosty

[Jolum]

I'm still using electric elements. No way on earth would my wife let me mess around with gas. I had to convince her that the CO2 for the cornies was safe before she'd let me in the garage with it..bless her.

[Scooby]

Cheers Scooby.

I was 99% sure that was the prob, nice to be reassured. Can I ask what size thermobox you've got? As I'm assuming that the size difference between a 38.5ltr and an 80ltr means more metal that needs to be warmed up and consequently more boiling water required for the pre-warming.

I must say to anyone thinking of getting one, they are excellent at holding their temp...just getting there is the trick

I used a 24l tun but don't have it anymore. There are many variables involved so it's difficult to give one exact procedure to fit all. The main thing is to fill the tun with 80c+ water which will heat the tun, and have your grain at room temp. When you find the strike temp that achieves you desired mash temp you'll find you will be able to repeat it accurately

[Jolum]

I used a 24l tun but don't have it anymore. There are many variables involved so it's difficult to give one exact procedure to fit all. The main thing is to fill the tun with 80c+ water which will heat the tun, and have your grain at room temp. When you find the strike temp that achieves you desired mash temp you'll find you will be able to repeat it accurately

I just re-read your reply and your previous one, I didn't realise that you'd said 'fill' the tun with 80C water. Did you really mean fill it? I've got a 38.5ltr and an 80ltr, I don't think I'd be able to fill the 80ltr and still have enough water in the HLT for the mash (the biggest HLT I've got is a 100ltr).

Anyhow, I was thinking about what I've been doing wrong and everyone's right, it is all down to the pre-warming. If you take my last brew:
Grains inside the house ~18-20C
Mash tun in the garage ~10-13C
Splashed in around 1.7ltrs of boiling water (a kettle full) for 5 minutes before filling with the mash water and....doh It's obvious now that's not enough. I should really have noticed that as the weather has got colder it's been harder to get to strike temp

Oh well, at least it gives me a chance to do some experiments

[SiHoltye]

I find if I take the temp at the top of the HLT the water running out of the tap at the bottom can be several degrees cooler. Stirring the HLT before taking the temp would mix the warmer and cooler water up and equalize it.

[Scooby]

Ah, I mean fill with the volume of water required for your mash and use that to heat the tun. As its over the temp required leaving with the lid on for 10mins preheats the tun, once it has dropped to strike temp the job is done and you can dough in. If the tun has been in the garage and is very cold it will take more heat from the water and a longer time to stabilise, likewise with the grain, that's why it's best to have them at room temp as that removes some of the variables and makes it easier to repeat with a certain amount of accuracy.

[Jolum]

Ah, I mean fill with the volume of water required for your mash and use that to heat the tun. As its over the temp required leaving with the lid on for 10mins preheats the tun, once it has dropped to strike temp the job is done and you can dough in. If the tun has been in the garage and is very cold it will take more heat from the water and a longer time to stabilise, likewise with the grain, that's why it's best to have them at room temp as that removes some of the variables and makes it easier to repeat with a certain amount of accuracy.

Ahh, I see. Sorry

I think the valuable lesson I've learn't is to bring the tun and grains into a warm room the night before I brew and let them come up to room temp. I'll give it a go tomorrow night, with just water, before my next brew (next weekend).

Thanks for all the help.

[BozBru]

I find if I take the temp at the top of the HLT the water running out of the tap at the bottom can be several degrees cooler. Stirring the HLT before taking the temp would mix the warmer and cooler water up and equalize it.

This happens with a homemade boiler I have. I purposely lifted the elements from the base around 3 inches to help with cleaning, but the water at the bottom dosn't get anywhere near the right temp. A quick stir and another temp reading does the trick. This isn't an issue with the rolling boil though.