Don't worry - There is nothing wrong with your Mash Tun!
We now have first-hand reports from a statistically very significant number of users (on top of our original internal test data from our own testing and beta / power user testing we have in recent weeks!)
The mash tun is great with temperature retention. We need to look first at process issue.
Here is a thread below that we've now seen like 3 times this week already. Bottom line, strike water temp needs to be higher than your mash target temp. And remember when you put grain into the water, that pulls the temp down also!
Here it is:
From: Ss FAQs <FAQ@SsBrewTech.com>
Date: Monday, July 20, 2015 at 3:25 PM
Subject: Re: CURTIS>> CUSTOMER X / MASH ISSUES
Hi Customer X,
Looking at what you said you did below -
It looks as if the 152F temp, was your intended Conversion Temp (Mash Temp).
In an infusion system, you need to adjust the temperature of your water to something higher than the conversion temp, called the Strike Temp.
So when you introduce your grist (which is cooler) the two temperatures will balance out to achieve the actual temperature you desire.
Below is a clip from Brewing Math which gives you all of the details.
When, I enter your data (what you noted below). . ..
Starting with 2.5gal of water at 152F, adding 5lbs of "room temp" grain
I get a Mash Temp of 145F, similar to what you experienced. . . Of course I only guessed at your Grain Temp.
There are a lot of Mash Calculators on line that you can use to calculate the Strike Water Temp.
On 7/19/15, 5:33 PM, Customer X wrote:
Well... Brew day is over and what a struggle today was!
I don't have a conical fermenter and another digital thermometer. I have
a bucket :)
Here is what I did today
1. I filled the mashtun with 7 gallons of 155F water for 10 minutes and
then emptied it. Put the lid on to not lose heat
2. I added 2.5 gallons of 152 water back to the mash tun . The
thermometer was not submerged.
3. Added 5 lbs of room temp grain to the mashtun - the thermometer was
now submerged and temp started dropping
The temp kept dropping and within 20 minutes it was down to 142F. I got
worried and had to remove 4 quarts of wort, heat it up on the side to
almost 180F and add it back in. Temps rose to about 148F again, but then
started dropping back again. When they got back to 144F, I had to repeat
the process again.
I was able to hit my OG, but what an ordeal!
The mashtun seems to have all the insulation you mentioned and it's
reasonably heavy too. I just don't know why that thermometer started
dropping temps like it did! I validated the temps with a regular lab
thermometer and it showed the same temps too!
Makes me think that the mashtun needs more than the measly 5lbs grain and
2.5 gallons of water in it to keep temps... Thoughts?