gushers due to high heat or infection?

I made a batch of NB's cream ale back in May, and bottled it in mid-June. I was then out of the country for several weeks, with the bottles sitting in a corner of the dining room in my apartment. While I was gone we had a week or two stretch here in WI of 95+ (over 100 on a few days) degree weather every day. Upon sampling the batch it was severely overcarbed and every bottle was a huge gusher; you could barely salvage 1/4 of the bottle to actually drink by the time the foaming died down.

My next batch was the NB Patersbier ( recipe here: http://www.northernbrewer.com/documentation/allgrain/AG-Patersbier.pdf). I let it sit in primary for 5 weeks before bottling and hit 1.013 for my FG. Now, 3 after weeks in bottles they're quite overcarbed as well, although perhaps not quite as bad as the previous batch.

I had thought that the 1st batch was overcarbed from being in 90+ degree heat for two weeks, but now I'm wondering if I might have a gusher infection. Would conditioning in such high heat contribute to overcarbination at all? What's the best way to tell if I've got a gusher infection? I've thought I've been pretty thorough with cleaning/sanitation. I've been quite bummed by this as I'm running out of decent beer to drink!

I have another batch ready to bottle, what precautions can I take to make sure this one doesn't end up with gushers too?

How long do you leave them in the fridge before opening? Do you weigh your primer?

I weigh my priming sugar, usually I use the calculator on the Northern Brewer site for the amounts. The 1st batch I did run out of corn sugar and had to use table sugar; for the Patersbier I used corn sugar. For the first batch I've had bottles in the fridge upwards of a week that were still way overcarbed. I've only opened a couple bottles of the patersbier that had been refrigerated for a couple hours. I put another bottle in this afternoon and plan on leaving it for at least 2 days before opening to see how it is.

Hmm do you recall how many oz in this last batch? Stupid question but the starting temp you entered into the calculator was accurate? What was the temp of the conditioning area?

I don't recall exactly, but I want to say it was around 2.8-2.9oz for a 2.5 gal batch at 75 degrees, measured with a recently calibrated thermometer.

Amount of priming could be the issue... I calculate needing approximately 1.6 oz of corn sugar to carb to 2.0 volumes of CO2 based on the figures you provided. Brewersfriend.com

Then again even with 2.9-3oz of corn sugar you would estimate 3 volumes and I wouldn't think that would lead to gushers.... ? Anyone else?

I carb my beers in an upstairs area that easily reached into the high 80s for weeks this summer. I went through about 8 batches with no issues with gushers so I don't think this is your culprit. I also carb my beers near your range (2.8 vols) so I don't know what to tell you.

I've only had one or two gushers ever but it was because they were not fully carbed and I only put them in the fridge for a day or two before I opened, if that helps

If you are fermenting a 2.5 gal batch then after fermentation is over you are not going to have 2.5 gal going into the bottling bucket you need to find out how much beer you have post fermentation. The temp really does not matter much the yeast can only eat the sugar you give it and will produce a set amount of co2. Beer kits use Oz per gal. for around 2.5 volumes of co2.

I have a batch of porter that has turned to gushers. I cannot detect any other sign of infection. I was also wondering about the heat, my cellar temp raised from 60F to mid 70s this summer.