reverse thermal shock?

brettmg

I'm about to install a new boiler system in my home which will incorporate a 50 gallon water heater used as a storage/buffer tank. My plan is to have the tank in a short primary loop with a primary pump that will operate whenever any of my heating zones, or indirect water heater require hot water. I'm planning to use a simple aquastat to maintain the tank between 170 and 190 degrees. The boiler will be piped in as a secondary loop. Whenever the tank water temp falls below 170, the primary pump would energize, the boiler would fire, and the boiler pump would provide hot water to the primary loop and tank. There are two primary reasons why I want to use this arrangement; first because I have multiple zones of low temperature radiant heat, and secondly because I'd like to minimize boiler run time. I'm using a cast iron boiler and I'd rather not maintain a minimum boiler water temperature. My concern is that the boiler could conceivably see a temperature difference as high as 100 degrees during summer months when the only hot water demand is from the indirect tank and the boiler is idle for long periods of time. It seems like its the opposite of what we normally see as thermal shock. Maybe I'm being a little too cautious, but I sure don't want to find a basement full of boiler water next August. Any thoughts?

Boilerpro

Starting to be recognized as a real issue

I've been pounding this issue for 7 years (hot shock of cold boiler) since I started seeing it in step fired multiple boiler installations. Glenn Stanton, of Burnham, first acknowledged my concern with it as a problem and I understand Burnham's engineers are working on rewriting thier installation instructions to address the issue. For a single cast iron boiler application I use standing pilots with a stack damper. I've found that this will maintain the boiler at 120F to 140F, reducing the delta teeto a minimum when the pump first starts up off a hot loop.

Boilerpro