Boilers expand and contract. It's better it do it on a solid foundation. Plus, many codes require a concrete base, and prohibit the use of blocks.
Vampiro
Uhhh which codes are you referencing that prohibit the use of concrete blocks to make a base for a boiler?
Uhhh, Denver. Also Cali requires them to be either bolted to a concrete floor, or be on top of and bolted to a concrete pad. Ny requires blocks that must be filled with concrete, brick base (using mortar) or solid pad. Plus, Weil-McClain boiler manual says to install their boilers on level concrete pads (aka housekeeping pads) along with other manufacturers.
Hollow blocks should never be used. Personally I believe such an install shows poor workmanship, and on top of that a risk of the block failing. If someone needs to use concrete blocks, make sure they are upright, filled with concrete and level. Never lay them on their side and leave them hollow.
Thanks for the reply Vamp. The OP is not in Denver and not in Cali. and not in NY. I have a severe pet peeve with people who try and apply code from a different state, borough, township, city etc to everything and everybody and quote it like it is law for everybody everywhere. Also your reference to WMCL boilers is nice but irrelevant as the boiler in question is not a Weil Mclain boiler. Does the Original Posters manufacturer require it be installed on a level concrete pad? No. it doesn't.
You said it properly when you stated "Personally...." It's bad form to try and pass off personal opinion as law, code, requirement, etc.
So where did I start off my reply to "try and apply code from a different state, borough, township, city etc to everything and everybody and quote it like it is law for everybody everywhere.", or pass off my opinion strictly based off of code? If you read my post, it started off saying
"A boiler setting is important. You should make a solid concrete pad for your boiler to do it once and do it right." It is good practice to install a boiler on a concrete pad regardless. The case I made for installing a boiler on a concrete pad is logical.
Then you even went as far to bring up the installation manual stating that it doesn't say anything about requiring a concrete pad. So tell me where the installation manual makes a case to install the LL 220 on concrete blocks? What the manual does mention is to make sure it is level. Which has more of a propensity to move or shift? A concrete pad, or blocks? The latter holds true. The PA boiler code might not even require housekeeping pads (for single family up to four and without a store) So because it doesn't say you must install it on a pad, throw good practice out the window, throw some blocks under there and we're good? Sorry, I don't build that way. Because a boiler manual doesn't say to put a drop header on a steam system, should we ignore a practice that makes for better efficiency and steam that is more dry? Nope, I use a drop header, As do others I've either helped, or worked with. Or, if a boiler manual doesn't stress the importance of venting the mains on a steam system, should we just forget about those Gorton #2's (or vent tree when there isn't enough room for the #2) and install one vent somewhere along the main? Going that extra inch or mile leads to a better, more professional install. So why not pass it off to the next person?
Both of your replies were nasty, while I was responding to the OP with good installation practices in mind that should be used.