I have a 1800 square foot garage with radiant heat in the concert. Overall I am very happy with the performance. The issue with my house have got me thinking. The current boiler in the garage( slantfin model Ec-13P)is set to 180 and I have the reg valve set to 100. Could I set the temp of the boiler to say 110 high and 100 low setting? Only purpose for the boiler is to provide heat to the radiant system. Would I damage the boiler with a suck close on and off settings. The garage is normally set at 50 and occasionally I set it to 60 if I will be working in it

They seem to imply that this boiler is allowed to run in a condensing mode, but they don't fully specify that:

http://www.slantfin.com/images/stories/Product-Literature/catalogsheet_ec_ec1020_10.pdf

When boiler is operating at low
water temperatures, water condensation
could form on the heat
exchanger. These specially integrated
channels direct water flow
to combustion chamber where it
is burned off. The formation of
condensation is allowed to occur
periodically when the outdoor
reset control operates boiler at
low temperatures.

If the high to low difference is sufficient to deliver 10 minute burns (or at least 5 minutes) it shouldn't negatively affect efficiency by running at low temperatures.

If you haven't already, it may be worth calling SlantFin and asking if they have a minimum temperature for continuous operation on that model.

Sounds like they sell an optional outdoor reset control. I'd ask them if you have it and if not, if you can safely add it. Heating to 180 when you only need 100 is inefficient.

Maybe consider a low temp mini-split.

Thanks for the reply
I called slant fin and I was able to turn the boiler temp down to 140 which is the min setting. I will see how this saves me oil this winter.