ToddinMaine
New Member
Once everything comes up to temp you are right back where you started if the boiler is that over fired and the radiation and heat loss are minimal.
Won't the circ. pump just draw water from the buffer tank until its' water temp drops enough to fire the boiler? Then the boiler's got to bring 30-40 gal. back up to the hi limit? Or am I missing the whole point.
As an interim measure, I've tied the two downstairs zones together by running them off one t-stat ... At no real sacrifice in comfort, I might add. Given the minor demand on the second floor fin tubes, I'm essentially presenting the whole house load at each burn. Additionally, I've set the max boiler output at 60%, so it doesn't rage up to setpoint temp (180 deg) and overshoot. Now, it will typically take 5-10 min. to make setpoint then fall back to 10-20% power until the T-stat is happy, which can be a half hour or so, given the slow response of the radient floor system. That's okay for now, but when the outdoor reset starts bringing the supply water temp down from 180 deg. the long burns will probably disappear without the added mass of a buffer.
I assume a number like 20% of max power represents 20% of the boilers' modulating range, in this case 80KBTU. So 20% power is 16KBTU plus the 20KBTU minimum rate, which = 36KBTU. Correct?
Is setting the output limit at something less than 100% a valid way to bring an oversized boiler into line? Why else might that adjustment be provided?
Todd