FCM 120 ODR Curve ?

SV9_9

Hello Folks, I have a question regarding ODR curve settings. The default supply water target temp settings on the Burnham FCM 120 ODR curve are 100F SWT@ 60F ODT to 180F SWT @ 0F ODT. If the upper target temp setting is reduced to 160F for example, how will this effect the overall curve? Will the curve be stretched out i.e. 160F SWT @ 0F or lower ODT or will it just flatten the curve from 15F ODT? I have included pics of the ODR curve from the IOM below with changes drawn in red and green marker. Do either of these correctly represent the adjusted curve? Thanks in advance. J

I have an unrelated question regarding the head loss in my DWH loop. I have a SSU 45 indirect piped with 76' EL of 1" copper, supplied directly from the FCM 120. I come up with 16' total head loss @ 8 GPM through this loop. Am I calculating this correctly? Thanks again for your thoughts.

NY_Rob

I find it very convenient to use excel when comparing ODR curves....

SV9_9

Thanks NY-Rob, I think that answers my question. So at 0 ODT and 160 SWT will the boiler modulate accordingly, or will it still run at high fire?
By the way, I repiped the expansion tank you had expressed concern about in an earlier post.

NY_Rob

SV9_9 said:

So at 0 ODT and 160 SWT will the boiler modulate accordingly, or will it still run at high fire?

Depends on your heatloss and boiler capacity....

If you have 35K BTU's heatloss at 0F and you have a 80K BTU boiler... it will start out on high fire, then modulate down once the DT between SWT and RWT narrows.

If your heatloss at 0F is close to max boiler output (which is unlikely on most systems)... it will stay at or near max output.

SV9_9 said:

By the way, I repiped the expansion tank you had expressed concern about in an earlier post.

Looks good!!