Hot water high limit setting

EBEBRATT-Ed

We get a lot of posts about HW boilers cycling and/or the building not making temp. Frequently they have the HL set at 160, 170,180.

This is too low. back in the 50s and 60 many MFGs designed systems that needed 200 degree water. Read some of the old books like the "Taco guide for hydronic Engineers" they promoted higher temps back then.

Yes, I am fully aware that the lower water temp you run the more fuel you will save. But you have to live with the system you have.

The boiler and the baseboard have to reach equilibrium and the HL needs to be set above this equilibrium temperature if it safely can be to keep the burner on.

Yes, if the boiler is massively oversized compared to the radiation the boiler will cycle. cycle on HL.Longer run times especially with oil promotes better combustion and less wear and tear on the burner.

The high limit is just the high limit. The thermostat and the baseboard run the show.

If you set the high limit higher its not operating the boiler at that temperature it will only get to the HL temp if it needs to to heat the system.

You would be surprised how many people think HW will boil if you go over 212 degrees. It won't the boiler is under 15 psi pressure.

And don't forget a 180 HL setting only gives you a baseboard temp average of 170 deg.