How long for hot water baseboard to recover from setback

NY_ART

I recently moved into a 1960's split level with 4 zones of hot water baseboard and a propane fired boiler. I am attempting to do night setbacks on the unused zones from 68 to 64 degrees. Unfortunately the recovery time is measured in hours, sometimes as much as 4 to 5 hours. What should be the expected recovery time for hot water baseboard? If I have a problem where should I start looking? Heat load calcs, etc?



I am used to forced air systems and steam radiators.



Thanks in advance.

Gordy

Depends

On a lot of variables.



Is the baseboard properly sized for the heat loss of the space. Undersized, or oversized.



Are the supply temps to the base board the proper temps for the given style of baseboard to get the rated output. Usually their output is rated at 180-160* supply temps.





So you see if your baseboard is properly sized but running less than 180* water it may not get the full output, and recovery will not be as fast. Or if the baseboard was properly sized, and insulation improvements were made since the house was built then the baseboard would be oversized, and recovery would be faster, and lower water temps could be used.





Another thought is do you here gurgling? If so there is air in the loop and it needs bled. This will hurt output.



What's the boiler temp set at? You are not using a very deep set back to take that long to recover.



Is it a condensing boiler, or cast iron? Are you using outdoor reset?