Honeywell L7248
The default differential on this unit is 10 deg F, but I've read on ehow.com:
Second question, I'm confused between the difference between "differential" and the High-Limit Setting (HLS) and the Low-Limit Setting (LLS). Isn't the difference between the HLS and LLS the differential?
So, if I wanted to operate this thing efficiently should I be thinking about the differential or the difference between HLS and LLS? Would a smaller or larger range be more efficient?
Thanks,
Bob
Addendum: I just found this in my manual for the aquastat
Thermostat calls for heat.
Circulator starts when water temperature is above Low Limit setting (if applicable) or above the Thermal Purge Temperature Limit (tPL) if Thermal Purge is enabled. Boiler temperature is checked. Burner starts when water temperature is below High Limit setting minus the differential or at or below the Thermal Purge Temperature Limit (tPL) for cold start boilers if the Thermal Purge Temperature Limit is enabled. If tPL is enabled, the burner may also start if the boiler temperature is cooling at 10 ºF or greater per minute or the Thermal Purge Time Delay (tPt) has expired. If Anti Short-Cycle Time is enabled, the burner does not start until the set Anti Short-Cycle Time between cycles expires after the previous call for heat was satisfied.
Boiler temperature exceeds the High Limit.
Burner is turned off. Burner restarts when the water temperature drops below the High Limit setting minus the Differential. If Thermal Purge is enabled, the burner is turned on when either the Thermal Purge Temperature Limit is reached, the Thermal Purge Time Delay has expired or the boiler temperature cooling rate exceeds 10 ºF/minute.
So, basically, the aquastat will keep the water in the tank in the range of the differential. That says to me that the smaller the differential the more often the burner will cycle on and off. Wouldn't we want the burner cycling less, not more? Isn't it more efficient to keep it on for a longer periods rather than cycling on and off every fifteen minutes?
The default differential on this unit is 10 deg F, but I've read on ehow.com:
The other setting on the aquastat is the differential, which is the temperature-degree difference between the low and high settings at which the boiler will continue to operate. The lowest differential is 10 but the recommended differential is 25, which will maintain higher boiler temperatures and offer more hot water than a differential of 10.
Read more: http://www.ehow.com/info_12183150_aquastat-boiler-work.html#ixzz2mQF6jdpM
Read more: http://www.ehow.com/info_12183150_aquastat-boiler-work.html#ixzz2mQF6jdpM
Second question, I'm confused between the difference between "differential" and the High-Limit Setting (HLS) and the Low-Limit Setting (LLS). Isn't the difference between the HLS and LLS the differential?
So, if I wanted to operate this thing efficiently should I be thinking about the differential or the difference between HLS and LLS? Would a smaller or larger range be more efficient?
Thanks,
Bob
Addendum: I just found this in my manual for the aquastat
Thermostat calls for heat.
Circulator starts when water temperature is above Low Limit setting (if applicable) or above the Thermal Purge Temperature Limit (tPL) if Thermal Purge is enabled. Boiler temperature is checked. Burner starts when water temperature is below High Limit setting minus the differential or at or below the Thermal Purge Temperature Limit (tPL) for cold start boilers if the Thermal Purge Temperature Limit is enabled. If tPL is enabled, the burner may also start if the boiler temperature is cooling at 10 ºF or greater per minute or the Thermal Purge Time Delay (tPt) has expired. If Anti Short-Cycle Time is enabled, the burner does not start until the set Anti Short-Cycle Time between cycles expires after the previous call for heat was satisfied.
Boiler temperature exceeds the High Limit.
Burner is turned off. Burner restarts when the water temperature drops below the High Limit setting minus the Differential. If Thermal Purge is enabled, the burner is turned on when either the Thermal Purge Temperature Limit is reached, the Thermal Purge Time Delay has expired or the boiler temperature cooling rate exceeds 10 ºF/minute.
So, basically, the aquastat will keep the water in the tank in the range of the differential. That says to me that the smaller the differential the more often the burner will cycle on and off. Wouldn't we want the burner cycling less, not more? Isn't it more efficient to keep it on for a longer periods rather than cycling on and off every fifteen minutes?
