Knight High Efficiency Boiler Set Point

[BoilerTweaker]

With an outdoor temperature at 5 degrees F, and the boiler set point at 135 degrees, this KBN151 boiler modulates down to 20%, enough to raise the room temperature to 68 degrees, but not enough to satisfy the room thermostat set at 70 degrees. Raising the set point to 145 degrees is enough to overcome the home heat loss when it is this cold outdoors, and start room thermostat cycling. Is there a way to use the unit's outdoor temperature sensor to automatically cam over to a higher set point when the outdoor temperature falls below a certain point, say zero degrees?

[snupytcb]

what are you heating with? radiant? if so what type?

[BoilerTweaker]

Old fashioned hot water radiators.

[snupytcb]

you should be running a higher temp anyway. where do you live? i would run atleast 150. the odr will still work.

[BoilerTweaker]

I was assuming the best efficiency would be to run the boiler at the lowest set point that will allow reasonable cycling. Perhaps a 135 degree set point does not provide enough differential to room temperature to allow efficient heat exchange from these classic radiators. I changed to your suggested 150 degrees and it went through an entire cycle, modulating down to 25%, in about an hour. Thanks. What role does the outside temperature sensor play in all this?

[BoilerTweaker]

Wonderful Wyoming is the location.

[snupytcb]

basicly, as the out door temp changes it adjusts water temp to improve efficiancy. as it gets colder outside it raises the wtar temp. visa, versa. and when it gets above a certain degree (what ever it is set at) it will shut down.

[hydronicsman]

With an outdoor temperature at 5 degrees F, and the boiler set point at 135 degrees, this KBN151 boiler modulates down to 20%, enough to raise the room temperature to 68 degrees, but not enough to satisfy the room thermostat set at 70 degrees. Raising the set point to 145 degrees is enough to overcome the home heat loss when it is this cold outdoors, and start room thermostat cycling. Is there a way to use the unit's outdoor temperature sensor to automatically cam over to a higher set point when the outdoor temperature falls below a certain point, say zero degrees?

I'm not familiar with Knights reset curve adjustments, but if you can shift it to accomodate the CI rad emmitters that would be good. Resets work linearly, as far as I know there is no bang on below a outdoor temp.

Try Knight tech, they should be able to help you out.

[yourairman]

Is there a way to use the unit's outdoor temperature sensor to automatically cam over to a higher set point when the outdoor temperature falls below a certain point, say zero degrees?

This should be the basis of what the outdoor sensor is used for. If design temp is 0 degrees than the boiler should be set up to run at 100% and water temp set to meet the demand. 150 would be the very minimum at which you would set the water temp in old style radiators and go as high as 180. The unit modulates down when the outdoor temp rises to achieve two things. Efficiency and extended run times which in return increases comfort by limiting the amount of time the boiler is shut off.

[hvacvegas]

Wonderful Wyoming is the location.

Please don't tell me thats wyoming ohio.