Question about Burnham ODR operation

Cliffy

We have a fairly new Burnham gas boiler with an ODR card installed.  The first gas bill was truly amazing - almost half what we would have expected to pay the oilman!  I have a question about the ODR operation.



With the old system, we were able to turn it off at night and in the morning it had enough uumph to make the house comfortable in about an hour. 



With the new system, if we turn it off at night it takes almost three hours to make the place comfortable in the morning. 



So we've heeded the advice posted here and elsewhere and turned the night setback down just a few degrees and all is well.  But I see on the thermostat that it's running about 4 1/2 hours overnight, and that seems wasteful.



If the hot water heater terminals on the ODR control are jumpered the boiler wants to reach 180.



What would happen if we were able to jumper those terminals an hour ahead of rising?   If that's even advisable, would the house become comfortable in an hour and would we save 3 1/2 hours of run time per day?

Mike Kusiak_2

Setback and ODR

Setback and odr don't always work well together. With a setback you are trying to recover in a short period of time while the odr is only giving you the minimum water temperature needed to maintain constant indoor temperatures, so there is an inherent conflict.



I do believe the Burnham odr has a programming feature that when enabled will progressively raise the water temperature during a setback recovery. As I recall it measures the time it takes to satisfy the thermostat. If it takes more than a certain time it raises the water temp in 10 degree increments until the thermostat setpoint is finally reached. If you refer to the odr card instructions it will tell you how to enable the feature.



Don't be overly concerned about the 4 hour run time shown on the thermostat. That is only the amount of time that heat is being called for, not the actual time the boiler is firing. The odr card is only letting the boiler fire for the time needed to supply the calculated water temperature and switching on and off as needed. The actual time the burner is firing will be much less.

furnacefigher15

Thermostat calling for heat

and boiler run time are not the same.



If the boiler is high efficiency, then the boiler is running at a lower firing rate at the lower water temps.



If it is a conventional boiler, the burner will cycle on and off to maintain the reset water temp.



If 140 reset temp, the boiler will turn on at say 135 water and off at say 145. and keep doing that until the thermostat is satisfied.



Over all you would burn about the same amount of gas to achieve the morning reheat.



Cause the boiler running at 180 will have the burner on for the full hour, where as the boiler at 140 may only have the burner on 20 minutes in each of the three hours.

Jean-David Beyer

ODR action.

"The odr card is only letting the boiler fire for the time needed to

supply the calculated water temperature and switching on and off as

needed. The actual time the burner is firing will be much less."



If that boiler is a modulating one, it is even better than that. If it is not too cold out, it will reduce the firing rate to get the desired water temperature. It will only turn the burner on and off to reduce the water temperature if the load is so low that it will not modulate down far enough. So even if the thermostat calls for heat for 12 hours, it may be running at a firing rate of only 20% or maximum.



"I do believe the Burnham odr has a programming feature that when enabled

will progressively raise the water temperature during a setback

recovery. As I recall it measures the time it takes to satisfy the

thermostat. If it takes more than a certain time it raises the water

temp in 10 degree increments until the thermostat setpoint is finally

reached. If you refer to the odr card instructions it will tell you how

to enable the feature."



My non-Burnham mod-con has that feature. I have a radiant slab zone that I do not use setback on. But I also have a baseboard zone that I could set back. For the first two years, I used 2F of setback there, but it took over 4 hours to recover from the setback because there was so much reset. This year I am experimenting with the boost feature, where after a time period, it raises the supply temperature 10F if the thermostat has not yet been satisfied. This feature works, but I am not sure how I want to set it. I initially put in 4F setback and a 2-hour interval before it boosts the temperature. With this, it recovers a little faster, but not a whole lot. I can set that interval to the nearest minute, all the way down to one minute with my boiler. But I want it fairly long so that it will normally follow the reset curve for long periods. In other words, if I used no setback and enabled this feature, I would like the circulator to run for 4 hours without raising the temperature of the water (provided it was exactly balanced with the actual heat loss) and not have this feature kick in. Yesterday, I set the setback to only 3F  and I will have to wait for another really cold day to see how it goes. No matter what I do, it has to be a compromise. I am not sure how much difference setback will really make for me with ODR in operation. I think with this kind of system, ODR is a better way to save fuel than setback because the amount of setback you can do without sacrificing comfort is pretty small.

Cliffy

Yes, it's a compromise

The system I was inquiring about is a cast iron Burnham rated at 85% efficiency.



The boost option on the oudoor reset mentioned above will raise the operating temperature of the boiler in 10 degree increments if the call for heat has not been met within a setting that ranges from 0 -30 minutes.  The factory setting is 20.



That can take a long time to bring the room to the desired temperature after a night setback.  Jumping the heater terminals on the outdoor reset would instantly bring the operating temperature to 180.  I don't know how well a boiler which holds a few gallons of water would function under that demand, or equally important if it's even advisable to jumper the hot water terminals for a temporary boost in temperature.



I see this as a way of saving with night setback, as has been done for years, by shutting the system down at night and utilizing the outdoor reset during the day. 

Furnacefighter15 mentioned run times.  Is there a way of knowing how long the burner and circulator are running, individually?   I know when it runs at night it's probably not firing gas all the time, and I'd expect once it reached 180 in the morning that it probabably wouldn't be firing gas all the time, either. 

furnacefigher15

Savings?

"That can take a long time to bring the room to the desired temperature after a night setback. Jumping the heater terminals on the outdoor reset would instantly bring the operating temperature to 180. I don't know how well a boiler which holds a few gallons of water would function under that demand, or equally important if it's even advisable to jumper the hot water terminals for a temporary boost in temperature.



I see this as a way of saving with night setback, as has been done for years, by shutting the system down at night and utilizing the outdoor reset during the day. "



I don't think you would notice a difference in your fuel consumption one way or the other.



You will how ever notice a difference in temperature.



I would use the boost feature if the morning warm up time is causing discomfort.



And have the t-stat go into morning mode a hour sooner