I recently replaced an older boiler in an apartment building i own with a Utica MGB-150 non-condensing boiler in hope that i would save some money on gas bills at the house. I also had 4 zone valves put in to replace the existing 4 pump system so that water would only circulate in each zone when it was calling for heat (with the pumps, water seemed to circulate even when the pump wasnt on, probably because of natural convective movement).
When I got my first gas bill, i was shocked that it was over 15% higher than with the old coal coversion boiler (some of the difference was due to higher gas costs). According to my gas statements, the new boiler seems to consistently use about 10% more therms per heating degree day than the older system.
The old system had an outdoor reset control (Johnson Controls A350R), and that was left in place by the heating contractor, but not used. My thought was to use the old reset control on the new boiler to keep supply temps lower when full blast is not needed.
I understand how to hook up the control, and how to adjust it, but my concern is about return water temperature and the flue gas condensing. Most websites i visited dont seem to make anything of condensation on cast iron boilers, but do if its a steel firetube type boiler. But i contacted the manufacturer by email and the reply says to "maintain return water temp of no less than 140F to prevent condensing and premature failure of the heat exchanger." If I set the minimum supply temp so that the return is always 140F, im probably not going to realize significant fuel savings and probably wouldnt waste my time hooking it up.
Another thought was to adjust the heat anticipators on the thermostats in the apartments to increase boiler run time. If only one zone calls for heat, the boiler's run time is fairly short (around a minute or two). I just dont want there to be too much overshoot because tenants are likely to turn thermostats up if they are uncomfortable because of large temperature swings.
Any input is appreciated -- thanks.
When I got my first gas bill, i was shocked that it was over 15% higher than with the old coal coversion boiler (some of the difference was due to higher gas costs). According to my gas statements, the new boiler seems to consistently use about 10% more therms per heating degree day than the older system.
The old system had an outdoor reset control (Johnson Controls A350R), and that was left in place by the heating contractor, but not used. My thought was to use the old reset control on the new boiler to keep supply temps lower when full blast is not needed.
I understand how to hook up the control, and how to adjust it, but my concern is about return water temperature and the flue gas condensing. Most websites i visited dont seem to make anything of condensation on cast iron boilers, but do if its a steel firetube type boiler. But i contacted the manufacturer by email and the reply says to "maintain return water temp of no less than 140F to prevent condensing and premature failure of the heat exchanger." If I set the minimum supply temp so that the return is always 140F, im probably not going to realize significant fuel savings and probably wouldnt waste my time hooking it up.
Another thought was to adjust the heat anticipators on the thermostats in the apartments to increase boiler run time. If only one zone calls for heat, the boiler's run time is fairly short (around a minute or two). I just dont want there to be too much overshoot because tenants are likely to turn thermostats up if they are uncomfortable because of large temperature swings.
Any input is appreciated -- thanks.