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Posted by J.C. on December 16, 2005 at 11:59:57:
In Reply to: Re: Energy Savings 101- Electric vs. Steam? posted by HeatPro on December 15, 2005 at 19:52:09:
: Reduction of burner input has a smaller effect upon an oil or power gas burner efficiency because the air input is tuned to the nozzle size for efficiency and the combustion chamber of such a boiler is a single vessel with exchangers, not individual burner chambers.
: A gas boiler usually has several passages above the burners and reducing the input increases air bypassing the burned gas column (secondary air), so may reduce efficiency. Baffling above the heat exchanger can force the gases to dwell in the pasages; but this requires modifying the burner outlet chamber, so can be dangerous. There is not enough gain by modifying the burner input, although slight reductions in gas pressure at the gas valve could make the boiler steam at a slower rate and hold steam longer. But this is not want you want in order to have a fast cut-off so you have lower house temperatures.
: In short, a steam system is not the best for achieving what you want. You can settle for the little gain you would get by just lowering the thermostat and using the electric heaters where needed.
: The oversizing has let you take the insulation off the downstairs mains to heat the basement somewhat, as there is excess capacity to handle the pipe losses. A boiler closer to the radiation minimum might have left some radiators cold by removing the insulation. However, unless the downstairs is occupied a significant amount of the day, the net result is a rise in the fuel consumption, which is not desirable for savings.
Thanks again for your input. Your explanation of the implications surrounding downsizing a steam boiler was laid out so logically that even I understood the issues. Bottom line - too little potential benefit (if any) to take the associated risks. I am also beginning to appreciate that steam systems are not nearly as easy to tweak as I had hoped.
I was able to talk to a Burnham technician via their customer service number. I primarily wanted to get their input on the effiency of my boiler versus their new model. While he seemed knowledgeable, extracting tidbits of information was like pulling teeth. Nevertheless, in the end, I concluded that there was very little, if any, difference between new vs old. As he put it, "there is nothing new in steam boiler technology". Given that, I proceeded to try to get an estimate of the fuel efficiency. In the end he speculated around 80%, but I sensed it could easily be less than that. As he put it, "steam systems are inherently inefficient".
So, my present inclination is to proceed a I started with maximizing my electrical supplementation. As you suggested, closely following my total energy cost and comparing it to old performance will be "the proof in the pudding". ( I have plenty of data = every monthly bill for the last 35 years! ) As an aside, my home has never had central AC, but I intend to install it this spring.( I know that this runs counter to my desire to cut energy costs, but you get to an age where you either rationalize that you need it or you simply cannot take the wife's complaints any longer! ) While it was going to be a straight AC only system, I have decided to at a minimum incorporate a sizable electric heating strip to provide greater future flexibility. At this point, I'm not sure whether it is worth the extra step by incorporating a heat pump.
One final item that I have yet to mention. I strongly suspect that my system is operating at too high a pressure. Recently I have not seen the boiler shutdown until the thermostat has been satisfied. My gauge has been reading virtually "0" so I replaced it with an old one of unknown accuracy. It started reading 13-15 #s which I know, if correct, is WAY too high. I tried to clean up my old gauge and re-inslalled it to now get readings in the 10-13 range - still way too high if accurate. A plumber is coming out next week ( under my service contract ) to replace the gauge and determine whether the pressuretrol ( a 25 yr old Honeywell PA404A ) is in trouble. If the system is truly operating near 15#s, is there any risk of short term damage, even though this appears to be within the operating specs?
Also, in my effort to save energy, I purchased two Honeywell V100P/T100B1035 Thermostatic Valve combinations to install on my upstairs bedroom radiators. My thought was to set the wall mounted temp dial ( capillary tube remote ) to allow heat up in the morning and then turn the setting down during the day when the rooms are not occupied. Unfortunately, I was not able to get the control I wanted. Even with the dial set to the lowest temp setting, the radiators still got hotter than desired. I removed them for fear that they may be getting forced open by higher pressure and be damaged. It may also be possible that these guys are simply not capable of doing what I want( a rather expensive mistake if so ). Any thoughts? Note that on the vents now installed, with their adjustment at the lowest setting, I still seem to be getting relatively more heat from them when compared to other downstairs radiators. Is this another possible symptom of overpressure? ( I guess I would not have expected the upstairs to be more effected by higher pressure. )
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