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Posted by J.C. on December 15, 2005 at 19:35:34:
In Reply to: Energy Savings 101- Electric vs. Steam? posted by J. C. on December 15, 2005 at 11:43:40:
: No, I'm not considering replacing my steam radiators with electric baseboards. At least not yet! However, like many others, I am exploring ways to offset the 50% increase in my NG cost. I have some thoughts on potential actions , but I'm a novice in this area and need someone to keep me straight. I have read enough of the posts on this site to know many of you possess the expertise and thankfully the willingness to do this. While I have a number of issues to run by you, it is probably best to address them in separate posts to avoid confusion.
: My situation : 75 year old single pipe steam system now powered by a 25 year old Burnham #406 boiler with a standing pilot. From data plate: 175,000 btu input ; 142,000 DOE output ; IBR steam btu 106,500 ; IBR steam Sq Ft 444. While the system has a few current operating issues that I intend to bring up in future posts, assume for now that it is functioning normally.
: So here is issue #1 :Electric vs Steam
: My electric rate increase has been minimal, suggesting that supplementing my steam system with electric may be a reasonable move. The intent would be to reduce the run time of the main steam system by using electric in the more heavily occupied living spaces. I have the ability to do this with greater utilization of several oil filled portables, a kitchen baseboard unit, and overhead radiant units in an addition very open to the main living area. ( I could obviously buy more portables should that make economic sense ).
: I believe I know the actual cost of the electric because of it's 100% efficiency. At $.0676 kWh, I compute this to be $1.98 per therm of heat. On the other hand, my NG cost is $1.65 per therm, but I obviously need to know my system's efficiency to estimate the actual cost per therm. This is where I need help because I get confused by the various specs. I have read articles that steam boilers of my vintage are typically only 55-65% efficient, which if true would certainly give support to using electric over steam. At those effiencies, NG cost would be $2.50-$3.00 per therm of output. However, when I compared my unit with a new Burnham #IN6 unit, the input, DOE, and IBR specs look very close. Since that unit lists an AFUE rating of just over 80%, am I right in then assuming that my old boiler is nearly as efficient? Even beyond that, is AFUE what one should use to calculate the true cost of energy? It appears that AFUE is calculated using the DOE output, but wouldn't it make more sense to use the IBR btu spec to be more accurate? In my case this would be 106,500/175,000= 61% efficient.
: I apologize for my lengthy post, but perhaps it will help other novices like myself who are struggling with the same issues. Thanks in advance for any help and feel free to poke as many holes in my logic as you care to. I'm a big boy who's been around long enough to take it!
Thanks Heatpro for your input. You are one of the experts that I had in mind when I posted and hoped to get a response from ( how's that for polishing the old apple! ) Of course, I have a few others in mind also ( can't afford to alienate them! )
I must admit, being the novice that I am, that it will take a little pondering for all of your concepts to sink in. I was happy to see that, since you do the same, supplementing electric is appropriate given the right situation. I was a bit concerned that some diehard steam enthusiasts would not consder doing this.
Your comments raised a few points that I was reserving for future posts, so I will address them now. Your suspicion that my house was probably around 2000 Sq Ft was close, except that my finished basement now brings the total to around 2800. While not constantly used, the basement needs enough warmth that supplemental heat can bring it relatively quickly to a living temperature. To this end I long ago stripped about 50' of insulation off the two mains to provide some basic heat. It seems to do this effectively without being too much. It is still significantly colder than upstairs and uninhabitable unless one turns on the portable electric radiant heater. Given that my boiler is probably oversized, was this a bad move? I guess I could re-insulate and install more robust supplemental heat, but it seems like I'd be just spinning my wheels.
As to oversizing, I'm sure your correct. My understanding is that a steam boiler size should be matched to the available radiation with an allowance for piping pickup. While my partially uninsulated basement mains may put me somewhat over the IBR 33% pickup factor, I am still probably well oversized. I measured my seven radiators and came up with 341 Sq Ft compared to the 444 Sq Ft IBR output of my boiler ( which I assumes incorporates the 33% pickup ). This suggests another possibility, does it make sense, economically or otherwise, to reduce the capacity of my boiler by reducing the btu input? I have heard this is possible to do within limits by reducing the orifice size of each burner.
Again, any input will continue to be appreciated.