district heat vs. using an on-site boiler

JB1977

I'm a member of a downtown church in Pittsburgh whose gas boiler failed in early march.  The boiler was apparently installed incorrctly and self destructed.  So, in the past three decades the build has gone through two boilers.  Prior to the 1980s, the building (which is 106 years old) used district steam.  I am encouraging the church trustees to take a serious look at not replacing the boiler and returning to purchasing centrally generated steam.  I was told the current price of gas is $5.78 per dekatherm and the current price of district steam is $21 mlb.  Does anyone have any experience on how to make any sort of useable comparison between the costs of central vs. on site generated steam?  There are so many variables to consider, like changes in gas prices, costs for water, electricity, boiler maintenance, and of course periodic boiler replacement,  that I'm having difficulty in forming a fact based argurment one way or the other.  Personally, I'm in favor of the district heat because I think it is greener to support the public infrastructure that already exists then to install a redundant system (the local steam generator is run by a non-profit).

Does anyone have experience with conversion to district heat for chruch buildings?  If so, were those who chose that system generally satisfied with the results from a long-range economic viewpoint?

Gordo

Just a Few Questions

Do you know why it was decided to go through the expense of putting in a boiler and going off the steam grid in the first place?



There may have been a compelling reason besides, say,  for example, a church member who was a contractor offering a good deal.



From what I've been told,  when a switch-over takes place, the water hammer noise increases.  This usually happens because the new pressure reducing valve on the steam line coming in to the building is over-sized and the high velocity steam storming into the system hunts down and kills all your steam traps.



Do you have a one-pipe or two pipe system?



How many steam traps do you have now?

Brad White

Terms and Therms

Every time I come across a utility comparison, the terms used vary, Dekatherm, MMTherm... sort of like expressing velocity in Furlongs per Fortnight.



But if I understand your local rate structure at $5.78 per 1 million BTU's input, that sounds like a very good rate. Is it a total rate or are there service and delivery charges added to that? Still good at $0.578 per therm.



The steam at $21.00 per thousand lbs. That will yield 960,000 usable BTUs.



To get the same usable BTUs out of gas at, say, 80% efficiency, you would have to burn 1.2 Dekatherms. At $5.78 per, that will run you $6.93 versus $21.00.  One-third of the cost, if I am grasping this correctly. Steam will be 100% efficient for our purposes. You use it all and probably, maybe dump the condensate. They might take it back, some utilities do. But call it 100% efficient.



Now, of course you still have to maintain the boiler, heck you have yet to BUY the boiler at this point.  But things like the traps, piping, insulation, all of that is common no matter what the fuel source.



We do not discuss contractor pricing here, but if you know the cost of installing the new boiler, we can get you to some semblance of an ROI figure.



Let's say the church has a heat loss of 500,000 BTUH on the coldest day and you have 6000 Heating Degree Days, have 80% boiler efficiency on gas. And let's say you keep it at 70 when it is 0 degrees outside. OK for Pittsburgh.



To heat that annually will cost about $4,460 at your gas cost. (7,715 therms per year.)

To heat that annually with steam will cost about $13,500 (643 Mlbs.)

Basically, gas will cost you about $9040 less per year than steam at that rate. That tells me that a boiler, properly done to assure longevity, will be a better deal. You have a factor of three there, if I understand your rate structure correctly.

JB1977

more info

The heating systems is a two-pipe system.  I contacted the church office and no one could tell me how many steam traps there are.  Apparently there present staff was not even aware that the building had ever used district heat, nor did they know district heat even was available for the building.  Some older members of the congregation told me that the church used district heat, because they could recall the time the first boiler was installed.  They did not know the reason the change over was made.  I suspect it might have had something to do with the local utility company selling the district system and the uncertainty of its future with the transition to non-profit ownership.

Thanks for your warning about the oversized pressure reducing valve.

JB1977

boiler longevity

I think the key to the equation is boiler service life.  For instance, if it costs $200,000 to install an new boiler and that boiler gives reliable service for 20 years, then that works out to $10,000 per year cost (plus maintenance) for the boiler.  Is it reasonable to expect a new boiler to last more then 25 years?  It would seem to me that a boiler would need to have a long service (I'm thinking at least 40 years) in order to have any appreciable savings.  It would be a shame have to install a system only to have the boiler fail just when the "break-even" point has been reached and savings could be realized.  I've been thinking about replacement windows as an analogy.  Experts now say that the payback period for the the average window replacement job is about 40 years; however, the replacement windows typically need replacement themselves after 20-30 years, which is long before any cost savings is realized.  I fear the same may be true with the boiler.

Charlie from wmass

We do not talk numbers

for pricing but I would estimate even in your area the boiler will work out far less expensive then the district heating given the costs per therm as established here. Also as far as "green " goes for the environment the question is how efficient is the district steam from fuel to use. If it is being distributed and produced in an environmentally clean manner then there is a willingness to pay a little more to save the climate. The thing is it would be said to pay more and create a larger carbon foot print.

Brad White

Window Longevity

Good analogy. At the risk of going off-topic, you are correct, a typical replacement window (the good Low-E glass types), indeed have payback periods in decades, 40 is not uncommon. (The window you are replacing may not be perfect but is doing something...).



Moreover, the window folks talk about this being a 20-year window as if it is a good thing, notwithstanding the fact that the window being replaced is OK after 120 years of service.



But a good steam boiler? I would expect 30 years median life, but to get there, one has to monitor your feed water to keep ahead of leaks. Fresh water is the enemy and you have to measure it to manage it.