Since 1850th steam heating system was system of choice in US. In 1920th hot water circulator introduction into market shifted preferences towards hot water heating thanks to drastic reduction of installation cost. In 1960th forced air systems became popular for the same reason.
Today millions of steam heating systems still deliver heat in residential, commercial and industrial buildings. After decades of poor or no maintenance and reckless “improvements”, it's not surprise that efficiency and comfort of these systems deteriorated. Knowledgeable maintenance would make wonders to the old steam system in many cases; unfortunately, expertise in “The lost art of steam heating” is very limited.
Modern trend is steam heating systems conversion into hot water heating (HWH), which is considered an advanced energy efficiency technology. Conversion of two-pipe steam system into HWH require steam boiler replacement/upgrade and fixing old pipes (often buried in walls) in order to run water at 30 – 100 psi instead of steam at 2 psi. Worn out pipes tend to fail, though, and usually do in a worst possible moment; flooding of down-floor apartments is costly consequence. So today’s solution is complete replacement of piping (and radiators). Conversion of single pipe steam systems is even more challenging because new return line have to be added and old radiators replaced.
After a long history of such conversions, there are yet many gaps and barriers; 2011 DOE Expert Meeting
on multifamily houses conversion indicated uncertainty in very basic questions:
• the cost of converting
• the difference in performance between a well-balanced, tuned up steam system and a hydronic system serving a similar dwelling
Probably, the same questions should be asked for conversion into HWH in building of any type/size.
Meanwhile, since 1900th simple and reasonably inexpensive conversion into vacuum heating boosted steam systems performance and on average saved 35% of fuel. Additionally, even heat distribution, broad interval of operating temperatures, better comfort and reduced corrosion were achieved. Some of those vacuum systems are still in operation, mostly in big/high-rise buildings. The old vacuum heating technology disadvantage was usage of steam traps on return line from each radiator; failure of only one steam trap out of a hundred(s) deteriorates the system performance. Requirement of steam traps routine inspections and high maintenance cost established strong biases against vacuum heating technology.
NextGen Vacuum Heating operates without steam traps, condensate is returned by gravity and small capacity vacuum pump employed for only 1-2 hours/day. Basic information on new system can be found in an article for IDEA 2014 magazine
. NGRID 2013-14 pilot study, - Figure 7
- demonstrated 26 and 35% fuel savings when distribution system was retrofitted into vacuum heating and connected to an old and new boiler, correspondingly. 50% fuel savings was achieved on new boiler connected to new vacuum distribution system. These are graphs of the last 5 years
monthly HDD (heating degree days) and heating bills before and after retrofit.
Compared to HWH system, significant installation and maintenance cost savings can be achieved. Additional benefits are as follows:
• Health and comfort (radiant heating against convection)
• Safety (vacuum versus 30 -100 psig)
• Reliability, low maintenance (the only moving part is a vacuum pump, employed for 1-1.5 hours/day))
• Minimal electricity dependence
• No frozen pipe problems
• No damage from leaks
• Reduced corrosion
• Broad interval of operating temperatures
• No pressure regulating valves and mechanical floors for high-rise buildings.
I'm looking for another bigger scale Demo project of steam (boiler/district) heating systems retrofit into vacuum heating.
The simplest/least expensive/minimal changes project would be a retrofit of an obsolete old vacuum heating system, - the more system is leak tight the better. System would be considered reasonably tight if vacuum drops from 20 to 10”Hg in time interval longer than 1 hour (optionally, - pressure drop from 20 to 10 psig). As an example, after fixing major leaks that is achieved on 100 years old single pipe steam system connected to new boiler.
Conversion of two pipe steam system into vacuum heating would require adding vacuum pump and more piping changes; for single pipe system conversion is feasible as well but more plumbing work is necessary for vacuum lines. Still, these conversions do not require decent shape steam boiler replacement by hydronic one, new circulators, pressure regulating valves, radiators, expansion tanks, etc. Again, leaks in a system would deteriorate performance but no water flooding down floors will happen.
For new installations Aquatherm
piping can be utilized for quick, easy and leak tight plumbing. Common in Europe cast aluminum radiators is another opportunity to reduce cost, saves space and improve appearance.
Financing is available through an efficiency services agreement (ESA), efficiency lease agreement (ELA), power purchase agreement (PPA) or a property-assessed clean energy (PACE) agreement; 100% of the assessment, design, equipment, and installation costs, and ongoing maintenance is funded. In turn, you pay via the savings achieved in energy and operating costs over the duration of the contract.
There is a great support from HeatingHelp.com
forum already, best of a crop HVAC experts would be interested to work on project in NYC, MA, MD, IL.
Please, let me know if you are interested to give it a try.