Joined on March 14, 2010
Last Post on March 25, 2013
@ March 25, 2013 11:00 AM in Integrated HVACThank you for this comment!
Martin Holliday's "Are HRV's Cost Effective" in Green Building Advisor provides interesting guidance. Yes, I intend to provide outdoor air, though controlled by CO2 and delivered to zones that are occupied, and limit ventilation to times of occupancy.
I want to go "all out" in the sense that all items of equipment that I already have that can be incorporated into a 95/95 space/dhw set up I'll keep. I'm going all out to explore the least cost means to achieve a 95/95 system in a large fraction of US housing.
With this objective I want to avoid cost of HRV if it is not justified. We'll use exhaust fans at bath and kitchen. By tightening house what are now house leaks to outdoor air supply terminals. Consider with a balanced HRV I have left house (wind and stack) leakage unchanged. HRVs may not be tolerant of large intermittent latent loads and airborne cooking stuff from these sources, so I'll need to have the bath/kitchen fans anywho.
BTW I continue to struggle with finding an HVAC installer who can work out the details of installation of this system. Fortunately, I have had plenty to do on other projects since initiating the search 2.5 yrs ago.
@ October 11, 2012 11:07 AM in Integrated HVACOur experience over past two years is to have installer come and take a look and then try to sell $$$$ packaged products that take us in an entirely different and inappropriate direction. Our shower produces 3/4 g/min mist, dishwasher is high eff, & there's 2 (count them, 2) ppl -- we really don't need a 60g storage tank!! We're both full-time energy auditors - not advocates of "deluge" shower!
We don't mind spending $$$ for expert services and believe one can achieve great efficiency with $$ products that are not a packaged commercial offering.
We take our failure to connect with an installer who has mastered combined water/air heating a blessing as we're now BPI test proctors and want to have combined heating AND retain our natural draft furnace. In addition to retaining our decrepit furnace we'll install a natural draft tank water heater to let candidates for BPI certification perform a complete equipment safety test on actual old and inefficient equipment. (Why a homeowner would not replace old inefficient equipment prone to hazard beats me, but that's another issue.)
Following is the revised system description that integrates heating & DHW AND integrates functioning old inefficient equipment that will be available when we proctor BPI field tests. Per initial post please direct me to other HH threads that may address specific questions (to avoid redundundancy) and I will report back on any elegant products and practices as we progress. I'll also track progress at ezing.tumblr.com where my wife and I place other info. We have one Chicago-area installer who seems interested, and we'd welcome another.
Combined Heating System with
Retrofit of Existing Furnace for Air Circulation
Use existing furnace which will remain connected and functional for use to conduct BPI equipment safety testing
Place hot water coil (“hydrocoil”) to receive heat from tankless boiler (Navien CH-180) that now provides only hot water. Possible coil locations: at opening to blower compartment or at supply plenum outlet or supply trunk, or other location. Heat loss from the trend of gas use to temperature indicates required peak heating capacity of 33,000 BTUh.
The coil placement should allow for a customary filter rack at the horizontal run of return next to the furnace. We assume filter will be ahead of coil if coil is placed at return.
Install variable speed fan motor in place of existing, brushless or ECM type.
Wire fan for set speed when furnace is operated, using existing “round” room thermostat. This fan mode will be used when we conduct BPI field test. It is acceptable to wire fan for fixed speed for air conditioning (see below), also using existing room thermostat.
Install outdoor reset thermostat sensor that activates tankless boiler temperature modulation. The sensor should be a standard accessory for the tankless boiler. Sensor may have been supplied with tankless boiler or it may require purchase.
Install pump between tankless boiler and coil. Advise about pump control, variable speed, how to activate pump on call for heating but not on cooling.
The furnace blower control: when furnace is operated to circulate heat from hydrocoil, vary from low speed when heating load is small and water from hydrocoil is least hot, to a higher speed sufficient to pull 33,000 BTUh from the coil when the set maximum temperature from the tankless boiler is called. To realize high efficiency heating, keep tankless boiler in condensing mode and operating at the lowest temperature that can provide comfort. It is desired to have long blower “on” time to enhance air mixing, also consistent with maintaining circulated air temperature at a relatively low temperature difference.
The tankless boiler control provides for scheduled temperature setback and
we anticipate using the programming features of this thermostat.
(See load derived from actual gas use and temperature below - also "graphical load calculation" post)
When old equipment is operated during BPI testing, the candidate will perform combustion safety test of both a standard tank DHW heater and on the furnace (see attached pics). We will maintain the vent and chimney for this purpose (the furnace is natural draft design). We plan to have a natural draft tank water heater installed to allow testing of the two appliances that may be found in older residences. Installation of a tank water heater, connected to the existing vent “T” and gas pipe, may be included with this work. An older functioning 30g water heater is preferred. Rather than pipe into house hot water supply this installation should include a “water use” pipe that is installed to a hot water tap at the near-by laundry sink.
When using the existing furnace gas burner when conducting a BPI test,
we will shut off tankless boiler operation. Perhaps “pulling the plug” from tankless
boiler will be OK, since the appliance is designed to retain settings during power outage. Keeping the existing furnace electric circuit intact, and separate from wiring for the boiler may require thought, especially how the blower is energized.
Other Efficiency Work for Future
We are interested in zoned comfort control, able to control air supply separately to the basement, rear bedroom , balance of 1st floor, and perhaps the 3-season porch and perhaps an attic expansion space. Zoned control will probably be done at a
later date, although the design of system should accompany zoned control. Trim blower speed based on pressure in supply duct?
We'd like to re-establish central AC with high efficiency equipment. We suppose that 1.5 ton capacity is sufficient (2 ton max) operated so as to maximize dehumidification. ( We've been OK except for a couple of days the past two summers w/ one 7kBTU window unit).
We'd like to install intentional ventilation, with a ducted connection between air handler and outdoors with control to provide outdoor air based on CO2 content of indoor air. With zoning (see above), we suppose this will maintain a minimum fresh air setting in areas that are occupied. Comment: with one sensor at the return, this may require bringing furnace blower on for a few moments on a schedule to “sense” CO2 at times when heating or AC are off. Perhaps not if the fan control maintains
operation for long cycles, and given occupant behavior to open windows in when
heating/cooling are not required.
It is desired at a later time to circulate ground-tempered water for sensible
cooling, to meet some of cooling load, in summer, and coil fittings should be accessible for this later installation.
I hope this is helpful for "wallies" who need a write-up of particular installation work.
@ May 16, 2011 6:56 PM in Zoning 1-pipeConcept
Best design practice for single pipe steam systems called for radiators with output sized to the heat loss of each room during the coldest weather (heating design temperature, -4°F in Chicago, IL). A boiler (typically one central unit) was selected with capacity to fill the steam distribution system completely. Balanced distribution would then fill all radiators simultaneously. The output
capacity of the boiler had to be at least equal to the total “equivalent direct radiation” (EDR) of the radiators. If radiator capacity equaled heat loss, and boiler capacity equaled radiator EDR, then the boiler would operate continually only during design conditions. Various controls were employed to limit boiler operation at other temperatures through the heating season. Most steam systems currently have a cycle or temperature control that responds in some way to indoor temperature. The comfort control prevents overheating by cycling the boiler on and off. Cycling reduces efficiency as the burner must produce steam before heat is delivered, and the boiler dissipates heat to the chimney after each burner cycle.
Now fast forward to an old steam heated building that has new insulation, new windows, and less air leakage. Heat loss could be half of that assumed when the need for radiation was calculated. This means the radiations, and the boiler, are twice as large as necessary. The boiler is matched to radiation capacity, though the amount of heat required to maintain comfort is now much less.
Now assume the distribution system can be divided in two, with half the total EDR in each of two zones (see graphic of zoned steam system). Many buildings already have two distinct steam supply piping “loops.” Work to re-pipe steam distribution to serve separate zones may only require limited work in the basement.
With the boiler only required to heat half of the radiation capacity at a time, satisfying the design heat loss of either of two equal zones will only require a boiler sized to serve the EDR present in either of the zones, not both. Control will be needed to assure that pipes and radiators are completely filled in each zone. This can be accomplished with zone valves on two pipes coming from the boiler connected to each of two zones. When the original boiler might operate half the time at design temperature, a new boiler will operate continuously, supplying heat to each zone alternately at these conditions. A boiler with output capacity matched to building
load will have longer on cycles and fewer off cycles. Operation through the heating season will be more efficient than a boiler with output capacity matching total radiation in the building.. On average a boiler properly sized to load will have half as many off cycles and the total time the boiler wastes heat while off will be half.
In some buildings, zones may be arranged to avoid energy waste due to overheating. Consider the common situation of zone discomfort due to external load. Say steam is required to maintain temperature at the north area of a building as solar heat enters windows of south apartments. Only admitting steam to the north zone, when the south zone thermostat registers within the comfort temperature, will prevent waste of unneeded steam and avoid overheating the south apartments.
When boiler replacement is planned or required due to irreparable breakdown, matching the new boiler to load rather than to total EDR may reduce the size and cost of a new boiler.
Where the existing boiler can be derated, longer burner cycles and lower flue gas temperatures can be expected. Derating is a method to increase the efficiency of the existing boiler. Zoning steam distribution and matching boiler output may offer improved efficiency of existing equipment or a newly installed boiler.
Improved boiler durability can be expected to result from fewer on/off cycles. In general, the proposed down sized or derated boiler will have less abrupt and less extensive change in temperature.
Providing steam throughout the distribution system quickly will improve comfort. Comfort is served by placing steam at each radiator in proportion to the heat loss occurring from the room(s) served by the radiator. In most cases steam balancing must compensate for a large volume of air to be pushed out of the piping and radiators, and a large thermal mass of the pipes and radiators to be brought to temperature. Having the boiler serve only a portion of the distribution system volume and mass as it fills the
system may improve comfort and reduce the cost to achieve balanced comfort by eliminating the need for some customary balancing work.
Low-pressure single pipe steam systems for heating buildings operate at temperatures slightly above boiling temperature.
Raising water to boiling eliminates cost for mechanical distribution of heat (no pump or fan) – typically 5 to 10% of the cost of a hot water or air system. A disadvantage of distributing steam is the loss of sensible heat of combustion gases, and latent heat of water vapor in these gases, to the chimney. While large systems are now available that recover heat from combustion gases, heat recovery is usually a separate flue device added to smaller boilers. Heat recovery is seldom installed, partly due to cost of equipment, though perhaps mostly due to lack of awareness of its potential and lack of training for installers. Heat recovered from flue gas may be used to pre-heat domestic water. Depending on heat available and DHW heating required, flue gas heat recovery may displace
half or more of water heating cost, or perhaps 10% of total gas heating expense. To the extent that heat recovery retrofit cost effectiveness is related to higher percentage of time that vent heat loss occurs, and to size of vent (size of recovery device), the cost to install flue gas heat recovery may be reduced by matching boiler output to present building heat loss rather than to EDR installed perhaps 100 years in the past.
@ November 20, 2010 12:15 AM in Efficiency options for 2-pipe, downfeed, vacuumThis is very helpful and will guide "boiling the options down" to those that achieve needed result in a direct simple manner.
I am working with this energy audit client to:
install gauge on vacuum pump,
have end of line vents evaluated for upgrade,
correct insulation defects of 1920's piping (limited areas)
insulate boiler room piping
install several TRVs to get the process down pat (most radiators have enclosures)
install motorized damper control of combustion air (may help separate hot water boiler having air/fuel mix thrown off). Dedicated DHW boiler may receive
motorized damper or upgrade to 90+ boiler depending on audit savings estimate
now being performed
several retrofits to DHW: pipe and tank insulation, pump control
Next steps to study energy use will be
temperature log to graph steam delivery over several days
observe vacuum pump performance once gauge is in place
selective review of steam trap function, and review of maintenance history
make a number of other observations and tests to get a better picture of
building air leakage, insulation of the enclosure, etc
Energy audit covers central and whole building: heating, DHW, insulation, air leakage, windows, lighting, pumps, ventilation. Audit will also provide information for residents to reduce energy use in dwellings. You're aware that heating efficiency options can extend to combustion air supply, burner, heat transfer, boiler operating controls, vent/chimney, comfort controls. At this point, steam enters the distribution system. That is, energy audit covers a lot of potential defects and opportunities.
I believe traps are probably well maintained, however I'm interested in
balancing the building using orifices and discontinuing traps. It seems
to me that vacuum system should work OK with orifice setting rate of steam to
radiators, especially if lines to radiators are aggressively vented. You
may have insight on this - I suspect vent system properly and install TRVs
where overheating is persistent and orifices will not be justified, or wait and
see, or maybe they don't make sense to begin with. I am interested in
having TRVs where needed, though limiting the cost of overall distribution
upgrade by having only the number of TRVs needed. Many residents now shut
off radiators on their own. I'm receiving difference of opinion whether
quarter turn valves make sense to let residents more easily control radiators
they already control manually.
@ November 8, 2010 11:19 AM in regulating temperature settings at nightTry changing from no set-back to set-back week-by-week, say Sunday night. Record utility use. Retrieve the hi/lo temps for each day (Sunday newspaper?) and average for the week. Graph use against temperature for both cases, as seen at Graphical Load Estimating Method on the Wall. Flip-flopping for a few months should account for weather variation as well as changes in habits. Avoid holidays, use of supplemental heat, and the myriad of other actions that can raise or lower utility use to isolate only the difference from reducing delta T between indoors and outdoors. It's not a large change. Canadians observed 6.5% in highly insulated house. Note that difference in weather-related energy use is "diluted" by non-weather (base) use.
I have spent hours debating set-back savings. I am open to any insights on this and have no interest in proving anyone wrong or reinforcing a particular opinion. It would be great to put set-back savings to bed!
@ November 8, 2010 12:51 AM in Efficiency options for 2-pipe, downfeed, vacuumI believe all energy auditors should seek information from firms that provide installation. I "walked" this job with BoilerPro a couple of months before the condo selected an audit firm. Several crucial observations were made at that time. The client requires an independent report before accepting a course of action, and this report will include observations properly acknowledged and a recommendation to work with an experienced firm.
@ November 8, 2010 12:32 AM in Efficiency options for 2-pipe, downfeed, vacuumSeveral strategies are available to balance steam supply in relation to steam supplied from top of building down, and to compensate for stack leakage that tends, like steam supply, to overheat the top of this building and underheat the bottom, listed at top of thread (Nov 5 “Efficiency options for 2-pipe, downfeed, vacuum”).
The following strategies also have to do with steam supply and control and address imbalance beyond downfeed steam supply and stack leakage.
I'm interested in a strategy to vary steam supply in relation to external loads that vary by orientation. Sticking with the definition of efficient distribution, we’d like to limit steam supply to zones that are less impacted by steady winds from one direction. Northwest winds prevailing in Chicago will increase heating requirements
at these orientations. A difference in heating requirement will evidence as temperatures dropping below the comfort range in apartments facing the wind.
Let's say a “cold spot” thermostat is placed where zone conditions may first drop below comfort conditions. The thermostat sets boiler to higher heat output, adjusting the outdoor reset to reflect that wind influences the setting that is based on outdoor temperature. Automatic control could increase the setting for boiler temperature, pressure, or cycle length. Apartments not exposed to wind load would perhaps overheat, though the zone with load would be controlled to not exceed comfort temperature in response to additional heat loss, limiting heating of the selected zone and avoiding unnecessary temperature increase elsewhere. I'm interested to hear experience or comments on prevent overheating with the following or other methods.
1) Close main air vents at risers serving orientations that are within comfort temperatures.
2) Close suction from vacuum pump at risers serving orientations that are within comfort temperatures.
3) Install sufficient TRVs to prevent overheating in zones that receive additional steam supply; enough TRVs to keep the orientation experiencing additional load at comfort temperature.
Steady wind loads from one direction might be addressed by “1)”
or “2)” above, though differences in winter (and fall and spring) solar loads on east and south orientations of this building are likely greater than wind. Solar loads vary by height in addition to orientation due to shading by neighboring buildings which are similar to this building’s 24 stories. The “cold spot” thermostat needs to be located near base of building to detect need for additional heat at apartments below the “shadow line” of neighboring buildings. The height of the shadow line will change
substantially from milder months to the coldest month of the heating season, making the selection of two zones (above/below shadow line) on the sunlit orientations of the building a problem. Splitting
steam supply pipe into upfeed and downfeed lengths (variation on option “b)” above) might provide zoning for solar heated and shadowed apartments, though the control complexity and cost of piping work seem to rule this out.
Variation of internal loads in apartments may cause overheating. We do not have data on extent and time of internal load variation in apartments, however it seems reasonable to assume there is no useful pattern that would lend to zoning beyond individual apartments. Internal loads that frequently cause overheating can be addressed by TRVs, especially targeting the room(s) where internal heat originates (e.g., kitchen). Apartments experiencing overheating once other balancing measures are in place can be individually addressed with a manual shut-off (for infrequent overheating) or TRV (see “f)” and “g)” options above).
We will try modeling the building using TREAT energy analysis software with central boiler and uniform steam supply and then with zones and steam supply set to temperatures in zones to get a sense of the savings potential of a zone control strategy. Zones will isolate each orientation, and further divide shaded orientations into a zone with portion of windows shaded, and separate zone with windows unshaded.
@ November 7, 2010 11:25 PM in regulating temperature settings at nightIn the case where boiler heats building without cycling on pressure I hear agreement that set-back savings will be achieved with steam as any hvac/building system: reduce the driving force for energy loss to the outdoors. Where cycling on pressure occurs during pick-up or recovery, I hear there will be a trade-off between cycling loss and energy saved by allowing temperature difference, building to outdoors, to drop. A next step: set firing rate to reduce in response to pressure, reducing firing rate before system fills (and venting radiators in relation to room loss). Would this allow the full potential of setback? Lowering the firing rate might produce savings greater than seen in fixed input furnaces and boilers. Certainly, the time allowed for recovery must account for the relationship between system capacity and loss rate.
Peterson illustrates fill/pressure relationship, and there is much discussion of multi-stage firing through numerous threads. MNCEE research > http://www.mncee.org/pdf/tech_pubs/85-8.pdf fig. 7
Comments on Canadian research that illustrates increased energy savings with larger set-back and longer set-back?
@ November 7, 2010 3:06 PM in regulating temperature settings at nightWe discuss whether one can set temperature back "too much" and somehow negate energy savings as the "recovery myth" in my Residential Energy Technology course. Of the 22 students In the most recent class, all believed. After we discuss myths at beginning of semester we ask students to explain the myth at mid-term, and then let students pick a couple of myths and ask them how they would explan to others why the myth doesn't hold water.
Energy loss from a building depends on loss rate (Uo) times temperature difference times time. For a given Uo and time, any reduction in temperature reduces the quantity of heat that moves outdoors. Whether heat moves from indoor contents to air and then outdoors is not the issue, as this can only happen as fast as temperature indoors drops. (So, houses with lots of indoor mass, or with good insulation and low air exchange save less.) As Indoor temperature drops, temperature difference to outdoors is less, and heat flow to outdoors is reduced regardless where the heat comes from.
Running equipment a while to restore temperature keeps equipment at steady state efficiency longer than if it cycled with no or smaller set-back. Follow the heat. It is a myth that more energy will be used for recovery than would have been used to maintain higher indoor temperature. We find in our class that about 1.5 hrs is required to dispel the myth, so powerful is its "common sense" appeal. See the Canadian study of two identical houses.at > http://www.cmhc-schl.gc.ca/odpub/pdf/63816.pdf
@ November 6, 2010 12:42 AM in Efficiency options for 2-pipe, downfeed, vacuumAttached file is graph of metered gas use for building with 2-pipe downfeed vaccum. Pattern of utility use can reveal efficiency opportunities. There are several interpretations for fuel use to flatten for billing periods at low temperatures, including inadequate boiler capacity. Based on information to-date the audit will seek to document imbalance. At the same time, we will seek to rule out steam imbalance causing higher rate of consumption during milder weather. This approach lets us become more certain what we're trying to correct, and the process usually lends some detail that marching forward with an assumption, however reasonable the assumption, might obscure.
@ November 5, 2010 1:46 PM in Efficiency options for 2-pipe, downfeed, vacuumIn 1979 the first condo board meeting entertained motion for an energy audit of the 24 story ‘20s two-pipe steam heated building. The energy audit is now in progress, and I invite comments on options for more efficient steam distribution. I define distribution efficiency as putting the right amount of steam to the right location at the right time (or replace “right amount of steam” with “acceptable comfort temperature”).
The boiler is a 20 year old three-pass fire tube with 83% thermal efficiency. The vacuum type distribution is downfeed with supply loop in roof crawl and “risers” connected at a crawl below first floor.
Overheating as low as 16th floor leads residents to keep most radiators shut off. We will survey the building to learn about windows kept open to control temperature. We will also inquire whether HeatTimer boiler control is set longer to maintain comfort at lower apartments. More heat can make imbalance worse if it leads residents to open windows at top. The neutral plane for stack air leakage moves upward and air entering lower apartments is driven in at higher pressure.
Other details: four large apts per floor, separate DHW system, no ventilation, window replacement by individual unit owners (about 50% after 20 years), top and bottom crawl spaces are quite air tight and stack air flow appears to be primarily from boiler room combustion air supply to space around boiler stack that runs through building.
Balancing comfort conditions may require both air leak reduction and control of steam delivery. Our current assumption: overheated residents open windows, and it is unrealistic to expect this mode of stack air movement to stop unless steam supply to the lower apartments increases relative to top floors.
Here are some ideas about increasing steam supply to lower apartments. I invite constructive response, pot-shots, what-have-you.
a) The vacuum pump runs continuously throughout heating season. We plan to check vacuum to assure that lack of vacuum causes poor steam distribution to lower floors.
b) Convert downfeed to upfeed. Assumi9ng adequate riser pipe size, this would require upsizing pipe at lower crawl space, changing pitch of pipes at upper crawl space, and boiler area piping changes including shifting the vacuum equipment to former riser.
c) Insulate steam piping from the top moving down, to limit that amount of heat provided by piping in overheated zone. Piping within view has corrugated paper insulation mostly in place. Risers are enclosed at sides of perimeter columns and this enclosure could be filled with insulation.
d) Upgrade capacity of riser base vents to let steam fill risers before entering radiators. I suppose this is the usual fill pattern for vacuum systems though I don’t know this detail.
e) Fit radiators with orifices at entry side and place thermostatic radiator valves at rooms that overheat, perhaps most of radiators at top of building. Vary system pressure on outdoor temperature.
f) Place TRVs on all radiators.
g) Quarter-turn manual (ball) valves to allow resident to easily activate or deactivate radiators.
Are there better options than the above? I see posts and threads on many of the above options, and hope to bring some focus to these with this thread.
It’s great to share knowledge and opinions about reducing energy use. It would also be great to have careful documentation of energy efficiency upgrades for a particular retrofit strategy applied to a particular system, like down-feed 2-pipe steam with vacuum. With thorough study, improvements that work can be knowledgeably applied to particular types of systems.
The best retrofit strategy will balancing steam supply in relation to differences in loads among apartments: external loads (solar, wind), and internal loads (e.g., cooking). I’ll follow with some options, one of which may work better with a particular “vertical balancing” option above.
@ October 29, 2010 9:50 PM in Integrated HVACInstaller is still searching for VS air handler that has water coil built in. We're looking for 2 ton capacity as current 2.5 ton AC does not run full time at most severe heating conditions.
People like to see system description as shown.
@ October 19, 2010 11:51 PM in Integrated HVACNavien installed. We'd prefer having 95% or better efficiency, and not sure why combi boiler functionality takes the tankless efficiency of 98% (thermal) to 91 AFUE (we have model 180). See http://www.navienamerica.com/PDS/ftp/CombiGasWaterHeaters/Brochure/Navien_condensing_combi_boiler_091103.pdf.
Pic of unit attached.
Suggestions of AHU having heating coil and VS are helpful and appreciated:
Thermo Products -
Perhaps tightening the house and supplying air at ventilation standard (see attached) has little cost premium compared to AHU.
@ October 3, 2010 11:53 PM in Graphical Load Estimating MethodMetered utility use can point to the likely required capacity of heating equipment. A method is shown on attachment. Comments are invited.
@ October 3, 2010 8:09 PM in Integrated HVACLooking for posts related to system I'm installing - pls direct if I've overlooked. I am installing an integrated HVAC system in my modest residence:
1. Install 95+ efficient tankless combined heating boiler (ModCon, sealed combustion) to supply DHW and hydro-coil (air handler unit or AHU) replacing 70AFUE FA (60k load), 0.55EF tank water heater, and 2.5T R22 AC w/ new type, retaining most piping and duct work.
2. Control flow from AHU, perhaps trimmed to supply pressure, to achieve variable flow (see #4) and to reduce fan energy.
3. Connect AHU to filtered outdoor air, controlled to limit interior
4. Zone dampers at air terminals to direct conditioned & fresh air supply only to occupied room(s).
5. AHU to accommodate AC coil, and zone control will be modified to maintain adequate air flow across coil.
Installers seem to have difficulty selecting an AHU w/ variable flow based on duct pressure, and accommodating a water/air heating coil.
I plan to install Navien CH unit to re-establish DHW (failed tank), though have not yet found AHU that will perform per above. Comments welcome. I can document system as it is installed.
I'm an energy auditor (finally making some change after 34 yrs) & intend this system to prototype what might be installed in any house having outdated FA, tank heater & AC, while working with existing piping & duct work.
@ April 9, 2010 3:12 PM in Steam Balancing Protocol
Steam Balancing Protocol
I have incorporated study results from the Center for Energy and Environment in energy audit work and the small amount of
field installation work I’ve done. MNCEE
(dot ORG) studies include balancing single-pipe steam, boiler vent dampers,
front-end boiler, burner tuning according to a protocol, conversion of steam to
hot water, (and others). George Peterson’s “Achieving Even Space
Heating in Single Pipe Steam Buildings, 1985” can be used almost directly
as a balancing guide and specification. Note
that studies of boiler performance were separate from balancing work, and
Peterson’s work assumes a well-functioning boiler. Peterson’s studies lead him to say (most below is paraphrased or re-stated from 32 pgs):
Steam system fill time is a function of mass of the
distribution system (including radiators) times specific heat (thermal
mass). The main determinant of fill time is the ratio
of the boiler output to the heat capacity of the distribution system.
Fill time for the distribution system is directly related
to initial temperature of the distribution system – cycle needs to be longer in
a given pressure the fill time of a radiator varies in proportion to its heat
capacity and in inverse proportion to
the venting capacity of the radiator air vent.
Proper air venting can be used to control the relative
speed of steam delivery to various radiators.
Beyond a certain open area, increased vent orifice size
has little influence on fill time.
Balancing can be achieved by following certain steps:
1) Increase main line venting and restrict steam to
radiators near the boiler (TRVs) as an initial balancing step.
2) Establish cycle length sufficient to fill all
radiators (if possible). Thermostat should have an adjustable dead band,
3) Correct performance problems of radiators (slope,
valve, replace missing, etc.),
4) Reduce operating pressure setting or lower the
temperature in the building until cold discomfort is reported,
5) Increase venting where cold discomfort occurs. Repeat reductions and “up venting” to balance
the building to the extent possible using variable orifice or adjustable
6) Place TRVs at locations distant from boiler that
overheat, and possibly thermostatic inlet valve for radiators near a brick set
boiler to restrict steam entry on the off-cycle.
7) Though a formatted approach can be used, at a certain
point in fine tuning, steam balancing transitions from “science” to “art”
temperature control is limited to about 4°F
for temperature differences between apartments and swings of temperature within an
apartment. Energy savings of about
10% are seen, although buildings that
have areas not kept at comfort temperatures may actually increase in energy
The original report contains a great deal of detail beyond this quick summary.
I hope to learn if this approach to balancing is
widespread and to hear about different practices and understandings.
@ April 9, 2010 10:09 AM in MizerCondensing boilers and furnaces do a good job extracting heat from combustion gases. For steam boilers, what is the potential efficiency improvement using stack heat recovery? From the excellent review at Energy Solutions Center (dot ORG), savings potential is based on the existing stack temperature, the volume of make-up water needed, and the hours of operation. Economizer would be more effective when it could pre-heat domestic water, and where boiler has been downsized or derated (see "Zoning 1-pipe," "Is EDR everything?" and threads on derating) thereby extending hours of operation. I can see a steam boiler using stack economizer functioning as a combined heating appliance - a nice proposition in multi-unit residences where DHW is a greater percentage of gas use. Let me know if there is already a well-developed thread on economizers - I searched several times.
@ April 8, 2010 7:46 PM in Can I "Zone" heat?What thermostatic radiator vent valve is best for 1-pipe vent control? I have used Macon vent valves in the past. Is there an established test for T-static vent valves? Sometimes there are differences in tehnology that make a difference for certain applications.
@ April 8, 2010 7:35 PM in Steamed BASMost times central conditioning systems in residential buildings provide heat at times when no occupants are present. And in most rooms occupancy follows a regular schedule. Shutting off radiators, perhaps with a manual valve that does not permit air venting (between radiator and air vent) might be acceptable in some circumstances. I suppose a quarter-turn ball valve would be OK.
An automated valve that linked to room or central control might also limit steam supply to times a room is occupied and to a selected temperature. I am interested to hear of experience placing steam terminals under BAS control by shutting off the vent rather than the main valve.
Response will be of value, and will be acknowledged, in “Steam Heating: Past, Present, & Future” presentation at the ACI 10 conference, April 2010
@ April 8, 2010 7:07 PM in Zoning 1-pipeNicholas - Thanks for this!
Owners of buildings where 1-pipe
steam will be maintained need a way to ONLY satisfy building heat loss, and
advantage themselves by installing a boiler that size if possible. Seems one way possible would be to have portions of distribution system w/ EDR no greater than total building loss, size boiler to total building loss, and alternate steam delivery to portions of deistribution system based on actual loss occurring. The objective: fully fill radiators during sequential fillings OR partially fill radiators, sufficient to meet loss. With either fill strategy one must carefully balance the portions of distribution system. I'd like to know of one building where this
was shown possible.
BoilerPro - Thanks for this, though I did not locate "Taking Another Look" resource. Have more specific directions to this?
@ April 3, 2010 3:25 AM in Is EDR everything?EDR can be calculated and matched to boiler rating,
however, EDR is the transfer of heat from radiator to room. The boiler
must also bring the weight of distribution system to temperature before
substantial heat transfer from distribution occurs (before EDR is fully a
factor). How is the thermal capacity of the distribution system
figured in to balancing, steam cycle length, deadband setting? I roughly calculate 1.5 hr full output to fully heat distribution system from room temp to 212+F.
I'm assembling a calculator to estimate thermal capacity of steam distribution system and please tell me if something of this sort exists (or tool for other purposes could be adapted).
Sorry for so many questions at once . . . hope they're good ones! I am an energy audit practitioner and have no issue with receiving corrections and information from installation practitioners.
Response will be of value, and will be acknowledged, in “Steam Heating: Past, Present, & Future” presentation at the ACI 10 conference, April 2010
@ April 3, 2010 3:04 AM in How do 1-pipe steam control devices compare?Steam cycle controlled by pressure automatically adjusted cycle length as differential took longer to be satisfied during mild weather when long cycles were required to fill piping/radiators. Likewise control by aquastat produced longer cycles during milder weather. Both controls could be adjusted to "mild" and "cold" weather settings. Thermostat control (sending room conditions) must lengthen cycles in mild weather. All Energy Star thermostats have adjustable deadband accessible as a program feature. For larger systems such as multi-unit housing, specialty thermostats for steam, such as R&D, have deadband adjustment as a visible switch. Setting steam cycle length with outdoor and main (return) pipe temperatures, e.g., Heat Timer, also addresses need for longer cycles in mild weather by initiating cycle length after steam has "made" main loop (similar to classic aquastat). Thermostat and cycle timer controls now dominate single-pipe system control. Have there been tests of control efficacy in one building that had two types of control alternately applied?