OUTDOOR RESET MODULE AQUASTAT ADJUSTER - CONTENTS: using an outdoor reset module, ORM, or boiler temperature manager to improve hydronic heating system (hot water boiler) efficiency & economy; manuals & guides to ORMs and boiler economizer controls.
Heating Boiler Energy Savings Devices & Control Manuals
Outdoor Reset Module Boiler Aquastat Adjustment for Outdoor Temperature
Question: boiler not heating house when an economizer or ORM module is in use
2017/04/23 Steve Carlson said:
I have a brand new Monitron Slant Fin electric boiler with floor heat in the basement and baseboard heat on the main floor. I have 5 zones (installed 20 years ago). I added the Outdoor Rest Module (ORM) to this system when the new boiler was installed. I live in northern Minnesota and when it's cold outside the system works very well. I have 2 questions:
1) The boiler is set for HL 180 degrees and LL 150 degrees. It stays within those parameters even when the thermostats are not calling for heat. Is that normal?
The issue is that the hot water "gravity feeds" the hot water through the upstairs baseboards even though the thermostats are not calling for heat. So this means if the outside temperature is 35 degrees the upstairs rooms get too warm (around 75 degrees). Shouldn't the boiler shut down if there is no call for heat?
2) If the outside temperature is 42 degrees and cloudy for several days, the ORM shuts off at 40 degrees (default setting).
Then, even if the thermostats call for heat, the boiler does not activate. Shouldn't the boiler kick in even if the outside temp is above the default temp setting? If I increase the temperature setting I get the problem stated in question #1.
In Minnesota we prefer to see the boiler run a bit hotter for efficiency and thus lower heating cost. You can set the HI limit to 200 as long as you don't see spillage at the relief valve. LO needs to be at least 20F lower than HI - so LO can go up to just under 180. The thermal conductivity of hot water in baseboards and radiators is exponentially greater at higher temperatures, so you in effect get more efficient heat transfer into the living area at higher settings.
It's normal for the boiler to remain between the HI and LO if your system has a tankless coil installed, since the boiler keeps water hot in case needed for the coil. Most aquastats are set up assuming that's the case. So IF your boiler doesn't include a tankless coil for making domestic hot water (washing and bathing) then you could change the aquastat settings and even disable the LO.
Details are at AQUASTAT HI LO DIFF SETTINGS inspectapedia.com/heat/Aquastat_Settings.php
Independent of the ORM module, when the room temperature is below the thermostat setting the circulator pump should turn on to send hot heating water to the radiating devices in the room. But the boiler's (gas or oil fired) burner won't turn on until the temperature drops about 15 degF below the HI setting. That may take a bit longer.
About the "Outdoor Rest Module (ORM)" you cite, I think you meant to say "Outdoor RESET Module " such as the unit produced by Honeywell. An ORM in essence re-programs the HI setting or boiler aquastat to what Honeywell thinks is the most efficient heat setting depending on outdoor temperature.
Using a "boiler reset" module or ORM is an old, well-established concept, idea, and device, though my point about thermal heat transfer being more efficient at higher remains true. There are two different economies in play:
1. Setting the boiler temperature HIGHER gives more efficient heat transfer from boiler and radiators into the heated space
2. Setting the boiler temperature LOWER causes the boiler to run for longer intervals. Keeping the boiler on longer burns fuel, particularly oil but also gas, more efficiently in that it takes a heating boiler as much as 5 minutes to get up to full operating temperature from when the burner first turns on.
How would I decide the balance of these two economies?
1. For a boiler without an ORM I would prefer the higher temperature settings
2. For a boiler at which I observe that in normal heating use under most conditions the boiler is staying on for 5 minutes or less there would probably be a significant improvement in boiler economy by using a boiler reset module or outdoor reset module to lengthen the boiler on-time runs.
3. For newer boilers that tend to be smaller in size and higher in efficiency, the boiler heats up quickly. For virtually all such boilers, a reset module or ORM should result in a good savings in heating costs.
4. Older heating boilers may not benefit or not benefit so much from a boiler reset module or ORM because at low outdoor temperatures the boiler may begin to run for too-brief intervals (short cycling); As I explained, a boiler whose burner on for just brief intervals will run inefficiently because at cooler boiler temperatures the fuel combustion is incomplete - we're wasting fuel. That's why oil heat service techs are taught not to measure boiler efficiency until the boiler is up to full temperature: about 5 minutes or so on older systems.
Watch out: running a heating boiler consistently at too low a temperature - say under 140F - risks formation of acidic condensate inside the unit, a source of corrosion and boiler leaks or damage.
A little alternative that gained some heating boiler efficiency on older heating systems using a thermostat like the Honeywell T87 that included a heat anticipator (search InspectApedia for HEAT ANTICIPATOR SETTINGS) would turn off the boiler a bit early at the end of a heating cycle, allowing the thermal mass of the boiler to provide heat to finish satisfying the room thermostat and to avoid overshooting the desired room temperature. Cast iron boiler heating systems and cast iron radiators or baseboards with lots of thermal mass particularly benefited from a heat anticipator or other devices to turn off the boiler's burner a bit early at the end of a heating cycle.
An alternative (or possibly supplement) to an ORM or boiler reset module that makes sense for older boilers that transfer heat less efficiently such as a fin tube boiler, a mixing valve on the heating loop that keeps the heating loop piping temperature down a bit (and keeps boiler temperature up a bit) will also produce heating cost savings.
Here is how Honeywell describes that device
Outdoor Reset Controls help save energy by operating a boiler at the most efficient setpoint based on outdoor temperature. As the outdoor temperature changes, the control adjusts the boiler to the optimum temperature that will ensure the homeowner stays comfortable. Some advanced reset controls also monitor indoor temperature when adjusting the boiler, to account for fluctuations within the home. The result:
• Heating costs reduced by up to 15 percent* • Improved indoor comfort with fewer temperature fluctuations • Reduced standby losses from the boiler and stack losses from the exhaust flue • Reduced equipment cycling for longer equipment life and more continuous, comfortable space heating
Here is information from Honeywell [PDF] describing the various models and options for their ORM
A variety of system configurations are used in North America to meet the heating and domestic hot
water needs of single-family homes. This includes, for example: warm air furnaces with electric water
heaters; boilers with integrated hot water coils; and boilers with “indirect” hot water storage tanks.
Integrated hydronic systems which provide both heat and hot water are more popular only in the
Northeast and mid-Atlantic regions.
For those making decisions about configurations of these
integrated hydronic systems, including control options, little information is available concerning the
annual energy cost implications of these decisions. This report presents results of a project to use a
direct load emulation approach to measure the performance of hydronic systems, develop performance
curves, and to provide decision tools to consumers. This is a laboratory measurement system involving
direct energy input and output measurements under different load patterns. These results are then used
to develop performance correlations for specific systems that can be used to predict energy use in
A wide range of system types have been tested under this project including
conventional boilers with “tankless” internal coils for domestic hot water production, boilers with
indirect external storage tanks, tank type water heaters which may also be used for space heating,
condensing oil- and gas-fired systems, and systems with custom control features.
It is shown that low
load and idle energy losses can have a very large impact on the total annual energy use and that the
potential energy savings associated with replacing old equipment with newer, high efficiency
equipment with low losses at idle or low load can be in the 25% range. These savings are larger than
simple combustion efficiency measurements would indicate.
Conclusions: Results of this study have shown that the input/output method, as is being developed by ASHRAE
Technical Committee 155, can be applied to residential integrated appliances and that these results can
be used to draw conclusions about energy use under a wide range of load and oversize scenarios. The
ideal case would be where the only testing required is idle loss and steady state thermal efficiency. For
some systems, however, the results are not quite linear and at least one intermediate point would
improve the characterization of the unit.
The units tested have a broad range of thermal efficiency levels and idle loss. The impact of thermal
efficiency on annual performance is expected. The idle loss is shown to also have a very large impact
on annual performance.
The energy savings that can be realized by upgrading old equipment is shown to be large – in the 25%
range, based on specific units tested under this program.
Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and
Boilers, American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), Standard 103-1993, 1993.
Methods of Testing for Rating Residential Water Heaters. American Society of Heating,
Refrigeration, and Air Conditioning Engineers (ASHRAE), Standard 118.2-2006, 2006.
Methods of Testing for Rating Combination Space-Heating and Water-Heating Appliances.
American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), Standard 124-1991, 1991.
Rosa, L. and Tosato, R. Experimental Evaluation of Seasonal Efficiency of Condensing Boilers.
Energy and Buildings, 14, pp 237-241, 1990.
BECKETT7512 HEATMANAGER Boiler Control INSTALLATION MANUAL [PDF] Excerpt: HeatManager automatically adjusts burner firing patterns and average boiler water temperature to match system heat load. Its action is similar to outdoor reset method, but does not require an outdoor sensor. HeatManager works with the existing boiler control/Aquastat to reduce fuel consumption, wear on parts and flue emissions.
BOSCH Greenstar Control Manuals for Gas-Fired Condensing Boilers, CZM100 Zone Module, CRC100 Room Control, CRC200 Programmable Room COntrol, FW200 Heating System Control, ICM Cascade Module, Manuals & Literature, retrieved 2017/04/24, original source: http://www.bosch-climate.us/support-center/download-center/downloads/bosch-manuals/gas-fired-condensing-boilers-manuals.html
The ICM Cascade Module for Greenstar Boilers designed to control cascade system–where several smaller boilers are connected in parallel to achieve a higher output.
Bosch CRC200 Programmable Room Control INSTALLATION MANUAL [PDF] Excerpt: Programmable controller with an integrated temperature sensor can be used as a boiler control or in conjunction with the CZM100 as a room controller. It comes with back light and features a time program for heating and indirect hot water tank.
BUDERUS AM10 MODULATING OUTDOOR RESET CONTROL INSTALLATION MANUAL [PDF], Bosch, retrieved 2017/04/24, original source: http://www.bosch-climate.us/files/201208201450530.0072186100_AM10_Installation%20and%20operating%20instructions_en_07-2010.pdf Excerpt: The AM10 is a modulating control for
Buderus boilers equipped with the EMS
bus. It sets the supply water temperature
based on outdoor temperature. The boiler
fires, runs and modulates based on the
information received from the AM10, and
the delta temperature between supply and
An ON/OFF signal from 3th party room
thermostats or zone controllers is used to
communicate a heat demand.
The AM10 offers warm weather shutdown
when the outdoor temperature rises above
an adjustabletemperature. To control and
stage multiple boilers, combine the AM10
with an MCM10 module.
Buderus Logamax Plus GB142 Gas Condensing Boiler MANUAL [PDF], AM10 - Outdoor Reset Modulating Boiler Control, MCM10 - Multi-boiler Cascade Module, RC35 - Energy Management System (EMS) with
Outdoor Reset, Room Reset, Zoning and Solar Thermal capabilities, Logamatic 4000 Control System, Bosch, retrieved 2017/04/24, original source: http://www.bosch-climate.us/files/201204202159400.GB142_applications_manual_01.2012.pdf
Excerpt: System 2000® combines heat and hot water to maximize efficiency in all seasons, with the additional benefits of virtually unlimited hot water and whisper quiet operation. In cold climates, heat and hot water account for up to 75% of household energy use, so savings can really add up. ... Digital Energy Manager
Hybrid Energy Recovery® Cycle makes sure that no heat is left wasted in the boiler and helps save fuel dollars. This cycle, combined with the low mass spiral boiler design, means high mass idle losses are essentially eliminated.
Better efficiency and performance than “outdoor reset” systems.
Matches energy usage to exact requirements of your home or building. ... As the "smart" central control device, Energy Kinetics' Digital Energy Manager provides continuous system monitoring and simple diagnostics for a virtually maintenance-free, combined heat and hot water system.
Watch out: Power sharing thermostats like Nest may cause false signals if not wired properly.
The company provides NEST THERMOSTAT WIRING INSTRUCTIONS for use with their Energy Kinetics 2000 MANAGER [PDF] ... for older Energy Kinetcs2000 boiler systems see CLASSIC SYSTEM MANAGER Diagnostics[PDF] The Classic System Manager was the precursor to the Digital Energy Manager, and monitors the need for heat, both in living areas and in the hot water storage tank. It is the smart central control for the heat and hot water system and is manufactured with solid state electronics. Similar to the Digital Energy Manager, the Classic Manager allows System 2000 to sit cold until heat is needed and provides the best performance with a closely integrated energy converter and hot water system.
HONEYWELL OUTDOOR RESET MODULE INSTALLATION MANUAL + Outdoor Sensor C7089U [PDF] Excerpt: The AquaReset™ Outdoor Reset Module, when connected to the
C7089U Outdoor Sensor, works with any AquaReset enabled
Aquastat® such as the L7224/48 via the EnviraCOM™ 3-wire bus
to optimize boiler efficiency. The Outdoor Reset Module enables
efficiency Aquastat functionality, such as Outdoor Temperature
Reset, a Boost function, and a Warm Weather Shutdown function
to generate average operational savings of up to 15%.
HONEYWELL AquaReset™ OUTDOOR RESET MODULE 50022037-002AU EnviraCom [PDF] Excerpt: We have integrated outdoor reset into our electronic Aquastat®,
making set-up as easy as one, two, three. Along with decreasing
installation time, the Honeywell AquaReset generates additional
revenue for you through sales of the module and outdoor
temperature sensor as well as upgrades from existing systems
to the more efficient Honeywell AquaReset.
And the Honeywell AquaReset can improve boiler efficiency by up
to 15 percent1
, enough to pay for itself in one to two years.
IntelliCon® -HW+ Hot Water Heating System ECONOMIZER MANUAL [PDF], Excerpt: The IntelliCon®-HW+ is a patented microprocessor-based fuel-saving
controller for hydronic heating systems up to 300M BTUs. It reduces fuel
consumption, wear on boiler parts and burner emissions by actively
managing the burner, in conjunction with the boiler operating-control, to
properly match the boiler output to the required load. This controller
indicates actual savings on a burner cycle by cycle basis and also
indicates the averages of these cycles. In addition, certain parameters
are programmable. All of the programmable parameters and savings
values are stored in memory that will not be lost in the event of the unit being turned off or a power failure.
WATTS TEKMAR® Boiler Reset Module 420 MANUAL [PDF] retrieved 2017/04/24, original source: http://www.tekmarcontrols.com/images/_literature/420_d_06.pdf?lbisphpreq=1 Excerpt: The Boiler Reset Module 420 is designed to operate all of the mechanical equipment in a hydronic heating system, except for zones, coordinating their operation through network communication. It can be used in applications ranging from a single zone of baseboard with an on/off boiler, to multiple radiant floor zones with a modulating/condensing boiler. This control regulates one space heating water temperature through Outdoor Temperature Reset and Indoor Temperature Feedback. It is capable of controlling a single on/off or modulating boiler, Domestic Hot Water, setpoint loads, and can expand up to 24 zones in total.
Continue reading at MANUALS for HEATING SYSTEM CONTROLS for a list of heating & air conditioner manuals, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Thanks to Bottini Fuel service manager Ron Thomas for discussing aquastat functions, low limit controls, oil burner short cycling causes, and boiler maintenance, reliability, and service contracts 4/13/2010. Bottini Fuel is a residential and commercial heating oil distributor and oil heat service company in Wappingers Falls, NY and with offices in other New York locations. Bottini Fuel, 2785 W Main St,
Wappingers Falls NY, 12590-1576
(845) 297-5580 more contact information for Bottini Fuel
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones