Smith Cast Iron Boilers GB100W User Manual

GB100IOM-7

GB100W

NATURAL OR PROPANE GAS BOILER INSTALLATION & OPERATING INSTRUCTIONS

DESIGNED AND TESTED ACCORDING TO A.S.M.E. BOILER AND PRESSURE VESSEL CODE, SECTION IV FOR MAXIMUM ALLOWABLE WORKING PRESSURE OF 50 PSI, 345 kPa WATER

NOTE TO INSTALLING CONTRACTOR: READ THESE INSTRUCTIONS CAREFULLY. THEY WILL SAVE YOU TIME IN ASSEMBLING BOILER PROPERLY.

WARNING: Installation and service must be performed by a qualified installer, service agency or the gas supplier in accordance with all local and national codes. Failure to comply with this warning can result in a fire or explosion causing property damage, personal injury or loss of life!

WARNING: If the information in this manual is not followed exactly, a fire or explosion may result causing property damge, personal injury or loss of life.

Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.

What to do if you smell gas:

•Do not try to light any appliance.

•Do not touch any electrical switch. Do not use any phone in your building.

•Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions.

•If you cannot reach your gas supplier, call the fire department.

Installation and service must be performed by a qualified installer, service agency or the gas supplier.

INSTALLER, THESE INSTRUCTIONS TO BE AFFIXED ADJACENT TO THE BOILER.

CONSUMER, RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE PURPOSES.

WESTCAST, INC.

260 NORTH ELM STREET WESTFIELD, MA 01085 TEL. [phone] FAX [phone]

In Canada: 7555 Tranmere Drive, Mississauga, Ont. L5S 1L4 [phone] Fax [phone]

Page 2	GB100W NATURAL OR PROPANE BOILER
	INSTALLATION AND OPERATING INSTRUCTIONS

AVERTISSMENT. Assurez-vous de bien suivre les instructions données dans cette notice pour réduire au minimum le risque d’incendie ou d’explosion ou pour éviter tout dommoge matériel, toute blessure ou la mort

Ne pas entreposer ni utiliser d’essence ou ni d’autres vapeurs ou liquides inflammables à proximité de cet appareil ou de tout autre appareil.

QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ:

•Ne pas tenter d’allumer d’appareil.

•Ne touchez à aucun interrupteur; ne pas vous servir des téléphones se trouvant dans le bâtiment.

•Appelez immédiatement votre fournisseur de gas depuis un voisin. Suivez les intructions du fournisseur.

•Si vous ne purvez rejoindre le fournisseur, appelez le service des incendies.

L’installation et l’entretien doivent être assurés par un installateur ou un service d’entretien qualifié ou par le fournisseur de gaz.

CONTENTS

Getting Started	page 2
Boiler Ratings & Capacities	page 3
Locating the Boiler	page 3
Combustible Floor Option	page 5
Air for Combustion	page 5
Chimney & Vent Pipe Connections	page 6
Heating System Piping	page 8
Gas Supply Piping	page 11
Electrical Wiring	page 12
Starting the Boiler	page 18
Operating the Boiler	page 20
Checking & Adjusting	page 23
Boiler Maintenance	page 24
Instructions to the Owner	page 25
Replacement Parts	page 26
Canadian Supplement	page 28
Health Warnings	page 30

BEFORE YOU START

WARNING: This manual must be read and fully understood before installing, operating or servicing this boiler! Failure to follow these instruction could result in a fire or explosion causing extensive property damage, personal injury or death!

These instructions cover the GB100W gas fired, low pressure, sectional, cast iron hot water boiler. GB100W boilers have been design certified by CSA under the latest revision of ANSI-Z21.13 for gas fired low pressure steam and hot water boilers, for use with natural and propane gas. Each unit has been constructed and hydrostatically tested for a maximum working pressure of 50 psi, 345 kPa in accordance with the A.S.M.E. Boiler and Pressure Vessel Code, Section IV for cast iron boilers. Each boiler has been equipped with a 30 psi pressure relief valve.

This manual covers the application, installation, operation and maintenance of a GB100W low pressure hot water boiler.

To obtain the safe, dependable, efficient operation and long life for which this boiler was designed, these instructions must be read, understood and followed.

GB100W NATURAL OR PROPANE BOILER	Page 3
INSTALLATION AND OPERATING INSTRUCTIONS

Direct all questions to your Smith Cast Iron Boiler distributor or write to the Customer Service Department, 260 North Elm Street, Westfield, MA 01085. Always include the model and serial numbers from the rating plate of the boiler in question.

The owner should maintain a record of all service work performed with the date and a description of the work done. Include the name of the service organization for future reference.

Where required by the authority having jurisdiction, the installation must conform to the Standard for Controls and Safety Devices for Automatically Fired Boilers, ANSI/ ASME CSD-1.

The installation must conform to the requirements of the authority having jurisdiction or, in the absence of such requirements, to the National Fuel Gas Code, ANSI Z223.1/NFPA 54-latest revision. In Canada, installation must be in accordance with the requirements of CAN/CGA B149.1 or 2 Installation Code for Gas Burning Appliances and Equipment.

BOILER RATINGS AND CAPACITIES

Before undertaking the installation of the GB100W check the boiler rating plate to ensure that the boiler is the proper size for the job. The “Net I=B=R Ratings” specify the equivalent amount of direct cast iron radiation that the boiler can handle under normal conditions. Also ensure that the boiler has been set up for the type of gas available at the installation site. Other important considerations are the availability of an adequate electrical supply, fresh air for combustion and a suitable chimney or vent system.

NOTES:

1.For altitudes above 2000 ft, 610 m, ratings should be reduced at the rate of 4% for each 1000 ft, 305 m above sea level, 10% in Canada.

2.If ordering a boiler for use with LP gas add a P to the model number, ie PGB100.

BOILER LOCATION

WARNING: This boiler is for installation on noncombustible floors only! A special base supplied by the manufacturer must be used to install this boiler on a combustible floor. Failure to comply with this warning can result in property damage, severe personal injury or death!

1.Locate the boiler in an area that provides good access to the unit. Keep in mind that servicing may require the removal of jacket panels. Accessibility clearances must take precedence over fire protection clearances.

2.An optimum site will be level, central to the piping system, close to a chimney and have adequate fresh air for combustion.

3.Ensure that the floor is structurally sound and will support the weight of the boiler. This boiler is designed for non combustible floors only! A special base supplied by Smith Cast Iron Boilers must be used if the boiler is to be installed on a combustible floor. NEVER USE A SUBSTITUTE BASE ON A COMBUSTIBLE FLOOR! Never install this boiler on carpeting!

4.DO NOT install this boiler in a location that would subject any of the gas ignition components to direct contact with water or excessive moisture during operation or servicing.

5.DO NOT place this boiler in a location that would restrict the introduction of combustion air into the boiler. NEVER store objects on or around the boiler.

WARNING: Never store combustible materials, gasoline or any product containing flammable vapors or liquids in the vicinity of the boiler. Failure to comply with this warning can result in extensive property damage, severe personal injury or death!

Page 4	GB100W NATURAL OR PROPANE BOILER
	INSTALLATION AND OPERATING INSTRUCTIONS

6.If the boiler is to be located in an alcove, closet or other confined space the distances from the boiler and it’s vent system to all combustible construction must be equal to or greater than the minimum clearances in Figure 1. When installed in a closet or confined space two permanent openings of equal area adjoining another room or rooms having sufficient volume to meet the requirements of an unconfined space must be provided. Each opening must have a minimum free area of one square inch per 1000 Btu/hr, 2200 mm2/kW based on the total input rating of all gas utilization equipment in the confined area. Each opening must be no less than 100 in2, 64516 mm2, in size. The upper opening must be within 12 in, 305 mm, of, but not less than 3 in, 76 mm, from the top of the enclosure. The bottom opening must be within 12 in, 305 mm, of, but not less than 3 in, 76 mm, from the bottom of the enclosure.

WARNING: Never install a PGB100W, propane boiler in a closet or other confined or enclosed spaceunless the installation conforms to the latest revision of the National Fuel Gas Code, ANSI Z223.1 and all applicable local building codes! Failure to comply with this WARNING could result in a fire or explosion causing extensive property damage, severe personal injury or death!

Figure 1: Clearances to Combustible Construction

					C
* NO FRONT WALL IN ALCOVE					TO
			A	COMBUSTIBLE
					MATERIAL
E	F
					D
			B
FRONT
					For
	AL		CL	Servicing
in	mm	in	mm	in	mm

A	24	610	51	1295	N/A	N/A
B	*	*	2	51	N/A	N/A
C	6	152	6	152	6	152
D	4	102	4	102	4	102
E	7	178	7	178	10	254
F	4	102	4	102	10	254

AL = Alcove

CL = Closet

*No Front Wall in Alcove

GB100W NATURAL OR PROPANE BOILER	Page 5
INSTALLATION AND OPERATING INSTRUCTIONS

COMBUSTIBLE FLOOR OPTION

The GB100W boiler has been designed for use on noncombustible floors only. If a GB100W boiler is to be installed on combustible flooring of any type, it MUST be installed using the Special Base designed by the Smith Cast Iron Boiler Co. Do NOT use any base other than the one specifically designed for it if installing a GB100W boiler on combustible flooring.

WARNING: Never install a GB100W boiler on combustible flooring without using the special base specifically designed for it by the Smith Cast Iron Boiler Co. Do not alter in any way the special base supplied by the Smith Cast Iron Boiler Co. Failure to comply with this warning may result in a fire causing property damage, personal injury or death!

To order the Special Base contact the nearest Smith Cast Iron Boiler distributor and ask for the “Noncombustible Floor Pan”.

Determine where the boiler will be located by following the instructions in the Boiler Location section of this manual. Place the Special Base in this location and fasten it in place to prevent it from moving while the boiler is being placed on it.

If the GB100W is being installed in an alcove or closet ensure that the minimum distance to combustible construction requirements, listed in Figure 1, are met.

Figure 2: Special Base Installation on

Combustible Flooring

FRONT	SUPPORT
GRILL	CHANNEL

Remove the sheet metal base pan attached to the boiler. Position the boiler in front of the Special Base. It’s suggested that two lengths of 3" pipe the width of the boiler, or longer, be placed under the boiler base side panels.

CAUTION: Be careful not to damage the burners, pilot assembly or any other gas train components during this procedure. If a component is damaged, replace it!

Carefully roll the boiler up to the front of the Special Base. Align the boiler base side panels with the Special Base support channels. Using great care, slide the boiler onto the Special Base.

CAUTION: Never lift the boiler by the jacket panels or flue collector/draft diverter or severe damage to the boiler may result!

Center the boiler from side to side on the Special Base. Ensure that the back of the burner base side panels are flush with the back of the Special Base support channels. Install the front grill supplied with the Special Base. Complete the installation in accordance with the instructions set forth in this manual.

COMBUSTION AIR

WARNING: This boiler must be supplied with combustion air in accordance with Section 5.3, Air for Combustion & Ventilation, of the latest revision of the National Fuel Gas Code, ANSI Z223.1/NFPA 54 and all applicable local building codes. Failure to provide adequate combustion air for this appliance can result in excessive levels of carbon monoxide which can result in severe personal injury or death!

Table 1: Vent and Chimney Dimensions

Boiler Size	3	4	5	6	7	8	9		10		11	12
(Sections)
Vent Pipe	5	5	6	6	7	7	8		8		9	9
Dia. (In.)
Chimney			8 x 8					8 x 12
Flue Size
Chimney	18	18	18	17	17	17	16		16		16	16
Height (Ft.)

Page 6	GB100W NATURAL OR PROPANE BOILER
	INSTALLATION AND OPERATING INSTRUCTIONS

To operate properly and safely this boiler requires a continuous supply of air for combustion. Oxygen is used by the burners in the boiler to burn the gas. In addition, air is also used to assist in the safe disposal of the products of combustion. This air is known as dilution air and mixes with the products of combustion to assist in it’s exit through the flue pipe and chimney. An adequate supply of outside air must be available to replace that used by these processes.

Older houses often have enough “leakage” to provide an adequate amount of combustion air provided that the demand for combustion air is not too great. Homes that are relatively new or “tight” will most likely require the installation of a fresh air duct or other means of providing air for combustion. Any home utilizing other gas burning appliances, a fireplace, wood stove or any type of exhaust fan must be checked for adequate combustion air when all of these devices are in operation at one time. Sizing of an outside air duct must be done to meet the requirements of all such devices.

Table 2: Combustion Air Duct Sizing

	Input Btuh	Input Btuh	Input Btuh
Fresh Air	1/4" Wire	Metal	Wooden
Duct Size	Mesh Screen	Louvers	Louvers
3" x 12"	144,000	108,000	36,000
8" x 8"	256,000	192,000	64,000
8" x 12"	384,000	288,000	96,000
8-1/2" x 16"	512,000	384,000	128,000

If the boiler will be located in an alcove, closet or any confined space refer to item 6 in the Boiler Location section of this manual.

CHIMNEY & VENT PIPE CONNECTIONS

WARNING: This boiler must be vented in accordance with Part 7, Venting of Equipment, of the latest revision of the National Fuel Gas code, ANSI Z223.1/NFPA 54 and all applicable local building codes. Improper venting of this appliance can result in excessive levels of carbon monoxide which can result in severe personal injury or death!

Chimney Inspection & Sizing

If this boiler will be connected to a masonry chimney, a thorough inspection of the chimney must be performed. Ensure that the chimney is clean, properly constructed and properly sized. Table 1 lists the flue size and chimney height required for this boiler.

When more than one appliance is connected to the same chimney flue, the flue must be large enough to handle both appliances.

The vent installation must be in accordance with Part 7 of the latest revision of the National Fuel Gas Code, ANSI Z223.1/NFPA 54.

WARNING : If an appliance using any type of a mechanical draft system operating under positive pressure is connected to a chimney flue, never connect any other appliances to this flue. Doing so can result in the accumulation of carbon monoxide which can cause severe personal injury or death!

VENT CONNECTIONS

Always use a type B or C vent pipe of the proper diameter for the boiler. Use the shortest, straightest vent system possible for the particular application. The vent system should be sloped up toward the chimney at a rate of 1/4 in/ft, 2 mm/m. Ensure that the flue pipe is properly supported and each connection securely fastened with at least 3 corrosion resistant sheet metal screws. The termination of the vent pipe should be flush with the inside of the chimney flue.

Always provide a minimum clearance of 6 in, 152 mm, between type C vent pipe and any combustible materials. Type B1 vent may be used, clearance between it and any combustible material must be as listed.

WARNING: Failure to maintain minimum clearances between vent connectors and any combustible material can result in extensive property damage, severe personal injury or death!

WARNING: Never modify or alter any part of the draft hood or vent damper supplied with this boiler. This includes the removal or alteration of any baffles in the draft hood or flue collar. Never install a vent pipe of a diameter different than that of the boiler draft hood flue collar, table 1. Failure to comply with this warning can result in severe personal injury or death.

Common Vent Systems

If an existing appliance is removed from a common venting system, the common venting system may then be too large for the proper venting of the remaining appliances connected to it. At the time of removal of an existing boiler, the following steps shall be followed with each appliance remaining connected to the common venting system placed in operation, while the other appliances remaining connected to the common venting system are not in operation.

Au moment du retrait d'une chaudière existante, les mesures suivantes doivent être prises pour chaque appareil toujours raccordé au système d'évacuation commun et qui fonctionne alors que d'autres appareils toujours raccordés au système d'évacuation ne fonctionnent pas: système d'évacuation.

GB100W NATURAL OR PROPANE BOILER	Page 7
INSTALLATION AND OPERATING INSTRUCTIONS

a)Seal all unused openings in the common vent system and repair any leaks.

Sceller toutes les ouvertures non utilisées du système d'évacuation.

b)Visually inspect the vent system to ensure that it is properly pitched and sized and that there are no structural deficiencies such as blockages, restrictions, leakage, or corrosion that could cause an unsafe condition.

Inspecter de façon visuelle le système d'évacu-ation pour déterminer la grosser et l'inclinaison horizontale qui conviennent et s'assurer que le système est exempt d'obstruction, d'étranglement de fruite, de corrosion et autres défaillances qui pourraient présenter des risques.

c)As far as is practical close all doors and windows common to the space in which the vent system and appliances connected to the common vent system are contained. Turn on all exhaust fans, clothes dryers, range hoods and appliances requiring air for combustion that are not connected to the common vent system. Ensure that all appliances operate at maximum speed. Do not operate a summer exhaust fan. Close all fireplace dampers.

Dans la mesure du possible, fermer toutes les portes et les fenêtres du bâtiment et toutes les portes entre l'espace où les appareils toujours raccordés du système d'évacuation sont installés et les autres espaces du bâtiment. Mettre en marche les sécheuses, tous les appareils non raccordés au système d'évacuation commun et tous les ventilateurs d'extraction comme les hottes de cuisinère et les ventilateurs des salles de bain. S'assurer que ces ventilateurs fonctionnent à la vitesse maximale. Ne pas faire fonctionner les ventilateurs d'été. Fermer les registres des cheminées.

d)Place in operation the appliance being inspected. Follow the lighting instructions. Adjust thermostat so appliance will operate continuously.

Mettre l'appareil inspecté en marche. Suivre les instructions d'allumage. Régler le thermostat de façon que l'appareil fonctionne de façon continue.

e)Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the flame of a match or candle, or smoke from a cigarette, cigar or pipe.

Faire fonctionner le brûleur principal pendant 5 min ensuite, déterminer si le coupe-tirage déborde à l'ouverture de décharge. Utiliser la flamme d'une allunette ou d'une chandelle ou la fumée d'une cigarette, d'un cigare ou d'une pipe.

f)After it has been determined that each appliance remaining connected to the common venting system properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other gas-burning appliance to their previous condition of use.

Une fois qu'il a été d éterminé, selon la métode indiquée ci-dessus, que chaque appareil raccordé au système d'évacuation est mis à l'air libre de façor adéquate. Remettre les portes et les fenêtres, les ventilateurs, les registres de cheminées et les appareils au gaz à leur position originale.

g)Any improper operation of the common venting system should be corrected so the installation conforms with the National Fuel Gas Code, ANSI Z223.1/ NFPA 54. When resizing any portion of the common venting system, the common venting system should be resized to approach the minimum size as determined using the appropriate tables in Appendix F in the National Fuel Gas Code, ANSI Z223.1/ NFPA 54 and or CSA B149 Installation Codes.

Tout mauvais fonctionnement du systéme d'évacution commun devrait étré corrigé de façor que l'installation soit conforme au National Fue Gas Code, ANSI Z223.1/NFPA 54 et (ou) aux codes d'installation CSA-B149. Si la grosseur d'une section du système d' évacuation doit étré modifiée, le système devrait étré modifié pour respecter les valeurs minimales des tableaux pertinents de l'appendice F du National Fuel Gas Code, ANSI Z223.1/ NFPA 54 et (ou) des codes d'installation CSA-B149.

Vent Dampers

This boiler comes from the factory equipped with a vent damper specifically engineered for it. The vent damper must be properly installed to obtain the high performance for which this boiler was designed. If the damper is damaged or missing do not install the boiler without it! Contact the nearest Smith Cast Iron Boilers distributor to obtain the proper vent damper.

WARNING: On boilers with a constant pilot ignition system, ensure that the hole in the damper blade is not plugged. Failure to do this could result in the spillage of carbon monoxide which can result in severe personal injury!

Vent dampers are designed for use with only one appliance. NEVER connect more than one appliance to a single vent damper.

Locate the vent damper so that it is accessible and the damper position indicator is visible. Maintain a minimum of 6 inches between the damper and any combustible materials!

Page 8	GB100W NATURAL OR PROPANE BOILER
	INSTALLATION AND OPERATING INSTRUCTIONS

Fasten the vent damper to the flue collar and vent pipe using at least 3 corrosion resistant sheet metal screws per joint. Connect the damper harness to the top panel with the BX connector supplied. Plug the Molex connector on the damper harness into the mating plug on the harness located inside the control compartment.

The vent damper is operating properly when it opens completely upon a call for heat and closes completely when the call for heat ends. The vent damper must be in the open position when the boilers main burners are in operation.

Figure 3: Vent Damper Location

DAMPER BLADE POSITIONED

FRONT TO BACK OF BOILER

MOTOR TO FACE

FRONT OF BOILER

FRONT OF

BOILER

Figure 4: Heating System Piping

DISCHARGE PIPE SIZE TO EQUAL VALVE OUTLET. DO NOT RESTRICT FLOW.

SUPPORT DISCHARGE PIPING SO AS TO AVOID STRAIN ON THE VALVE BODY.

FOR DISCHARGE

THROUGH ROOF

CONSULT THE

SMITH CO.

1" CLEARANCE MUST BE MAINTAINED BETWEEN HOT WATER PIPING AND COMBUSTIBLE CONSTRUCTION.

DISCHARGE SO AS TO AVOID EXPOSURE OF PERSONS TO HOT LIQUID OR VAPOR. LEAVE OPEN END VISIBLE FOR PERIODIC INSPECTION FOR SLOW LEAKAGE OR DRIPS.

HEATING SYSTEM PIPING

CAUTION: All piping must be installed by a qualified technician in accordance with the provisions set forth in the applicable ANSI/ASME standards and local building codes and regulations. Improper piping of this boiler can cause flooding, extensive property damage, heating system damage or damage to the boiler.

The GB100W hot water boiler comes from the factory ready to be piped to the heating system. Each boiler is equipped with a safety relief valve. This valve must be piped in accordance with the ANSI/ASME Boiler and Pressure Vessel Code, Section IV. Figure 4 provides a pictorial description of the boiler and piping components.

GB100W NATURAL OR PROPANE BOILER	Page 9
INSTALLATION AND OPERATING INSTRUCTIONS

The boiler should be placed in the location selected for it. Refer to the BOILER LOCATION section in this manual. Ensure that the boiler is level from front to back and from side to side. Use metal shims to level the boiler. NEVER use wood, plastic or other combustible materials as shims.

All heating system piping must be installed in accordance with the ANSI/ASME Boiler and Pressure Vessel Code, Section IV, and ANSI/ ASME CSD-1, Standard for Controls and Safety Devices for Automatically Fired Boilers. All applicable local codes and ordinances must also be followed.

If the boiler is installed above any radiation elements it must be fitted with a low water cutoff device, L.W.C.O., installed above the normal boiler water level.

Circulators

A TACO 007 circulator has been supplied as standard equipment with the boiler. The 007 is sized for use in a closed heating system with a 30 psi, 207 kPa, maximum operating pressure. If the 007 circulator furnished with this boiler does not have the required capacity for the system in which it is to be installed, an extra zone circulator must be provided. A circulator with a higher capacity may also be used. Figure 5 depicts the performance curve for the TACO 007 circulator.

Piping For Use With Cooling Units

The boiler, when used in connection with a refrigeration system, must be installed so the chilled medium is piped in parallel with the boiler. Appropriate valves must be used to prevent the chilled water from entering the boiler. See Figure 6 for the proper piping layout.

When a boiler is connected to a heating coil that may be exposed to refrigerated air from an air handling device, the piping system must be equipped with flowcontrol valves or some other automatic means of preventing gravity circulation of the boiler water during the cooling cycle.

Figure 5: TACO 007 Performance Curve

10

8

WATEROFFEET-	6
HEAD	4
		TACO 007 CIRCULATOR
		PERFORMANCE CURVE
	2
	0
	0	5	10	15	20	25

FLOW - GPM

Page 10	GB100W NATURAL OR PROPANE BOILER
	INSTALLATION AND OPERATING INSTRUCTIONS

CAUTION: To prevent damage due to excessive condensation, one of the following piping options should be used.

System Bypass

For systems using a circulator on the return as either a single zone, or multiple zones with zone valves, install a system bypass line between the supply and return on the suction side of the circulator, see Figure 7. Install a metering valve in this bypass line to regulate the amount of flow that will be diverted to the return. A plug valve offers the best control for this application. Although other valves may be less expensive, a plug valve will be easier to set accurately.

In the absence of a flow indicator, set the metering valve using temperature as a guide. The accompanying diagram suggests one scenario. This addition requires only two tees, a plug valve, and a small amount of pipe and offers the simplest approach to reliably control condensation. For this system and those that follow, be aware that you are using a percentage of the pump capacity to blend, but the friction loss for the entire pump flow has been reduced. In most cases, the standard pump packaged with the boiler has enough capacity to feed the baseboard distribution system and the bypass line.

Figure 8: Pump Away Bypass

	SUPPLY	RETURN
	50%	50%
		120° F
	160° F
		50%
		160° F
	100%	100%
	160° F	140° F

PUMP AWAY

BYPASS

Pumped Blend

An additional circulator can also be used to provide a return water temperature blend. This method works well with systems with multiple zones with circulators, see Figure 9. The dedicated bypass circulator provides a strong blending flow without diminishing the flow available to any heating zone. Any residentially sized circulator is adequate for this purpose.

Figure 7: System Bypass

SUPPLY	RETURN
50%		50%
		120° F
160° F
	50%
100%	160° F	100%
160° F		140° F

SYSTEM

BYPASS

Pump Away Bypass

For systems that use a single circulator to pump away from the boiler, the bypass should be installed on the discharge side of the circulator, see Figure 8. Full temperature water supplies the baseboard distribution system as before. Half of the circulator’s volume moves through the bypass, blending and heating the cooler return water. Again, the cost of installing the bypass is small and setting it by temperature can be accomplished with a contact thermometer.

Each of these bypass solutions also has the added benefit of increasing circulation in the boiler which will maximize tankless coil output and increase the accuracy of temperature sensing controls.

Figure 9: Pumped Bypass

	SUPPLY	RETURN
	100%	100%
		120° F
	160° F
		100%
		160° F
	200%	200%
	160° F	140° F
	PUMPED
	BYPASS