Maxitrol MR212H User Manual

M/MR Modulating Valves

For Atmospheric, Infrared, and Direct Fired Burners

TABLE OF CONTENTS

Description/Specications..................................................... 1

Introduction .......................................................................... 2

Direct Fired Applications (Negative Pressure) ..................... 2

Direct Fired Applications (Positive Pressure) ...................... 3

Indirect Fired Applications ..................................................... 3

‘H’ Sufx M/MR Valves ......................................................... 3

Applications Table ................................................................. 4

Dimensions .......................................................................... 5

Capacities ............................................................................ 6

Typical Gas Trains ............................................................... 7

Typical Installations ............................................................. 7

Model Designations ............................................................. 7

design certied

DESCRIPTION

Models:

M M411, M411H, M511, M511H, M611, M611H, M420,

M420H, M520, M520H, M620, M620H, M451, M551, and M651.

MR MR212D, MR212E, MR212G, MR212H, MR212J

(Flanged), MR251D, MR251E, MR251G, MR410, MR410-1, MR410H, MR410H-1, MR510, MR510-1, MR510H, MR510H-1, MR610, MR610-1, MR610H, and MR610H-1.

NOTE: “H” sufx models for use with LP and other applications:

M420H, M520H, M620H, MR410H-1, MR510H-1, MR610H-1

• Absolutely NO EXTERNAL MECHANICAL ACTIVATION required.

• MR Valve (only) performs dual function of modulation and pressure regulation.

• Provides innite, continuous ame adjustment.

• May be factory installed or added in the eld.

• Capacities to 30,000 CFH.

• Available in a wide range of body styles and pipe sizes.

• Designed for use with the Maxitrol Selectra systems - or SC11 Signal Conditioners convert computer/PLC controller signals if standard Maxitrol companion controls are not specied.

Whether your needs are problem-free stabilized area heating, elevated heating, consistent higher baking/drying temperatures or other process applications, maintaining consistent temperatures is no longer a problem.

series of modulation

Figure 1 : MR212

SPECIFICATIONS

Gases:

Natural, Manufactured, Mixed, Liqueed Petroleum and Liqueed Petroleum Gas Air Mixtures. H, H-1 models for use with Liqueed Petroleum and other applications.

Certications:

M611, MR212D, E, & G with Series 14: CSA listed to certify compliance with nationally published safety, construction, and performance standards.

M411, M420, M420H, M451, M511, M520, M520H, M611, M620,

M620H, MR212D, E, G, & J with AD1094 controls: CSA listed to certify compliance with nationally published safety, construction, and performance standards.

MR410, MR410H-1, MR510, MR510H-1, MR610, and MR610H-1: CSA certied to Z21.18 and CSA 6.3-M82.

M611, MR212D, E, & G: UL recognized for compliance to nationally published safety, construction, and performance standards.

Vent:

Models M411, M511, M611, M420, M520, M620, M420H, M520H, M620H, MR410H-1, MR510H-1, MR610H-1, M551, M651: Vertical vent outlet 1/8” NPT - 12A06 installed.

Models MR212 and MR251: Two vents located in upper housing, both equipped with vent limiting means.

The unique Modulator or Modulator/Regulator valve, the heart of the Selectra precise, non-uctuating, instantaneous temperature control without requiring a motor or mechanically driven buttery valve.

Electronic Gas Flame Modulating System, provides

Ambient Limits:

Operating ......................................... -40º to 125ºF (-40º to 50ºC)

Non-operating .................................. -50º to 185ºF (-45º to 85ºC)

Mounting:

Must be mounted in upright position in horizontal pipe run, downstream of all other controls except high pressure cut-off switch if used (see Typical Installations, page 7).

M/MR Series Literature

INTRODUCTION

To evaluate which valve will satisfy your needs, it is necessary to determine the application. The rst, and most basic breakdown, is direct versus indirect red appliances.

Direct red units do not have a heat exchanger and all products of combustion generated by the gas burning device are released directly into the airstream being heated. They are commonly used in space heating or make-up air applications, process drying, and baking ovens.

Direct red burners have raw gas injected into the burner and the burner relies entirely on the air being pulled across the burner for combustion air. It may take advantage of the mixing effects of the blower by using a pull through system which locates the burner on the suction side of the blower. This means the air being pulled across the burner is at a negative pressure (usually not greater than

-1.5” w.c.). Other direct red applications may use a push through system, which locates the burner downstream from the blower. This means the air being pushed across the burner is at a positive pressure (usually not greater than 3” w.c.).

Direct red burners can be of extremely high turn down ratios, in some instances, 30:1. The high turn down ratio allows the minimum temperature rise to be low enough that the unit does not have to be cycled on and off to maintain temperature.

Indirect red appliances use a heat exchanger and all products of combustion generated by the gas burning device are vented outdoors. They are usually supplied with an atmospheric burner or a power burner.

With an atmospheric burner, the air being supplied to the burner is at atmospheric pressure. They have limited turndown ratios (maximum input: minimum input) of usually 3:1 or 4:1. Due to the limited turndown ratio, the minimum temperature rise cannot be held low enough, and as a result, the main gas valve must usually be cycled to maintain temperature.

A power burner is a burner in which either the gas, air, or both are supplied at pressures exceeding line pressure for gas and atmospheric pressure for air. Maintaining the proper gas-air mixture for modulation usually requires pressure control of both the air and gas. Burners of this type are usually not capable of modulation with the Maxitrol Selectra® system. (See Exa Star modulating valves or ratio (zero) regulators for these applications.)

With the main valve closed, an adjustable bypass provides a minimum ring rate to the burner whenever the safety shut-off valve(s) is open. This is low re to the heater. Since the pressure regulator maintains a constant supply pressure, the minimum ring rate is also held constant. The MR212’s regulator is an integral component while a seperate upstream pressure regulator is required for the M411, M511, and M611.

As voltage is applied to the control’s solenoid, a magnetic force is applied to the plunger. The plunger in turn pushes down on the main diaphragm of the M411, M511, and M611 valves or allows pressure to develop in the upper chamber of the MR212 valve. These forces on the main diaphragm are very similar to the spring loading of a gas pressure regulator. When the force is sufcient to overcome the counter spring, the main valve will open and gas will ow through the main valve in addition to owing through the bypass. With sufcient voltage, the main valve (modulator valve for the MR212) will fully open and the pressure regulator will limit the burner pressure to the desired amount, thus establishing a controlled maximum high re condition.

We now have two extremes. The rst is low re with no force on the plunger and ow through the bypass only. The second is high re with sufcient force on the plunger to fully open the valve (modulator valve for the MR212), with the gas pressure regulator controlling the maximum ring pressure. Force on the plunger between these extremes results in modulated gas ow. The voltage versus outlet pressure curve, throughout the modulating range, is fairly linear.

There are also applications where it is desirable to have two seperate high re burner settings. Typical applications would be a two speed fan operation or LP natural gas change over. This is accomplished by adding an adjustable resistance to the circuit, thereby limiting voltage to the valve. Changing from one setting to another is done by connecting a single pole single throw switch (customer supplied) that when in the open position allows the outlet pressure to be adjusted up to 2” w.c. below normal maximum high re. Negative pressure valves designed for dual pressure settings are designated with a “- 2” sufx (example: MR212D-2). Field conversion kits (KT/10542) to modify single pressure valves are also available.

The working voltage to operate the modulating controls can be supplied by the A1014, A1024, A1044, A1494 and AD1094 Ampliers or the SC11 Signal Conditioner. (Refer to Bulletin SEL1444_CC_EN, SEL94_CC_EN, and SC11_MS_EN.)

DIRECT FIRED

Valves designed for direct red applications (negative

pressure/pull through) M411, M511, M611, MR212D, MR212E, MR212G, and MR212J.

These valves are designed exclusively for negative pressure (pull through) applications. They use a counter spring to keep the valve in the closed position despite the downward pull of negative pressure. M411, M511, and M611 valves are set for applications up to 1.5” w.c. and are not adjustable. MR212 valves are factory set for applications up to -1.5” w.c. and are eld adjustable for up to -3.5” w.c.

Valves designed for direct red applications (positive

pressure/push through) MR212D-1, MR212E-1, MR212G-1, and MR212J-1.

The valve’s operating principles are identical to the negative pressure MR212. The only difference is the valve has been designed to operate on positive pressure (push through) applications. Positive pressure valves designed for dual pressure settings are designated with a “- 3” sufx (example: MR212D-3).

M/MR Series Literature

INDIRECT FIRED

Valves designed to operate on indirect red atmospheric

burner applications M420, M520, M620.

These valves function in the same manner as the direct red M valves. A pressure adjustment spring has been factory set to obtain an outlet pressure slightly above atmospheric pressure (0.1” w.c.) with the bypass closed and zero voltage being applied. The minimum ow rate is now adjusted through the bypass.

NOTE: Minimum outlet pressure is always above 0.2” w.c. Maximum outlet pressure is 7.0” w.c.

The valves are driven by the A1094 and AD1094 Ampliers or SC11 Signal Conditioners. (Refer to Bulletin SEL94_CC_EN & SC11_MS_EN.)

Valves designed to operate on indirect red atmospheric

burner applications M451, M551, M651, MR251D, MR251E, MR251G.

These valves function in the same manner as the direct red M valves. Minimum input pressure is set using a minimum adjustment spring - the valves do not use a bypass.

They are used in applications where the minimum input pressure to burner is between 2.0” and 4.5” w.c. Maximum obtainable outlet pressure is 7.0” w.c. above minimum input pressure.

‘H’ SUFFIX MODELS

Valves designed with wider modulation span for use with

LP (liquid propane gas) and other applications MR410H-1,

MR510H-1, MR610H-1, M420H, M520H, M620H.

Can be congured for indirect red atmospheric burner applications, as well as those with direct red burners.

‘H’ models are designed for applications where outlet pressure is greater than 7” w.c. Minimum outlet pressure is factory set to 1.75” w.c. - remaining set pressure is obtained through bypass. The ‘H’ models are capable of a total modulation span of as much as 10” w.c. These models are not recommended for applications with a total modulation span of less than 7” w.c. - the sensitivity of outlet pressure change relative to voltage change could cause hunting to occur.

‘H-1’ models are designed for applications with a total modulation span greater than 7” w.c. Minimum outlet pressure range of 1” to

2.8” w.c.

NOTE: Temperatures shown in text are for Maxitrol’s Selectra®

systems. Valves may be used for any temperature range or application the user’s controller can handle. When using valves for other ranges, a Maxitrol SC11 Signal Conditioner can be used in conjunction with the valve. (Refer to Bulletin SC11_MS_EN)

The valves are driven by the A1094 and AD1094 Ampliers or SC11 Signal Conditioners. (Refer to Bulletin SEL94_CC_EN & SC11_MS_EN.)

MR410, MR510, and MR610

These valves use two springs in order to set the high and low re settings. One spring (min.) surrounds the solenoid and is always in contact with the diaphragm assembly. The other spring (max.) is located above the plunger. With zero voltage applied, the minimum and maximum spring’s down force, along with plunger weight, pushes down on the diaphragm thereby setting a regulated high re. A seperate pressure regulator is not required. As voltage is applied, the plunger pulls up sufciently until all plunger weight and maximum spring force is removed. The pressure is now controlled with the minimum spring setting giving a regulated low re condition. Force on the plunger between the extremes results in modulated gas ow. The voltage versus outlet pressure curve, throughout the modulating range, is not linear.

These valves are driven with the A1010 or A1011 Amplier or SC11 Signal Conditioners. (Refer to Bulletin SEL2030_2131_CC_ EN & SC11_MS_EN)

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