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Installing new Burnham ES2 boiler - installation questions concerning valves

I'm replacing an older cast iron boiler with a Burnham ES2. My system is split into three zones using White Rodgers zone valves and a single circulator (B&G Series 100). The System Piping diagram for the ES2 can be found  <a href="http://s3.pexsupply.com/manuals/1253196590775/17467_PROD_FILE.pdf">here</a>.

I have three questions concerning the System Piping diagram for my new boiler:

1) The System Piping diagram for this boiler shows an connection with an

isolation valve between the return and supply, and is shown with an

arrow pointed toward the supply side. What is the purpose of having this

valve? My current boiler piping has no such valve or connection.

2) How important is the flow control valve on the return side? Is that

only to keep heated water from rising in the return line after the boiler shuts off? My

current boiler does not have a flow control valve.

3) My system uses three zone valves. How important is the

pressure-reducing valve shown between the supply and return? My zone

valves complete the call for heat only when fully open, so it does not

seem that I would need the pressure-reducing valve, unless that is

needed for the case when only one zone is open and the pump is supplying

too much pressure (new pump is a B&G Red Fox NRF-22, pump on

existing boiler is a B&G Series #100). My current boiler does not

have a pressure-reducing valve and has been working fine for years, including heating a single zone. I'm thinking of keeping the current circulator.


Eric Peterson


  • CMadatMe
    CMadatMe Member Posts: 3,086

    That is not an isolation valve. It's used as a by-pass valve to keep the boiler from seeing cold return water temp. It's shown in realtion to the installation utilizing the Outdoor reset card.

    If zoned with zone valves there is no need for the flow checks. Zone valves are a postive shut off.

    Pressure reducing valve? I;m assuming you mean feed valve and it is important to have.It makes sure the system is seeing the 12lbs it needs at all times.

    There was an error rendering this rich post.

  • Eric Peterson_3
    Eric Peterson_3 Member Posts: 55
    Reply to Comments (Burnham ES2 Installation Guide)

    Hi Chris,

    If you refer to Figure D-W2 on page 39 of the Installation Guide here, just above the boiler the diagram shows what sure looks like an isolation valve to me. I don't understand the connection with that valve to Outdoor Reset.  If the intent is to prevent cold water shock wouldn't the arrow be pointing the other way?

    No, I did not mean feed valve. That is for the intake water. I am talking about the heating circuit. The same diagram clearly shows a pressure reducing valve between the supply and return on the portion labelled "Zone Valve Option".


    Eric Peterson
  • Ironman
    Ironman Member Posts: 7,379
    The Isolation Valve

    Is necessary, as Chris said, if the outdoor reset card is used. It would have to be adjusted to maintain a minimum return temp.(140deg.) to the boiler to prevent thermal shock and flue condensation. The arrow is pointing correctly as the purpose is to "bypass" some of the flow around the boiler to allow it to heat up quicker.

    Regarding the PRV, I think the tech writer intended for it to be a bypass relief valve in case too much head developed when most of the zone valves closed. It's probably not necessary with your setup if the end switches on the zone valves bring the boiler and the circ. on.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Eric Peterson_3
    Eric Peterson_3 Member Posts: 55
    ES Installation


    Isolation valves are intended to be open or closed, so I don't get that one would be used for the purpose you describe. The instructions don't make any mention of this either. I'm going to try and talk to someone at Burnham tomorrow.

    After looking at the diagram again, I think the valve is there to protect the pump if the boiler supply and return isolation valves are closed, say for maintenance near the boiler, in which case that third valve would be opened during the maintenance operation, then closed during during normal operation. I would think it would be simpler just to make sure the pump did not run during any such maintenance.

    Eric Peterson
  • Steamhead
    Steamhead Member Posts: 16,893
    If your system las large pipes and radiators

    a bypass or some form of low-return-temp protection is needed. But on a lower-mass setup it's not needed, according to the manual. Here is our first ES-2 install, in a low-mass system using three zone valves and an indirect:

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Eric Peterson_3
    Eric Peterson_3 Member Posts: 55
    Reply to Comments (Burnham ES2 Installation Guide)


    Yes this install has radiators and some large (3") pipes. Although not shown in any of the Burnham piping diagrams the installation guide does recommend a system or boiler bypass, or P/S loop to prevent thermal shock and condensation in this type of application.  The ES2 minimum return temperature is pretty low, 100°F. I found an old thread concerning using Danfoss ESBE valves for this situation, they make a 113°F version that could be installed on the return, combined with a mixing valve this looks like a good, simple solution.

    Eric Peterson
This discussion has been closed.