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Primary/Secondary & outdoor reset ,indirect+zone valves

<span style="font-size:12pt">If  you had a primary / secondary piping

loop on a cast iron  type FHW boiler

with a primary loop pump and the supplied Honeywell aquastat relay, a

indirect water heater teed off the primary loop(parallel) with it own

pump and the supplied

aquastat controler/ thermostat ,  4  Taco zone valves on the secondary loop

with it's

own pump and  a

Weil Mclain WM-ODR .  How would you wire in the the FHW boiler system

pump to run all the time during any type of call for heat but cycle the

burner on and off with the ODR , plus  wire in the indirect water

heater pump and aquastat along with the pump for all the space heating? </span>

Comments

  • polyj79
    polyj79 Member Posts: 8
    Hand drawing of heating system

    This is what the system looks like.
  • JStar
    JStar Member Posts: 2,752
    ...

    First, I would put the air separator on the baseboard loop. Then I would pump the boiler loop away from the common piping. After that, I only run the boiler pump when the burners are on.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    Contact weil

    They have wiring diagrams if you do not have the installation manual any more.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    edited June 2010
    Why are you doing primary secondary if I may ask?

    a variable pressure pump or a delta T pump would steam line your wiring and piping.I could see doing primary secondary if you were using pumps to the zones but not with zone valves.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • EricAune
    EricAune Member Posts: 432
    edited June 2010
    Maybe another control?

    I would prefer to use a Taco ZVC406EXP & PC700 boiler reset control.



    You will get the boiler reset will full function parameters in a simple plug-in installation, along with control for three circs. (system, boiler and DHW) along with extremely easy wiring of all zone valves and thermostats.  Add built-in diagnostics and its a pretty nice package.



    **Edit**  I tried to attach pdf's for the taco pc700 and ZVC406 manuals to show diagrams....didn't work
    "If you don't like change, your going to like irrelevance even less"
  • polyj79
    polyj79 Member Posts: 8
    Reason for primary/secondary

    Reason for primary/secondary is, It short cycled and I tried to eliminate it. What is the the best way to wire the system as it is now?
  • CMadatMe
    CMadatMe Member Posts: 3,085
    Wiring

    Simple....Get a Taco ZVC Relayy. Open the cover and the diagram is inside.

    Main end switch to TT at boiler to run the boiler pump and then use the extra end switch to run the system pump. Wire your zone valve to the control as shown.



    PS. Boiler is short cycling because it's too BIG! Real fix..Get the manual down fire if oil, as Eric said plug in the PC700 card and off you go. Treat the pri loop now as boiler protection if needed.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • JStar
    JStar Member Posts: 2,752
    Just a thought.

    Wouldn't p/s looping make the boiler short cycle even more?
  • CMadatMe
    CMadatMe Member Posts: 3,085
    Your probably Right

    It may but alteast if he get's it on reset he has a better chance of slowing the rate of shorts down. Boiler probably needs to be downfired if oil, may even want to throw on an heat manager. Don't know if its oil or gas he never said.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • polyj79
    polyj79 Member Posts: 8
    DV 100 UTICA BOILER

    I cannot reduce the input to this boiler.

    I not sure but wouldn't  I wire the reset in the low voltage side of the boiler  ( in series with the  limit )?
  • Jay_14
    Jay_14 Member Posts: 39
    tekmar House Control 400

    You may want to consider the tekmar House Control 400. It's designed specifically for this type of installation. Simple two-wires per thermostat, has communication so each thermostat can show the outdoor temperature, and its cost competitive to a Taco PC control with a ZVC.

    Here's link to the design guide:

    http://www.tekmarcontrols.com/literature/acrobat/a002web.pdf



    Jay @ tekmar
  • Dave in QCA
    Dave in QCA Member Posts: 1,766
    short cycling

    The effect of the outdoor reset limits the water temperature based on outdoor temperatures.  This greatly improves performance on zoned by prevent wild swings on water temperature which can cause room temps to overshoot.  However, since you do not have a modulating firing rate on your boiler, the observed operating characteristics in mild temperature will be short cycling.  This is simply becuase the boiler has warmed up to the variable ODR set point. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Dave in QCA
    Dave in QCA Member Posts: 1,766
    edited August 2010
    Similar System in 1985

    I installed a similar set up in 1985 using standard controls.  There wasn't much available in the way of electronics at that time.  There was no secondary loop.

    The boiler was a WM 350,000 cast iron boiler, installed ca 1967, connected to ample CI radiation with a B&G Model 2" circulator with a 1/6 HP motor. 

    The house was 4000 sq ft, divided into 5 apartments with wildly varying heating loads because of different wall construction and solar gain in different parts of the building.  Fortunately, the piping ran out in 3 separate loops from the boiler.  I ran 2 additional return lines so that the second floor could be zoned in 2 separate zones.  Thus, I ended up with a zone for each apartment, situated as 1st flr North, 1st flr South, 2nd flr North, 2nd flr South, 1st flr back (only one story), and a zone for the domestic hot water tank, 6 zones total.  After the building was restored to a single family residence, the system continued to work very well.

    CONTROL SET UP

    I used 1" honeywell 2-wire zone valves with built-in end switches, honeywell round thermostats, an adequately sized 24v transformer for the zone valves, Honeywell T475A1032 outdoor reset control, a 24 volt/24 volt relay,  a 24v/115v pump relay, second 24v relay for boiler controls and and gas valve.  The existing B&G 2" pump was used.

    Zone valves were installed on the return line.  Room Tstats were wired to the zone valves and 24v transformer.  The end switches on the zone valves were all wired parallel.  If any zone was activated, the valve would open.  As the contacts on the end switch closed, they activated a 24v pump relay.  This also supplied 110v to a second 24 transformer.  This second transformer supplied 24v to the boiler firing circuit, connected in series through the high limit, ODR, and gas valve.  As the boiler would warm to ODR set point, the ODR would shut down firing until the boiler cooled, but the pump would continue to run as long as any zone was calling for heat.  At any point, if all zones were satisfied, the pump and boiler fire would deactivate. 

    I Set the ODR which had a 1:1 ratio at 90F.  Thus at 50F Outside, the boiler was 110F, -20F outside, the boiler was 180F. 

    The difficulty in the set up is that an ODR controlled boiler will not heat domestic water unless it is VERY cold outside.  Therefore, I used an additional 24v relay.  The coil side of the relay was wired parallel to the zone valve serving the domestic water tank.  The N.O. contacts were wired in parallel to the ODR contacts, thus creating a short around the ODR and overriding it.  Therefore, whenever the domestic water tank called for heat, its zone valve would open, the relay would activate, and the ODR would not have contol.  Boiler temp would rise up as high as the high limit setpoint, 180F.  When domestic water was satisfied, its zone valve would close, the shorting relay would deactivate, and ODR would again contol boiler temp.



    This system worked great, and continues to do so.  A subsequent owner decided that the boiler looked old, and installed a new WM, but the controls and valves are still in use.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
This discussion has been closed.