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taco outdoor reset PC 700-2 on burnham boilers

Dick_3 Member Posts: 60

It would be useful if Taco would show these options (and maybe more) on the factory wiring schematics that come with the controls. The existing Taco schematics seem to be limited.

You'll sell more controls if you provide good information on optional/different/typical applications. Honeywell always seemed very good on offering different applications on their controls with the enclosed literature with each control.

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  • keith_20
    keith_20 Member Posts: 11
    outdoor reset taco PC-700-2- burnham boilers

    i have two burnham installs done this fall that are using taco exp relays. i would like to install the PC-700 outdoor resets on both. never worked with these resets before. not sure what tempertures to install on the setup of the reset. i have read the manual but would like some more opinions. thanks
  • tom_49
    tom_49 Member Posts: 269


    We have installed a couple of these. They are real easy to install and program. Great for the $$$.

    As far as what temps you can run, that will be based on the type of boilers, piping lay-out, type of transmitters ( bb, radiant, hydro-air,etc. ) and load calc on the building.

    Put it in, and experiment.

    Good luck, Tom
  • A.J.
    A.J. Member Posts: 257

    These controls are great to convert one big bioler to two smaller ones. I've used them several times and all of the settings for the control is explained in the instructions.All you have to do is get into the adjustment screen and put in the parameters you want to see, like minumin boiler temp.,outdoor design,max temp. The control does the rest,including firing the second boiler when needed.
    The best thing about it is that it always gives your customer some heat if one of the burners goes down.
  • Singh_4
    Singh_4 Member Posts: 21
    Boiler piping

    I just added one of these on an existing system. Great for the price. Plug right into exisiting SR control.

    I would add however if your current set up does not have a by-pass piping , add one. I think it is a good idea. It's not in Taco 700 manual, they just tell you to set up min. SUPPLY temps to 140* which I believe is incorrect, the return should be 140*. Of course you can go lower if you protect the boiler from flue gas condensation.
  • Dick_3
    Dick_3 Member Posts: 60

    If you have a primary pump, you'll need to add relays off of each zone to operate the pri pump when you switch the reset/normal switch on the exp to reset. If the reset/normal switch is set to normal, you can run the pri pump off of the ZC/ZR contacts on the exp board - the pri pump will operate when any zone calls (but you can't use the reset module).

    Asked the Taco tech service why the ZC/ZR terminals change operation when you switch the reset/normal switch on the EXP, but there has been no response in two weeks. Maybe they don't know either. To control the pri pump in the reset mode off of the ZC/ZR terminals would just be too easy I guess.

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  • Joe Mattiello
    Joe Mattiello Member Posts: 703

    The SR503-EXP 3 zone capacity switching relay control will interface with the PC700-2 outdoor reset control microprocessor for outdoor reset operation. If you have primary secondary piping with a primary circulator, you cannot use the ZR terminal for a primary circulator because the PC700-2 modulates the boiler through the XX terminals. XX terminals use the same relay as ZC/ZR terminals causing ZR terminal to continuously open, and close causing the primary Circulator to stop running with the boiler. If you have primary secondary piping and you need a primary pump to run, you might consider using the PC702 2 boiler staging control which interfaces with the TT terminals on the boiler directly.
    Incidentally, if you’re having a problem locating a replacement ice-cube relay, call me I have a few here in my office.

    Joe Mattiello
    Technical Support Engineer
    Tel. 401-942-8000 X 484
    Fax. 401-942-2360
    1160 Cranston St
    Cranston, RI 02920
    [email protected]
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • Joe Mattiello
    Joe Mattiello Member Posts: 703
    The wiring diagrams are available

    Attached is the Taco zone control wiring guide found on the Taco web site at www.taco-hvac.com along with a search engine for successfully finding the wiring diagram that best meets your system design criteria for the RMB-1. There is also a Radiant made easy guide to help select the best components when engineering your radiant system.
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • tk_3
    tk_3 Member Posts: 36
    Which model boiler is this?

    If this is the Revolution there will be a differant approch than the other boilers.
  • keith_20
    keith_20 Member Posts: 11

    ron, the first boiler is a revolution rv-5 with three zones and a indirect. the oither boiler is a series 2 with one monoflow zone.
  • TK03
    TK03 Member Posts: 54

    The series 2 can be treated like every other boiler. The Revolution has the 007 built into a blending loop, which is only energized when T-T is energized. On a standard outdoor single stage reset control and the system temp satisfies the reset temp, the T_T is de-energized and we also loose the internal circ. This can cause severe short cycling of the boiler. Easy fix and utilizing stored energy in the cast iron and some water volume is to bring the internal circulator on first, and if needed fire the boiler. A two(2) stage outdoor reset such as the PC702 with an SR50?-EXP resolves this easily and efficiently. Stage one(1) will start the internal circ and stage two(2) will energize T-T. Also keep in mind this boiler can return water as cool as 55f. So set minimum return water setting below 140f. This will allow you to use residual water first, fire the boiler when needed and allow reset down to maximum savings. Use the Revolution to it's fullest capacity. If you want a wiring diagram please e-mail and ask I will supply.
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