Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Should the pump keep running when the set point is reached :/

Alistair
Alistair Member Posts: 3

Hi - any of you geniuses know why my boiler's pump does what it does?

I'm a homeowner with a Weil McLean Ultra 230. I think it's oversized for the apartment and certainly for any one of its three zones. Combining zones and turning the firing rate down has largely solved that. But sometimes the temperature still creeps above the setpoint and eventually hits the shut-off temp, set to 170+10 right now.

Then the burner turns off, but the pump keeps running. As far as I can see this pushes 'return' water through the boiler, so the 'supply' temperature falls to that level quickly. And the burner turns on again, quickly gets back up to the shut-off temperature and I have short cycling.

The whole cycle is then 2 minutes long.

When the room gets up to the thermostat setting though, and the heat call stops, the pump and burner stop together, and the 'supply' temperature falls much more slowly. Isn't that what should happen when the shut-off temperature is reached? Seems like that would lengthen the on/off cycle. Or does the water have to keep flowing because reaching this temp is bad for the system maybe..?

Anyone?

Comments

  • pedmec
    pedmec Member Posts: 1,026

    No, the circulator keeps running because you still having heating demand. The burners shutting down because you have reached the operating limit set point (170). if the circulator stopped every time you reach the target set point you'll most likely never satisfy the heating demand

    HomerJSmithAlistair
  • HVACNUT
    HVACNUT Member Posts: 6,238

    What series Ultra?

    Which circulator? There should be at least two.

  • Alistair
    Alistair Member Posts: 3

    It's Series 4.

    I don't know enough to answer the question! The sytem has one pump I can see, a Taco cartridge circulator beside the boiler. If I look at the Circulators entry in the boiler settings, all are 'Off' for Priority 2. There's no HW from this boiler - there is a separate heater for HW.

  • HVACNUT
    HVACNUT Member Posts: 6,238

    All piping in the manual shows Primary/Secondary piping, with a Boiler circulator and at least one System circulator.

    Alistair
  • Alistair
    Alistair Member Posts: 3

    Hmm. Well I hope it's not crucial :)

    HVACNUT