Ignoring the outdoor reset on Lochinvar Knight

russiand

I need to have just one of the built in heating zones on a Lochinvar Knight ignore the outdoor reset. Whats the easiest way to do this? Thanks in advance!

Ironman

Is the zone for space heating or domestic hot water?

russiand

Space heating, but don't want to honor the outdoor reset just on that one.

Henry

You will not reap the benefit of the Lochinvar condensing mode due to O.R. You will have to run the boiler at high temperature.

Ironman

Do you have an indirect connected?

russiand

Yes, I do have an indirect already connected. And yes I do realize that I will not enjoy the benefits of ODR on the zone I am trying to make ignore it. But I still want to find a way to do it.

Henry

You will have any ODR for any zone. You will have to run the boiler at high temperature continuously

russiand

So it's all of them or nothing, there is no way to get just one zone to ignore ODR?

Ironman

The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently. Simply program the ODR curve for that zone to give you the same SWT that you want at the top and bottom of that curve. Also, set the WWSD for that zone as high as needed.

The demand signal will have to be wired to the corresponding terminals on the Knights control board.

Dave H_2

or.....
Use a zone controller. Depending upon how your system is zoned, pumps or zone valves you can use a multizone controller for that one zone and the DHW indirect zone.
Take the XX terminals from this controller and go to the DHW input of the boiler. Use the priority setting on the controller so that the DHW still runs in that mode.

Dave H

NY_Rob

Ironman said:

The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently.

That's an awesome feature!

But, what happens when more than one t-stat is calling for heat and both zones have different ORD curves? Say it's 30F outdoors and one zone calls for 120F SWT and the other zone calls for 135F SWT.
The boiler can't supply two or more different SWT's can it?

Leon82

> @NY_Rob said:
> The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently.
>
> That's an awesome feature!
>
> But, what happens when more than one t-stat is calling for heat and both zones have different ORD curves? Say it's 30F outdoors and one zone calls for 120F SWT and the other zone calls for 135F SWT.
> The boiler can't supply two or more different SWT's can it?

The highest temp is used

russiand

I love the idea of connecting another zone controller to the DHW terminals. I will do exactly that, that's exactly what I need. Thank you so much for all the suggestions!!!

Rich_49

What is connected to the zone you want to ignore ODR on ? Why are you interested in doing this ?

NY_Rob

@Leon82...

Thanks for your reply!

Boon

I may not be interpreting what is going on here exactly but I think I’m reading that a space heat call will run through a zone controller and land on the DHW terminals at the boiler. Is that right?

That would avoid the ODR but it would be subject to the DHW anti-cycling parameters.

NY_Rob

Most ODR "sensors" are just NTC (Negative Temperature Coefficient) thermistors.
You could run one of the thermistor leads to the NC terminal of a SPDT micro relay, bridge that to a high value (68K Ohms maybe) resistor connected to NO relay terminal. Connect the common terminal back to the thermistor lead that runs to the boiler. Wire the relay coil to the t-stat hot lead. When the t-stat is calling for heat, the relay coil energizes and you add 68K ohms to the thermistor value which would fool the boiler into thinking it's -5F outside. Once that zone is satisfied, the relay coil releases and the thermistor value is normal again.

Total cost would be under $20 if that much.

Ironman

Boon said:

I may not be interpreting what is going on here exactly but I think I’m reading that a space heat call will run through a zone controller and land on the DHW terminals at the boiler. Is that right?



That would avoid the ODR but it would be subject to the DHW anti-cycling parameters.

I think what Dave is proposing is using a 2 zone pump control like an SR502 and running both the DHW circ and the High temp zone into it. Then use the "X X" terminals on it to signal the DHW terminals on the boiler. The "Priority Zone" on the SR502 or 503 would have the indirect connected to it. It's a sound idea.

The only holdback that I see would be if the HIGH temp zone requires a sustained heat, then the priority function in the BOILER would have to be set to a very minimum time depending upon the likelihood of this.

A similar issue is there if you setup one temp zone on the boiler to override the ODR: that will cause the boiler to go to the highest SWT calling and that would send 180* to every zone that's calling until the High temp zone is satisfied. A mixing valve(s) would then be necessary for the other zones to prevent over heating. Lochinvar has an add on module to do this, but it also requires motorized valves on the zones. Not cheap.