Revision history [back]

What is the recommended method to implement outside air reset for a boiler with a primary-secondary loop? This is more complicated than a primary-only loop since there are two setpoint managers.

I haven't implemented outside air reset yet, and have the following settings which work fairly well for the non-outside air reset scenario:

1. Boiler setpoint of 140F with a delta of 20F.
2. Secondary loop setpoint of 135F.

What is the recommended method to implement outside air reset for a boiler with a primary-secondary loop? This is more complicated than a primary-only loop since there are two setpoint managers.

I haven't implemented outside air reset yet, and have the following settings which work fairly well for the non-outside air reset scenario:

1. Boiler setpoint of 140F with a delta of 20F.
2. Secondary loop setpoint of 135F.
3. The "water heater" doesn't have any heating components, and is only heated from the source side connections to the boiler.

What is the recommended method to implement outside air reset for a boiler with a primary-secondary loop? This is more complicated than a primary-only loop since there are two setpoint managers.

I haven't implemented outside air reset yet, and have the following settings which work fairly well for the non-outside air reset scenario:

1. Boiler setpoint of 140F with a delta of 20F.
2. Secondary loop setpoint of 135F.
3. The "water heater" doesn't have any heating components, and is only heated from the source side connections to the boiler.
4. Primary loop pump is constant speed and flow rate is auto-sized.
5. Secondary loop pump is variable speed with a minimum flow rate of 0.5 gpm for re-circulation purposes, and auto-sized beyond that to mimic the city water pressure.

What is the recommended method to implement outside air reset for a boiler with a primary-secondary loop? loop, and a storage tank (i.e. un-fired Water Heater (WH)) connecting the loops? This is more complicated than a primary-only loop since there are two setpoint managers. managers (SPM).

The below scenario worked best for me. I haven't implemented outside air reset yet, and have the following settings which work fairly well for the non-outside air reset scenario:couldn't get the idle boiler return water to track the tank temperature as close as I think it should (it is proportional but offset by ~5°F), but perhaps that is moot since my BoilerEfficiencyCurve is flat.

1. Boiler setpoint of 140F with a delta of 20F.Primary loop pump is intermittent constant speed, and flow rate is auto-sized.
2. Secondary loop setpoint of 135F.
3. The "water heater" doesn't have any heating components, and is only heated from the source side connections to the boiler.
4. Primary loop pump is continuous constant speed and flow rate is auto-sized.
5. Secondary loop pump is variable speed with a minimum at a selected flow rate of 0.5 gpm for re-circulation purposes, and auto-sized beyond that 40 gpm.
6. The boiler is constant flow, `BoilerEfficiencyCurve' is constant, minimum part load ratio (PLR) is 1, the water delta is 20°F, and the design outlet water temperature is 150°F.
7. Un-fired WH has a source side effectiveness of 1.
8. The secondary loop serves domestic hot water and heating hot water coils.
9. Primary loop SPM: An SPM:Scheduled at ~>10°F than the highest secondary loop supply water temperature during the year. I used 145°F per the screenshot below. In reality, my 20°F-delta intermittent-constant-flow boiler return water temperature should track the tank temperature when idle (it is proportional but offset by ~5°F), and yield a 20°F delta when firing (it does the latter). A dual setpoint SPM in the primary loop didn't help.
10. Secondary loop setpoint control: A custom outside air (OA) reset OS:Schedule:FixedInterval, since OA reset SPMs can't be applied to mimic the city water pressure.WH objects. My maximum setpoint is 135°F, my minimum setpoint is 120°F, and my WH differential is 5°F.