CONTROL METHODS HeatNet Control V3
Page 18
Fault tolerance allows for one boiler in the Priority 1 system
to fail and any boiler(s) in the Priority 2 system to fail and
still provide near linear (continuity) BTU response when
adding boilers. This is illustrated in the following examples
using the Boiler System Response graphs.
The Torus Series/Futera III/Fusion-Series Mixed Boiler
System (examples) is advantageous in providing low BTU
input for light loads and high BTUs for heavy loads. The
effective system turndown minimizes short cycling when
light loads are present by assigning smaller boilers to
Priority 1, running them first, and then stopping them last.
In order to achieve the high effective
turndown, smaller boilers are required
(plumbing considerations need to be
considered here due to differing flow/volume
characteristics through the large and small
boilers).
Example Systems:
Non-Mixed Boiler System Examples
With the traditional non-Mixed boiler system, the effective
turndown increases by the turndown ratio for every boiler
added. The min fire rate is equal to the minimum BTUs that
can be delivered to the system.
Number of boilers * Turndown Ratio = Effective System
Turndown: 5 * 5:1 = 25:1.
Mixed Boiler System Examples
With the mixed boiler system, a lower minimum fire
rate/BTU can be delivered to the system by using small
boilers with larger boilers. This works in much the same
way as base loading.
Torus Series 1250 – 4000 Modulation
Parameters
When selecting the Priority 1 boiler(s) for a high effective
system turndown, the BTU Min Input is selected first. (See:
Torus/CK/Futera III/Fusion Boiler Btu Chart). Next, the
MOD-MAX value of this Priority 1 boiler needs to be
greater than:
Mod MAX % =
(Priority 1‘s Min Input + Priority 2‘s Min Input)
Max Input of the Priority 1 boiler
The reason for this is to keep the continuity of BTUs linear
without a BTU bump (discontinuity) when boilers are added
or shed. The Mod Max % can be adjusted to the high side to
allow for tolerance (about 10%) as is indicated in the tables.
This is illustrated in the Boiler System Response 2 graph.
If redundancy is not required, the min inputs of the
Priority 1 boilers may be summed to lower the Mod Max %
value so smaller Priority 1 boilers can be used. The sum of
the min inputs would then need to be divided by the sum of
the Max Input of the Priority 1 boilers. The effect of this
would create a higher turndown. See: EXCEPTION NOTES:
Mod MAX % =
(((Priority 1 Min) * (#Priority 1’s)) + Priority 2 Min)
To Next Page
Loading...
Need help?
General