The Evolution Of Radiant Mixing How why and

The Evolution Of Radiant Mixing How, why and when to mix with a valve

Why Mix? • CI boilers – Need lower temp for radiant – Multi-temp, multi-load – Zone by zone mixing • Mod/Con boilers – Boiler makes hi-temp – Need to mix for lower temp radiant – Zone by zone mixing

Mixing Options • 3 -Way tempering valves • Motorized setpoint valves • Motorized reset valves

Mixing Options • 3 -Way tempering valve – Fixed water temperature – Simple, thermostatic, non-electric – MUST ZONE radiant system properly/aggressively – Must pipe bypass to protect boiler

Boiler Piping

3 -Way Tempering Valve Boiler Supply Boiler Return Radiant Supply Radiant Return

Protecting The Boiler 1800 Out Globe Valve Mix Point >1350 1150 Back

A System Sizing Problem

A System Sizing Problem • Find the flow rate – GPM =ΔTBTUH x 500 30, 000 – GPM =10 x 500 – GPM = 6

Sizing The Pipe • • • 2 -4 GPM = ¾” 4 - 8/9 GPM = 1” 8 -14 GPM = 1¼” 14 -22 GPM = 1½” Based on max velocity of 4 feet per second for copper 1” pipe 6 GPM = 1” pipe

Flow & Head Loss • Find radiant tube head loss • Measure total run • Multiply by 1. 5 • Multiply by. 04 – 4’ head/100‘ equiv. length • 60’ x 1. 5 = 90 • 90’ x. 04 = 3. 6 feet of head Radiant Tube Head Loss – 5’ 60 feet

What About The 3 -Way Valve? • 5’ + 3. 6’ = 8. 6’ • 1” valve Cv = 3. 8 – 3. 8 GPM = 1 psi – 1 psi = 2. 31’ head • (Flow 4 Cv)2 x 2. 31 = head loss • (643. 8)2 = 2. 5 psi • 2. 5 X 2. 31 = 5. 8’ • 8. 6 + 5. 8 = 14. 4’

i. Valve Reset • Outdoor reset – more effective, efficient system • Simple wiring – low voltage • Can reset individual zones • Provides boiler protection • Available in 2, 3 and 4 -way models

Understanding Reset

Changing Conditions • Heat loss change every day • Fixed water temp = variable run times = cycling in mild times • Variable water temp = fixed run times = less short cycling = greater efficiency Fixed SWT Variable SWT Heat Loss Variable SWT Fixed Variable Run Time Variable Fixed

How Does It Know? • Four key numbers – – Outdoor Design Temp Mix Design WWSD Mix Start • Reset ratio = Mix Design Temp - 720 – Design Outdoor Temp

Let’s Do One… • Mix Design = 130, Outdoor Design = 0 • 130 – 72 = 72 - 0 • 58 = 0. 8 72

What Does 0. 8 Mean? • Radiant water temp increases 0. 8 of a degree for every 1 degree drop in outdoor temperature • To program: – Move dial on i. Valve to correct ratio

Cast Iron Boilers • Reset the delivery – Boiler operates on high limit – Requires >1350 to prevent condensing • Boiler fires more effectively, efficiently – Take advantage of thermal mass – Can add boiler reset, as well

Mod/Con Boilers • Multiple water temperature system • Resetting off the reset – Lower return water temps – Greater efficiency

Wiring This Bad Boy… • 3 sensors – Boiler return, radiant supply, outdoor – Outdoor sensor on north side, out of sunlight, above snowline • 24 v power in • Zoning/circulator control done externally

4 -Way Valve • One more hole… • Higher Cv – For higher flow rates – ¾” – 7 Cv – 1” – 9. 3 Cv • Same wiring • MUST pipe primary-secondary!!!

Piping & Sizing • 6 GPM, 5’ head radiant • 1” pipe, 10’ total length = 0. 6’ head • ¾” valve = 1. 7’ head • Total head = 7. 3’

Which Circulator?

Why No 1” Valve? • • Could have, but… 1” valve = 1’ head loss Same circulator Why not use less expensive valve? • Smaller valve – tighter water temp control • Size valve to flow, not line size

2 -Way i. Valve • Use for “injection” • Higher Cv than 3 -way valves – ½” = 4. 9 – ¾” = 10. 3 – 1” = 8. 9 • Can handle higher flow rate applications

Injection “Variation” • Injection without an injection circulator • Bypass, globe valve needed • Size to flow, not line size

Pipe & Pump Sizing • 6 GPM, 5’ radiant head loss • Bypass, manifold supply piping - 1” • Injection pipe sizing: – GPM = 30, 000 55 x 500 – GPM =1. 09 – Valve/pipe = ½” –. 11 feet of head through valve ½” 30, 000 BTUH 1350 SWT 1250 RWT 1”

Additional Features • Min/max system supply water temperature • Minimum boiler return temperature – Set with dipswitch – 120 or 135 – Disable by not installing boiler return sensor • WWSD -- 70 degrees or off