Variable Speed System Pumping Theory Application Why use

Variable Speed System Pumping Theory & Application

Why use a Variable Speed Circulator? • Good Question… • What do they do? - Vary speed based on changing loads - Use external loads • Best applications - System circulator with zone valves - Radiant with multiple zones

Universal Hydronics Formula • GPM = BTUH ÷ ∆T X 500 GPM = Gallons Per Minute BTUH = Heating Load ∆T= Design Temperature Drop • 20˚ for baseboard • 10˚ for radiant 500 = 8. 33 x 60 x 1

Sample Project • Heat loss = 75, 000 BTUH • Design temperature = 0˚ • 3 zones fin tube • 25 K BTUH each • 20˚ ∆T

Do the math! • BTUH ÷ ∆T X 500 • GPM = 75, 000 20 x 500 • GPM = 75, 000 10, 000 • GPM = 7. 5

For each zone… • 25, 000 BTUH each • GPM = 25, 000 20 x 500 • GPM = 25, 000 10, 000 • GPM = 2. 5

Pipe Sizing • • • 2 -4 GPM = 3/4” pipe 4 -8/9 GPM = 1” pipe 8/9 -14 GPM = 1 -1/4” pipe 14 -22 GPM = 1 -1/2” pipe Min/Max velocity • 2 -4 FPS • >4 = Velocity Noise

Let’s Pipe ‘Er Up!

Head Loss

Head Loss • Longest run = 15’ (Including element) • Multiply by 1. 5 (to allow for fittings, etc. ) • 150 x 1. 5 = 225’ • Multiply by. 04 • 4’ head / 100’ of pipe • 225 x. 04 = 9’ head loss • 7. 5 GPM @ 9’ head

Pick the Pump… Taco 008 Pump Curve

System Curve

As Zone Valves Close…

As Zone Valves Close… • GPM = BTUH ∆T x 500 • GPM = 50, 000 ∆T x 500 • Delta-T is lower than design • Poor heat transfer • Less efficient boiler • Velocity noise

What do we do about it? • Ignore it? • “That’s just the way these systems are!”

A good solution. . .

A “Flat” solution.

A Better solution… Variable Speed pumping! Actual flow rate = 9 GPM

Universal Hydronic Formula • GPM = BTUH ∆T X 500 • GPM = BTUH x ∆T X 500 • ∆T = BTUH ÷ 500 GPM • ∆T = 75, 000 ÷ 500 9 • ∆T = = 16˚ • ∆T = with 2 Zones = 15˚ • ∆T = with 1 Zone = 12˚ • Under DESIGN conditions!

But what if Delta-T was fixed? • GPM = BTUH ∆T X 500 • GPM = 25, 000 20 x 500 • GPM = 2. 5 • The flow will vary!

A Better Solution… 15 10 5 5 10 15 20

An important Consideration… • Calculate max flow rate • Estimate Head loss • Length x 1. 5 x. 04 • Head loss at MAX flow loss • Actual flow rate much less • Can overestimate head by 50% • ∆T circulator “Self-Adjusts”

Taco 00 -VDT • • • Variable speed ∆T circulator Control built in Simple to install Simple to program Simple to understand 008, 0012, 0013 VDT

A simple solution

Setting it up • Range Dial • Adjusts to desired ∆T • Dip Switches • Switch 1, 3 ON • All others off

Wiring it up… • H-N to ZVC • Supply sensor to S 2 & Com • Return sensor to S 1 & Com Supply Sensor Return Sensor

Delta-T vs. Delta-P • ∆T directly related to flow rate • Pump speeds adjusts to required BTU/hr • GPM = BTUH/∆T x 500 • ∆T always runs at lowest required speed • ∆P adjusts only to pressure change • Needs accurate head loss calculation - not estimation • Doesn’t know which zones are open/closed • May not be able to satisfy heat demand

Energy Consumption k. W consumed, 2, 500 hour heating season Assuming 12. 5 hours of operation daily ECM circulators draw constant 5 k. W in “standby” mode to keep memory powered – for 6, 260 non-heating hours annually Taco 00 VDT draws NO power when off – runs off standard relay or zone valve controller 117 k. W 102 k. W 36 33 137 k. W

Cold hard facts. . .

What about system efficiency? • Big difference between Delta-T & Delta-P • Cast Iron Boilers • ∆T circulator controls return water temp. • Reduces short cycling • Uses less fuel • Bigger impact with “mod-con”

Delta-T and Boiler Efficiency

A quick comparison…

Some parting thoughts • • ∆T directly related to flow rate Pump speed adjusts to required BTU/hr ∆T ensures optimum performance ∆T does not “flat line” ∆T always runs at lowest required speed Many models EASY to set up!