Control Concepts for Hydronic Systems Using Renewable Energy Heat Sources (Part 1)

Control concepts for hydronic systems using renewable energy heat sources (part 1)

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September 17, 2020 1:00 PM

Moderated by: Sue Dougherty Clean Heating & Cooling program NYSERDA [email protected] presented by: John Siegenthaler, P.E., ASHRAE member Principal, Appropriate Designs Holland Patent, NY www.hydronicpros.com

© Copyright 2020, J. Siegenthaler all rights reserved. The contents of this ﬁle shall not be copied or transmitted in any form without written permission of the author. All diagrams shown in this ﬁle on conceptual and not intended as fully detailed installation drawings. No warranty is made as the the suitability of any drawings or data for a particular application. Control concepts for hydronic systems using renewable energy heat sources (part 1)

Description: The controls used in hydronic heating systems supplied by renewable energy heat sources, such as biomass boiler, heat pumps, and solar thermal collectors have proven to be an area in which installers have some difﬁculty. This webinar will emphasize “universal” control concepts used in these systems, and shows how they are implemented with off-the-shelf hardware.

Speciﬁc topics include: • Basic switch and relay logic • setpoint temperature control • staging control • differential temperature control • sensor mounting

Part 2 of this webinar will cover additional control concepts such as outdoor reset control, and mixing control. Design Assistance Manual for High Efficiency Low Emissions Biomass Boiler Systems

It’s available as a FREE downloadable PDF at: https://www.nyserda.ny.gov/-/media/Files/EERP/Renewables/Biomass/Design-Assistance-Biomass-Boiler.pdf Switches, relays, & ladder diagrams contact designation switch contacts

Switches: Poles and Throws ! Single Pole Single Throw! pole 1 ! Switches and relays are classiﬁed based SPST on their poles and throws. ! The number of poles is the Double Pole pole 1 Single Throw! number of independent and ! pole 2 DPST simultaneous electrical paths through the switch. ! pole 1 Triple Pole Single Throw! pole 2 DPDT ! pole 3 The number of throws is 3PST the number of position pole 1 A ! settings where a current Single Pole B Double Throw! pole 1 can pass through the ! pole 2 C SPDT switch. D ! Double Pole pole 1 Double Throw! ! pole 2 DPDT pole 1 A ! pole 1 B Triple Pole Double Throw! pole 2 pole 2 C ! 3PDT pole 3 D DPDT center off Relays contact designation switch contacts relay contacts ! Single Pole Single Throw! pole 1 pole 1 ! SPST Relays are electrically operated switches. spring enclosure pivot ! coil Double Pole pole 1 pole 1 pendulum Single Throw! pole 2 pole 1 wire ! Same methods of DPST normally closed! identifying poles and contact (N.C.) ! pole 1 pole 1 throws. Triple Pole Single Throw! pole 2 pole 2 ! pole 3 pole 3 coil! 3PST terminals common terminal Two main components normally open! normall-closed terminal ! contact (N.O.) Single Pole pole 1 normally-open terminal common contact of a relay: Double Throw! pole 1 ! • coil SPDT

"Normal" mode: No • contacts ! pole 1 voltage is applied to coil Double Pole pole 1 (terminals A and B). Spring Double Throw! holds pendulum so the ! pole 2 common contact touches DPDT Design tip: Always verify the normally-closed contact. pole 2 Current can ﬂow from terminal 1 to terminal 2. pole 1 that loads are within the ! pole 1 Triple Pole Double Throw! pole 2 maximum current and 1 2 3 A B ! 3PDT pole 3 voltage ratings of pole 2 pole 3 switches and relays Energized mode: Voltage is applied to coil (terminals relay coil A and B). Pendulum pivots toward coil. The common relay coil contact touches the R1 normally open contact. relay contact, normally-open (N.O.)! Current can ﬂow from (closes when coil is energized) terminal 1 to terminal 3. relay contact, normally-closed (N.C.)! (opens when coil is energized) 1 2 3 A B Relays

One of the most versatile relays is a “general purpose relay.”

These are some time called “ice cube” relays.

Design tip: Be sure to pay attention to the pin numbers.

Design tip: I like a 3PDT relays from W.W.Graingers (5X840 w/ 24 VAC coil) (5X841 w/ 120 VAC coil) (5X853E socket) very versatile... “hard wired control logic diagrams

contacts in series represent an AND decision. All contacts must be closed simultaneously for a complete circuit.

Often used for wiring multiple safety devices. high limit controller, or outdoor reset LWCO controller service switch MRHL L1 line ! voltage! N burner

contacts in parallel represent an OR decision. Any contacts that’s closed allow the signal to pass.

Often use to operate heat source when any one or more thermostats call for heat. Ladder diagrams

Two sections in a ladder diagram: • Load section at top (line voltage) • Control section at bottom (low voltage)

• Horizontal lines are called rungs

• Typically create hard wired logic in low voltage control section.

• Line voltage loads circulators, fans, line voltage controller connect across load portion of diagram.

• Main switch at top removes power from entire ladder.

Design tip: Ladder diagrams are an EXCELLENT tool to both “synthesize” the operating logic, and document it for installation and servicing. Ladder diagrams

1. main switch closed to power the system. 2. thermostat contact in low voltage section close to give a demand for heat. 3. 24 VAC for transformer secondary energizes the relay coil.

4. Normally open relay contact in load section close. 5. Line voltage is passed to operate the circulator.

Design tip: Simple concepts like this can be extended to multiple load. Just make the ladder diagram longer as necessary. Ladder diagrams (Example system)

Air-to-water heat pump provides space heating and primary portion of domestic hot water.

outdoor! temperature! (S2) sensor

outdoor! pressure INSIDE

OUTSIDE (ORC) reset regulated! zone! controller variable thermostats speed circulator (T1-T8) manifold valve actuators (P4) (P3) (VA1-VA8) (ETWH) antifreeze! zoned radiant ceiling panels protected! (S1) circuit

DHW

CW (P1) (HX1) (P2) (HX1) make up water

air to water heat pump ﬂow switch buffer tank

Design tip: Always make sure that all electrically powered components have the same designator in the piping schematic and ladder diagram. Switches and relays:

240 VAC Ladder diagrams (Example system) L1 L2 L1 L2 L1 N 120 VAC main! switch (MS)

DHW! electric! circulator (R1-1) tankless! water! (P3) heat! heater distribution! pump circulator (R2-1)

R W (P4) HP - HX! (R1) circulator (R3-1)

(P1) HX - tank! circulator (R3-2) (FS1) (P2)

transformer 120/24 VAC 24 VAC outdoor! temperature! (S2) sensor thermostat (T1) outdoor! pressure INSIDE (VA1)

OUTSIDE (ORC) reset regulated! zone! thermostat ! controller variable M thermostats speed & valve actuator circulator (T1-T8) manifold valve actuators (P4) (P3) (VA1-VA8) thermostat (ETWH) (T2) antifreeze! (VA2) zoned radiant ceiling panels protected! (S1) thermostat ! M circuit & valve actuator

DHW

CW (P1) (HX1) (P2) (HX1) make up water thermostat (T3) (VA3) air to water heat pump thermostat ! M ﬂow switch buffer tank & valve actuator

(R2) Design tip: Always make sure that all electrically relay (ORC) outdoor! powered components have the same designator in sensors R C reset controller (S1) (R3) the piping schematic and ladder diagram. (S2) relay Temperature setpoint control Temperature setpoint control: Used for On/off control based on temperature

All on/off controllers have to operate with a differential. This is the difference in the controlled variable between the process is turned on, and when it is turned off.

Differential below setpoint Differential center on setpoint

contacts open contacts open typical temperature response typical temperature response setpoint temperature! setpoint temperature!

differential differential

setpoint - differential! contacts close temperature contacts close temperature time time

If the differential is too wide, the variable being controlled can drift far from the target. If the differential is too narrow, the device being controller can “short cycle.” Design tip: Common differentials for heat source temperature control are 5 to 10 ºF Temperature setpoint control: Used for On/off control based on temperature

Use a thermistor sensor Some are powered by 120 VAC, others by 24VAC

Some can switch line voltage loads at several amps, others are limited to switching in 24 VAC Design tip: Always check max circuits sensor wiring distance, and use 18 ga copper twisted pair or Some are single stage, others are two stage shielded cable when running long Sensor can be a long distance (several hundred distances (minimizes electrical feet) from controller. noise interference) Differential temperature control Differential temperature controller On/off control based on difference between 2 temperatures

ON differential typically 5-10 ºF OFF differential typically 2-4 ºF

Some offer viable speed outputs via AC Triacs rather than relay contacts (only for PSC type wet rotor circulators).

Some controllers are powered by 120 VAC, others by 24VAC

Some offer 2 ∆T functions as well as I/O collector ! temperature to handle other control aspects of system ON ! (e.g., aux. heat source, mixing valves). differential thermal storage ! temperature

Design tip: In addition to solar thermal temperature applications, DTCs can be used in other OFF! renewable heat source applications to differential move heat from source to storage (wood time of day

ﬁred boiler applications). OFF ON OFF Heat source staging control Staging control:

The ability to match heat output to load can be improved by dividing the heat output into multiple smaller parts that are independently controlled.

output = L output = L/2 output = L/2

design load = L 2-stages of heat input design = single stage heat source cycling of stage 2 load L stage 2 on ! continuously heatingload (Btu/hr) heatingload (Btu/hr) stage 1 on continuously

time (hr) cycling of stage 1 time (hr) single stage control two stage control Staging control:

output = L/4 output = L/4 output = L/2 output = L/2

output = L/4 output = L/4

stage 4 stage 3 design design 4-stages of ! load = L 2-stages of heat input = L stage 2 cycling of stage 2 load heat input stage 2 on ! stage 1 continuously heatingload (Btu/hr) stage 1 on continuously heatingload (Btu/hr)

time (hr) time (hr) cycling of stage 1 four stage control two stage control In theory, the great the number of stages, the better the ability to match heat output to load. However, the cost of the installation also increases with increasing number of stages.

Design tip: In residential and light commercial buildings, it is generally not cost effective to use more than four stages of heat production. Design tip: In larger buildings, up to eight stage of heat production are used in systems when all heat production takes place in a central mechanical room. A typical “lead/lag” multiple boiler application

multiple boiler controller Boiler controller measures outdoor temperature sensor supply water temperature at (S2) supply water purging / isolation valves (typ.) temperature sensor (S1), and compares it sensor spring check valve to the “target” supply water (S1) temperature. hydraulic load "short/fat" headers separator If temperature at (S1) is lower than target temperature, one boiler is ﬁred.

Boiler controller then uses PID logic to determine if more heat input is need. If it is, the other boiler is ﬁred.

When all boilers are identical, the boiler controller typically “rotates” the ﬁring order to create about the same run time boiler #1 boiler #2 for each boiler.

boiler staging rotation If boilers are different, one is designated as the “ﬁxed lead” boiler, the other as the “lag” boiler. Hybrid staging of pellet boiler & auxiliary boiler Think of the pellet boiler, combined with thermal storage as a “heat source” device

tank circulator heated water output

HEAT biomass SOURCE boiler anti-condensation details pellet boiler fuel circulator input biomass boiler + thermal storage tank "heat source" It’s “intuitive” for designers to create systems where the biomass boiler is treated as a “ﬁxed lead” stage, and the auxiliary boiler is the “lag” stage.

multiple boiler controller (or BAS) (S2) outdoor temperature sensor

(P4) (S1)

hydraulic

separator load

(P2)

∆P valve (P3)

thermal biomass storage boiler tank

auxiliary boiler anti-condensation details LAG stage boiler (P1) circulator

biomass boiler + thermal storage tank "heat source" FIXED LEAD stage Preferred piping With this arrangement (and proper controls) energy added by aux boiler can be kept out of thermal storage. Assuming (P2) ﬂow rate ≤ (P4) ﬂow rate, the coolest water is returned to the lower tank

connection. multiple boiler controller (or BAS) outdoor temperature sensor

closely closely space spaced tees from load tees to load (P4)

(P2)

(P3)

thermal biomass storage boiler tank anti-condensation details

boiler (P1) circulator auxiliary boiler biomass boiler + thermal storage tank "heat source" LAG stage FIXED LEAD stage The glitch… A standard multiple boiler controller “doesn’t know” if the biomass boiler is offline, due to a fault, or if the tank is cooler than the minimum “useable” temperature of the distribution system. The boiler controller only “understands” that multiple boiler controller (or BAS) the fix lead stage is not creating the outdoor temperature sensor (T256) necessary supply water temperature at (S1) closely closely space spaced tees (S1) from load tees The boiler controller turns on to load stage 2, and keeps stage 1 on. HEAT LOSS ON HEAT LOSS (P2) The result: The circulator creating flow between the (P3) tank and system remains on. thermal storage Heat produced by the auxiliary biomass boiler tank boiler is inadvertently carried OFF into thermal storage, increasing heat loss to (P1) surrounding space. auxiliary boiler HEAT LOSS This really happens…

Ketchikan, AK new Public Library This really happens…

Electric 500,000 700 gallon auxiliary Btu/hr pellet thermal boiler boiler storage tank

When visited in March 2017: • pellet boiler had been off for about 1 month awaiting service • tank-to-load circulator was running • boiler-to-tank circulator off at service switch, but on at BAS output • tank temperature about 145 ºF, all heat coming from electric aux boiler • If boiler-to-tank circulator had not been manually switched off, 145 ºF water would be circulating through boiler, creating jacket heat loss, and convective air currents up ﬂue (no ﬂue dampers on pellet boilers). The solution is a simple differential temperature controller (or equivalent BAS functionality) single stage outdoor reset controller (or BAS) outdoor temperature sensor

(T156) (T256) Compare the temperature differential (S2) closely temperature closely space controller spaced at the upper tank header tees (S4) (S1) from load tees (or BAS) (S3) to the return to load temperature of the distribution system (S4).

(P2) Circulator (P2) (tank to load) is only allowed to (S3) (S3) run when the tank can (P3) make a positive energy thermal contribution to the biomass storage system. boiler tank IF (S3) ≤ (S4) + 3 ºF, THEN (P2) is OFF anti-condensation details IF (S3) ≥ (S4) + 5 ºF THEN (P2) is ON LAG stage boiler (P1) circulator auxiliary boiler biomass boiler + thermal storage tank "heat source" LAG stage FIXED LEAD stage Using two simple, inexpensive controllers to manage heat ﬂow to load

single stage outdoor reset controller (or BAS) outdoor temperature sensor

(T156) (T256) differential (S2) closely temperature closely space controller spaced Circuitry to manage tees (S4) (S1) from load tees (or BAS) heat input to to load distribution system

L1 N 120 VAC

(P2) 24 VAC

contact closed when differential (S3) any zone (T156) temperature demands heat (S3) (P3) controller

(S3) (S4) (P2) thermal (T256) aux boiler high limit controller biomass storage outdoor set to 180 ºF tank reset boiler controller

(S1) (S2) T T

anti-condensation details normally open contact aux boiler LAG stage closed if (S1) ≤ Ttarget-0.5*DIFF1 burner open if (S1)≥Ttarget+0.5*DIFF1 boiler (P1) (P3) circulator auxiliary boiler normally open contact closed if (S3) ≥ (S4)+5 ºF biomass boiler + thermal storage tank "heat source" LAG stage open if (S3) ≤ (S4) + 3 ºF FIXED LEAD stage Temperature sensor placement & mounting Poor sensor placement or lack of insulation Controllers can only react to what temperatures their sensors “feel.” Solution: Surface mount sensors must be ﬁrmly attached, stay attached at elevated temperatures, and be insulated from surrounding air temperature.

Correct

non-insulated surfaced mounted temperature sensors Some sensors have a concave shape to ﬁt OD of pipe. Poor sensor placement or lack of insulation

Pipe-mounted sensor with sealed CORRECT insulation jacket Poor sensor placement or lack of insulation Solution: When measuring the temperature within heat sources, or thermal storage tanks, use a sensor well, and thermal grease.

sensors in wells

Honeywell 121371B $15-25 Simple way to built a sensor well

3/4" FTG x 3/8"C reducer (3/4" side up)

3/4" dielectric union Thermal grease zip tie (strain relief) in syringe: $7, eBay tank connection

sensor leads

3/8" copper tube

sensor thermal paste Honeywell copper cap 121371B $15-25 RHNY Incentives

Program System Type Installation Incentive Additional Incentive

Advanced Cordwood Boiler 25% installed cost - - with Thermal Storage ($7,000 maximum)

Recycling ≤120 kBtu/h 45% installed cost Small Biomass Boiler - (35 kW) ($16,000 maximum) $5,000/unit for Small Pellet Boiler Thermal old indoor/ with Thermal Storage ≤300 kBtu/h 45% installed cost Storage Adder outdoor wood - (88 kW) ($36,000 maximum) boiler $5/gal for each or 65% installed cost gal above the $2,500/unit for Large Pellet Boiler ($325,000 minimum old wood Emission with Thermal Storage thermal storage Control >300 kBtu/h maximum) furnace Large Biomass Boiler requirement System (88 kW) 75% installed cost Tandem Pellet Boiler ($450,000 with Thermal Storage $40,000 maximum)

Recycling

$1,500 $500 Residential Pellet Stove Pellet Stove ($2,000 for income qualified - - (income residents) qualified residents only) LMI Incentives - Boilers

Market Rate LMI Program System Type Installation Incentive Installation Incentive

Advanced Cordwood Boiler 25% installed cost 65% installed cost with Thermal Storage ($7,000 maximum) ($18,000 maximum)

Small Biomass Small Pellet Boiler Boiler ≤120 kBtu/h 45% installed cost 65% installed cost with Thermal (35 kW) ($16,000 maximum) ($23,000 maximum) Storage

For more information: • “Google” Renewable Heat NY • contact Sue Dougherty at NYSERDA [email protected] Future online training opportunities

October 29 / 1:00-2:00 PM Topic: Control concepts for hydronic systems using renewable energy heat sources (part 2) Description: This webinar will be a continuation of the September 17th discussion. It will discuss Outdoor reset control, mixing control, designing control systems using ladder diagrams, and present examples of complete control systems.

November 12 / 1:00-2:00 PM Topic: Case study - Pellet boiler system at the NYSDEC boat maintenance facility at Lake George DescriptionThe NYSDEC boat service facility at Lake George uses a pellet boiler as the primary heat source for a ﬂoor heating system. This webinar exams the details used in this system, including fuel supply, boiler, thermal storage, and the distribution system. It will also discuss some of the monitored performance for the system, and some of the initial challenges met in ﬁne tuning system operation.

All training is provided free

Courtesy of RegisterThermAtlantic here: https://www.nyserda.ny.gov/All-Programs/Programs/ QUESTIONS ? Become-a-Contractor/Renewable-Heating-and- Cooling/Renewable-Heat-NY-Contractors