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Flow Control Valves

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3350 pressure reducing valve, PRV cartridge a replaceable part? What is the part number?

Yes, the cartridge can be replaced with part number 3350-004RP. The same cartridge fits all sizes.

Are taco heat motor zone valves suitable for use outdoors?

Taco, does not offer weather resistant valves, or valves suitable for Exposure to the elements directly.

Can I use a current robbing thermostat with a Taco zone valve and what does current robbing mean?

Yes, but because the internal switch opens and closes the circuit when the valve is operating, a resistor will have to be installed across terminals #1 & #2 of the zone valve power head to maintain a continuous circuit. The thermostat uses the power from the 24volt transformer through a continuous zone valve circuit to power the thermostat. If this does not happen the program will be lost the first time the zone valve operates. The thermostat manufacturers are now supplying the required resistors in the package for use when a heat motor type Taco zone valve operator is used. This resistor is around 1000 ohms, .5 watts. Contact the thermostat manufacturer for the proper size.

Can the 570-2 series zone valve be used in an open system, such as domestic water?

No, the materials of construction are meant for a closed loop system where the same water goes around and around in the system. Our 560-G2 and 5101-G2 are recommended for open systems.

Can the Accu-flo circuit setter be used in a system with cutting oil?

Unfortunately not, Accu-flo valves use EPDM elastomer o-ring that are not compatible with any petroleum based products.

How do I pipe the Taco three way (bypass) zone valve?

The 560 series valves are designed to be installed down-stream of a fan coil unit. The discharge of the fan-coil would be connected to the unit connection of the valve. A tee would be installed in the upstream side of the fan-coil supply line. The branch connection of the tee would be connected to the bypass connection of the valve. The main side of the valve would be connected to the return main of the system. The system fluid flows through the bypass connection to the return main when the valve is not energized and from the unit connection to the return main when the valve is energized. The bypass connection is not a positive shut off when the valve is energized.

How to tell if your 500 Series Zone Valve is good?
  1. First, you can take a voltage reading across terminal 1 & 2 of the zone valve head, to see if you have 24 volts from the transformer, to rule out a bad transformer. If you have the 24 volts, then you would disconnect either terminal 1 wire or terminal 2 wire from the zone valve.
  2. You then can take an Ohm reading across terminals 1 & 2. You should read between 20-23 ohms.
  3. If this checks out reconnect the wires, energize operator with operator on valve body.
  4. Wait 1 1/2 to 2 minutes for the valve to open and then pull down the manual lever. If the lever move freely all the way the valve is open. If it starts easy and then goes hard, the valve is not open. This indicate the operator is bad and needs replacing.

Caution: Do Not Remove Operator From Valve When Energized

I am having a problem maintaining temperature at my zones when my taco zonevalve model 570 is in auto mode. Any suggestions?

There are many reasons why your rooms are not reaching temperature. What is the outdoor temperature at the time the rooms would not heat? Were the zone valves open? You can check by pulling down on the manual lever. If there is no resistance, the valve is open. You should read 24V across terminals #1 and #2 if the zone valve is activated.

  • If you have baseboard heat, the top louvers should be open.
  • Was the circulator running? If it’s a Taco 007, get a screwdriver and place the tip to the casing and the handle to your ear. Have someone turn the boiler switch on and off. Listen to hear the pump slow down and then speed up. The pump is so quiet, you would normally only hear a hum if it is running or not.
  • Have you changed thermostats lately? The heat anticipator should be set for 1.0 Amps.
  • Have you had anything changed in the system lately which would require draining the system, which might have caused an air block?
I have a 3-zone residential system with a 219 Flo-Chek on each zone. The manual override thumb screws are all open ~2 turns. Should these be fully closed?

The bypass knob should be turned clockwise all the way for normal operation. For bypass mode, turn the knob counterclockwise until you have reached the position desired.

I have a Taco IFS flow switch that is not tripping when the flow travels through the piping. What’s wrong?

Remove the switch cover and turn the sensitivity adjustment screw clockwise to increase the flowrate required to to actuate the switch, or turn the screw counter-clockwise to decrease the flow rate required to actuate the switch.

I’m having trouble setting up the differential bypass valve model number 3196. Can you help?

There is an 8 step process on the instruction sheet reference #102-163. You have to turn the adjustment dial all the way to the left. Make sure all the valves are open, and calling for heat. Turn the valve’s indicator counterclockwise until you notice an increase in temperature out of the valve. Once you reach this point turn the indicator approximately one full turn clockwise to stop flow through the valve with all the zones open.

Attachment: 3196 Instruction Sheet 
Attachement: 3196 Catalog

I’m using the 788 differential pressure gauge with the Accu-flo and I’m not able to get a reading.

The Accu-flo requires a differential gauge that measures in inches of water. The 788 gauge measures in feet and is not sensitive enough to measure below 1 foot, the 779 gauge is recommended as it measure in inches.

I’m using this valve is a well pump application, but the valve is allowing flow through when not calling for heat?

This is a high head capacity valve typically used in high rise applications. The heavy duty construction allows this valve to operate at head pressures up to 150 ft. However, if the pump head is greater then the 150 ft, it will lift the seat and allow flow through. Check the pump head output, and throttle the flow down to reduce the differential head.

Is the Taco zone valve a three wire zone valve and how do I wire it?

No, it is a 3 TERMINAL zone valve. One terminal of a 24 volt, 40VA transformer is wired to one side of the thermostat. The other side of the thermostat is wired to terminal # 1 of the zone valve operator. The #2 terminal of the zone valve operator goes back to the other terminal of the transformer. There is an end switch connected between terminal #2 & #3 of the zone valve operator. To activate the boiler control we run another wire from #2 terminal to one of the T terminal of the boiler control. We run another wire from the #3 terminal of the zone valve to the other T or TV terminal of the boiler control.

Is there any power between terminals #2 and #3 of the zone valve operator?

No. Terminals #2 and #3 are only connected to a micro switch and there is no power across them. They are called dry contacts.

May I have some information on balancing valve flow corrections for glycol solutions?

These correction factors are applied to the differential reading which is taken with a differential pressure gauge. The corrected reading is applied to the flow chart. If you have a formula that the differential is applied to, the correction is the square root of the difference in specific gravities of the flowing fluid, divided by the specific gravity of the standard fluid, water at 60°F. The viscosity does not affect the flow meter but can slow the flow due to the added resistance in the system.

My home oil burner serves two zones that are zoned using 573-2 and 572-2 zone valves. The 572-2 only works by opening manually. It worked fine for years. How do I check and possibly repair the valve without replacement?

The valves you have are 572-2 and 573-2 zone valves. There should be 3 terminals marked #1, #2 and #3. #1 and #2 should have 24 volts going to them when the thermostat is calling for heat. If you have 24 volts, the valve should open after 1½ minutes. If you don\’t have 24 volts, the problem is with the wiring, the thermostat, or the transformer. If other zones are operating off the same transformer and working fine, the problem isn\’t with the transformer. If you have 24V at #1 and #2, then it is internal to the operator.

Remove the wire from the #1 terminal and apply an ohm meter across terminals #1 and #2. The meter should read 22 ohms +/- 1 ohm. If the meter needle doesn\’t move or the digital reads 0.L, the circuit is open or the internal contact of the internal leaf switch is dirty. If you get an ohm reading of 16 to 22 ohms, the circuit is good but there might be a failure of the heat motor. With the #1 wire removed from the operator for 5 minutes, you can twist the operator and remove it from the valve body. The replacement power head part number is 555-050RP. You don\’t have to change the whole valve and the operator can be removed without taking the pressure off the system. When you remove the power head, if you see a dark brown wax around the piston, then the diaphragm in the heat motor has failed.

My system pressure keeps rising and causing the relief valve to spew water out, do I need to replace the pressure reducing valve, PRV?

You can try adjusting the valve using the adjustment knob at the top of the valve. If the pressure continues to fluctuate, you could have a faulty expansion tank.

My Taco iSeries valve is not working properly.

As in any troubleshoot procedure it is important to isolate the problem. The error messages greatly simplify troubleshooting the valve. If the diagnostic lights are flashing identify the coded flash using the matrix found at the end of the instruction manual 102-145

My Zone Sentry Zone Valve has a blinking green light. What’s wrong?

The rapid blinking light indicates the valve is charging. if the blinking light comes on while the capacitor control failure. You may have to replace the control.

My zone valve power head was removed while it was still hot. Causing the piston in the power head to cool and harden in the open position. How do I replace the powerhead?

Push the piston back into place using a blunt object, and then place the power head back on the valve body & apply power to reheat the head. Power head will return back to its normal operating mode once it is reheated.

Taco no longer makes the 568. Are the newer thermostats with no heat anticipators compatible with Taco zone valves? The instructions with the 571 valve say that the thermostat heat anticipator must be set to 0.9A to match the valve. Will the valve function correctly without a heat anticipator in the zone?

Taco still offers a thermostat #568-20. It may not look like your original, but it functions the same. Many people mistakenly think the 571 zone valve is a 3-wire zone valve because it has 3 terminals. All the Taco 500 series zone valves are 2-wire, 3-terminal zone valves. The heat anticipator has no bearing on the operation of the zone valve. Its purpose is to trick the thermostat into shutting off ahead of time, allowing the heat left in the piping system to dissipate into the room and not overshoot the temperature setting. The current draw of the circuit had to be matched to the heat anticipator so it would work properly. A lot of the new thermostats do not require a heat anticipator. All of the battery operated thermostats will work with the resistor and the units that require a third wire (C) to get power from the transformer. It is the digital units that either steal power, need the resistor, direct power, or battery. All the other conventional units work, but make sure they handle a current rating of 1 Amp.

The Zone Sentry actuator has a sticker warning against using this valve on an indirect water heater, and suggests using a tempering valve.

The Taco Zone Sentry Zone Valve could fail in the open position, which can raise the DHW temperature to the same temperature as the boiler water. The tempering valve will help protect against scalding if the valve fails in the open position.

What causes my thermostat to short cycle?

Electro-mechanical thermostats have a small variable heater built into them. It tricks the thermostat into thinking that the room temperature is satisfied so the temperature doesn’t overshoot.

The setting of the heat anticipator is based on the current draw of the connected zone valve wiring. A low current drawing valve requires a longer heater wire to create the same amount of heat. A high current draw circuit requires only a short heater wire.

Taco zone valves of the 550, 560, and 570 series draw about 1 amp, so the heat anticipator should be set accordingly. If the thermostat is short cycling, increase the setting to a higher amp setting.

What else do I need to complete the installation other than the valve?

Water heater drip pan or other suitable device that will allow the water to rise to a level of 7/8″. See sizing chart below. – Two ¾” male threaded x sweat adapters – Two lengths of copper(or other approved tubing). Length will vary by installation. Connection from cold water supply line to valve and from valve to the “cold in” port of the water heater. – Two to four (depending on the installation) 90° copper (or other approved) elbows. Drip Pan Sizing: Water Heater Diameter Up to 17.75 = min. 20″ pan 18″ – 23″ = minimum 24″ pan 24.5″ = minimum 26″ pan.

What is the formula for calculating the pressure differential for a given flow when using the Accu-Flo valve?

The chart on the submittal data sheet is the flow chart for measuring the flow. The actual pressure drop, with the balancing valve wide open, can be calculated by using the Cv or the slide rule.

The formula would be (flow required/Cv) squared X 27.72 = resistance in inches of water at the required flow rate with the valve wide open. For resistance reading with the balancing valve throttled, you need the slide rule. Example: (106.8/212) squared X 27.72 = 7.03 inches of water resistance.

What is the general purpose of Venturi Tees?

To help divert flow from a given zone to a bypass loop when the flow is not adequate to satisfy the load at that branch of the main loop.

Attachement: Venturi Tee Catalog

What is the minimum pipe length required on the inlet side of the Accu-Flo valve?

Although, a minimum length is required on most circuit setters, the Accu-Flo does not require a minimum because of the differential across the fixed Venturi orifice with minimal turbulance and optimal accuracy.

What is the purpose of the Flo-Chek?

The Flo-Chek serves two purposes: It prevents flow from going in reverse direction from the arrow on the valve, and it prevents thermosiphoning when the pump is not running. Thermosiphoning is a condition in which water in a heating system rises when it is hot and sinks when it is cool. The home can be heated if the pump is not working by manually lifting the disk of the Flo-Chek. This can be done by screwing the stem counter clockwise, which will lift the stem and disk.

Why do you supply a dam and condensate drain tube with the valve?

In some installations, code requires that no standing water (usually condensate) be present under the water heater. In those cases the condensate drain tube is placed under the dam so standing water can be diverted through the drain tube to a drain line. The dam is installed over the tube, so in the event of a failure the water would accumulate quicker then the flow through the tube and would be able to reach a level of 3/4″ in the pan, triggering the valve.

Why does my Flo-Chek leak by?

Typically, this is caused by debris accumulating on the disk or seat. This would be the case if the valve worked fine when it was first installed. You will have to take the valve apart and clean the seat, disk, and stem to bring the valve back to original. The stem should be vertical.

Why does my hot water circulate when my Taco pump is off?

Something has adhered to the Flo-Chek seat or disk. The Flo-Chek is a weighted disk check valve that normally prevents thermosiphoning. That is, it prevents the lighter, hot water from rising to the radiation and the heavier, cool water from sinking, causing a flow in the system without a pump. If the system worked fine before and then started to act up, the disk is stuck or something is on the seats.

Why does my zone valve let flow through it when it is not powered?

There are several reasons: 1.The 570 series can only hold back 50ft of head and if you have a pump upstream of the valve producing more than 50 ft, the valve will be pushed open. 2.If the manual lever has been pulled down, the valve will be manually opened. 3.Depending on the environment the zone valve is in could cause the piston of the operator to stick and not allow the valve to close.

Why does the voltage read across terminals #1 & #2 vary between 24 & 28 volts?

For the first 1½ minutes, you will read 24 volts across terminals #1 and #2. The valve will have reached its operating stroke in that time. An internal switch will open the circuit to allow the heater to cool and control the length of stroke of the valve. When the circuit is opened, the load is taken off the transformer and the voltage jumps up to 28 volts. Once the valve gets into its cycle, there will be a current draw for 10 seconds and no current draw for 20 seconds.

Why is my check valve Taco flow chek making a rattling noise?

Normally, a check valve is noisy if the valve is oversize for the flow going through the valve. The flow velocity is not high enough and can not lift the disk all the way open so the weight bangs within the body of the valve.

Why is my Flo-Chek or MPV noisy?

Normally, a check valve is noisy if the valve is oversized for the flow going through the valve. The flow cannot lift or swing the disk all the way open so the disk bangs back and forth within the body of the valve.

Why is the valve not allowing flow through to the system?

The most likely cause of flow not going to the system is the boiler protection is engaged. Disconnect the power supply, and then disconnect the boiler return sensor from the valve. Reenergize the valve with 24 volts, and the valve will work normally. You must find an alternative way of protecting the boiler, if the return temperature will be less than the boiler manufacture recommends.

Why would I need a buffer tank in my hydronic system?

If the heat source can not keep up with the high demand at peak times, and the system dynamics can not achieve this, the buffer tank is stored energy that will help satisfy the load when the demand is the highest.

Attachment: Buffer Tank Catalog

I have an old Taco PANELTROL valve in my radiant heating system. Does Taco still make this product and are there any replacement parts for it?

Taco no longer makes this product and we don’t have any replacement elements. The PANELTROL was designed to reduce the water temperature being supplied to a radiant panel loop. The reduction in water temperature allowed the radiant loop to operate at a lower temperature than the boiler, which might be needed for other higher temperature requirements. The return water from the radiant loop is used to temper the hot water. Taco does make a new tempering valve, the 5000 Series Valve, that could take its place. The PANELTROL had 1¼” connections but our 5004-C1 should work.

I have a Taco 5000 series mixing valve that I’m experiencing erratic flow at the point of use. What’s wrong?

If it’s a tankless heater application the coil may be fouled from high lime content in the water. Try using a lime X to clean the heat exchanger so the water passes through the coil easier. Fouling is typical when using a heat exchanger.

What is the best way to pipe a 5000 Mixing Valve when used for radiant heating?

Pipe the system as primary /secondary with a pump circulating the primary loop and using 2 tees close together with the branch of the one Tee supplying the hot connection of the tempering valve and the return from the radiant loop supplying the cold connection of the valve and the branch of the other Tee. A pump, sized for the radiant loop or loops should be pumping the mixed port of the valve and supplying the radiant loops.

When I try to adjust my 5000-2 tempering valve to a low temperature the stem starts leaking.

You have turned the stem down too low so back off (counter-clockwise) 2 turns to assure a good seal. This will be the lowest temperature you will be able to achieve and is also based on the cold water entering the tempering.

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