• Canadian Hydronics Council
  • Industrial Pipe, Valve & Fittings Council
  • Plumbing Industry Advisory Council


Why is it that when I use the manual operator to force open the zone valve, the auxiliary contact does not close?

Manual operators are intended to be used during installation (soldering) or during power failure. Opening the valve manually will allow water circulation via gravity (circulator being out of power). Normal operation will resume when power is restored; the motor will unlatch the manual operator on its first cycle.

I am getting water hammer, noise and chattering when my valve is closing. How can this be?

Water hammer is a complex issue and can be caused by one or more of the following situations:
  • The valve is trying to close off against high velocity water
  • There are air pockets in the system
  • Loose pipes
  • The valve motor is closing too fast
  • The valve is installed backwards
  • The location of the valve

Solutions would be:
  • Slow the circulator velocity down and/or install a regulator between the supply and return lines.
  • Remove air from the system using air vents.
  • Tie down pipes with additional support.
  • Use a slower closing motor and/or add water hammer arrestors (available at hardware stores). Do not remove one of the return springs as this unbalances the shaft and can lead ultimately to leakage at the valve stem.
  • Make sure the valve is pointing in the direction of the flow of water and reverse the body if needed. The valve must close against the water flow. Do not rely on the valve location in the radiator, some valves are installed on the supply side and some on the return.
  • Install the valve on the return side of the system where water temperature is lower.

Why is it that normally open valves do not seem to last as long as their normally closed counterparts?

Normally open valves are used where convective flow of the boiler water is desired to slow building cool-down. These valves must be constantly powered to keep them closed. During the summer where there is no heating demand, the valve can be powered for an extended period of time, excessively stressing the motor.

Simple solutions include closing the main isolating valve and shutting off the power supply to the valves, or turning the boiler off and setting the "Normally Open Valve" thermostat to full heat for the summer period.

I have a 100,000 BTU propane boiler servicing a single zone baseboard heating system in the house that has 40,000 BTU approximate excess capacity. I would like to take the chill out of the basement using a fan-assisted coil unit. Can you recommend a suitable unit and advise if I will need another circulation pump and zone valve?

If the existing boiler has extra capacity, then you can easily hook up another terminal (of any kind) to heat the basement. If your existing pump can handle the increased flow, you could simply install the new unit with an electric zone valve. If the existing pump is on the small side, add a separate zone with pump and thermostat to heat the basement. Look for devices that protect the zone from unwanted heat due to gravity circulation into the idle zone. You may not need them if the basement zone elevation is lower than the source of hot water.

I recently installed a new high-efficiency boiler in my house. The old boiler had two supply and return lines going in and out of the old boiler. Each line has a pump. The new boiler has only one return and one supply outlet, so the two supply and return lines had to be tied into the new boiler. Since the new boiler has been installed, I can no longer get any heat out of two basement radiators that are at the end of each loop.

Various things could be happening to explain why you are not getting heat at the end of those loops. Call a representative from the boiler company to help find a qualified contractor to help you solve this. Here are a couple of things to check in the meantime:

1) Is the new boiler big enough?
If it doesn't have enough heating capacity, the end radiators won't get hot. Since you can get heat when you shut off one loop, this may be the case.

2) You could have air trapped in the radiators.
If the new boiler has a lot more pressure drop than the older model, there may not be enough velocity in the radiators to pick up air and bring it to the point of air separation.

I cannot read the valve where water comes in from the outside water source because of dripping from another pipe above - separate from the heating system. If the relief valve releases steam and water, what causes this? Should the temperature drop when the pump comes on?

You have a waterlogged tank. Let the system cool down to below 100 degrees. Ensure the supply valve from the city is closed. Now open the vent screw until the water level returns to normal. Assuming the correct sized screw is installed, drain until no water comes out. You should be back to the proper air to water ratio in the tank.

Why did you lose your original air charge?

When you bled the air out of your system, you lost the room you had for the water to expand as it heated up. Figuring how the air got from the tank into the system is not as important as ensuring that once it is in the system, it returns to the tank and remains there. Next, ensure any air in the system goes to the tank. Check your air separator. If you don't have one, try an inline air separator or an enhanced air separator.

Automatic air vents are used with pre-charged air tanks. To drain your system, ensure that the city water supply is closed, open the drain valve. Opening a vent will help drain the system. To fill the system, close the drain, open the city supply, use a Pressure Reducing Valve. Bleed out the air through the vents. Open the tank fitting vent until you see water come out. You should now have the proper charge. To clean your system, ask your local supply warehouse for what would be the most effective materials based on your system. Make sure they know about the pump seals so that there is not a compatibility problem. You should get rid of most foreign materials when you drain the system. If the system is truly closed, draining it will introduce oxygen, hence corrosion. You don't want to drain it unless you have to.

I have trouble providing hot water to my radiator upstairs - it is the furthest from the pump. Any suggestions?

If you have tried to bleed air out of the radiator and you don’t get any air, then the most likely cause of your problem is inadequate balance. Some of your closer radiators are getting far more flow than they need, starving the farthest one. Install a balancing valve in the closer circuits to reduce flow there and force the water out to the farthest one. If you do get air every time you bleed that farthest radiator, then you have an inadequate air separator or compression tank system.

How does one determine the flow in a hydronic system?

Flow is calculated based on using two variables and one constant value as in the following formula:
Q= BTU/ hr
500 X Delta T
Q= flow (USgpm)
BTU/hr= Output British thermal units per hour produced by the boiler
Delta T = Change in temperature (in ºF) for sizing purposes. This value is most commonly 20ºF in radiator heating and 10ºF in in-floor systems.

Where is the best place to put a pump in a primary loop?

The best place to put a pump on the primary heating loop is directly after the expansion tank to ensure positive pressure on the pump suction and after the boiler (pumping away) to avoid potential cavitation conditions. Traditionally, the pump was installed on the return side of the boiler to see the coolest possible water temperatures. Modern pump designs are capable of handling up to 288ºF water temperatures and can be easily installed on the supply side of the boiler.

How does a mixing injection pump work?

A mixing injection pump works on the following principal: in every heating system there is a primary loop and any number of secondary loops. The purpose of the injection pump is to control the rate of hot water injection from the primary to the secondary loop. The speed of the pump is based on the differential temperature between the supply and return water. For example, if the difference in temperature between the supply and return is 5º degrees, the pump will be running at a slow speed. If the difference is 20º degrees, the pump will be at maximum speed in order to keep up with heat demand.