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Boiler Zone Heating Circulation ProblemBoiler Zone Heating Circulation Problem - Hello, I have a Peerless boiler and recently it had been inspected by a buddy who has been in the business for 35+ years. He installed a new pressure reducing valve in the rear which was leaking very little. I have 3 zone valves in a split level ranch home. One for the finished basement and two for the 1st floor ( upstairs), It is obviously a split off. Anyways, I am getting heat upstairs, but the pipes don’t tick like they used to and also one of the return lines to an upstairs zone valve is lukewarm and the other is hot. Now the basement gets plenty of hot water going to it, but the pipes don’t tick at all and the return is cold to its zone valve.

Boiler Zone Heating Circulation Problem

I am thinking circulator personally, but I wanted your opinion, please. I checked the voltage to all 3 zone valve and they are set at 24 volts. Then I checked the voltage inside the control panel and C1 and C2 came up 120 volts. I Then opened up the electrical box on the circulator itself and checked the voltage coming into the circulator, it was at 120 volts. When the burner kicks on I feel the vibration on the circulator pump but no more vibration than the pipes that lead into it. The circulator also gets very warm, ( not very Hot, But very warm) but the water above the circulator and below the circulator does get very warm, but not always. I also checked the wires connected to the circulator inside the electrical box and they seem fine… Would you please respond with your thoughts? Oh and by the way, all 3 zones have been bled and I have the pressure set at 18-20 PSI max within the boiler. Thank you!

Where to Start - Boiler Zone Heating Circulation Problem

  1. 18 to 20 seems to be at the upper level of a boiler pressure setting (see that ink about boiler pressure settings) unless you have the boiler water loop piping going above two-stories. Even then, it is still high.
  2. Taking voltage at C1 and C2 simply proves you have voltage but it does not mean it is getting to the circulator pump. You need to do two things here: 1) go to the relay and do the same test. Across the contact points for the control relay, you should have 120 volts when the relay is open. That means the system is not running or calling for running. On a call for heat for that zone, the relay contact points should be closed and a voltage reading across the contact points should be zero.
  3. To really know if the circulator pump motor is running, you need to take an amp ready. To do this, you need an amp clamp-on meter. The reading you get on this meter should < or equal to the rated amp draw on the motor data plate with the motor running. If it is higher than the rating on the data plate then it is possible you have a bad impeller.
  4. As noted above, just because the motor is running does not mean the circulator is circulating water. To test this you need to take a delta T temperature reading from the supply to the return A difference in temperature no more than 20 to 30° is recommended. Any more than that and you risk a thermal shock to the boiler.

This would be a simple two-wire thermostat for the thermostat wiring. If you have more terminal designations on the thermostat than two you will want to use the R terminal and the W terminal for the zone valve. That would correspond to the red wire (24-volt hot) and the white wire (heat) for thermostat wiring colors.

Calculations and Adjustments - Boiler Zone Heating Circulation Problem

Take temperature readings of the convectors (radiators or baseboards) and come up with an average. Also, compare temperatures from the first convector to the last convector in the loop. If the temperature difference (delta t) is greater than what is mentioned above then the design of the system is flawed. You need to break that zone up to lower the delta t to prevent problems with the boiler as noted above. You can also do this with the circulator pump and increasing or decreasing velocity. At that point, you really need a boiler professional to look at the system to make adjustments and changes. A lukewarm feeling on the return pipe is okay provided it does not exceed the temperatures noted above for a proper delta t. This means the system is heating. The convectors are heating and the return is returning the cooler water to the boiler for reheating. A return that has a low delta t is not really delivering the heat as it should and is inefficient. All it is doing is churning hot water around a loop with no heat being delivered. This too needs to be looked at by a boiler professional to make adjustments if necessary. Circulator pump and pipe sizing are important.

Conclusion - Boiler Zone Heating Circulation Problem

As I’ve noted in other articles, no two boiler systems are the same. While it’s not rocket science it does require skill to properly install a boiler system. Additionally, it requires some skill to properly troubleshoot boiler systems including boiler problems and loop circulation problems. The skills include electrical troubleshooting, piping systems troubleshooting, control systems troubleshooting, and combustion systems et al. Do yourself a favor and get a boiler professional to go over the system. There are some plumbers and many HVAC people who specialize in boilers and boiler loops. The can properly balance the system and save you time, money, and lots of frustration in the future. It will also make your boiler system very efficient. Good Luck.

You can also check out this boiler loop circulation problems article for further information.

Boiler Zone Heating Circulation Problem

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