Commissioning (Cx) any type of HVAC equipment is many different procedures from the beginning of the commissioning process to the end of the process. One of the most important procedures during the Cx process is functional testing. The functional testing always precedes the final testing where a test of all the combined equipment is done in an integrated systems testing. Once successful testing is completed and all discrepancies corrected a final commissioning report is generated including all the test data and information collected during the entire process of testing and commissioning.
Building Automation Program Display
Functional testing of a hot water boiler in the commissioning process can be streamlined if coordinated properly. Much of the Functional Testing Procedure can be accomplished by coordinating with the start up technician or engineer and the test and balance crew. During start up the boiler start up technician should test and verify the proper function of the boiler per manufacturers specifications. During and after the start up the technician should generate a report of all start up work done including adjustments, calibrations, and test data collected during the start up. The Cx Technician or Engineer can then verify first hand essential data needed to complete the Functional Testing Procedure document. The same applies by coordinating with the Test and Balance crew.
After the start up and test and balance is complete and all final reports are received from the start up and test and balance crews then the Cx tech can perform a thorough functional test of the boiler or boiler system. The following are not all inclusive to every boiler installation. The list should be tailored for each individual installation. Initial checks of the boiler should include:
Outside equipment should be checked for proper insulation
Equipment is clean and free of any physical damage including any debris inside of any control panels.
All unit identification tags, piping labels, operating manuals, maintenance checklist, and basic documentation are with the boiler(s).
All pipes have been flushed and strainers cleaned.
All electrical connections are tight including all ground connections.
All breakers for the boiler system including associated pumps are labeled properly for the source.
Boiler drain is accessible and can be drained to a sanitary drain near the boiler drain.
If the boilers are controlled by a building automation system (BAS) ensure the BAS system is checked while performing the procedure. All program functions including alarms, program lock outs, and other BAS variables are checked and ready for testing. Temperature sensors need to be verified for proper installation and location according to representative graphics on the display monitor. All set points and rest schedules need to be verified including the outside air temperature device calibration. Lock outs and reset schedules in the BAS and otherwise needs to be taken into consideration before functional testing. Once all the basics are checked the next step is physical testing as follows:
Start all pumps individually. Check for any noises and for unusual vibrations originating with the pumps individually running and all running at one time. If the pumps are controlled by any speed drives ramp pump up to maximum operating and back down to minimum speed and check for vibrations and unusual noises.
Check all valve actuation for supply, return and any bypass valves.
Test all automatic dampers for combustion air, ventilation and exhaust dampers for proper operation before starting boiler.
Reset all pumps and valves for normal automatic operation and fire the boiler. For dual fuel systems test both different fuel types. Again check for any unusual vibrations and noises. If boiler is a modulating boiler run boiler as minimum, maximum and various stages and verify no unusual noises or vibrations.
On shut down after basic testing ensure proper shut down sequence of the boiler.
Start boiler and shut off pump. Ensure boiler shuts down based on loss of flow. This should be indicated as an alarm with the BAS. After successful testing is complete restore all settings to normal.
Test the high limit setting on the boiler by lowering the temperature setting on the high limit control. Check that boiler shuts down and that the BAS system indicates an alarm.
Test the low water cut-off by disconnecting the wire to the low water cut-off. Ensure the boiler shuts down and all alarms are indicated at the BAS.
Test any safety controls including safety switches such as temperature limit switches.
Check back flow preventer. Ensure no water is leaking from the device.
Test the boiler pressure relief valve by lifting the test gate. Ensure water drains from pressure relief valve.
The test is not all inclusive as the functional test script must be generated and tailored using the mechanical drawings, equipment schedules, project and equipment specifications along with the owner requirements.
If you are in need of commissioning services or written scripts contact High Performance HVAC using our contact page.
Richard, we have a hot water boiler and we are having problems with the circulation of the water. The radiators are cool and we don’t seem to have good heat. The boiler seems to be working fine but the radiators are cool. Can you give me some insight into my boiler circulation problem? Kate
This pump has a coupling device between the motor and the impeller.
Kate, there can be several things wrong that keeps the water from circulating through the water loop. The first place to start is the circulator pump which should be located near the boiler in the near boiler piping. I would check the aquastat to make sure it is engaging the circulator pump as the aquastat has relay that turns the circulator on when there is a call for heat and temperature inside the jacket is the right set point temperature according to what the aquastat is set for in temperature ranges. The best way to do this is with a multi-meter to make sure the out put to the pump is 120 volts as most pumps for residential systems work off of 120 volts. If you have 120 volts on the terminal connections where the wires go to the pump then the aquastat is good and the relay is working as it should. Now you should check the pump. You want to know if there is flow going through the pipe from one side of the pump to the other. Some pumps have a linkage or coupling device that goes from the motor to the bearing assembly where the impeller is located. The impeller pushes the water through the pipe and some pumps do not have a coupling devices but are direct drive. In other words the pump motor is directly attached to the impeller with certain pumps. Pumps with coupling devices need to have the coupling device inspected to make sure it is not broken. If the coupling device is broken it needs to be replaced and that was your circulation problem. If it is a direct drive circulator pump then you need to inspect the impeller to make sure it is good. Impellers do go bad from time to time and need to be replaced. If this is the case you should really call a boiler technician to fix the problem as many will have the parts on their truck and can have you up and running in an hour or so. They will also know the correct procedure for replacing the impeller without causing additional problems which if you really do not know what you are doing you can cause additional problems. Other problems with the circulator can be the a bad motor or a leaking bearing assembly. Some circulator pumps require maintenance while other pumps are maintenance free.
Automatic Air Vent or Automatic Air Bleeder
The next thing that can cause the water not to circulate in the water loop including to the radiators is hydronic air lock. This is when you get air into the loop. Air will build up usually on a riser or in a radiator. It is necessary to remove the air from the system. Many radiators and even baseboards have manual air bleeders on them. The air bleeders require a key to open them and hopefully you have an air bleeder key. If you have an air bleeder key then you can go around to all your radiators and open these air bleeders with the key. Take a rag with you and open the air bleeder until you get water. In some cases you will get water only and in other cases you will get lots of air. Let all the air bleed from the system. As much as possible. Your system should also have automatic air bleeders or automatic air vents located somewhere in the loop. Typically these are located on the risers of the piping and they automatically vent any air that gets into the loop. The are usually very reliable and need little maintenance but time to time they can stop working and need to be replaced. Again if these need to be replaced an HVAC technician should replace these.
One last thing you can check if you have circulation problems is the shut off valves in the piping. If someone haphazardly played around with one of these valves and turned it off then you will definitely not have flow going through the water loop. Check to make sure these valves are open. Hopefully it is as simple as opening a valve but probably not the case. Good Luck to you and I hope your problem gets solved soon.
Pressure Reducer – Blue Arrow & Backflow Preventer – Red Arrow
Pressure Reducer Valves are used for boilers to decrease the pressure supplied to the boiler from the make-up water feed. The make-up water feed originates from the city water source or well water source. The same water source you use for showering, washing dishes, and sometimes drinking water depending on the quality. In many case the pressure reducer valve or PRV is set to 12 PSI on most boilers. This is the pressure needed for many residential and commercial boiler water loops.
In most cases, the make-up water supply is 40 or 50 psi and higher and this will exceed the safety rating of the lower pressure requirements of the boiler water loop. It will also exceed the pressure rating on the pressure relief valve on most residential boilers. For this reason a PRV or pressure reducer valve is needed to decrease the pressure supplied to boiler.
To find the PRV or pressure reducer valve simply follow the water source from the city water or well water supply. Follow it to the boiler. In many cases it is half inch copper and sometimes 3/4 inch copper line which feeds the boiler water loop. You should see the PRV or pressure reducer valve in line with the back flow preventer. After the PRV it will feed into the boiler water loop usually near the expansion tank in many cases. Both the PRV and the back flow preventer should have some sort of strainers inside of them and sometimes these strainers can get clogged up with trash so if your boiler is having a water feed problem check the strainers to make sure they are clean and so not have trash or debris clogging the strainers. If you are checking the strainers make sure you turn the water source off.
In the photo above the pressure reducer valve has a bypass lever on the top. This is typically used when filling the loop after initial installation or after a major loop repair such as replacing a pump or other boiler water loop work. This lever should be closed when the boiler is in normal operation. If the lever is open then the pressure will be too high the pressure relief valve will likely vent and you will have a water spill to clean up. If you have pressure problems it is always good to check the pressure reducer valve to start. In some cases, if it was installed by a good contractor you will pressure gauges on both sides of the pressure reducer valve so you determine absolutely that the proper pressure is being supplied to the boiler water loop. Other areas to when you have pressure problems or too high pressure are the boiler expansion tank. With a bladder type expansion tank you need to check to make sure it is properly pressurized with air and that the bladder inside the tank is not broken or busted. For steel type expansion tanks make sure the expansion tank is not over filled. A steel type expansion tank should be a 3/4′s full to work properly.
All steam boilers need a constant supply of water from a make-up water source. In a steam boiler system there are steam vents that vent condensation produced by the steam. The steam vents can be found on the radiators and throughout the steam pipe system especially on large steam systems that serve larger buildings. Venting is limited to a small amount of the entire water and steam volume inside the steam piping and radiators but does need to be replaced. Most of the steam condenses and is returned to the boiler through the return piping system either by gravity or a steam condensate pump. As the system uses steam it vents the condensation or steam and this displaces water from the steam system that needs to be replaced and the replacement water comes from a make-up water source.
Steam Boiler Make Up Water
Steam Vent on a steam radiator
The make-up water source usually comes from the city supplied water source and is controlled by an automatic water feeder that is directly controlled by a low water cut-off control located on the boiler. The low water cut-off has a float inside of it that measures the level of the water inside the boiler. At a specific level the float activates a switch that sends power to the automatic water feeder that feeds water to the steam boiler system when the level inside the boiler drop below a critical level. This refreshes the water and fills the boiler to safe levels. There are some maintenance requirements on most steam boilers for the low water cut-off and if proper maintenance is not done as required by the manufacturer the system can foul and prevent proper functioning and even a dangerous condition of the steam boiler system.
Low Water Cut-Off Maintenance for Steam Boilers
Low Water Cut-offs on steam boilers typically have a lever on the cut-off itself. On a regular schedule the lever should be turned and the water from the steam boiler purged. The purging is referred to as a blow down of the steam system. What will come out of the steam system is dirty water. The system should be purged until the water becomes clear.
If this has not been done on a regular schedule the boiler system can become fouled with much. The much will foul up the controls and eventually will not function properly and lead to failure of the system especially the low water cut-off and the other controls in the steam boiler system.
Flushing The Steam Boiler with the blow down valve on the low water cut-off
The Burners under this small boiler are round and extend under the boiler
Before beginning boiler maintenance or repair including cleaning the gas boiler burners on any boiler it is important to follow all safety procedures. Turn off the gas to the boiler at the gas cock located on the gas line and turn off the gas valve on the boiler. Additionally turn off the main power to the boiler at the circuit breaker.
Periodically it helps to check and clean the gas boiler burners for a couple of reasons. First of all it ensures the burners are in proper mechanical order and that the burner will reliably do the job of properly and evenly burn the gas in the combustion chamber of the gas boiler. It also adds life to the gas boiler burners if the burners are properly cleaned. So the benefits of cleaning the burners helps keep the boiler running and adds life to the gas boiler system. This article DOES NOT apply to condensing boiler systems and it is recommended that you hire a plumbing or HVAC professional to perform periodic maintenance on condensing boilers as condensing boilers are more complex than the atmospheric boilers referred to in this article. Additionally, Pulse type gas boilers will also require the attention of a trained professional for periodic maintenance. Continue reading “How to Clean Gas Boiler Burners – Maintenance” »
There are many different types of boilers in the boiler room today in a variety of heating applications. There are two main categories of boilers among the different types of boilers and those two categories are steam and hot water boilers. Either of those categories can be fueled by oil, gas, or electric (although electric is uncommon for steam boilers). They have different designs and piping configurations as a steam boiler system is designed to turned the water into steam and uses gravity and pressure to deliver the heat and the hot water boiler systems are designed to simply make hot water to be circulated (by a circulator or pump) through a piping system to provide heat. Typically, hot water boilers are more efficient than steam boilers for a few reasons. First, there is less heat loss throughout the hot water piping and the shell of the boiler because the hot water boiler operates at a lower temperature than the steam boiler. This means there is less heat loss throughout the entire boiler and piping system. Secondly, because the hot water boiler operates at a lower temperature, it requires less fuel or energy to convert into heat. What kind of boiler do you have in your boiler room?
We are looking at replacing our boiler with a new boiler. The HVAC contractor, I suppose he is the salesman for the HVAC contractor, is trying sell us what he refers to as a rest control for our boiler. He tells us it will save us more money by making our boiler more efficient. I think I understand how it works but my wife is not entirely sure about it. Can you tell us what you think about a boiler reset control and how it works?
Thanks and we have learned so much from High Performance HVAC. Keep up the good work.
This is a photo of a boiler stainless steel flue exhaust stack which is used for venting corrosive boiler flue gases. As the flue gases leave the boiler they cool and depending on the dew point of the gas the gas will experience a change of state from a gas to liquid. This liquid is highly corrosive and only special flues like stainless steel flue vet can be used when this occurs to prevent premature failure of the boiler flue vent. There are many considerations to consider with a new installation of a furnace or boiler and the type of flue to be utilized to vent the flue gases from the boiler or furnace.
The boiler circulator pump induces the flow of hot water through the boiler and the boiler loop. Usually the boiler circulator pump is controlled by the boiler aquastat however there are various levels of control that can be found that control circulator pumps. One way is by the boiler aquastat as mentioned above. Another way is by an end switch in a zone valve. A thermostat in a particular zone will call for heat and the thermostat calls for the >zone valve to open. When the zone valve is fully open an end switch closes the circuit to energize the circulator pump. Typically, the circuit is a control circuit so when the end switch closes it closes the circuit for a relay to energize the circulator pump Continue reading “Boiler Components: Boiler Circulator Pump” »
Residential and Light Commercial Low Pressure Steam Boilers
The residential steam boiler is still alive and well despite the fact that some HVAC professionals refer to it and the steam boiler profession as the dead mans club. However, there are not a lot of HVAC boiler technicians or HVAC companies that specialize in steam boilers because there are not a lot of the steam boilers used for residential and light commercial applications. People have either converted their old boiler steam systems over to hot water or have gone with forced air systems. The concept is simple but the mechanics of it can be frustratingly complex when a problem occurs unless you have the experience and knowledge that comes with working on the residential or light commercial steam boilers. Before we dive into some of the problems that arise with steam boilers, we’ll cover safety first. After all, HVAC safety is the most important aspect to any home heating system.