We have our 15-year old Colorado mountain cabin. Boiler supporting 5-zones of radiant, 2-zones of baseboard, and a domestic hot water tank. Just had our fourth zero pressure with glycol mix leaking out of one of two air vents. Also have one spirovent. Worst case was 10-years ago when both air vents and spirovent were leaking mix. Determined that the boiler manufacturer hadn’t cleaned all casting sand out of boiler and vents were jammed. All pressure losses have been linked to air vents. I was thinking of capping them off and periodically bleeding them manually. We are scared if we lose pressure we will damage boiler. Any negatives on capping vent?
Closed Radiant Heat Leaks?
- Thread starter FraserJim
- Start date
Users who are viewing this thread
Capping a vent means that the system can't self-purge any air. Depending on the pumping & plumbing configuration there is a possibility that even if purged well at the beginning it can pull in air over time.
There is almost no way to damage the boiler from low pressure. If the house is occupied the sizzle-pop-bang of the micro-boil going macro on the heat exchanger plates when the pressure is too low gives plenty of warning ahead of time. Even when making all that "kettling" noise it's not doing damage to the boiler, but it does cut into heat transfer efficiency. But if you're the type to worry leaving it for a week (or a month) unattended, installing a low pressure cut-off switch to inhibit the boiler from firing below a pre-set pressure would be a potential solution.
Water leaking out of a vent is a slow process, even when jammed with grit, but any decent filter should be able to catch particles as large as casting sand.
There is almost no way to damage the boiler from low pressure. If the house is occupied the sizzle-pop-bang of the micro-boil going macro on the heat exchanger plates when the pressure is too low gives plenty of warning ahead of time. Even when making all that "kettling" noise it's not doing damage to the boiler, but it does cut into heat transfer efficiency. But if you're the type to worry leaving it for a week (or a month) unattended, installing a low pressure cut-off switch to inhibit the boiler from firing below a pre-set pressure would be a potential solution.
Water leaking out of a vent is a slow process, even when jammed with grit, but any decent filter should be able to catch particles as large as casting sand.
Sponsor
Paid Advertisement
Thanks Dana. Some questions?
How can water enter the system once it is purged and no additional water is added?
I installed a LWCO. it’s electronics failed after two years and shutdown boiler. Weakest link?
What type of filter are you referring to?
It I cap the vents and there is a small residual amount of air in the system, what are the potential consequences?
Jim
How can water enter the system once it is purged and no additional water is added?
I installed a LWCO. it’s electronics failed after two years and shutdown boiler. Weakest link?
What type of filter are you referring to?
It I cap the vents and there is a small residual amount of air in the system, what are the potential consequences?
Jim
How can water enter the system once it is purged and no additional water is added?
An auto-fill valve can put more water into the system.
Or did you mean to ask how can air enter the system?
Air can enter the system when it's under-pressurized, putting the highest elevation of the system at risk of being below the localized air pressure. It is further aggravated by negative pressures induced on the return side by pumping. Air can also enter the system from high turbulence creating very localized low pressure spots at ells and tees when pumping. This is more common in systems on 2-3 story or taller houses/buildings with the boiler in the basement. Over-pumped system with high velocity / high turbulence sections can potentially even pull air in even from vents.
I installed a LWCO. it’s electronics failed after two years and shutdown boiler. Weakest link?
Maybe. But low water isn't your problem, low pressure is. A low pressure switch is a MUCH dumber-simpler electromechanical device than a LWCO- it's a set of switch contacts, one of which is on a diaphragm that flexes only when the pressure changes.
What type of filter are you referring to?
There are any number of "magnetic boiler filters" that have both a fine screen or filter medium as well a magnetic for catching granular crap (including ferrous sludge, rust, crud) from hydronic systems. They're a "must have" for old systems using iron plumbing & radiators, not so much for stainless boilers and PEX or copper, but since your system has a history of grit problems, and (I'm assuming) a cast iron boiler it's not a bad idea to install one on your system. There are also dirt separators that use primarily gravity and a low-turbulence low- velocity chamber to allow stuff denser than water to settle to the bottom, which should take care of silica sand or chunks of rust/scale. Spirotherm, the makers of Spirovent also makes several "Spirotrap" dirt-separator models suitable for residential systems.
It I cap the vents and there is a small residual amount of air in the system, what are the potential consequences?
If all the air collects in one spot it can form a vapor lock, with little or no flow on some branch or another. That's the primary symptom most people are concerned about, since no flow = no heat.
Air in the system will also oxidize/corrode ferrous system components (such as cast iron boilers), creating rust/crud/sludge. There may be some oxidation of the anti-freeze too.
An auto-fill valve can put more water into the system.
Or did you mean to ask how can air enter the system?
Air can enter the system when it's under-pressurized, putting the highest elevation of the system at risk of being below the localized air pressure. It is further aggravated by negative pressures induced on the return side by pumping. Air can also enter the system from high turbulence creating very localized low pressure spots at ells and tees when pumping. This is more common in systems on 2-3 story or taller houses/buildings with the boiler in the basement. Over-pumped system with high velocity / high turbulence sections can potentially even pull air in even from vents.
I installed a LWCO. it’s electronics failed after two years and shutdown boiler. Weakest link?
Maybe. But low water isn't your problem, low pressure is. A low pressure switch is a MUCH dumber-simpler electromechanical device than a LWCO- it's a set of switch contacts, one of which is on a diaphragm that flexes only when the pressure changes.
What type of filter are you referring to?
There are any number of "magnetic boiler filters" that have both a fine screen or filter medium as well a magnetic for catching granular crap (including ferrous sludge, rust, crud) from hydronic systems. They're a "must have" for old systems using iron plumbing & radiators, not so much for stainless boilers and PEX or copper, but since your system has a history of grit problems, and (I'm assuming) a cast iron boiler it's not a bad idea to install one on your system. There are also dirt separators that use primarily gravity and a low-turbulence low- velocity chamber to allow stuff denser than water to settle to the bottom, which should take care of silica sand or chunks of rust/scale. Spirotherm, the makers of Spirovent also makes several "Spirotrap" dirt-separator models suitable for residential systems.
It I cap the vents and there is a small residual amount of air in the system, what are the potential consequences?
If all the air collects in one spot it can form a vapor lock, with little or no flow on some branch or another. That's the primary symptom most people are concerned about, since no flow = no heat.
Air in the system will also oxidize/corrode ferrous system components (such as cast iron boilers), creating rust/crud/sludge. There may be some oxidation of the anti-freeze too.
Similar threads
