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Last fall I had installed a Royall 6200 outside wood boiler which worked well until recently. It was 10:00 P.M., February 25, 2007, snowing and 30°F when I fired the boiler for the night (the last forecast I heard was for a low of 20°); shortly after, I turned down the thermostat from 71° to 67°and went to bed. My wife and I slept comfy and warm until 1:30 A.M. – that was when the drama began.
The Royall 6200 is a 200,000 Btu closed system with a blower-induced draft controlled by an adjustable aqua-stat. Through the winter I learned to adequately heat my home by setting the aqua-stat at 185° and adjust the manually operated draft damper according to outside temperature, wind direction and speed, type of wood and solar heat gain – all elements that impact heating/draft requirements. Also, to meet standards, the boiler has a 30 psi relief valve manufactured by Conbraco Industries.
The boiler supplies our hot water heating system through 1 ¼” pex tubing (Rehau Insulpex). The tubing is buried for 75’, enters the basement wall and then continues for another 15’ where it makes a transition to 1 ¼” type M copper.
Like I said, it worked all winter: So, what happened? At 1:30 A.M, a deafening explosion actually rocked the house, causing my wife and I to bolt from bed and shout in unison, “What the hell was that?” She thought an airplane hit the house but I, retired but with 33 years of metro firefighting experience, knew what it was by what I heard after the blast – high pressure steam.
Just like back in the day, I immediately dressed, put on boots and began processing a plan of action. Hot steam pushed around the basement door so I reached in with a gloved hand just to turn on the light; then I went outside and opened the cellar door, releasing enough steam so I could enter to shut off the heating system’s power and water supply – I was separated from the rupture by 30’ and a wall. I then scrambled to the boiler and filled the firebox with snow. Okay, with everything under as much control as I could exert and the sound of rushing steam replaced by dribbling water, I reentered the basement to determine what happened.
I discovered a one foot catastrophic rupture of the Insulpex tubing where it entered the basement from the wall. I was amazed, wondering what could have caused the (reported) highest quality pex transfer system to fail so disastrously, but, moreover, I was thankful the blast did not occur while I worked on a project or when I sent one of my grandkids down to fetch canned goods. Since only a few gallons of water stood on the basement floor and steam’s expansion ratio is 1,600 to 1, the system failure could have yielded almost 30,000 cubic feet of scalding steam.
What I’ve learned since the disaster:
Rehau Insulpex: Like all pex, it is rated for a maximum of 80 psi at 200° F. Speaking to a Rehau engineer, he stated – off the record – they test Insulpex for other applications at 240° without failure. So why did it fail?
Was it my entire fault? The boiler obviously became overheated. On the night of my disaster, the weather forecast I heard said the low would be 20° so I set the draft damper at 1/3. But, in fact, the temperature rose to 35°. Had I known that, I would have set it to about 1/6 open.
The relief valve: Conbraco Industries told me their relief valve (10-407) was the safest thing on the boiler and that it absolutely would release at 30 psi. They also stated that the installed valve was not suitable for the application. He told me to read the tag affixed to the valve – I did. “4) DO NOT use this valve on a coal or wood boiler having an uncontrolled Btu heat input.” Since my boiler has a manually operated damper, it is uncontrolled. (A controlled boiler would be one where the aquastat not only stops the draft motor at a set temperature, but would also automatically close the draft opening.)
I kept digging because the Insulpex “should” have withstood up to 240° at 80 psi and the relief valve should have released at 30 psi despite the boiler’s lack of draft control. I found the answer when I discovered a steam temperature/pressure chart. At 30 psi, steam is 274° F. Somewhere below 30 psi – 29 psi @ 270°, for all I know – the superheated water entered the pex within the basement. At that point, free from the pressure of 4’ of compacted cold earth and exposed to room temperature, the pex softened and expanded, ultimately exploding the supply tube. At the moment of rupture, the pressure within the tube became 1 atmosphere, allowing all the water above 212° to directly become steam which caused the violent and instantaneous steam release.
Appraised of the facts as I knew them, I contacted the installer who came to the site within 8 hours – he scratched his head in disbelief. He said he had seen these boilers reach 240° with Insulpex installed with no adverse effect. In fact, I had noticed my boiler reach that temperature several times whereupon I immediately closed the draft and turned up the thermostats to use up the accumulated heat.
I then contacted the Royall manufacturer who nearly immediately told me that over-fired boilers voided the warranty. I told him that the instruction booklet had no directions for setting the aquastat and the draft, that the relief valve was not the proper type, that the boiler should have a temperature/pressure (T&P) relief valve much like a hot water heater, that his boiler should have an automatic draft damper and that pex tubing (something Royall recommends under a different brand) could not withstand the boiler’s potential output. He said he would get back to me.
Recommendations:
Anyone with a Royall boiler, or one with its characteristics, who installed pex supply tubing with its terminus inside the house, should immediately shut it down until a transition to copper is made outside the building. The below-ground pressure and temperature keep the pex intact but catastrophic failure is likely when the tubing is relieved of pressure within a warm basement. If in close proximity, one may expect injury or death from shrapnel, a steam-burned airway and extensive 3rd degree burns.
Additionally, if the boiler (closed system) is not refitted to limit its output to 200° F, one can expect buried pex tubing to fail prematurely.
This recommendation does not apply to open systems and those boilers equipped with a properly rated T&P relief valve and equipped with an automatic damper control.
In Conclusion:
I’ve heard nothing more from the installer and manufacturer. I believe justice indicates they should make things right, so, if they make light of this experience, I’ll be forced to litigate.
http://www.royallfurnace.com/OutdoorPressure.htm
http://www.rstreps.com/pdf/INSULPEX 855[1].806.pdf
http://www.conbraco.com/products/safety/techtemplate_1.asp?pid=10-Series
Last fall I had installed a Royall 6200 outside wood boiler which worked well until recently. It was 10:00 P.M., February 25, 2007, snowing and 30°F when I fired the boiler for the night (the last forecast I heard was for a low of 20°); shortly after, I turned down the thermostat from 71° to 67°and went to bed. My wife and I slept comfy and warm until 1:30 A.M. – that was when the drama began.
The Royall 6200 is a 200,000 Btu closed system with a blower-induced draft controlled by an adjustable aqua-stat. Through the winter I learned to adequately heat my home by setting the aqua-stat at 185° and adjust the manually operated draft damper according to outside temperature, wind direction and speed, type of wood and solar heat gain – all elements that impact heating/draft requirements. Also, to meet standards, the boiler has a 30 psi relief valve manufactured by Conbraco Industries.
The boiler supplies our hot water heating system through 1 ¼” pex tubing (Rehau Insulpex). The tubing is buried for 75’, enters the basement wall and then continues for another 15’ where it makes a transition to 1 ¼” type M copper.
Like I said, it worked all winter: So, what happened? At 1:30 A.M, a deafening explosion actually rocked the house, causing my wife and I to bolt from bed and shout in unison, “What the hell was that?” She thought an airplane hit the house but I, retired but with 33 years of metro firefighting experience, knew what it was by what I heard after the blast – high pressure steam.
Just like back in the day, I immediately dressed, put on boots and began processing a plan of action. Hot steam pushed around the basement door so I reached in with a gloved hand just to turn on the light; then I went outside and opened the cellar door, releasing enough steam so I could enter to shut off the heating system’s power and water supply – I was separated from the rupture by 30’ and a wall. I then scrambled to the boiler and filled the firebox with snow. Okay, with everything under as much control as I could exert and the sound of rushing steam replaced by dribbling water, I reentered the basement to determine what happened.
I discovered a one foot catastrophic rupture of the Insulpex tubing where it entered the basement from the wall. I was amazed, wondering what could have caused the (reported) highest quality pex transfer system to fail so disastrously, but, moreover, I was thankful the blast did not occur while I worked on a project or when I sent one of my grandkids down to fetch canned goods. Since only a few gallons of water stood on the basement floor and steam’s expansion ratio is 1,600 to 1, the system failure could have yielded almost 30,000 cubic feet of scalding steam.
What I’ve learned since the disaster:
Rehau Insulpex: Like all pex, it is rated for a maximum of 80 psi at 200° F. Speaking to a Rehau engineer, he stated – off the record – they test Insulpex for other applications at 240° without failure. So why did it fail?
Was it my entire fault? The boiler obviously became overheated. On the night of my disaster, the weather forecast I heard said the low would be 20° so I set the draft damper at 1/3. But, in fact, the temperature rose to 35°. Had I known that, I would have set it to about 1/6 open.
The relief valve: Conbraco Industries told me their relief valve (10-407) was the safest thing on the boiler and that it absolutely would release at 30 psi. They also stated that the installed valve was not suitable for the application. He told me to read the tag affixed to the valve – I did. “4) DO NOT use this valve on a coal or wood boiler having an uncontrolled Btu heat input.” Since my boiler has a manually operated damper, it is uncontrolled. (A controlled boiler would be one where the aquastat not only stops the draft motor at a set temperature, but would also automatically close the draft opening.)
I kept digging because the Insulpex “should” have withstood up to 240° at 80 psi and the relief valve should have released at 30 psi despite the boiler’s lack of draft control. I found the answer when I discovered a steam temperature/pressure chart. At 30 psi, steam is 274° F. Somewhere below 30 psi – 29 psi @ 270°, for all I know – the superheated water entered the pex within the basement. At that point, free from the pressure of 4’ of compacted cold earth and exposed to room temperature, the pex softened and expanded, ultimately exploding the supply tube. At the moment of rupture, the pressure within the tube became 1 atmosphere, allowing all the water above 212° to directly become steam which caused the violent and instantaneous steam release.
Appraised of the facts as I knew them, I contacted the installer who came to the site within 8 hours – he scratched his head in disbelief. He said he had seen these boilers reach 240° with Insulpex installed with no adverse effect. In fact, I had noticed my boiler reach that temperature several times whereupon I immediately closed the draft and turned up the thermostats to use up the accumulated heat.
I then contacted the Royall manufacturer who nearly immediately told me that over-fired boilers voided the warranty. I told him that the instruction booklet had no directions for setting the aquastat and the draft, that the relief valve was not the proper type, that the boiler should have a temperature/pressure (T&P) relief valve much like a hot water heater, that his boiler should have an automatic draft damper and that pex tubing (something Royall recommends under a different brand) could not withstand the boiler’s potential output. He said he would get back to me.
Recommendations:
Anyone with a Royall boiler, or one with its characteristics, who installed pex supply tubing with its terminus inside the house, should immediately shut it down until a transition to copper is made outside the building. The below-ground pressure and temperature keep the pex intact but catastrophic failure is likely when the tubing is relieved of pressure within a warm basement. If in close proximity, one may expect injury or death from shrapnel, a steam-burned airway and extensive 3rd degree burns.
Additionally, if the boiler (closed system) is not refitted to limit its output to 200° F, one can expect buried pex tubing to fail prematurely.
This recommendation does not apply to open systems and those boilers equipped with a properly rated T&P relief valve and equipped with an automatic damper control.
In Conclusion:
I’ve heard nothing more from the installer and manufacturer. I believe justice indicates they should make things right, so, if they make light of this experience, I’ll be forced to litigate.
http://www.royallfurnace.com/OutdoorPressure.htm
http://www.rstreps.com/pdf/INSULPEX 855[1].806.pdf
http://www.conbraco.com/products/safety/techtemplate_1.asp?pid=10-Series
