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If you like iron radiators--either old or \"new\"
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Mike T., Swampeast MO
Member Posts: 6,928
[I wrote this at oldhousejournal.com in response to someone wanting to know how to size iron radiators for a new system in an old house. While long, I believe it covers much and will allow homeowners/DIYers to ask the "right" questions of the "pros". Contractors working on websites or other literature are free to use any or all, but authorship credit would be appreciated. Specific product recommendations are based SOLELY on my opinions and I have ZERO ties to ANY manufacturer. While some opinions may be contentious, observation leads me to no other conclusions. Michael W. Thies]
--------------------------------------
There are some old radiator sizing formulas but they will most often produce wildly oversized systems.
If you're good and accurate with measurement, are quite familiar with the construction of your home and like doing "new" things go to www.hvaccalc.com and download the one-time use program for a modest fee.
To know a bit of what you'll need: surface area of walls exposed to the outside; surface area of glass; surface area of ceilings & floors; surface area of partions adjoining "unheated" or "less heated" areas; levels of insulation in all these areas; basic type of construction to include sheathing, doors, windows, etc. Much of the surface areas can be calculated automatically given dimensions. Since spaces loose most of their heat through the ceiling, it is important to be EXTREMELY thorough with ceilings and a given room will often have MULTIPLE "types" of ceiling; i.e. a room under a finished attic (the eave space will be different even if unheated), a projecting bay window, stairwell or a "bump-out" addition.
An ACCURATE heat loss calculation will tell you how much heat the structure requires as a whole and how much each space requires as well.
Radiators are sized based on their Equivalent Direct Radiation or EDR. This is an OLD throwback to the oldest form of radiator that was essentially a flat panel looking something like a mattress. EDR is measured in square feet and sizing data is readily available for most old rads and all new rads.
Unless you're REALLY handy and are willing to study quite a lot, installing a good hydronic system isn't a DIY project. Even if you size everything and run your own piping have a pro install the boiler--or at an absolute minimum pay them well to review your boiler installation.
Once you've computed your heat loss, the next step is to determine the general temperature at which you want the system to run.
Remember that radiators DO radiate significantly and that radiation is generally regarded as the most comfortable and efficient method of space heating. In general, the lower the temperature of the radiator the higher its proportion of radiation; the higher the temperature the higher its proportion of convection.
In other terms, you can (within limits) make radiators as small or as large as you like--they just have to ALL be reasonably proportional to the heat loss of each space.
There are however are some problems if you plan for large radiators with low temperature requirement: 1) heat loss calculations are based on an "average" LOW winter temperature in your area--consequently the system will rarely be loosing the "full" amount of the heat loss. 2) Many boilers do not "like" low temperatures and as manufacturers have wrung the last drop of efficiency out of traditional designs their sensitivity to low temperature has increased greatly. 3 ) Traditional boilers achieve their best efficiency at higher temperatures around 180°.
Consequently, a system with low temperature requirement teamed with a traditional boiler MUST have measures taken to protect the boiler from low temperatures--there are a number of ways but all add complexity, cost and are generally counter-productive fuel-wise.
Condensing boilers are fairly new. They are INTENDED to operate at low temperature and achieve their best efficiency when supplying water BELOW 140° or so. In general, the lower the supply temperature the higher the boilers' efficiency.
Like condensing warm-air furnaces, some have had problems dealing with the mildly corrosive nature of condensate and consequently heat exchangers are made from rather exotic and expensive materials. Again, like condensing furnaces, condensing boilers all have "forced" draft--a fan of some type supplies combustion air to the burner instead of plain ambient air in many conventional models. Some forced draft equipment is quite loud--both inside and at their exhaust port outside. Condensing boilers MUST NOT be vented through a typical old house chimney!
Europeans (particularly Germans) are WAY ahead of the U.S. regarding condensing equipment. One of the main reasons for this is the fact that hydronics have a very limited market in the U.S.--thus less money available for research and development. Even if a U.S. mfgr WOULD make their own condensing boiler the standards by which they are rated (the AFUE "number" you see from ASHRAE) DOES NOT ACCURATELY PORTRAY THEIR TRUE EFFICIENCY AS INSTALLED IN A SYSTEM!!!
While a few condensing boilers may "appear" American, they are really assemblages of "stock" parts from all over Europe. The condensing boiler with the longest and best "track record" assembled by an American company is most likely the Monitor MZ, www.mzboiler.com Most "simple" condensing boilers can be fueled by natural gas, propane and fuel oil.
Once your heat loss is complete, you have sized your radiators and designed a system appropriate to the temperature at which it will operate you must consider how the system will be controlled.
The most common way (in the U.S.) is digital--the wall thermostat that everyone knows. The flow of heat is either "on" or "off" NEVER "in-between." Even if the system is divided into "zones" you can rest assured that the system IS digital if it is controlled by wall thermostats.
The other method to control (VASTLY superior by the way) is proportionally. The amount of heat delivered to a radiator depends on the temperature OUTSIDE and the desired temperature INSIDE--it is not "on" or "off" in most circumstance, but continually and automatically changing based on conditions--both IN AND OUT OF YOUR CONTROL.
While this may sound fantastic and hideously complex, IT IS NOT! Fully self-contained devices called Thermostatic Radiator Valves (TRVs) have existed for DECADES and are known for high reliability, high efficiency and incredible comfort. These devices are REQUIRED in much of Europe. While there are many manufacturers (some even in the US--even if they do actually make them in Mexico) the "best" are likely from a Danish company named Danfoss. As even "plain" radiator valves have become a specialty item in the US, the cost of TRVs is not particularly high and WELL WORTH THE COST. You wind up with the ability to keep each and every space at whatever temperature you desire with amazing accuracy. While some systems using TRVs will still have a wall thermostat, the better way (in my mind) has NO indoor thermostat save the TRVs installed on EVERY radiator.
Until quite recently ALL boilers available for sale in the U.S. have been digital--i.e. full fire or no fire--nothing in between. In an attempt to reduce fuel use, many systems (both digital and proportional) use outdoor reset. Outdoor reset adjusts the temperature in the system based on the temperature outside--i.e. as it gets colder outside, the water gets hotter. Reset certainly works well and can certainly save energy, but those "problems" with low temperatures in conventional boilers can really bite you in the a## when teamed with reset.
Enter the condensing, modulating boiler. There are not many available in the U.S. at the current time. Of those few that are assembled in the U.S., problems (warranty-required INSIDE heat exchanger cleaning requirement in one and questionable exchanger material/longevity in another) preclude my recommendation. The "best" is likely the Vitodens by Viessmann (Germany) www.viessmann.us/
The Vitodens has an absolutely unique "burner" that does not produce flame in the conventional sense--it transfers the vast majority of its heat to the water via radiation. When installed in a system that has variable flow (TRVs), even the built-in circulating pump modulates. On such a system the burner will almost always be "on" at some level as long as the structure requires heat. Real-world "numbers" coming from this boiler are absolutely extraordinary regarding efficiency. Flue gas temperature is only a few (often less than five) degrees higher than the temperature of the supply water! Of course it is highly complex and very expensive but based on its use in Europe for much longer and stellar reputation for Viessmann reliability it really deserves the highest consideration. Remember that it is designed in Germany where TRVs are REQUIRED in any space larger than a closet and it will achieve its best efficiency when TRVs are used.
Standing water-filled cast iron radiators have been associated with gentle even heat, comfort, efficiency, reliability, cleanliness, adjustability and safety since their inception. While some may view them as clunky and hopelessly old-fashioned, no other space heating method in common use today offers this wonderful mix of qualities. Systems using standing iron radiation have ALWAYS been expensive. They have always required SKILLED labor to work at their best.
No other space heating systems has (or likely ever will) exist that actually IMPROVES with age and whose lifespan is truly "indeterminate" with CENTURIES actually possible!
How, you ask, can a heating system possibly IMPROVE with age? Much of the system remains reasonably accessible in the event of any problems. Continued improvements in both boiler and control technology will be always be able introduced with little or no modification. As homes age they become "leakier" as do forced air systems--hydronic systems MUST stay sealed to operate and they will NOT introduce pressurization problems as the home proper ages. Any conceivable new and fantastic energy technology is CERTAIN to be able to heat a liquid that in turn heats a physical object like an iron radiator.
As a "heat only" source, you will NEVER have to replace both heat and cooling simultaneously as often happens with combined forced air systems. Combined heat/cool forced air systems by the way ALWAYS have concessions that make them less efficient/comfortable with either heat or cooling. Standing iron will ALWAYS make a bold statement of "permanence" to many home buyers and resale value is maximized for those who demand quality over "flash."
--------------------------------------
There are some old radiator sizing formulas but they will most often produce wildly oversized systems.
If you're good and accurate with measurement, are quite familiar with the construction of your home and like doing "new" things go to www.hvaccalc.com and download the one-time use program for a modest fee.
To know a bit of what you'll need: surface area of walls exposed to the outside; surface area of glass; surface area of ceilings & floors; surface area of partions adjoining "unheated" or "less heated" areas; levels of insulation in all these areas; basic type of construction to include sheathing, doors, windows, etc. Much of the surface areas can be calculated automatically given dimensions. Since spaces loose most of their heat through the ceiling, it is important to be EXTREMELY thorough with ceilings and a given room will often have MULTIPLE "types" of ceiling; i.e. a room under a finished attic (the eave space will be different even if unheated), a projecting bay window, stairwell or a "bump-out" addition.
An ACCURATE heat loss calculation will tell you how much heat the structure requires as a whole and how much each space requires as well.
Radiators are sized based on their Equivalent Direct Radiation or EDR. This is an OLD throwback to the oldest form of radiator that was essentially a flat panel looking something like a mattress. EDR is measured in square feet and sizing data is readily available for most old rads and all new rads.
Unless you're REALLY handy and are willing to study quite a lot, installing a good hydronic system isn't a DIY project. Even if you size everything and run your own piping have a pro install the boiler--or at an absolute minimum pay them well to review your boiler installation.
Once you've computed your heat loss, the next step is to determine the general temperature at which you want the system to run.
Remember that radiators DO radiate significantly and that radiation is generally regarded as the most comfortable and efficient method of space heating. In general, the lower the temperature of the radiator the higher its proportion of radiation; the higher the temperature the higher its proportion of convection.
In other terms, you can (within limits) make radiators as small or as large as you like--they just have to ALL be reasonably proportional to the heat loss of each space.
There are however are some problems if you plan for large radiators with low temperature requirement: 1) heat loss calculations are based on an "average" LOW winter temperature in your area--consequently the system will rarely be loosing the "full" amount of the heat loss. 2) Many boilers do not "like" low temperatures and as manufacturers have wrung the last drop of efficiency out of traditional designs their sensitivity to low temperature has increased greatly. 3 ) Traditional boilers achieve their best efficiency at higher temperatures around 180°.
Consequently, a system with low temperature requirement teamed with a traditional boiler MUST have measures taken to protect the boiler from low temperatures--there are a number of ways but all add complexity, cost and are generally counter-productive fuel-wise.
Condensing boilers are fairly new. They are INTENDED to operate at low temperature and achieve their best efficiency when supplying water BELOW 140° or so. In general, the lower the supply temperature the higher the boilers' efficiency.
Like condensing warm-air furnaces, some have had problems dealing with the mildly corrosive nature of condensate and consequently heat exchangers are made from rather exotic and expensive materials. Again, like condensing furnaces, condensing boilers all have "forced" draft--a fan of some type supplies combustion air to the burner instead of plain ambient air in many conventional models. Some forced draft equipment is quite loud--both inside and at their exhaust port outside. Condensing boilers MUST NOT be vented through a typical old house chimney!
Europeans (particularly Germans) are WAY ahead of the U.S. regarding condensing equipment. One of the main reasons for this is the fact that hydronics have a very limited market in the U.S.--thus less money available for research and development. Even if a U.S. mfgr WOULD make their own condensing boiler the standards by which they are rated (the AFUE "number" you see from ASHRAE) DOES NOT ACCURATELY PORTRAY THEIR TRUE EFFICIENCY AS INSTALLED IN A SYSTEM!!!
While a few condensing boilers may "appear" American, they are really assemblages of "stock" parts from all over Europe. The condensing boiler with the longest and best "track record" assembled by an American company is most likely the Monitor MZ, www.mzboiler.com Most "simple" condensing boilers can be fueled by natural gas, propane and fuel oil.
Once your heat loss is complete, you have sized your radiators and designed a system appropriate to the temperature at which it will operate you must consider how the system will be controlled.
The most common way (in the U.S.) is digital--the wall thermostat that everyone knows. The flow of heat is either "on" or "off" NEVER "in-between." Even if the system is divided into "zones" you can rest assured that the system IS digital if it is controlled by wall thermostats.
The other method to control (VASTLY superior by the way) is proportionally. The amount of heat delivered to a radiator depends on the temperature OUTSIDE and the desired temperature INSIDE--it is not "on" or "off" in most circumstance, but continually and automatically changing based on conditions--both IN AND OUT OF YOUR CONTROL.
While this may sound fantastic and hideously complex, IT IS NOT! Fully self-contained devices called Thermostatic Radiator Valves (TRVs) have existed for DECADES and are known for high reliability, high efficiency and incredible comfort. These devices are REQUIRED in much of Europe. While there are many manufacturers (some even in the US--even if they do actually make them in Mexico) the "best" are likely from a Danish company named Danfoss. As even "plain" radiator valves have become a specialty item in the US, the cost of TRVs is not particularly high and WELL WORTH THE COST. You wind up with the ability to keep each and every space at whatever temperature you desire with amazing accuracy. While some systems using TRVs will still have a wall thermostat, the better way (in my mind) has NO indoor thermostat save the TRVs installed on EVERY radiator.
Until quite recently ALL boilers available for sale in the U.S. have been digital--i.e. full fire or no fire--nothing in between. In an attempt to reduce fuel use, many systems (both digital and proportional) use outdoor reset. Outdoor reset adjusts the temperature in the system based on the temperature outside--i.e. as it gets colder outside, the water gets hotter. Reset certainly works well and can certainly save energy, but those "problems" with low temperatures in conventional boilers can really bite you in the a## when teamed with reset.
Enter the condensing, modulating boiler. There are not many available in the U.S. at the current time. Of those few that are assembled in the U.S., problems (warranty-required INSIDE heat exchanger cleaning requirement in one and questionable exchanger material/longevity in another) preclude my recommendation. The "best" is likely the Vitodens by Viessmann (Germany) www.viessmann.us/
The Vitodens has an absolutely unique "burner" that does not produce flame in the conventional sense--it transfers the vast majority of its heat to the water via radiation. When installed in a system that has variable flow (TRVs), even the built-in circulating pump modulates. On such a system the burner will almost always be "on" at some level as long as the structure requires heat. Real-world "numbers" coming from this boiler are absolutely extraordinary regarding efficiency. Flue gas temperature is only a few (often less than five) degrees higher than the temperature of the supply water! Of course it is highly complex and very expensive but based on its use in Europe for much longer and stellar reputation for Viessmann reliability it really deserves the highest consideration. Remember that it is designed in Germany where TRVs are REQUIRED in any space larger than a closet and it will achieve its best efficiency when TRVs are used.
Standing water-filled cast iron radiators have been associated with gentle even heat, comfort, efficiency, reliability, cleanliness, adjustability and safety since their inception. While some may view them as clunky and hopelessly old-fashioned, no other space heating method in common use today offers this wonderful mix of qualities. Systems using standing iron radiation have ALWAYS been expensive. They have always required SKILLED labor to work at their best.
No other space heating systems has (or likely ever will) exist that actually IMPROVES with age and whose lifespan is truly "indeterminate" with CENTURIES actually possible!
How, you ask, can a heating system possibly IMPROVE with age? Much of the system remains reasonably accessible in the event of any problems. Continued improvements in both boiler and control technology will be always be able introduced with little or no modification. As homes age they become "leakier" as do forced air systems--hydronic systems MUST stay sealed to operate and they will NOT introduce pressurization problems as the home proper ages. Any conceivable new and fantastic energy technology is CERTAIN to be able to heat a liquid that in turn heats a physical object like an iron radiator.
As a "heat only" source, you will NEVER have to replace both heat and cooling simultaneously as often happens with combined forced air systems. Combined heat/cool forced air systems by the way ALWAYS have concessions that make them less efficient/comfortable with either heat or cooling. Standing iron will ALWAYS make a bold statement of "permanence" to many home buyers and resale value is maximized for those who demand quality over "flash."
0
Comments
-
well done
I kept looking for contentious opinions but didn't find any :-)
Mark0 -
Nice work there MT
I failed to find anything I would call contentious. Some may disagree or have other opinions on boiler brands but Viesmann's lead is virtually indisputable when it comes to the Vitodens. I know of no other company that has a burner like that available in the USA or a boiler that does as many things as that one does right out of the box.
As far as the jist of the article....... You hit the nail on the head. A heating system that can modulate its input AND output continuously and simultainiously is truly the Holy Grail of BTU delivery. I don't know of anything that matches this type of delivery for overall comfort and efficiency. Some might disagree with that, arguing that a radiant floor is more comfortable and that is a debatable point. While the warm floors are indeed delightful, they are difficult to control during sudden temp changes when you are dealing with that much mass. the best in my hunble opinion would be a combination of a floor warming system working in conjunction with a radiator which picks up the quick changes in room temps that are always encountered.
Again, Nice work! I wish everyone in America would read that and be able to grasp what you a talking about. It would probably cut or national energy use by 10% if the whole country heated in this fashion.0 -
Contentions...
Let a formally trained U.S. heating engineer (or worse yet one of their teachers) get hold of this and they'll likely find all manner of wildly unsubstantiated claims.
Of course their "proof" will be that it doesn't conform to their rigid and hopelessly simple method of trying to apply REAL WORLD results to their laboratory models.0 -
Very Well Written
couldn't have said it better myself.
To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting0 -
An education for all
well written Mike. Mad Dog
To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"0 -
My soul thanks you Steve, et.al.
"I wish everyone in America would read that and be able to grasp what you a talking about. It would probably cut or national energy use by 10% if the whole country heated in this fashion."
EXACTLY why I spend so much time and effort thinking about this stuff and why any "good" that may come from it is MUCH more valuable than money.
"...the best in my humble opinion would be a combination of a floor warming system working in conjunction with a radiator which picks up the quick changes in room temps that are always encountered..."
And it can be done with nothing more than a standing-pilot cast iron boiler, mechanical reset, a SINGLE circulator and TRVs. It's just not as efficient as possible, but MUCH more efficient than with "just" the boiler.
Please, people, don't take any of this as arrogance, ego-massaging, preaching, bragging, nagging, etc. Believe me, the LAST thing I need is a boost of my ego--I've been called "gifted" all of my life by people of many statures, positions, incomes and levels of education. "Gifts" become "curses" when wasted!
A BIG part of me right now is screaming, "YOU WANT OUT OF SWAMPEAST MO! You can organize ANYTHING and break even the most complicated program into manageable pieces. That boiler design in your head could turn some American company into a rival to Viessmann and control it in ways that even their engineers may not have considered."
The building housing my store burned over the weekend, my crippled mother died a few months ago and the roots holding me here grow ever weaker.
Those roots still scream, "You're nobody. Why would anyone believe you and even if they do most have no REAL interest in actually saving energy and will actually work AGAINST you!"
Offers from anyone to see which "side" of me is right???0 -
Mike, you'd be very welcome
in Baltimore. Contact me!
To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting0 -
offers
I can't make an offer, but I will make a wager. The quieter side is the wiser one. Many of us have those voices of doubt and incompetence, but they never seem to show up in the eyes of the people who know us.
I am sad to hear of your losses and wish for the best on any path you take. Your knowledge and concern has been a gift to me.
jerry
0
This discussion has been closed.
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