Replacing my very old boiler in a gravity hot water system

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  #1  
Old 09-22-05, 10:06 PM
hkycchrick
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Replacing my very old boiler in a gravity hot water system

To anyone with experience in this matter:

I run a gravity hot water system to heat my circa-1900 2 story house and it works wonderfully. However, higher gas prices and recent cold winters have made my monthly heating bills skyrocket to several hundred $$$ esp. in Jan. and Feb.

My furnace is an old cast-iron coal burning weil-mclain that has been converted to natural gas and I estimate running at approx. 40 percent efficiency. Every contractor I have talked to has told me I need to switch to a circulating hot water system for better efficiency and all quotes have been in excess of $11,000 for this type of boiler replacement.

I am concerned that a switch from gravity circulated hw to pump circulated may severly screw up the current perfectly balanced system of distributing heat in every single room of my house. Turn of the century cast Iron radiators are the only type that I use - some have "hand crank" flow control valves on them and some don't have any. Pumped hot water will have to somehow be able to reach the 2nd floor where my good 'ol gravity system uses the laws of physics to bring the heat "upward".

Is there any way to replace my old inefficient boiler that works so well with an efficient model - without having to add the considerable cost of installing newer control valves on every single radiator in my house? Is gravity still a viable and efficient option in these days of increasing fuel costs?

I appreciate any kind of feedback that may help me solve this problem economically.
 
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Old 09-23-05, 06:18 PM
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Gravity H/W system

Having a gravity system is like throwing money into the ocean. Getting the heat to the second floor is not a problem. Balancing the system may take some work but it can be done. If possible/practical I would highly recommend separating the first & second floors into their own zones. The price tag does not surprise me.
 
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Old 09-24-05, 08:22 AM
hkycchrick
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re: gravity system

Thanks for the quick response. I completely understand where you're coming from - you are not the first person who's described my heating system like this.



Originally Posted by Grady
Having a gravity system is like throwing money into the ocean. Getting the heat to the second floor is not a problem. Balancing the system may take some work but it can be done. If possible/practical I would highly recommend separating the first & second floors into their own zones. The price tag does not surprise me.
 
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Old 10-06-07, 12:31 PM
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Converting open boiler system to closed

Like the original post, we have a gravity hot water system to heat our 1905 2 story house and it works wonderfully. However, our monthly heating bills can be several hundred $$$ esp. in Jan. and Feb. And the bottom of the tank has started appearing damp -- so it appears that a replacement is needed.

The furnace is an old cast-iron coal burning that has been converted to natural gas. Every contractor we talk to tells us to switch to a circulating hot water system and all quotes have been in excess of $11,000 for this type of boiler replacement.

We are also concerned that a switch from gravity circulated hw to pump circulated may mess up the current system that heats well and evenly through turn of the century cast iron radiators.

Is there any way to replace an old inefficient (and leaky) boiler that works so well with an efficient model and maintaining the open system. It seems crazy to add so many extra parts - circulator, etc and then to replace parts that are working fine -- like the cool old overflow tank upstairs and many of the pipes in the basement. Is gravity still a viable and efficient option in these days of increasing fuel costs?

We would appreciate hearing from the original poster or anyone else who has converted to a closed system. Are you satisfied. Did it really lower your bills considerably? We would also appreciate any kind of feedback that may help us solve this problem economically.
 
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Old 10-06-07, 12:50 PM
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I suspect that the original poster no longer visits this forum since they have had no additional posts in the last two years.

I don't know what you mean when you write, "And the bottom of the tank has started appearing damp -- " Do you mean that the boiler is beginning to leak?

In order to have a gravity system work well you need a large amount of water in the boiler. This requires large amounts of fuel to be burned at (relatively) infrequent times to maintain the water temperature and that translates into a highly INefficient system. Modern boilers (and entire hydronic heating systems) have a fairly small amount of water and fire for longer periods to achieve higher efficiencies.

In order to have a new boiler and yet retain the "charm" of your existing system you would need a large "accumulator" tank to hold a large amount of water that would gravity circulate in your system. Such a tank could be installed and well insulated but the boiler would still require a circulating pump and all the "accessories" of a modern installation. You would have poor control of the heat and I doubt that you would like it much.

You CAN have a new, efficient, modulating boiler installed along with the necessary "accessories" to keep the existing system working but it WILL be expensive. You may need to have extensive piping replacement because the "open" system you now have is highly prone to oxygen corrosion. Your "cool old overflow tank upstairs" is a disaster waiting to happen. The piping in the basement may also contain asbestos insulation as will the existing boiler.

I strongly suggest that you listen to the experts in regard to this system.
 
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