steam to hot water


Old 04-01-02, 09:36 AM
J. Novak
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steam to hot water

I currently have a steam single pipe system(1970's furnace) and I'm thinking about changing to a
hot water system. I'm not a plumber but I do know some things. Where do I find informatin on design and installation procedures so that I, as a handy man can understand and can do this project.
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Old 04-01-02, 12:23 PM
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Why do you want to change from steam to hot water heating ?

In theory is is possible, but requires a lot of work.

1) All hot water systems require that the radiators have a feed and a return pipe. Do your radiators have an opening for a second pipe connect to them ?

2) Your piping system needs to be modified in one of three ways.
- A single loop where the radiators feed and return hot water on the same pipe which starts and terminates on the boiler. Essentially the radiators feed and return a couple of feet apart on the same pipe.
- A series loop where the return of one radiator goes into the feed of the next radiator and so on. Problem is the radiators at the end of the chain tend to be cooler than those at the start.
- A two pipe (or parallel) system (the best, but most expensive approach) where there is two dedicated pipes from boiler: for feed and return hot water pipes

3) Your steam boiler needs to be replaced with a hot water boiler.

4) You need to add several supporting peripherals like circulator pump, aquastats, expansion tank, etc.

Some good sites that explain the differences are below:

Old 04-01-02, 02:30 PM
J. Novak
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steam to hot water

Thanks for the reply Zman.

First I want to get rid of all the clumbsy radiators in the house and all that pipe which needs forever painting. Second, I want to finish the attic and I need heat up there. Third
the house is large enough to someday turn it into a duplex so I want to zone it seperately. I wired it for a duplex already years ago when I rewired it. It's an old system, I'm sure I can get better efficiency from a new boiler. I understand the concepts you mentioned but physical installation is another story. How much would something like this cost for approximately 3000 sq ft house?
I'm a draftsman by trade so the plan is no problem
the design and the BTU thing is what I need to know how to do as well as how it is actually installed. ie In the loop style, will I have more than one register per room, when the pipe exits the register to go to the next, does it drop back down and run under the floor and then come back through the floor to the next register, what I mean to say is does the pipe that continues from register to register run above or below the finished floor?

Thanks again
Talk to ya

Old 04-02-02, 06:45 AM
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Hello John,

Are you trying remove old cast iron radiators and replace them with low profile conventors. (i.e. radiators with two or three copper pipes with aluminum fins along their length) ?

If that is the case, do not toss out your old cast radiators. They are worth are lot of money in the old architectual artifact market. Many people restoring old homes love the classical look of cast iron radiators.

BTU requirements are dependant on several things.

1) Square footage of the room. More sq ft = more BTUs
2) Area of the windows in the room. Large windows (or inefficent windows) = more BTUs
3) Insulation and its R-value (in outer walls, floors (for rooms over garages), ceilings (for upper floors)). Less insulation = more BTUs

I am not an expert on BTU calculations, but can suggest where you can get the information.

On the following website, click on "Free Heat Loss Calc".

He offers a free CD on how to calculate heat loss and boiler specs.
This would help you generate a materials list and you could price the cost of the conversion.

The cost of the conversion depends on if you are doing most (or all of it) yourself or subcontract parts of it. If you are doing most of it yourself, then your cost is mainly for materials. Labor would easily consume 50-80% of the cost of the job, if you hired someone to do the job completely.

The single loop method of hot water delivery, I believe, works well for single floor or small houses. Since you have a big house, the parallel method is probably better. Check out the websites I mentioned in my previous reply, the experts go into more detail about which method is best.

Single loops and series loops are not well suitable for zoned systems. Parallel piping is the way to go for zoned systems.

Good Luck


Last edited by TheZman; 04-02-02 at 01:06 PM.

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