We Got "Hot Water" Heat

djthx

I've decided to convert my steam into hot water heating system.  My current steam boiler is oversized, outdated, and is on its last legs.  I'm finishing my basement, and will need heat down there.  And, the radiators I have are the hot water (corto tube) type.  I'm pretty handy, and am up for the task of running new copper piping.  I read somewhere that it is possible to run pex tubing (at least for the returns); is this possible, or should I stick with copper?



Finally, I just ordered Dan's "Pumping Away".  Is this a good place to start learning about basic hot water heating?  Is there a comparable book on hot water heat that will teach me as much about hot water heating that "We Got Steam Heat" taught me about steam heating?



Thanks.

Steamhead

This question keeps coming up

You really need to do your homework on this. There are many pitfalls.



First, the radiators have been running at less then 2 pounds for generations. Hot-water needs at least 12 pounds, and more if the building is taller than 3 stories. This much-higher pressure can lead to leaks.



Second, the radiators may not be big enough to heat the house on hot-water. Have you done a heat-loss calculation to make sure?



Dan has written about this, in the Hot Tech Tips section under "Resources". He goes into much more detail there.



The simplest way to add heat to the basement is to use a hot-water loop off a new steam boiler. This automatically "zones" the system, and since it's a separate zone you don't have to use the same type of radiation.



Here's a pic of one we did. The loop was already there when we replaced the boiler, but we added the proper piping and controls to make it work right.

djthx

Sizing a Hot Water Boiler

It's for my one story 860 sq ft home.  I've insulated the walls, added 30 R insulation to the attic (total of 49 R), and the basement will become a heated space.  I've done the heat loss calculation (on a room by room basis and by whole house), and it comes out to 18,000 BTU/H (21,600 when you add the 20% safety factor). 



The current radiator's EDR are 273 sq ft, which results in 40,950 BTU/H of hot water radiation.  Clearly, the radiators capacity is enough to heat my small home.  The basement will need another 19,500 BTU/H (including the added 20%). 



When sizing a hot water boiler, should I just go by the total heat loss load of about 41,000 BTU/H?  Or should I get a boiler that will match the current radiators capacity of about 47,100 BTU/H (including the .15 pickup factor) and add the capacity of the baseboard radiators that I will be installing in the basement?



BTW, I did read Dan's article on converting the system from steam to hot water.



Thanks

Jamie Hall

Good luck to it.

I have to admit that I would use Steamhead's approach.  This type of conversion has been a rather hot topic on the Wall, off an on for years, and while it appears that some people have had quite good success with the conversion, others have had truly catastrophic experiences.  I myself have always said "it depends"; I have to admit that in your situation, I would assuredly go his route, rather than trying to convert something which works and works well.  However.  That is very much your choice; you are, after all, the owner and somebody's client.



That said, you should be able to use the actual heat loss in sizing the new hot water boiler.  You will be able to run the radiators at a much lower temperature, which will automatically reduce their output to more like what is required.  However, if you do that, you will have to use proportionaly more radiation in the basement, to compensate for the low temperature.  Conversely, you could size the boiler larger, and run the circulators less often, and size the baseboard in the basement for the higher temperature.



As I say, I wouldn't do it that way, and would not take the job on that basis, but it's your choice.

Charlie from wmass

If we can not talk you to stick with steam.

Then at least make sure your pipe choice has an oxygen barrier. Also a dirt separator would be good as those old cast iron radiators will be happy to paint the inside of your new boiler really quick. Are you going with a Mod-Con? Some require separation, like brazed plate heat exchangers or other device when cast iron is used as radiation. 

djthx

Dollars and Sense.

Thanks for your input.



Thanks to Dan's book, I had my old Thatcher Red King boiler operating as best as possible.  However, I always felt I was paying too much for heat.  After doing the heat loss calcs, I realize I was right.  My radiator's EDR of 283 sq ft translates into 90,000 BTU/H (including the .33 pickup factor).  My boiler's specs tag is missing, but I have to assume that it's also oversized and inefficient.  Say I get an efficient .90 steam boiler.  I'm still going to be paying 100,000 BTU/H to heat my 90,000 BTU/H radiators to heat my home which only requires about 22,000 BTU/H (as per heat calcs).  



We all understand that you need to figure out your radiator's EDR before sizing a replacement steam boiler.  But since your investing in a new unit, shouldn't you first do a heat loss calc first to "determine" (confirm) whether the radiators are ovesized.  And if they are oversized, shouldn't you considering replacing or reducing their size?  And if you're considering replacing the oversized radiators and boiler, shouldn't you also consider replacing not just the system, but also the system type?



As previously mentioned, I'm finishing my basement, and it will need heat.  I also plan on adding a second story to my home.  As much as I'm nostalgic about steam heat, right now I'm more concerned about dollars and sense.  And in my case, steam heat just doesn't make sense.

djthx

Hot Water Radiators

Thanks for your suggestions Charlie.



Does the oxygen barrier prevent corrosion in the radiators and/or the boiler itself?  How is copper used for hot water radiation (if it doesn't contain an oxygen barrier)?  And by suggesting pipe with an oxygen barrier, does this mean that you're allowed to use PEX with hot water radiators (supply and return)?  

I do plan to use a dirt/air separator. 



I am considering a modulating unit, and was unaware that some required separation.  I'll look into that.  Do even new cast iron radiators require separation if I go with a Mod-Con?  What other type of hot water radiators are there?



At this point, I'm thinking about reducing the size of my radiators.  I can rearrange them so they can better match their radiation requirement (as per their heat loss calcs), and mechanically reduce the leftover, oversized ones.  And if I can't take apart and reduce the oversized radiators, then I'll consider replacing them.

Steamhead

Couple of things

First, you're right about that Red King- it's an oil company's dream. Even the smallest size, rated 300 square feet steam, had a firing rate of 1.20 GPH! OK, that was with an old-style burner- with a modern flame-retention burner you'd fire it at 1 GPH, but that's still outrageous. No wonder your fuel consumption is so high.



For comparison, the Smith 8-S-3 at the lower of its two firing rates needs 0.75 GPH for a rating of 283 square feet steam, and the Burnham MegaSteam 288 (my favorite for oil firing) gets a 288 square foot rating from the same input. That would be a 25% reduction right off the top, by simply replacing the boiler with a modern steamer.



BTW, the pickup factor is included in the boiler's rating, no need to add it again. Either of those two boilers I mentioned will handle your radiation (and a hot-water loop) with no problem as long as the pipes are insulated and the mains are vented properly. The Smith can also be had with a power gas burner, as shown in the photo.



And if you're thinking of reducing the amount of your radiation, you can make it even smaller if you stay with steam.

djthx

Still doing my Homework

First of all, I want to thank you for your time and input. 



I forgot to mention that the my Red King was (somewhere down the line) converted to a gas-fired boiler.  But it still is, in my opinion, way oversized.  Do they make mod-con steam boilers?  If so, are there any ones you can recommend?  What conventional steam boiler would you recommend for my situation?  Have you ever reduced the amount of radition?  Is it something that's regularly done; do you recommend it?  How do I figure out how much I can safely reduce it to?



If I go with the loop, aside from the pipe, what adapters are required?



I still have not ruled out hot water heating.  But if I do the conversion, I'll probably design a new system from scratch. (The more I learn about converting the steam to hot water radiators, the more reluctant I get about doing it.)     

Steamhead

Use either the Smith G-8

which is pictured in my above post (8 series with gas burner = G-8), or a Slant/Fin Intrepid with gas burner as pictured below. Both will give better thermal efficiency (before AFUE is even calculated) then the typical atmospheric gas boiler by 6-7%. These are the only two residential wet-base boiler lines whose manufacturers have approved their use with gas as well as oil burners.



For your house, the G-8 is the better choice, since it's offered in a smaller size.



90%+ IS possible on steam, but American boiler makers haven't come out with anything yet.



Size the radiation to the heat loss of each room.

MikeDaugherty

re-assembling cast iron radiators

i have some corto style radiators that were leaking. so we took them apart to change out gaskets between each section. we used o rings over top of reverse thread nipples. does anyone know or have some suggestions as to a better sealing method. the o rings would tear creating leaks. thank you. these were originally steam and were switched to hot water these have five tubes. does anyone know or may have some old radiators that they could direct me toward. i could really use some help with this. thank you