Hot Water Zones on a Steam Boiler [Moving thread here from The Main Wall]

brian in e.mass

Hi, I'm a homeowner in Massachusetts.  I need to replace an (out of warranty) oil-fired steam boiler that has an internal coil for domestic hot water and also serves a hot water zone for 24 feet of baseboard heat in the basement.  I haven't decided whether or not to convert to natural gas (that's a separate thread).



The contractors I've worked with have given varying gas proposals on the baseboard loop and domestic hot water solutions.  In particular, having any hydronic loop off of the steam boiler seems to be an issue with some contractors.



One contractor would take the baseboard loop off the boiler ("too much turbulence") and put it on his proposed gas-fired water heater tank (or optionally tankless).  This combination would seem to restrict future replacement choices.



Another would allow the baseboard to stay on the boiler but would opt for a gas-fired tank for the DHW (or go on-demand).  His oil proposal would leave the baseboard loop on the boiler, but use an internal coil combined with a booster tank for the DMH to take one hot water zone off the boiler.



One says there is no problem with the hot water zones on the steam boiler, as long as it is piped correctly, and would keep the baseboard loop on the boiler and install an indirect tank, hence keeping both hot water zones on the boiler.



The main concern seems to be that the hydronic loops (baseboard and indirect water heater) could/would significantly shorten the life span of the boiler.



Are these concerns valid?

What do you recommend?



Should I take the middle approach of keeping the basement baseboard (not heavily used) on the steam boiler and moving the DHW to a gas-fired water tank?



Thanks,

Brian 

brian in e.mass

Looking for Help

Any one agree or disagree with the idea that having hot water zones (terminology?) are inherently harmful to a steam boiler?

Charlie from wmass

Hot water zones when done properly

on a properly installed and sized boiler will not create any additional wear and tear. I seldom see them done properly. Aside from the other guys here on the wall and our own installations I have not seen a hot water zone properly piped off a steam boiler.

brian in e.mass

Thanks Charlie

Ok, so it can be done without harming the performance or life of the steam boiler.



In my case, the hot water zone for the baseboard loop would be used infrequently.  So, if piped correctly, that seems like a good zone to put on the steam boiler.



Presuming the plumber knows how to pipe the hot water zone correctly, what would you recommend on the domestic hot water?  An indirect fired tank, creating a second hot water zone on the steam boiler, or move the DHW off to a separate water heater?

Steve_210

systems

i know theres some good info in the systems section of this site  

Steve_210

found it

its under condensate HW heating

AF

i am trying to do the same

what did you end up doing? im also looking at running some zones off my steam boiler and my plumber says im better off getting a small boiler or tankless hot water tank to run it off- but that will add significant cost to the job

brian in e.mass

not yet

sorry AF, I haven't yet decided.  I've been working on other things while waiting to see if the gas company was going to install a gas line to my house, which provides more options for the hot water than oil.  they just installed it today, so I'm back looking at this.



how did you make out?

brian in e.mass

great article for this topic

Thanks, sprinter, for digging out that article.  I have to admit that when I first read it shortly after you posted, I didn't quite get it.  I'm back to looking at this issue and I think I understand it a bit better, but as a layman, not fully.  It really hits on the issues at hand for me because it talks about a hot water heating zone, indirect hot water, and steam boiler replacement.  Especially interesting to read is how, and when, the pick-up load is available capacity to the hot water zones.  thanks again.



however, I'm still left with my basic question, which I'll post at the end of this thread...

brian in e.mass

Which way to go?

Clearly, the hot water zones can be piped onto the steam boiler.



I'll have the basement baseboard heat piped from the steam boiler as a hot water zone.



But for the domestic hot water...Indirect or separate gas-fired water heater?

(I've already ruled out tankless on-demand)



The feedback here indicates that the indirect hot water could also be piped on the steam boiler, and if piped correctly, it shouldn't harm the overall system.



But just because the DHW can be implemented this way, should it?



Or would it just be better overall to install a separate gas-fired water heater (e.g. 10yr tank)?

Steamhead

Go with the indirect

the SuperStor is the best choice for running off a steam boiler. Here's an example of how to pipe it.

brian in e.mass

Indirect

I like the pics.  I really value your opinion.  I'd just like to understand the reason for picking the indirect over the separate heater.



It is the SuperStor that has been proposed, but at a cost that is more than the combined cost of the 10 yr tank and its first replacement combined.  I think I can deal with the cost difference if I can understand why the indirect is better (in addition to the hot water zone for the baseboard heat in the basement).

brian in e.mass

Why Indirect?

Is the Indirect going to be way more efficient overall?  Should I expect it to pay for itself in a few years (fuel savings vs. installation costs)?



I can see that it must be much more interesting to install, and I should end up with a good system (if piped correctly).



Why should I go Indirect over a separate gas-fired water heater?

Steamhead

Two reasons

1- there is more heat-transfer surface in an indirect than a standard gas-fired WH. This means it can produce much more hot water, much more quickly. Compare the first-hour rating of a SuperStor with the same size standard gas unit and you'll get the idea.



2- An indirect does not have a flue running thru it, so it doesn't cool down nearly as fast. So it uses less fuel when maintaining temperature.



Bottom line is you get more hot water for less energy use with the indirect.

brian in e.mass

Indirect it is!

Steamhead, thank you so much for your explanation and advice.  thanks to Charlie and sprinter for the same.  I appreciate your time and sharing your experiences.



I'm going with the indirect (SuperStor)!