Enough BTU? convert to hydro-air from steam?

3familyowner

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> we have a 3 family brick building in Massachusetts

and



we are our converting our steam system from oil to gas.







we decided on two gas boilers...>



155,000 BTU Weil McLain with 80 gallon indirect Super Store



 for domestic hot water, to heat one first floor zone and for future

basement expansion -



288,000 BTU gas boiler for heating the three floors







The 155,000 BTU Weil McLain is installed.







We are now reviewing our options to heat the 3 floors.







our goals are:



    Direct vent (ie not vent through chimney -avoid lining costs

and chimney repair)



    Using a less expensive gas utility company sponsored boiler



             

Burnham PIN6PV - 175,000 BTU and 454 sq ft steam



             

(it is the highest BTU that can be power vented)



   Using a boiler requiring minimal setup. the next larger boiler 

is the Burnham IN7 (7  sections) which requires additional labor to setup

the sections.



   Meeting the heating requirements to properly heat all 3 floors



   Possibly installing AC



             



sq ft steam **



lst floor   160 sq ft steam 



2nd floor 204 sq ft steam > 2nd & 3rd floor 497 sq ft steam



3rd floor  293 sq ft steam >



total         657 sq ft steam







unfinished basement :1800 sq ft area







**(these figures do not include a 15% heat loss factor which



some contractors add to the total and others don't)







Option 1- use Burnham IN9 280,000 BTU 725 sq ft steam> to heat all three

floors



               

Problem: Increased labor to build 9 sections; chimney vented-repair



                                 

and line chimney; lose option to have AC







Preferred option:



Option 2 - use Burnham PIN6PV 175,000 BTU 454 sq ft steam> to heat 2nd &

 3rd floors. use Weil McLain to heat

first floor (in addition to domestic hot water,



one bedroom zone and future basement (1800 sq ft area))



            

Replace Steam radiators with Hydro Air vents on first floor allowing



             for

A/C in summer and moisturized forced hot air in winter

















 





            

Problem: We are short  43,000 BTU short (497 vs. 454 sq ft steam)













         Questions:



             What

are the options to overcome this deficit of 43,000 BTU?





              Will the

system work harder to overcome the deficit? Is that “ bad” for the boiler





                  i.e.

does that add extra cost  and wear &

tear to the boiler?





              Or

should we shut off some radiators?





              Are

there any other options re: steam heat to heat the 3 family?





              Can we

assume that the 155,000 BTU Weil McLain can heat the first floor (in addition

to domestic hot water, one bedroom zone and future basement (1800 sq ft area))

?





(the IBR net rating is 123 steam MBH; using 240 sq ft btu

that equates to 513,000 sq ft steam)





              Do we

need to add the 15% heat loss factor into sq ft steam calculation?

Steamhead

Don't bother with ductwork

keep the radiators and use a ductless mini-split A/C system. That way you get the best of both worlds. 

nicholas bonham-carter

Using a less expensive gas utility company sponsored boiler

remember that you will often get what you pay for!





when you have a gas company-installed boiler, can you be sure that you are getting a system designed for economy-or excessive consumption?





stick with the steam, by getting another estimate from a real steam pro!







--nbc

jpf321

slantFin Intrepid?

Perhaps you can look at a Slant Fin Intrepid. The 5-section TR-50H has more than enough sq ft EDR capacity at 746. PDF: http://is.gd/gvB7z You may also be able to get by with a TR-40 since 1.33 pickup factor is added to that number (see footnote) .. but pickup-factor only matters while you are bringing all your iron up to steam temp, then it is bonus capacity. A knockdown TR-40 is resonably priced @ simplyplumbing.com (http://is.gd/gw7Ii) but this is less burner and LWCO but since you are firing gas, you would want it less burner anyhow. I know that you can gas fire on Intrepids, not sure about direct vent at this size.



Perhaps the labor/equipment savings on this unit would vs. the Burnham would allow budget to repair/line the chimney.



Maybe Steamhead or Boilerpro will have a comment. Something to think about though.

3familyowner

thanks for response-what about sizing of new boiler?

We are short  43,000 BTU short (497 vs. 454 sq ft steam)



























         Questions:







             What



are the options to overcome this deficit of 43,000 BTU?











              Will the



system work harder to overcome the deficit? Is that “ bad” for the

boiler











                  i.e.



does that add extra cost  and wear &



tear to the boiler?











              Or



should we shut off some radiators?

jpf321

TRVs may....

.. be your answer .. do you have 1-pipe or 2-pipe system? As TRVs close (meaning the room is at the desired TRV temp setting), you are shedding connected load. But then you may run into the problem that Rod alluded to in a recent thread, whereby your boiler is now oversized. TRVs are likely one of the cheapest options ..



Another option would be to better seal the envelope, insulate, caulk, new windows, etc. Then it could be the case that the rads themselves are oversized to the space due to less heat loss. If you find that you reach desired temp in a space and your rads are now only heated 2/3rds across, then rad is oversized by 1/3rd and a new EDR can be calculated.. BUT you have to figure this on design day (typically the coldest expected day(s) of the year for your location)



There are other threads and off-wall (http://www.heatinghelp.com/resources) articles specifically addressing ways to deal with an undersized boiler. There is also a topic which I'm not qualified to speak about called "overfiring" your boiler (basically giving it more fire than it is rated for). More often, people have oversized boilers which they would like to "downfire" (provide less fire heat to).



But to answer your question, I think that TRVs may be your most economical bet since by closing they are eliminating load. Perhaps you only need to install a TRV on a couple of rads to eliminate the equivalent of your 43K (180sq ft) load deficit.

jpf321

whoa .. hold on ..

how are you arriving at the figure of 43K BTU deficit? you mention 497 vs 454 sq ft which happens to = 43. are you getting 43,000 from a sqft difference of 43?



43,000 BTU / 240BTU/SF = 179 sq ft difference

43sq ft * 240BTU/SF = only 10,320 BTU difference not 43,000



240BTU = the number of BTUs that 1 sq ft of EDR produces for steam at 1PSI (215degF). At least that's what I'm told.

jpf321

you also mention

you also mention that 123MBH = 513,000 sq ft of steam .. this is incorrect it is rather 513sq ft of EDR NOT 513,000. You have noted alot of numerical information, but I fear that you are confusing things a bit. You may need to sit down and re-work your design based on 123MBH = 513sf EDR. and 43,000BTU = 179sq ft EDR

jpf321

i stand corrected ....

You cannot convert reliably from Boiler Spec BTU to SQ FT of steam. Because vessel volume matters ... and different brands have different vessel volumes.



Consider for a moment that your vessel only held 1 cup of water .. you could heat it with 2million BTUS but you would never get more than a cup's worth of steam sq footage.



As I said at the outset, once you stray from that single column on the boiler spec sheet "STEAM SQ FT" things get very confusing. It's best to work with only that column and if you feel that pickup factor is a substantial issue, leave a little bit of steam spec'd sq ft extra.

3familyowner

jfp321 -thanks. I made a few errors.

I have a one pipe system.



I am not familiar with terms TRV & EDR..please explain

Is the TRV a special type of adjustable air vent?



re: we are short 43 sq ft of steam .not BTU you are correct



re: 123MBH output = 513 sq ft of steam;  you are correct again



question:

Is the deficit of 43 sq ft of steam (or 10,320 BTU) significant

enough to dissuade me from this solution or will

the boiler have to work harder ( and cost more

in energy and repairs) ?



question:

what are the pros & cons of having 2 smaller PV boilers vs

one large chimney vented boiler?

(besides the obvious venting and easy of installation issues)

is it difficult to coordinate 2 boilers to support three apts?

the heating contractor seemed to frown at this option.

jpf321

a few things ..

TRV - thermostatic radiator valve .. there are numerous posts here about TRVs .. please search for "TRV" "All Time" "All Categories"



EDR - equivalent direct radiation .. simply the same as sq ft of radiation .. sq ft is the units for EDR ..



no, i corrected myself .. 123MBH cannot be changed into sq ft .. steam sq ft from a given boiler is determine in part by vessel size .. i used the example .. imagine you have a 1gallon teapot .. you can heat it with a jet engine (2,000,000,000 btus let's say), you will still only get 1gallon's worth of steam ..



depending on the size of the boiler .. what percentage of the boiler capacity is 43 sq ft? it may be a difference, it may not ..



when the question of installing multiple boilers has come up before .. the recommendation is mostly NO .. there are some cases where it may be warranted .. but from initial system design, no. think of all the troubleshooting, problems, balancing, equipment issues, blowdowns, draining, flushing, skimming that people on here discuss for a single boiler multiply that by 2 and then by 2 again for a complexity factor. if you have the option to do the entire dwelling with a single boiler, I think most people would say do it that way. if there are real practical reasons why 2 boilers would be better, they have to overcome a factor of 4 in terms of problems, equipment repair, complexity etc. i don't think there are many cases where installing a 2nd will EVER pay for itself vs. 1 larger one.