Gas Boiler Decision: Mod/Con vs. Standard Eff.

[Jersey]

Hi- First, I wanted to thank all the professionals for posting on this forum. I have learned more from this site/posts in the last week than I have in the past several months of searching for the right solution for my situation.

Problem: I am replacing a 25-year old oil boiler with a natural gas boiler. I continue to see different posts going back and forth for utilizing mod/con vs. standard eff. boilers with copper baseboard (aluminum radiators). I have a 3000 sq.ft. 25-year old house (~R-13 insulation) in Northern NJ (6428 Heating Degree Days). The contractor is performing a heat loss analysis however wont get it back for a week. Currently, my system temps average 190 degree (output) and 145 degree (return) with fall outside temps (60 degrees) don’t have colder temps yet! RARELY utilize 1st and 3rd zones as we utilize wood burner heavily on cold winter days.

My system will be 4 zone. 1 for each level of the home and an indirect domestic tank.

Questions:
1) ModCon or standard boiler? Why?
2) Any Brand specifics? I have seen all listed in forum but many contractors in area are WM lovers.
3) Only 2 people live in the house utilizing little domestic hot water- any reason not to put in 30 gal or smaller indirect tank?

I really appreciate any advice or thoughts.

[DesMech]

Hi- First, I wanted to thank all the professionals for posting on this forum. I have learned more from this site/posts in the last week than I have in the past several months of searching for the right solution for my situation.

Problem: I am replacing a 25-year old oil boiler with a natural gas boiler. I continue to see different posts going back and forth for utilizing mod/con vs. standard eff. boilers with copper baseboard (aluminum radiators). I have a 3000 sq.ft. 25-year old house (~R-13 insulation) in Northern NJ (6428 Heating Degree Days). The contractor is performing a heat loss analysis however wont get it back for a week. Currently, my system temps average 190 degree (output) and 145 degree (return) with fall outside temps (60 degrees) don’t have colder temps yet! RARELY utilize 1st and 3rd zones as we utilize wood burner heavily on cold winter days.

My system will be 4 zone. 1 for each level of the home and an indirect domestic tank.

Questions:
1) ModCon or standard boiler? Why?
Mod/Con with outdoor reset, it will save money even on copper fin tube.
2) Any Brand specifics? I have seen all listed in forum but many contractors in area are WM lovers.
The W/M Ultra is fine, but go with what ever your contractor is most familiar with.
3) Only 2 people live in the house utilizing little domestic hot water- any reason not to put in 30 gal or smaller indirect tank?
If you aren't filling a whirlpool tub 30 gallons should be plenty with an 80,000 btu boiler.

I really appreciate any advice or thoughts.

Make sure your contractor does an accurate heat loss calc to size your boiler.

[larobj63]

Yeah, I don't get - and have never had anyone explain their side of the story - why some pros think mod/con is not a good match for copper fin.

I think it is perfectly fine! A mod/con boiler with outdoor reset will save you money whether the heat is lost through cast iron radiators or fin tube.

Fin tube is largely convection current, wheras CI radiators are radiation, but lower temp fin tube will still convect, so, again, mod/con will work with either.

Anyhow, I hear good things about Munchkins and Lochinvar Knight boilers.

[beenthere]

WM Ultra's do a great job on copper baseboard systems.

If your leaving water temp is 190, and return water temp is 140.
Either you aren't waiting long enough before checking temps.
Or, there is a problem with your piping, or circulator.

I have several Ultra's on baseboard systems, those customers love them.

[Jersey]

Thanks so much for the information- I think I will go with the W/M just waiting on the heat loss analysis to come back for BTU sizing.

My contractor wants to go with a Burnham Alliance SL 35 gal indirect tank. This is a hydrostone tank which is supposed to be good considering I am in the NorthEast and have acidic water. Any recommendations on tank lining? Also, not impressed with the heat loss rate of .97 degrees an hour on the Burnham, was looking for a little more efficient being that we dont use that much domestic hot water.

[beenthere]

I prefer the WM indirects. Less then ½° loss an hour.

You may be able to wrap the Burnham.

Of course, on a 35 gallon tank, .97° an hour, is only 290 BTUs an hour.
On a ½° an hour, its 144 BTUs an hour.

So adding a R4 wrap would probably get a Burnham close to WM's rating.

[flange]

Mod cons are fine with baseboard, but may need a little tweaking. Cast baseboards and rads heat up slowly, and cool down slowly allowing you to run steady cool water temps in mild weather. Baseboard does just the opposite, so slightly higher temps may be needed to offset the quick cycle. If you went with constant pumpimg and reset water temps to match heat loss it would work well. Your measured temps as stated are either a) you looking at it too soon when the circ start, or b) low flow casued by various things, or C) original design was a bit whacked. The Weil is a great product. I lean toward the Triangle tube, but thats just me. I install whatever the client wants, brand does not matter to me only functionality , features, and likelyhood of being problem free. Dont like callbacks.

[New Home LI]

I have to replace and eletric boiler on a house we just bought
I have a brand new oil burner with no coil - so an indirect tank seems to way to go- I looked at the aliance and the 50 gallon model does have a heat loss rate fo .56 - (according to alaince web site )http://www.burnham.com/PDF/IO/Alliance%20SL.pdf

my concnern is how effeciant over all would this be compared to a seprate oil fired hot water burner ?

[johnsp]

and it's better to keep a boiler running all year long. Much less stand by loss durring the winter, the boiler has to run for heating anyway. The vent for the a gas or oil fired tank is another place that's sucking the heat out of the water and your home.

[beenthere]

Oil fired water heaters have a lot more stand by loss then an indirect.
With all that basement air being drawn through and then heating up teh chimney.