New Boiler on gravity system question

gerry gill

seemed to know what he was doing...radiators are measured for steam..heat loss is done for water.

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Russ_9

New Boiler on gravity system questions

I currently have a gravity fed, one story, 8 radiator system. My gas bill for last month was about $250, so I'm looking to upgrade. The house has no insulation in walls, and minimal only around the outside 5 feet in the attic. I plan to blow in more insulation in the very near future.

I got 5 quotes from different local companies. Most were in the 125000BTU - 140000BTU range, with varying efficiencies. One contractor, however, quoted an 80% efficient 105000BTU, and a 93% 90000BTU. These were both Lochinvar, the 93% a Knight.

Is there a reason that these two quotes were so many less BTU than the others? Another contractor quoted a Weil-Mclain Ultra at 150000BTU, and two guys quoted Munchkins at 140000BTU. These are all modulating, yet the Knight was much smaller, why? Bad sizing? Will it hurt the performance/cost more to run a smaller boiler?

Also, is it worth spending more on modulating, condensing boiler with an outdoor reset on a gravity conversion, or should I stick with an 80%-90% standard boiler?

I've attached the prices and models here for some clarity. The fifth guy actually hasn't gotten back to me yet, but he measured nothing when he came, no radiator size or house size, so I wasn't very impressed.

Thanks in advance, sorry for the length.

Wayne_10

Its not gas but its oil check out the new Peerless 93+ effiency steel boiler (144 pass). Last I knew it was in Newhampshire for a year and a half its running at a 97 1/2 effiency. Wow about time!

gerry gill

did anyone actually run

a heat loss analysis? or are they guessing..yes a high efficiency unit will save you big bucks..you'd be nuts these days to not use one..a modulating boiler like the munchkin will help once your house gets insulated..i'd be surprised if an 80,000 btu unit wouldn't work..8 radiators isn't much, so the structure can't be that big.

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Russ_9

1350 sq. ft. in the house.

Contractor 1 measured each room's size and did a heat loss calc. Everyone else measured all radiators, and I assume calculated heat gen.

Floyd

Keep on looking...

unless your house is built worse than most barns.... the Ultra 80 would heat it fine... if the Lochinvar 90 is actually the 93%, and not the way you have it in your spreadsheet.... that is the best quote you have now... but you should be able to do better.

my .02 worth

Floyd

Russ_9

The guy quoted two different Lochinvars, the 93% efficient Knight and a "standard" 84% efficient boiler. The knight was sized at 105000BTU. I guess back to my original question, why is the Weil-Mclain Ultra sized at 150000, while the Knight is sized at 105000? The current boiler has no marks on it whatsoever, and the guy that did the heat loss calc also sized the Munchkin at 140000. This leads me to believe the Knight is undersized at 105000, but I could be wrong. Is this reasonable to assume?

Russ_9

I don't know if keep looking is an option. These 5 companies were pretty much all the big companies in the area. There are still some smaller local guys, but I doubt the smaller installers will be cheaper, could be wrong, and there are like 10 of them. The only real method I have is the Yellow Pages, as I haven't lived here that long. A couple of these guys that I already got quotes from do a lot of commercial work, whether thats good or bad I don't know.

Maybe someone has some recommendations in the Pittsburgh/Wheeling area?

brucewo1b

Contractor #1 did right

Russ_9

From what I read on here, that's what I was thinking as well. However, with exception of #2, everyone else got the same sizes as #1. #2's boilers are both about 40000 BTU smaller.

Floyd_25

Just for reference....

Russ,
Just consider this...my house is well over 4k sq. ft., brick with no insulation anywhere, walls or attic, 1940's windows.
I heat with a Ultra 155 backed down to 100k max., you can do that with the Ultra...I'm in N. Central Pa. and it can get to well below 0... now if your house is 13k+ than the 90-100k range is more than enough to heat you just fine.

I am wondering what your beef is with the smaller Co.'s in your area... I'm a small deal and I know that I would give you a better deal than the big guys every day of the week nad espec. on weekends, but that another .....
You could well find that a small guy will give you a much better job for less money.

Remember here that big is not better.... hang out here awhile and get educated....lots of HO's have learned more here than many heating guys know....

Floyd

Russ_9

I apologize for any slight against smaller installers. It's just like I said, I have no way to know who's reputable, etc. other than the yellow pages, which tells me nothing. Contractor #3 is actually a smaller dealer that's close to my house, and they were no cheaper than the others. Everything I can find seems to only advertise forced air heat, trane, rheem, etc. It seems that all these places do boilers "on the side" or at least not the majority of their business. I have nothing against a smaller installer, they probably do a better job since they have less employees, if not doing the work themselves, but I've seen these other companies doing work around town, so I figured more customers=pretty reliable.

What method would you suggest to find a good installer?

Russ_9

Per your advice, I called all the remaining contractors in the yellow pages. Only 4 even handle boilers, and one guy said "I'm equipped to install them" which tells me he rarely does. All are coming in the next week or so, so I should have even more options at that time. Thanks for your feedback.

Stirling Boston

Maybe I can help

If you let me know where you are located, I may be able to help you find a contractor that would be willing to do a heat loss calculation for you and then bid the boiler based on that.

MIke_Jonas

Condensing boiler on rads?

Why would you spend the money on a condensing boiler when the radiators you have require 160 plus water temp? So you spend the money on the higher efficiency, but will you ever have low enough return water temp to take advantage of the condensing boiler? Doesn't seem like it to me. I know, I know, you can add all sorts of controls to get the return temp down to an acceptable level for a condensing boiler, but it seems like a wrong application to me. I run into this all the time..Homeowner buys a condensing boiler..'cause it's 95 % efficient!!!!, then I find it's hooked up to 180 d fin tube baseboards. So they spent beuacoup dinero and wind up with, what, an 87 % boiler?? I'd ask the contractors how they intend to get that kind of efficiency out of a raditor system, and what kind of supply and return temps they're shootin' for.

Unknown

I guess I disagree

Oversized water radiators are PERFECT for condensing systems.

It's pretty close to what they use in Europe, and it seems to work pretty well.

Noel

Mark Hunt

It's called


outdoor reset and it works GREAT on cast rads.

Those radiators will still provide heat even with low temp water running through them.

I finished an install a few weeks back where we replaced a FHA system with HWBB. The system is designed to keep the house at 70 degrees when the OD temp is -10 using no more than 140 degree water.

The world does not revolve around 180 degree water Mr.Spicoli.

Mark H

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Brad White_152

Mark and Noel nailed that one down.

Firstly, Mr. Spicoli, the radiation was likely sized for the original structure (which will be improved very soon). It is not enough to say that the radiators need 160 degree-plus water without knowing the relationship of radiator surface to actual heat loss.

Even so, if the radiators require 160, 170, 180 degree water on the coldest day, that is but a fraction of the heating season. The rest of the year is savings time with proper outdoor reset.

Secondly: As for fin tube, the Brookhaven National Laboratory (BNL) performed a study a couple of years ago under Dr. Butcher, which deterimined that even fin-tube sized for 180 on a design day would have enough days in the heating season that the return water temperature makes condensing possible hence cost-effective.

Throw in modulation and you are in for real savings.

With this information available to you (even if you doubt it) and you were faced with the decision to replace your own boiler, what would you do?

Mike T., Swampeast MO

Converted gravity systems with standing iron radiators are among the (if not the) best existing systems to fully exploit the advantages of condensing/modulating boilers.

Add TRVs (thermostatic radiator valves) to all the rads and you'll have a new system of such comfort, versatility and efficiency that it will rival any fuel burning system ever available at any cost.

Jimbo_5

TRVs

I like the sound of this. But what if you cannot fit ALL the standing ci rads with TRVs? I have a few rooms, such as the bathroom, where I cannot fit a TRV to the ci baseboard. Some rooms I can install the TRV with a remote sensor, but a few simply don't allow for it. Will this make much difference to the operation of the new Ultra? I've got 7 large ci rads and 3 rooms (20 ft or so) of ci baseboard.

Mike T., Swampeast MO

Shouldn't be too much of a problem if you're just talking about bathrooms with iron b/b. Some sort of valve allowing fixed flow regulation would probably be a good idea--while true metering-type valves are the best, quality full port ball valves are sometimes used.

Some do intentionally leave the TRV off of one radiator and install a thermostat in that room. This creates a "master zone" with all of the rest (with TRVs) becoming slaves. Of course the room without the TRV and with the thermostat should be well-suited to be a master...