Going from oil to Mod/Con LP...boiler thoughts......


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Old 05-19-11, 05:31 PM
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Going from oil to Mod/Con LP...boiler thoughts......

So ive done a lot of research about this topic...talked to guys in the field....customers of mine who have converted, but still not sure about the boiler. The first one i had in mind was the Embassy Onex combi boiler. Seems to fit the bill, good temp rise on the DHW, straight forward install good price. But now im wondering if going with a Triangle Tube Solo 110 or a GB142 with 40 gallon indrect would be a better choice? Did some math on the comfort calc web site and says i could do ok with a 27 gallon. I will be adding a third zone in the basment to bring to total to 3 zones not including the indrect. Our house is 1400 SQ and 5 years old. Last person said my heat loss is around 67,000btu (this was the guy who wanted to install a EK2000 system). I like that the Onex i can program to only fire to 80,000 or what ever, but im not sure if it will be a wast to heat DHW ondemand as needed or to store it.
Sorry for the long winded post...
Any thoughts would be great!
Ben D
Cost wise the Onex is cheaper as it has a built in boiler circulator, so i would need on the pumps for the zones.
The TT or GB142 run more when you add pumps, controls and a tank.
 
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Old 05-19-11, 08:39 PM
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For propane I would strongly consider one of the down-fired modcons like TT Solo or the new Lochinvar fire-tube design (http://www.knightheatingboiler.com/knight/pdf/WHN.pdf).

Major reason is that propane can produce funkier by-products than NG and having a nominally self-cleaning heat exchanger would help flush things out.

Both the TT and the Knight come with controls.

At 1400 sf and 67,000 BTU/hr and five years old, your house either has a wall missing or you live in the coldest place in the USA. And even then it's still likely you have a wall missing. That heat loss can't be right. Probably half of that if you live in a climate with less than about 7000 heating degree days.

40 gal indirect is fine.
 
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Old 05-20-11, 12:08 AM
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I am sure someone will state it here, that it might be better to stay with oil then going to LP.

Aren't the mod/cons eff ratings based on 140f temps, such as HW, and radiant heating? So what does that advertized 95% eff turn into?

Heating Help

What do you have installed currently in a 5yr old house?

You should have something like these.
Find Oil Boilers & Oil Fired Boilers | Weil-McLain
MPO-IQ Boiler - U.S. Boiler Company - an American manufacturer of Burnham Products including Boilers, Water Heaters, Hydronic Heating Systems, Control Systems, Baseboard Systems and Radiators for Residential Use

But this is kind of cool.

Modulating oil 98% eff with a built in 30 gal DHW tank.

http://www.viessmann.com/com/en/prod...ens_333-F.html

Mike NJ
 
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Old 05-20-11, 09:08 AM
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Our climate shows we have 8000 heating degree days. North west NH. Im probably off on the heat loss, like i said that was the guess from the installer from a heating company..

I currently have a Peerless WBV03 with a tankless DHW coil that is junk. And also (this is a big also) i had converted a mercedes to run on veggie oil.Did this for 200000 miles and had converted my boiler to run on WVO did this for 3 years(bigger chamber, air atomizing nozzle with heater and return loop, ect) long story short this trashed the boiler as a good amount of the exchanger fins fell off inside the chamber. One more thing is i get a $1per gallon break on propane from my useage at our shop. I was hoping to gain space in the basement as well. Lastly i love a good project.
 
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Old 05-20-11, 09:35 AM
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Just a suggestion, it would be better to have a calculated heat loss number rather than a guess from anyone. Actually I'm surprised a heating contractor would give you that low of a number. I'm sure you could calculate your own heat loss and then you wouldn't be surprised down the road.

Bud
 
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Old 05-20-11, 10:41 AM
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Take into a consideration that a smaller output boiler will affect indirect recovery times.
 
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Old 05-20-11, 02:34 PM
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Working on the correct heat loss cacultions. Seems the Embassy Onex is a bit unknow as no one has weighed in on there thoughts about it.....

I know a smaller boiler would mean slower recovery times but i think im to size the boiler to the heat loss..yes?
 
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Old 05-20-11, 04:11 PM
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yes, size boiler to heat loss. use priority on the indirect and as long as your anticipated dump loads are reasonably well met you will be just fine.

useful formula example

lb of water per gal * gal * temp rise = BTU required

8.33 * 40 * 80 = 26,656 BTU

which is to say that for a 40 gallon indirect at an 80F temp rise (say from 50-130F), you need about 27k BTU. A 50k boiler at 85% efficiency (which would be a modcon in high-temp non-condensing mode) puts out about 42.5k, so 27/42.5 = .64 hr or about 40 minutes to recover fully, an entire tank. Roughly. There is still some lost efficiency in the piping, transfer to tank, etc. But that's the ballpark.
 
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Old 05-20-11, 04:13 PM
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I know a smaller boiler would mean slower recovery times but i think im to size the boiler to the heat loss..yes?
It's always going to be a compromise decision because the heat loss of the home is usually less than the ratings on the water heater.
 
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Old 05-20-11, 04:18 PM
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You can also get a larger indirect and keep the water hotter to offset slower recovery times. How far down does the boiler you want modulate?
 
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Old 05-20-11, 04:36 PM
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If the contractor guessed 67,000 you can bet it is less than that. As everyone already stated don't size to the indirect. I also would go to a 27 gallon indirect since you get the same amount of hot water from both. Heating less water is cheaper. I always would like to see less zones not more zones on mod/cons. Make sure the boiler fan speed can be different for heat and hot water.
A benefit to doing heat loss and measuring radiation you can determine the high and low water temps required for the ODR.
 
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Old 05-21-11, 06:42 AM
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The Onex boiler with mod down to 30000btu.If i stick with that boiler then i don't need to worry about an indirect as it has DHW. but the GB142 would be another matter and i think that also has a 5:1 turn down and will mod to 35000BTU. Im planing on adding only one more heating zone to the basement to bring it to a total of 3 if i use the Onex, there would be 4 with a GB142 (4th the indirect)
 
 

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