Confused about boiler options

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Old 02-24-16, 05:57 AM
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Confused about boiler options

My oil boiler just went, so I've decided to switch over to propane. I currently have:

2400 square feet
Forced HW baseboard
2 1/2 baths, 4 bedrooms
Well water and Septic
Live in New Hampshire

I have two proposals, one for a Weil-Mclain 97+ 110 and Super Stor 45
the other is Triangle Tube Prestige Excellence 110. I don't know if this is considered a combo since it has a 14 gallon indirect tank in the unit.

Does anyone have experience with these units? The Triangle Tube is coming in at about $1800 less, but I've never used a unit like this, so I'm unsure about the amount of water I'll be getting or potential issues with well water.

Suggestions welcome. Thanks!
 
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Old 02-24-16, 04:02 PM
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Did any of the contractors do a "heat loss" calculation? It's really the first step in this kind of thing, something to have in hand before comparing different brands and types.

See: http://www.doityourself.com/forum/bo...lculators.html
 
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Old 02-24-16, 04:06 PM
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No. Not a single contractor did one.
 
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Old 02-24-16, 04:27 PM
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If you take a little time you can do one yourself. It's good information to have.

After that, you can discuss the numbers with your contractors and have them confirm that the boilers they are recommending are the correct size and type for your application.
 
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Old 02-24-16, 04:42 PM
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Hi Marlet and welcome to the forum.

Not a pro on heating units but following along. While I watch I get to comment . I assume you are switching from oil to propane? How old is the current one and what failed to necessitate replacement? If the old one could hang on until warmer weather you would have more time to shop.
When you or they do a heat loss one of the added benefits is, it will point out where you are losing the most heat and best places to make improvements.

Best, be watching
Bud
 
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Old 02-24-16, 04:52 PM
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If you have oil why are you switching to propane??? Its far more expensive..

Also I like the superstor indirect but why are you looking at condensing boilers?

There are many negatives IMO and being on a well is one of them.. More controls to go wrong too... If you do the math your payback will be a long time to recover... If you ever do..


How many sq ft is the home?
Is the baseboard finned tube?
Whats the make and model of boiler there now?

Lets start here...
 
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Old 02-24-16, 04:58 PM
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Oh sorry lol.. 2400 sq ft...

If the house is not real drafty your looking at 60000 btu boiler more or less..

How many ft of baseboard is in the home? Not the covers but the finned part?

Well water will do more harm IMO to aluminum heat exchangers in the condensing type units unless you really control the PH and hardness...And there is a debate about softneing the water and using these type heat exchangers...
 
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Old 02-24-16, 05:29 PM
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Thanks for the replies. Essentially, my Burnham V83 has sprung a leak. I've been researching these for about three weeks. They said it will likely last the winter, except that it's leaking in the basement, but that's not guaranteed.

I was thought the Weil-McLain and Triangle Tube both had stainless steel heat exchangers. Aren't they more resistant to corrosion? The PH and Hardness of my water isn't bad, but I've been thinking of getting a whole house treatment system down the road.

The baseboard is finned tube, but I'll have to check how many feet there are.

So, in a nutshell, I'm not in a super rush to switch but I'd rather not drag my feet, either. Since I was doing a new install, I thought I might as well look at switching to propane. The biggest reasons for considering propane is the noise of the power vent (no chimney), smell, and horrible hot water supply (which will be fixed no matter which option I choose). Additionally, most of the technicians I've spoken to strongly suggested a switch to propane.
 
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Old 02-25-16, 06:36 AM
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oil / propane

When you're comparing, remember oil contains more BTUs per gallon than propane.
Don't quote me, but I think oil is around 130,000 compared to 92,000 for propane.
Oil prices have dropped dramatically lately, who knows about the future? Also, some say propane units don't require as frequent service compared to oil. Lots to think about. Good luck with your search- Steve
 
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Old 02-25-16, 11:07 AM
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I have 115 feet of baseboard heater, for those that asked.
 
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Old 02-25-16, 02:02 PM
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When sizing a boiler you never want a larger boiler than the amount the radiation can output. On average the baseboard puts out about 600 btu's per ft so 110 x 600 = 66,000 btu's. How about that right about where lawrosa guessed.
With a good heat loss the boiler will normally be smaller than the connected load (radiation). That my friend is why you go to propane or an MPO-IQ rated at 74K output and an indirect water heater.
With that being said remember a high efficiency boiler you can turn it lower to match the heat loss and it will modulate down to much less than that about 60% of the heating system.
As far as service (cleaning) they all need to be checked every year. Maybe not cleaned but the annual service is to also check all the safety's and look for minor problems before they become bigger problems.
One last thing to add about another 15%+ savings look at the US boiler K2-080 (k2boiler.com)with the zone control. You program the zone control to the heat loss of the zones and the boiler never fires above the required btu's per the zone or minimum fire. It adds the zone heat loss up as more than one zone calls and resets the input to the total of the two or more zones. Chances are you will never see the boiler run at maximum input.
 
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Old 02-26-16, 10:42 AM
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rbeck's saying a boiler output should not exceed terminals output ratings is just plain wrong. The opposite is always true. Boiler output should exceed the needs of building heat load and provide a safety factor for contingencies. Having a boiler run 24 hours a day at design temp is too marginal for me. A slight breeze and it will be a cold place.

On very cold days a used boiler output will be less than new rating. Someone is going to have a cold house. There are many ways for things to go wrong that will reduce a system's ability to main satisfactory temperatures. Except for things like fuses and safety links good design always builds in a safety factor. With those added safety comes in using lower ratings.
 
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Old 02-26-16, 04:21 PM
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rbeck's saying a boiler output should not exceed terminals output ratings is just plain wrong. The opposite is always true. Boiler output should exceed the needs of building heat load and provide a safety factor for contingencies. Having a boiler run 24 hours a day at design temp is too marginal for me. A slight breeze and it will be a cold place.
Your opinion taken, but you are mistaken. How long are the design temps in amount of days?
Dont you think if there was a wind and my home was still 68 instead of 70 that it would suffice for the one week or so at design?


On very cold days a used boiler output will be less than new rating. Someone is going to have a cold house.
How cold? Cold for you may be warm for others.. Show us data....

There are many ways for things to go wrong that will reduce a system's ability to main satisfactory temperatures. Except for things like fuses and safety links good design always builds in a safety factor. With those added safety comes in using lower ratings.

Boilers have a 20% fudge factor built in.. Even if you go by DOE youll probably still be oversized..

And consider a whole home heat loss with multiple zones... All zones will rarely be on at once... So in essence you have micro zones. The boiler on design days will more then adequately keep up with these zones...

Remember your sizing a boiler for a 1 or maybe two week period... All other times the boiler will be over-sized...
 

Last edited by lawrosa; 02-26-16 at 05:41 PM.
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Old 02-26-16, 05:28 PM
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Just to add, not that all heat loss calculations are performed in the same way, but they all relate in some way to heating degree days and the HDDs are based upon the inside set temperature. If you reduce the set temperature from 70° to 65° you reduce the heat load by 19%. If the house were to cool to 60° the heat load would drop 35%. Point here is that the self regulating aspect of a house and its heat loss will prevent a properly sized heating system from falling desperately behind.

There's more. Much of that heat loss is based upon the air temperature directly adjacent to the exterior shell. Under extremely cold conditions those surfaces become colder before the interior temps drop. Again, a variable that helps to compensate for cold conditions.

Bud
 
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Old 02-26-16, 06:01 PM
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Oil heats best

A good CAST IRON oil boiler is what I would strongly consider. Suggest a Biasi or Buderus, but both of those require a storage tank (indirect) for hot water....which will add some serious $$ to the install cost.

Your V83 is unfortunately, is/was never a good cast iron oil boiler.....and not representative of what a quality oil boiler can offer.
 
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Old 02-26-16, 06:19 PM
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Since boilers only run a few days a year at design temps why obsess in sizing to match it. Over size it and not worry about unforeseen issues.

If you have ever designed heat exchange systems you know that, to a point, efficiency increases as thru put is lowered. Dropping the firing rate of a burner lowers stack temperature increasing boiler efficiency. Look at any chart of efficiency vs stack temp.

The label on my 60 year old Weil McLain reads 1.80 gph. It is now fired at 0.79 gpm measured. At stack of 350F, minus 70F room, net stack is 280F net. On the Beckett chart that is over 86% efficiency. At outside design temp of zero deg F the burner runs 8 hours/day or 33% of the time. From another prospective that is 3 times the capacity needed at max load conditions.

Even if you want to question some of the numbers the house is warm, cost is low and the wife is happy.
 

Last edited by doughess; 02-26-16 at 08:37 PM.
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Old 02-26-16, 06:40 PM
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Since boilers only run a few days a year at design temps why obsess in sizing to match it. Over size it and not worry about unforeseen issues.
Why? Why have the boiler short cycle its whole life... Explain more why you wiuld oversize... Have you not read all and any technical data regarding this?

At stack of 350F, minus 70F room, net stack is 280F net. On the Beckett chart that is over 86% efficiency.
Ill have to research that but I doubt it... 70 year old boiler is high mass. How many btu to heat all those gallons of water in your system... Tell me your comfort and efficiency in the sholde rmonths....
 
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Old 02-27-16, 09:17 AM
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Short Cycling Is More Efficient!

I have never seen any data supporting the widely held idea to avoid short cycling. There is extensive data showing efficiency declining from start of burner cycle to "steady state" and then decline after that.

Oil burners are not like cars and other systems where frequent starts have negative impacts. The MTBF on burners is influenced more by run time than number of cycles

Condensing systems high efficiency comes from low stack temps. Non-condensing systems are kept at 140F and above to avoid condensation. Look at the data charts, as stack temp decreases from 600F, efficiency goes up as it drops to 300F. Shorter cycles have lower stack temps. There is a bottom or lower limit and aquastat set at 140F takes care of that.

Actually a good place to see this is on a round water heat with central stack pipe. Compared to boilers they are not as efficient heat exchangers and stack temps run higher. Water heater with aquastat a 10F delta T, stack might be between 600F to 700F. Drop delta T to 5F and stack will be between 500F and 600F. Again look at the charts to see increase in efficiency. It might run longer for the same number of btu but at higher efficiency.
 

Last edited by doughess; 02-27-16 at 10:49 AM.
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Old 02-27-16, 10:34 AM
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Non-condensing systems are kept at 140F and above to avoid condensation. Look at the data charts, as stack temp decreases from 600F, efficiency goes up as it drops to 300F. Shorter cycles have lower stack temps. There is a bottom or lower limit and aquastat set at 140F takes care of that.
I dont know... Example..

I am over radiated. I lowered my boiler water temp to 150F last winter. Since my boiler is a 50 year old 85k btu and I have 45 k of radiation. 82 ft baseboard. 60 ft down stairs and 22 ft upstairs. I can geat my home at those boiler temps..

But the boiler fire time is short. the circ basically runs until t stat reaches temp. Comfort level was good with this method. Slow to heat the home but a constant heat output...

Boiler fired many many many times from 150 to 135f per aquastat.. With that said I burned more fuel that year over a comparrison of the years before per my gas bill..

Where stack temps lower? Probably. So IMO my eff went down..


Now I went back to 180f aquastst. Burn times are longer for sure, but because the boiler is oversized I still only get say 3-7 min burn times.. Home heats faster and my fuel usage is lower in this scenario...

With that said when and if it comes time to replace my boiler I will be looking at a 30 k btu boiler for my 1200 sq ft home.. The crown boiler aruba 38k btu would be my choice. Its a doe 32k.

That should heat my homes 33k of radiation on the coldest day of the year down stairs. Adding upstairs that has 12k of radiation make it about 45k.

Even if both zones came on with a doe of 32 trying to heat 45k of radiation im sure the temp will be reduced in the boiler, but being over radiated I can heat my home at the 150-160f water..

From what I know a boiler is most eff when its firing nonstop...



http://www.crownboiler.com/documents...Literature.pdf
 
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Old 02-27-16, 10:49 AM
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I see what you are saying here...

http://www.cleaver-brooks.com/refere...ncy-guide.aspx
 
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Old 02-27-16, 07:11 PM
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The link key part is at end of page 6:

" The lower the stack temperature, the more effective the heat exchanger design, and the higher the fuel-to-steam efficiency."

Put it another way any heated air/gases going up the stack is wasted energy. Since most residential boilers are over sized there is room to cut firing rate lowering the stack temp and increasing efficiency. An easy way find out how much can be lowered is to find out how many hours the burner runs on coldest day.

Wire an elapsed time clock into the burner solenoid. Log the run time, oil consumption and degree days for a week or so.

From that data it is easy to figure degree days per gallon, actual nozzle flow rate, coldest day/design temp boiler run time and determine excess capacity. Then plug in the numbers for a smaller nozzle and see what it does in terms of run time at design temp.
 

Last edited by doughess; 02-27-16 at 07:47 PM.
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