basic boiler questions

Bill_101

I wish to add another radiator to my hot water heating system. How do i know how much water to add after it is installed
Thank you

Bryan_24

basic boiler questions

Hello

I’m considering replacing my 40 yr old boiler because a serviceman noted severe corrosion of steel around the firebox. However it is working fine so far and may have many (?) more years left in it.

I was wondering if anyone could help me with a few basic questions. First, what is the best type of boiler for my application, standard or condensing? The current 160k BTU boiler heats a 2500 sq foot home, 3 zones, with baseboard heating units in Colorado. I would like to increase efficiency, but have heard that condensing boilers are more efficient when running lower temperatures than are used in baseboards, is that correct?

Second if a condensing boiler is not going to really boost efficiency enough to justify the cost, what are the pros and cons of cast iron vs copper tube boilers?

Many thanks. Also I have surely left out plenty of other important questions that simply haven’t occurred to me yet so please feel free to make other comments that may help. Thanks!
Bryan

Unknown

do some figuring

first i would do a heat loss calculation to figure out what size boiler you really need, as well as determining if your existing radiation would be a good match with condensing. you would be surprised at how low you can really run baseboard convectors, a lot of times in the old days they would run them wall to wall witch makes it usable sometimes as low as 110 at design conditions!

Slant Fin Baseboard Ratings

Bryan_24

One contractor measured all the baseboards and did a calculation (I'm not sure if it was a full heat loss calculation, since I don't know what that is) and he recommended a smaller boiler, 120K down from 160. So that'll help with efficiencly there.

Unknown

heat loss calculation

a heat loss calculation is a formula either long hand or software based that allows you to determine how much heat is lost from each room in your house. there are many factors that are considered: location/weather, r-value of walls, area of outside walls/roofs, ventilation losses, area of windows/outside doors etc. take the total and thats your heat source size required, take each room loss and use that to size your heat emitter for that area (radiator, baseboard convector, radiant in-floor, whatever)

there is a free program from Slant/Fin: Hydronic Explorer a little confounding for beginners, but sure beats long hand.

KCA_2

Condensing vrs non condensing


Hi Bryan..

I would have thought that you would have received more thoughts on this issue. It is a controversial issue to some extent though. In my thoughts the condensing boiler is better used in a situation where the water demand is at or below 120deg F. In a radiant heating application or possibly in a baseboard application where you would have designed the baseboard to operate at these temperatures at a given outdoor temperature. I would think that a reset control would be the minimum to use in this design. In a situation where you are replacing a boiler within a 40 year old design and aren't initially considering a control to operate it, the non condensing boiler would be a way to go.

Now the question of Cast-iron vrs. copper tube.

Come on guys!! can't we give more opinions than mine?

I've got to run but I'll watch this post and if no one comes on to give an opinion then I'll come back..

:-) KCA


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Phil_17

more reasons

for installing condensing boiler than just the extra possible efficiency. When I had to take out my 100 year old converted boiler because it was damaging my chimney, I chose the condensing type as I could use the old chimney for PVC flue and vent and stop the damage to the mortar. Not a very compelling reason for many, but one that should be broached to your clients with old houses or bad chimneys.

Phil_17

more reasons

for installing condensing boiler than just the extra possible efficiency. When I had to take out my 100 year old converted boiler because it was damaging my chimney, I chose the condensing type as I could use the old chimney for PVC flue and vent and stop the damage to the mortar. Not a very compelling reason for many, but one that should be broached to your clients with old houses or bad chimneys.

PS_2

Assuming you have gas to fuel the boiler - condensing is just the icing on the cake. The boiler's ability to modulate to meet the variations in load is where it's at. IMHO, the modulation aspect gets you the most bang for your buck, and with constant circulation and a dialed in ODR you increase the opportunities to condense.

Allen_8

boiler question

When we put in a Hot Water Boiler eg: Utica 125,000 BTU Model MGB should we put the Taco 007 on return or supply?
Thanks, Allen

KCA_2

Circulator position


Hi Allen;

It's a good practice to install the circulator on the Supply (outlet) side of a boiler. I'm not familiar with the Utica but I pulled it up on the Net and it appears that the boiler comes with a circulator.
The 007 has such a low head that it probably doesn't matter but a higher head circulator could cause problems. The pressure from the circulator adds itself to the working pressure and results in something that could blow off the pressure relief. Other issues exist as well. You might ask the manufacturer but I can't think of a reason. The best book to read for this type of info is Pumping Away.. likely in the bookstore as our host wrote it.

Hope this helps

:-) KCA



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Bryan_24

thank you so far

Thanks everyone for the comments so far. I'll try the heat loss calc this weekend and see if I can determine my BTU requirements.

I mistakenly said earlier that a contractor came up with 120,000 BTU. That should have been 140,000.

Any opinions about the pros and cons of cast iron vs copper tube? I understand iron is more massive, and more stable but requires more time to heat. Is that accurate for a start? Does one work better for baseboard heat? Are there longevity concerns with copper?

RE: a boiler "reset control," do I have this right: its a device for adjusting boiler temp based on the outdoor temp? This generally comes standard with condensing boilers but not conventional?

B

Bill_101

add on

I wish to add another radiator to my hot water heating system. How do i know how much water to add after it is installed
Thank you

Bill_101

add on

I wish to add another radiator to my hot water heating system. How do i know how much water to add after it is installed
Thank you

PS_2

Do More Research

Bryan,

You are correct in that the reset control adjusts HW supply temps using outside air temps as a reference. However, on a standard bang-bang boiler, this can result in short cycling unless a mixing valve is included, and even then - you should include something for boiler protection from too low HW return temps. With a mod-con, no protection is needed and you can reset your HW temps below the standard boiler's limit of ~ 150-160 degF. Again, the ability to modulate your boiler's output to the load (~ how cold it is outside)is where the greatest savings and efficiencies are realized.

Don't be misled by AFUE numbers for standard vs mod-con boilers. It is not an apples to apples comparison, and IMO the mod-con's efficiencies will always be greater, even when it is not condensing. Of course, if you don't have NG or propane - all the pro mod-con arguments are moot.

AFA your existing baseboard emitters, there are several threads here (do a search for baseboard, emitters, etc) that have documented savings and efficencies when mating a mod-con to baseboard systems. Don't give up on the mod-con because of first costs. Remember, you will be paying fuel bills for a long time and the difference in lifecycle costs may surprise you. Constantin provided a pretty good spreadsheet here to help you figure total costs. I will try to find it and post the thread link.