Boiler replacement recommendations

Reply

  #1  
Old 01-02-17, 05:49 AM
Member
Thread Starter
Join Date: Jan 2017
Location: USA
Posts: 7
Received 0 Votes on 0 Posts
Boiler replacement recommendations

I currently have a furnace (gas), rated at 120K BTU, for radiator heat and hot water. This unit is 15 years old and started to have some issues. Maybe it's time for replacing it...

How would I size the new furnace/hot water heater? Should I look for the same BTU rating?

My house is 1,300 sqf ranch style house, with two zone heating. The primary zone has radiators (7), while the secondary has a single baseboard alongside the long wall of the room. The windows had been updated couple years ego with energy efficient ones, installation added to the side of the house around the same time.

Is there a way to calculate the BTU needs for this house, or "the higher is better"...

The replacement unit should have a high efficiency rating and provide hot water as well. What are the brands I should be looking for? Any suggestions would be appreciated...

TIA...
 
Sponsored Links
  #2  
Old 01-02-17, 06:51 AM
Member
Join Date: Jan 2014
Location: USA
Posts: 62
Received 0 Votes on 0 Posts
Others can answer your post because they know more than I. However, you want to say "boiler" and not furnace. Furnace=blown hot air heat. Boiler=hot water heat
 
  #3  
Old 01-02-17, 07:40 AM
poorplmbr's Avatar
Member
Join Date: Feb 2003
Location: long island ,new york
Posts: 296
Received 0 Votes on 0 Posts
"The higher the better" is MOST certainly NOT the way to size you new boiler! There are "rule of thumb" ways to do it and that will give you a rough estimate. Then there are detailed heat loss calculators that are more precise. Just using a rule of thumb, your current boiler is probably more than twice what you need therefore using more fuel that you need to keep your home at a comfortable temperature. The only reason you might want more BTUs is for making hot water. Here is a free heat loss calculator you can use to figure your sizing. Slant/Fin Heat Loss Calculator - Slantfin
 
  #4  
Old 01-02-17, 08:18 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Received 0 Votes on 0 Posts
Bigger is most certainly NOT better. There are a number of programs online to help you calculate the heat loss of your house. The calculation is called a Manual J. One program I've used was hvaccomputer.com

After determining the heat loss, you should determine how much heat you can put into the house via the existing radiators & baseboard. Fin tube baseboard emits about 500 btu/hr/foot.

Oversized equipment not only costs more to buy & install but also more to operate in terms of fuel usage.
 
  #5  
Old 01-02-17, 09:05 AM
Member
Thread Starter
Join Date: Jan 2017
Location: USA
Posts: 7
Received 0 Votes on 0 Posts
Thanks everyone for your advice...

The current boiler/HW unit had been recommended and installed by a local HVAC company 15 years ego. Not knowing much about BTU sizing, etc., in selecting the correct boiler, I've relied on their recommendation. The current TriangleTube Phase III Boiler/HW served us well, even if it is oversize. It replaced a 160K BTU unit that had been converted from oil to gas. We did notice substantial reduction in the heating bill after the replacement.

I'll look into the different heat loss calculators and try to get an estimate for the BTU size. Energy saving is important, especially when it'll impact my wallet in addition to its environmental impact. And I can tell you that at this time, I will ask the HVAC company for their BTU calculation.

There are many different brands of gas boilers available for replacement. Maybe I am looking at them wrong, but most if not all of them are just boilers without providing hot water as well. Due to the space limitation, 4.5'x5' room if you can call it that, I have no room to add a separate water heater.

Can you recommend a relatively small size boiler with hot water heater?
 
  #6  
Old 01-02-17, 11:11 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Received 0 Votes on 0 Posts
Some of the new boilers are quite small & will even hang on the wall. There are also water heaters which are wall hung. A boiler with a domestic coil for hot water is the most energy wasteful creature in captivity since it has to stay hot 24/7/365.
 
  #7  
Old 01-03-17, 06:05 AM
Member
Join Date: Apr 2014
Location: us
Posts: 603
Received 4 Votes on 4 Posts
A boiler with a domestic coil for hot water is the most energy wasteful creature in captivity since it has to stay hot 24/7/365.
Using a boiler with tankless coil during the winter/heating season is better and more efficient than firing directly a water heater. In the summer fire the water heater directly.

In winter I use a small Taco 007 activated with 1 deg F control to circulate tankless coil hot water to maintain tank temperature.

Summer oil consumption is 25 gallons. In the past when boiler was run all summer used 60 gallons.
 
  #8  
Old 01-03-17, 03:11 PM
Member
Thread Starter
Join Date: Jan 2017
Location: USA
Posts: 7
Received 0 Votes on 0 Posts
So, after some research the wall mount combo unit looks promising:

NCB-240E | Navien

The only thing that worries me is the hot water flow rate of 4.5 GPM. That's roughly half the flow rate of the 1/2" copper pipe. That might not provide enough hot water for the house.

Does anyone have/had experience with this Navien unit, did it provide enough hot water?
TIA...
 
  #9  
Old 01-04-17, 09:15 AM
Member
Join Date: Dec 2016
Location: Canada
Posts: 220
Received 0 Votes on 0 Posts
I have a similar sized home, with old style radiators and a couple of radiant floor loops in an addition, with some insulation and modern windows, etc. The btu rating of the original unit seems about right, indeed probably oversized for the needs, but perhaps necessary for the domestic hot water volumes you require. What is more important is for the unit to modulate lower, as too much horsepower and not enough modulation and you end up with short cycling, heat spikes, and such. I have replaced and 17 year old Baxi combi unit with a Baxi Luna Duo-Tec 40GA, it modulates very well which is desirable with the different loop heat requirements, and has more dhw volume than my older unit so I am very pleased with the unit. It is a condensing boiler so you do need a drain for the acidic condensate, your old unit would not have required that. I am not necessarily sold on the condensing technology, but that is the way things are going, indeed non condensing boilers seem to be getting phased out in some markets. I did look at a few other units that modulate, but found the Baxi quality to be good, and they have a large euro installed base so there should be parts for a long time to come. As usual, you need a good installer who will be able to parts and service the unit over time.
 
  #10  
Old 01-04-17, 04:15 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,799
Received 10 Votes on 8 Posts
1300 sq ft you provbably need around 32k btu heat loss. Avg sealed home

A somewhat drafty home would be about 45k btu.

How much money you want to spend?

My advice since you have a small space is to install a wall hung boiler. And with the new found floor space add an indirect. ( But IMO condensation boilers are problematic )

Since your home is as big as mine I have done all the research for if and when I was to change my boiler.

This is what I would do if the mod con route


I would look at the peerless purefire PF 50. It will be plenty for your home IMO.. Max burn 50K btu and modulates down to 16K btu.. Cant beat that IMO. 95% eff.

About $3000

Peerless® PUREFIRE®



0007001 - Peerless 0007001 - PF-50 - 40,000 BTU Output PUREFIRE High Efficiency Residential Boiler (Nat Gas)


Now the best indirect to get best hr rating is IMO to couple with that boiler is a super stor contender..

SSC 35 3 ft height
23" round

http://www.htproducts.com/literature/lp-66.pdf

This unit only needs 50K btu to get the max hr rating. ( About 125 gallons an hour @ 130F)

If you chose any other indirect your HW recovery will be reduced by 1/2 or more.

This can be had for around $800..

Superstor Contender, SSC-35, Glass Lined Indirect Water Heater


You can lower your cost if you get a conventional boiler that will fit in that room with this water heater..

Examples

$1600 for this peerless 50K

0103014 - Peerless 0103014 - MI-03 - 50,000 BTU Output Intermittent Ignition Packaged Residential Water Boiler (Nat Gas)

And since I am cheap I would probably opt for a $1300 new yorker 50K btu.. Because in the end if I get 15 years out of them Ill drop another $2000 to replace and still be ahead..

http://www.supplyhouse.com/New-Yorke...w-LWCO-Nat-Gas


So New yorker and superstor $2000. Find a local guy to install it all.. Maybe $2000 or so ..

$4000 total... wow...

Last..

With cast iron radiators a boiler bypass must be installed.. If the installer dont know what that is find a new guy..
 
  #11  
Old 01-07-17, 05:02 AM
Member
Thread Starter
Join Date: Jan 2017
Location: USA
Posts: 7
Received 0 Votes on 0 Posts
@larosa, flatcrank... Thank you for your suggestions...

The indirect water heater does sound like a good solution. Unfortunately, it would not fit in to the small room with two doors, for backup entrance/exit for the house, not mention the brick chimney (or whatever it's called) in one corner.

The condensing, wall mounted Navien HW heater and separate boiler would cost me roughly $5-6K installed. Both come with 5/10 years warranty, parts and heat exchanger. The Peerless boiler looks good, but its warranty doesn't. It only has one year full warranty for parts, the heat exchanger's full warranty is for seven years. Beyond that, the heat exchanger warranty is pro-rated, pretty much like when you buy tires.

I did research the issue related to condensing boiler. Yeah, you've scared me enough for that...

In a nutshell, the issue is the acidity of the condensed water. The flue gas condensate has a pH level of 2-5, the higher is better, depending on the type of fuel utilized; oil on the low end, while gas is on the high end. Interestingly, the flue gas condensate pH level of 4-5.5 for LG/NG is pretty much the same as rain water.

There are number of neutralizing solution on the market that cost between 20-40 bucks per year for home use. Depending on the state, this solution may even be required by code. Unless I am missing other issues with the condensing boilers, this is pretty much a non-issue for me.

As the matter of fact...

My current NG fired non-condensing boiler has flue gas going out through the brick chimney. Some of it I am certain that will condensate inside the chimney. Most of it condenses on the SS chimney cap and on cold days, it forms icicles. I've seen it many times.

So, the environmental impact of the flue gas, the non-condensing boilers are worse than condensing boilers with neutralizing solution in place it seems...
 
  #12  
Old 01-08-17, 06:52 PM
Member
Join Date: Apr 2014
Location: us
Posts: 603
Received 4 Votes on 4 Posts
How would I size the new furnace/hot water heater? Should I look for the same BTU rating?
Is there a way to calculate the BTU needs for this house, or "the higher is better"...
The best and most accurate way to find heating load for boiler sizing is to collect data on current boiler performance. It is doing the job now so just find out what it is doing. It is real time data, not calculated estimates.

Simply wire an elapsed time clock to primary burner control oil solenoid. For a few days log run time, degrees days and oil consumption. You can use an ordinary 12 hour clock but is has to be check daily.

Using this data there are various ways to find/calculate current boiler BTU output.

To reduce nozzle size on over fired boilers you first must find the number of degree days at design temp. Divide degree/days per hour data into the number of degree days on a design temp day.

If burner is running 25% of the time on design days then pick one runs longer say 35% of time, but leaving a good safety buffer to avoid ending up with a cold house.

Compare stack temps before and after to see improvement in efficiency.
 

Last edited by doughess; 01-08-17 at 07:29 PM.
  #13  
Old 01-12-17, 06:35 PM
Member
Join Date: Jan 2017
Location: USA
Posts: 36
Received 0 Votes on 0 Posts
I have a 1729 sq ft split level with about 450 sq ft unfinished basement 114 ft of old baseboard element from the original 1962 build. The home has a 30 yr old Weil Mclain gas boiler rated for 100k btu. The boiler has developed a small leak either where the press/temp gauge is or just below it from what the tech could see. I have been reading through threads here and know that the current boiler is overkill and that I should be ready to replace it. The house was zoned previously by the shut off valves in the basement and the t stats in different levels, but there are no zones plumbed in anymore. I have had air in the system and finally got rid of that, then the temp/pressure gauge was stuck and I replaced that myself. I wonder if all the times the system was flushed is what caused my leak bc of the fresh water. A few weeks ago it sounded like a thunking noise in my bedroom after the burner got going, but when at the boiler it sounded like a percolator in the back of the boiler. I am looking for size and configuration recommendations. I have a stand alone hw heater that is 9 yrs old and would like to make 3 zones for the 3 levels of the house. It is a 1962 built split level half on a concrete slab that has a supply line run in the slab and half basement. Looking forward to your responses. Thx Steve
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: