Boiler size question

MattSwabb

First post here. I’m looking to replace my current boiler with a more efficient and larger unit. Currently I have a Crown Boiler XE-5 sold as a Sears boiler that was installed around 1985.

The boiler data plate says 150,000 input BTU/hour and 124,000 output BTU/hour. Last year we had a service guy come out and gave it a once over. He did a gas pressure adjustment while monitoring the flue gas (the pressure was high). I asked what the efficiency of the boiler was and he looked at his device and gave me a # in the low 80’s. I can’t remember exactly what it was.

The house is 105 years old and was originally a gravity system. Big radiators, lots of windows, 2700 square ft, no insulation. Last 2 winters we had a few days that with the wind and cold the boiler didn’t quite keep up.

We had the same company that did the service give us a quote for a new boiler. I wasn’t home but my wife said he counted the radiator sections and that was it. He came back with:

LAARS Neotherm 105,000 BTU, 96% efficiency.

I don’t think this is big enough. So if I take 80% of my 150,000 BTU I come up with 120,000 BTU. And the LAARS 105,000 x 96% I come up with 100,800 BTU. The salesman says my boiler is running at 55-65% and the service guy says low 80’s. I know I need a little more than I have from the experience the past 2 winters.

Is my thinking right? Or is his?

Here's a pic of the current setup"
http://i492.photobucket.com/albums/rr281/mattswabb/D567FF2F-EA56-4E19-8F37-A7F57B7BEABE_zps5a34ci9f.jpg

Thanks.
Matt

Jamie Hall

Hot water heat... the number you need is the design heat loss of the building. Whoever is specifying the boiler needs to do a complete heat loss for the building! Counting radiator sections isn't that. Nor is guessing from the size of the installed boiler. Nor is basing the number only on the size of the building.

Fortunately, doing the heat loss calculations isn't hard -- there are a number of on line applications or, for that matter, apps that will do it.

Once you have that, then you know how much heat output you need from the boiler. And once you have that, you can figure out the capacity of the radiation you have (this is where counting the sections can be somewhat helpful) and figure out what temperature water you need to have...

Rich_49

55 - 60% sounds about right for that boiler . Sounds as if your service guy just read the AFUE on the boiler plate . Low 80%s would suggest that it is operating as if brand new and set up absolutely perfect .
A room by room heat loss must be performed . Counting the sections of rads will not do , the boiler will be sized to the radiation and leave you no opportunities to use ODR or lower water temps . Find someone who is capable of and willing to perform this work for you .
Counting the sections and finding the EDR should be done but not to size the boiler . It should be done to see how oversized the radiators are and to determine what water temp you can really run through them and heat the house .
Don't know where you are from but another good idea is to have a blower door test performed to determine how leaky it is and determine ACh of the house , with this and a room by room done you can really set it up sweet .

MattSwabb

Thanks for the replies. BTW I'm in Elyria Ohio on the west side of Cleveland.

Any suggestion to a good online heat loss calculator? I looked at a few last year when we first started looking into this but didn't find one that seemed right. I expected this requires inputting a lot of info and measurements and the ones I found were too simple and I didn't trust them.

KC_Jones

Slant fin has a pretty good one on their site that you use on a tablet or smartphone which I found quite convenient since I could enter the data as I walked around the house. Being in Cleveland I suggest you contact this contractor, he does amazing work...one of the best.
https://heatinghelp.com/find-a-contractor/detail/g-w-gill-plumbing-and-heating
http://www.gwgillplumbingandheating.com/

Rich_49

That would be the right phone call to make .

j a_2

A room by room heat loss is nice but not needed to just replace a boiler…By doing a whole house heat loss you will be just fine…You have as you say an old but great gravity system…So one would assume you have cast iron radiators, most likely a wee bit oversized….Me, I would suggest, a nice cast iron boiler, I like peerless…Piped primary/secondary or at min. a boiler bypass…If you decide to chase rebates, and go with wall mount/side wall venting…Save the rebate, you will most likely need it for very near future repairs…and yearly maint…Don’t get hung up on the boiler efficiency thing, just look at the bill, and maybe a meter clocking..Stay way away from briefcase, shirt and tie salesmen…salesmen make a living off of there sale….and as a general rule, are clueless…Check the adds here on this site, and when you do get a proposal, post it but NOT the pricing, as its not allowed…Good luck, and all above is strictly my opinion…Based on 36 years of installing….Dont much care what others say

j a_2

Thanks for the backup.

MattSwabb

I downloaded the slant fin app and over the next few days I'll plug in the measurements for the heat loss calculator. I'll post my results when I'm done.

ja - yes cast iron radiators. So you would suggest a regular cast iron boiler? Not a high efficiency one?

j a_2

In theory, a condensing boiler would work great…However that said my choice for lots of reasons is to stay with the work horse of our heating industry, A nice American made cast iron boiler, piped correctly with a boiler bypass at minimum…Maintained,that baby should last 30 years plus….I know some of the guys here may differ in opinions…But you asked and thats my opinion…And I am sticking with it Good Luck

Paul48

You don't see Laars boilers being recommended here. I don't know why that is. Maybe it is just availability. There are contractors here from all over the country, and I can't recall one ever being recommended.

Abracadabra

Paul48 said:

You don't see Laars boilers being recommended here. I don't know why that is. Maybe it is just availability. There are contractors here from all over the country, and I can't recall one ever being recommended.

I have encountered numerous issues with older Laars MightyTherm boilers. MightyTherm2 look like they've learned a few things with their mistakes with the previous version though. Time will tell though.

MattSwabb

Looking at the slant fin app. should I do room by room or just floor by floor? I've been looking at other calculators and they seem to do a floor by floor approach.

I plan on doing the calculations this weekend and will do a few different calculators and see what the range is.

How do I account for all the exposed pipes in the basement?

Rich_49

Room by room if you're interested in seing what rooms require and how much the installed baseboard can output at what SWT in each . You may be able to use lower temps .

Insulate them .

MattSwabb

It's an unheated basement and I do use it for woodworking projects. I always felt that the exposed pipes took the edge off the cold and also kept the floor less cold. I have given thought to insulating the pipes and using my kerosene space heater when I'm working down there.

Jamie Hall

Watch that kerosene heater. If you are going to use it -- which I do NOT recommend -- you must, absolutely must, have a CO detector in the same space, and never ever leave it unattended.

ChrisJ

I didn't notice any pictures of the radiators.
Can you post some?

MattSwabb

Yes we will have a detector anytime we use the heater. We have 4 in the house. 2 are combo units in the smoke detectors and 2 are plug in ones that monitor over time. One of those caught the bird in the flue pipe a year ago.

Here's a typical radiator. Some are shorter for under the windows.

http://i492.photobucket.com/albums/rr281/mattswabb/West ave/45A1E3E5-D134-497D-9FF2-49346B90FEE7_zpsg9rw5jb4.jpg

Steamhead

Those beauties are "Rococo" radiators, made by American Radiator Co. Output-wise, they're standard column rads.

Paul48

Unless that is metallic paint. Then the output is somewhat less.

bob eck

Get a good heating contractor and have them do a heat loss on the house.
Questions.
With the current system do all radiators get hot?
Do any of the radiators have covers over them? Radiator covers hold a lot of heat back from getting away from the radiator?
Do you use a set back energy saving thermostat? If you do set the temperature back there is a lot of water in your boiler system that the boiler needs to bring back up to temperature to heat the house. This can cost you a lot of $$$$.
I would get a price on a good condensing gas boiler with a fire tube design heat exchanger. Make sure the contractor installs the outdoor reset sensor control. Weil Mclain has this type condensing gas boiler. Price a GV90 Weil Mclain 90% AFUE gas boiler. Burnham has the ES2 that is 85% AFUE. Get a price on all three.

MattSwabb

I did the slant fin calculator tonight. Came up with 116,000 btu's. Since the boiler is located in an unheated basement should I use the IBR rating for boilers? I'll try a few different calculators and see if they agree.

To answer the above the most of the radiators are uncovered. 2 long ones have a window seat over them.

Also we do set the temp back at night from 68 to 66. I've often wondered if that was the smart thing to do.

Jason_13

Use the DOE output on the boiler for sizing when doing a heat loss.. I will assume the cooler feeling last winter may have been more of just uninsulated walls or bad boiler piping , pump sizing or control setting. No bypass will take much longer to heat the home on this type system.
I also agree piping the boiler primary/secondary beit high efficiency or cast iron to control the delta-T on the boiler better. If you choose cast iron with p/s no bypass required if you just valve it and adjust to a 35 - 40f delta-T through the boiler.
Once the heat loss is done calculate the sq. ft. of radiation to be able to calculate system water temperature on your ODR.