Replacement Gas Boiler Size

PurpleThumb

Good Morning!

New To This Forum…Hello All.

I Need A New Gas Boiler For Baseboard Radiators

Home Location: Southern New Jersey

Constructed: 1985

Square Footage: 2400sf, Two Story

Insulation: Good ( 6" Exterior Wall Studs )

Current Boiler: Gas, Original To House

Three Zones: 1 Zone Upstairs, 2 Zones Downstairs ( All With Setback Thermostats )

Manufacturer: Utica Boilers

Name Plate: 125k Input BTU

Total Feet Of Existing Baseboard Radiators ( As Measured ) 116 Feet

Situation:

System Struggles To Maintain 68 Degrees When Outside Temp Falls Below 25 Degrees

System Is losing Water Somewhere, No Signs Of Leakage In House

Could It Be Boiler Leak Going Up The Chimney As Steam?

I Want To Replace The Current Boiler ( 40 ys old, Efficiency Unknown )

With A New 95% Efficient Unit

Questions:

Is The Current Boiler The Correct Size?

What Would Be The Reccomended Size Unit?

Thanks For Reading.

Have A Wonderful Day!

EBEBRATT-Ed

If you want someone good to replace it PM @EzzyT or @clammy

With only 116' of baseboard the boiler is most likely too large.

The winter is over don't rush into this do your research and find the right contractor. The two I listed are among the best.

pecmsg

Why 95%?

You'll only see that when running low water temperatures. Less than 140°F. Your emitters are rated for 180° water.

Your old boiler is probably 85% efficient and lasted over 40 years. The highly efficient won't last 1/2 that!

Ironman

Your Baseboards are only capable of 58k BTUs output. So yes, you’re present boiler is oversized.

The issue of loosing water is very serious and needs to be addressed. Your lack of heat in some areas is probably related to it.

I have to respectfully disagree with the comment about your present boiler being 85% efficient; it’s probably closer to70%. And a new mod/con operate In condensing mode the majority of the heating season when the out door reset is properly setup. You only need 180* water at design temperature (the coldest night of the year).

PurpleThumb

Hello And Thanks For The Replies…

Question..If My Current Ancient Boiler Is Too Large, Can Anyone Explain To Me Why It Won't Keep The House Warm ?

Current Running Water Temp Is 180 Degrees.

I'm Considering 95% To Keep Heating Costs Lower…Am I Wrong?

How Much Boiler Over Capacity Is Considered Too Much?

Best Regards.

pecmsg

@PurpleThumb I'm Considering 95% To Keep Heating Costs Lower…Am I Wrong?

It will only be 95% when running below 140°F water temp. That might be only 10 or 20% of the time! That boiler WILL require a lot more maintenance than a cast iron and there go your savings!

PurpleThumb

Hello Again…

Added Note… Boiler Fires Up About every 20 Minutes On Cold Days ( Less Than 25 Derees ).

Is This Normal?

And won't warm the house above 65 degrees.

Thanks & Regards.

PurpleThumb

Hello..

I'm Wondering Why High Efficieny Boilers Require More Maintenance.

( Sorry For The Ignorance )

mattmia2

an ancient boiler would be like 1940. 1985 isn't all that old for a cast iron boiler. no reason to replace it if it isn't leaking. hot water boilers will leak liquid water if they have a significant leak.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1854634#Comment_1854634

hard to say, either the baseboard is undersized or some of it isn't heating for some reason. the boiler can't put any more heat in the house than the baseboard can output. your boiler is trying to put about 2/3 more heat in to the baseboard than it can output.

PurpleThumb

It's losing Water Somewhere… There Is No Auto Feed Replenisher, And I Have To Add Water Every Other Day

To Keep It Near 20 PSI Hot Temperature Pressure.

PurpleThumb

Thanks For The Reply…

Maybe The Original Installer Did'nt Install Enough Baseboard?

mattmia2

is there water coming out the relief valve? that amount of water should be visible as a liquid somewhere

Mad Dog_2

They are alot more complex & finicky…require much more attention & annual maintenance. Mad Dog

PurpleThumb

Hello…

Bucket Under The Relief Valve… Dry.

After Filling & Bleedng The System, Runs Quiet For 24 Hours Then Starts Major Gurgling Upstairs.

Removed Every Baseboard Cover And Checked For Moisture… None.

Regards & Thanks.

mattmia2

Does it have a bladder type expansion tank or a conventional compression tank?

Some amount of air will come out of the fresh water but if you are removing that air when you add water that should stop after a couple weeks or less. Is there any buried piping that goes around a door or something?

PurpleThumb

Hello…

New Bladder Expanrion Tank Charged To 20 psi

Regards & Thanks

PurpleThumb

Hello…

No Sign Of Leaking Water Anywhere…

Tested The Relief Valve… Working OK.

Regards & Thanks

hot_rod

2400 sq ft with 58,000 btu/hr of fin tube may not be enough. If it has always struggled, it is probably undersized. Are the fins clean, installed facing up?

Any upgrades you can make to the structure will reduce the load, reduce fuel costs. Insulation, weather strip, window shades, etc.

If you boiler short cycles from being oversized, it could be running 70% or less efficient.

Just the modulating feature of a mod con will help lower fuel consumption even at 85%

How long do you plan on living there?

Build a graph like this from online temperature data for your area. It will show how many days you need 180 SWT

EBEBRATT-Ed

I agree that it is possible the house is lacking baseboard. My house was 1000 sq feet with 90 feet of BB and a boiler and heat loss of around 50K

But that house was pretty leaky with block/stone and no wall insulation.

I would guess a HL of 80k and more baseboard is needed.

But @PurpleThumb the water loss and a heat loss needs to be addressed by a professional someone like I posted above

EzzyT

@PurpleThumb I can reached at 2018878856

PurpleThumb

Hello…

Is Cycling Three Times An Hour Considered "Short Cycling" ?

Heat Fins Are Clean.

All Windows Double Glazed & Tight.

R-38 Insulation In Attic.

Wife & I Plan To Stay Here 20 Years More ( Last Home We Will Own ).

Regards & Thanks.

mattmia2

3 cycles in an hour is not short cycling if the burner is actually firing the whole time there is a call for heat. Get ezzyt to look at it, he is one of the best.

MikeL_2

The continuous addition of fresh water will add heating cycles & contribute to air in the system.

Is there at least 1.5" clearance from the bottom of the baseboard front cover to the finished flooring? Is the baseboard damper fully open?

Adding to the existing baseboard will allow lower swt and perhaps you can gain the full benefit of a modulating condensing boiler.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1854674#Comment_1854674

Ideally it runs for 10 minutes anytime it fires. This allows the firebox and flue to dry opt and the return temperature should be at or above 130°‡

With that size boiler, and low mass fin tube I assume it heats up quickly? On a mild day I would bet it only fires for a few minutes?

If the system has multiple zones, modulating boiler is an ideal fit.

ALL boilers should have periodic maintenance, mod cons can run several years between clean and checks.

PurpleThumb

Thanks!

tcassano87

chiming in late here but do you have pictures of your boiler and system you can post?