Do I have an over sized steam boiler and under sized radiators for my house?

thisnismine

Hi All, new homeowner here having some issues with the oil steam boiler short cycling.
After doing some research and troubleshooting I think the boiler is over-sized for the home and possibly the radiators are undersized?
The boiler is a Burham Model#: 101341-04 and under NET I=B=R RATINGS, it shows STEAM: 396 Sq. Ft.

This is detached house, 2 stories with a basement. It's about 1,000 sq ft. Insulated roof and basement, plaster walls for the walls. Located in Long Island, NY.

There are 5 radiators in total, they appear to be the Burham slenderized painted in silver. Adding up the steam BTU output numbers, it totals at 30,000 BTU (124.8 EDR) for the radiators. This is a one-pipe system.

I hope I'm providing enough information. Appreciate any insight. Thank you

Fred

Do those radiators do the job of keeping the house temps comfortable? Have you had the system running at design temps (in your area) and did the house maintain temps? Do you see any indications of radiators having been removed? The total of 124.8 EDR does seem light and based on that number, yes the boiler is about 3X the size needed for the connected EDR. The question is: What is the needed Radiation? If the connected radiation does not satisfy the set temps for the house, you may need to do a room by room Heat Loss and determine how much radiation is needed and where.
If the radiators are painted a shinny silver, you may want to paint them a flat color. The metallic paints tend to suppress radiation. You may also want to look into a two stage gas valve, once you determine the needed radiation. Even a two stage gas valve may not allow the boiler to step down to the needed EDR but it will put you closer. I don't think anyone makes a boiler small enough to satisfy a total connected124 EDR.

SeymourCates

@thisnismine

30,000 BTU for a 1000 sq. ft. house is fine. 30 BTU/square foot will easily heat it on the design day unless you're in Alaska.

The boiler is obviously well oversized.

New England SteamWorks

It would be a first if the radiators were under-sized!

An every day occurrence if the boiler is over-sized...

thisnismine

Thanks for the responses!

I have only had the system running for 1 winter and have not calculated the needed radiation per room. The current set-up seems to be getting to the set temps (65-70), but it does take awhile to get up (say 5 degrees) as the boiler short cycles every few minutes.

The radiators are new, the previous sellers changed it out prior to the purchase of the house.

I do plan to do an oil to gas conversion sometime soon. So I've been trying to learn more about the current set-up and learn how to improve it.

So, I should be downsizing the boiler + add two stage gas valve + painting radiators flat color to help with the EDR difference. If there is no boiler to satisfy the connected EDR, then I'm assuming I will still be faced with the short cycling?

KC_Jones

thisnismine said:

get up (say 5 degrees) as the boiler short cycles every few minutes.

Are you doing 5 degree setbacks? Just curious why you need to raise the temperature that much.

thisnismine said:

The radiators are new, the previous sellers changed it out prior to the purchase of the house.

That is a strange thing to do, they are still cast iron correct?
Any idea why they changed the radiators?

Fred

Did the previous owner change them out for baseboard radiators< Did he, by chance leave the old ones stuck in a corner of the basement or garage? (Wishful thinking).
If you are using set-backs, you'd be better off not using them with a boiler that much over sized. The longer the boiler has to run the more short cycles you will experience. Once the house is up to temp, the boiler doesn't have to run to long to reheat all the pipes, rads, and bring the house and everything in it back up to temp.

thisnismine

Yes, I am doing 5 degree set-backs for when I travel a few days for work. (I can stop this) They are still cast iron radiators but they are the slenderized ones, 4 tube - 19 inch high. I believe they did since it left a smaller footprint.

@Fred They did not leave the old radiators. I'm getting the sense that you think I should add some radiators to the current set-up?

KC_Jones

If you are gone for days on end I don't see an issue with 5 degree setback. It's more when people do them on a daily basis that it doesn't always make sense.

Fred

@thisnismine , if the new radiators maintain the temp, especially during a design day, you don't need to add radiators. I was just trying to determine why the previous owner went with a boiler that is 3X what was needed. I know people sometimes just replace a boiler based on what was already there but this one seems excessive. If you can get a two stage gas valve and run it on low fire most of the time, except when you need to recover from a set back and control that, based on pressure settings, you will be much, much closer to matching the connected radiation.

NTL1991

If you want to hang on to oil a bit longer, you could have the burner's nozzle replaced with a smaller one to downfire the boiler a bit. There are limits, though, as downfiring too much can cause your flue gasses to cool to the point of condensing. This would need to be done with a proper combustion analysis. It'll get your boiler somewhat closer to your installed radiation.

Even the smaller version of this boiler, the V8H3S, is rated at 283 sq ft of steam, twice your connected radiation.

thisnismine

Thanks for the suggestions! Think I'm going to convert to gas and downsize the boiler this summer. Called a few installers and they work with Burham, Weil-Mclainn and Williamson.

I've looked up some boilers and I'm leaning towards the Burham IN3. Any thoughts on this boiler for my set-up?

NTL1991

That looks like a good fit for your particular setup. There aren't a lot of options for small amounts of radiation, but that's at least in the ballpark.

If I were you, I'd have that boiler piped with a drop header to keep your steam nice and dry. I'm not sure if the IN3 has two riser tappings, but if so, be sure they use both. This will cut your velocity in half as the steam leaves the boiler and ensures that water isn't carried off into your system.