Oversized Boiler and Adding New Radiators

AdmiralYoda

I have a oversized 42 year old Peerless boiler and a one pipe counterflow steam system. I have an EDR or 219 and a capacity of 318 sq. ft. The system runs well and I have no complaints other than it cycles on pressure when it gets colder outside.

I have been spending more time in the basement and the temperature is usually in the 50's. What effect would adding a couple radiators above the water line have on the boiler? If I were to add two radiators with a combined total EDR of 50...would it take more fuel to heat the larger system?

Or, since my system is oversized...do I have spare capacity? My upstairs radiators will still fill with steam at the same rate but I would short cycle less because my system is less oversized and with a warm basement as a bonus?

Thoughts? Thanks!

bburd

You certainly have the boiler capacity to serve additional radiators, but there is no free lunch in physics. You will burn more fuel to keep that basement warmer. The burner will run longer to fill all the radiators before it is turned off by the pressuretrol or satisfies the thermostat. 

EdTheHeaterMan

I have a oversized 42 year old Peerless boiler and a one pipe counterflow steam system. I have an EDR or 219 and a capacity of 318 sq. ft. The system runs well and I have no complaints other than it cycles on pressure when it gets colder outside.

I have been spending more time in the basement and the temperature is usually in the 50's. What effect would adding a couple radiators above the water line have on the boiler? If I were to add two radiators with a combined total EDR of 50...

Then your system would go from 45% oversized to 18% oversized.
Depending on your skill level and knowledge of The Lost Art we speak of herein, you may or may not get noise.

If the boiler operates longer to feed those extra radiators, then the amount of fuel used may increase.
Since the basement is currently 50° then the heat loss between the outside air temperature and the basement is less than it would be in the other case where the basement temperature is 70° compared to the identical outdoor temperature.

So Install the additional radiators, the fuel bill will stay identical because it is the same house with the same heater. It is all in the math.

Italics = Sarcasm

mattmia2

I would suggest you feed fin tube off of a hot water loop. The boiler controls would be more complicated but it could run independently of the steam system so it would heat when it needed heat, not when the rest of the house needed heat, you could only turn it on when you needed it without having to open and close valves and you wouldn't have to hang several hundred pounds of cast iron from the ceiling.

Long Beach Ed

The hot water loop is the way to go. Steam radiators in a basement require specific piping considerations which usually put them up high on the walls. Most folks find that less than ideal.

A hot water loop will give you a separate zone with the benefits outlined by Mattmia2 above. As a separate zone you can operate it only when needed, resulting in a fuel savings over added steam radiation.

ethicalpaul

But a hot water loop isn't going to help your boiler being oversized in the same way that additional steam radiation would.

It will tend to reduce your cycling a little, sometimes, because the boiler will have to heat up the water more than it usually would...sometimes. On cold days I think you'll see almost the exact same cycling as you do now.

Long Beach Ed

Paul is correct, of course. Additional steam radiators should reduce any velocity problems, but piping basement radiators in steam would be difficult, which is why you see so many up on basement ceilings in the old days.

AdmiralYoda

Thanks guys! Just for the record the radiators I was planning were the lighter steel tube type, not heavy cast iron. No they don't radiate nearly as well but they are fairly lightweight. I was planning on mounting them about halfway up the wall with the steam coming from the main two feet above it and the condensate draining to below the water line of the boiler.

But after hearing what you guys have to say it sounds like a hot water loop is much more efficient and probably a lot easier as well. The only scary part is figuring out if I have the tapings for them in my 42 year old boiler and if I feel brave enough to try and crack them open!

mattmia2

You can probably tee it in to some piping that is already connected to the boiler.

ethicalpaul

The ever-helpful article here will show you some tricks for how to pipe it into existing pipes:

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

AdmiralYoda

@ethicalpaul Thank you! That was a great article! I'd probably set it up to provide heat to the zone IF the boiler water temp was above a certain minimum.

Since this is an unfinished basement and the purpose of the zone is to warm me up while I'm tinkering down there, I wouldn't want the boiler to run just to heat the basement if I forgot to turn the thermostat down.

Something like:
If the boiler water temp is greater than 120F (or something reasonable), allow the circulator to turn on. If it is colder than that...I'm not going to get much heat out of the radiators anyways....so stay off.

If my boiler is essentially cold, chances are it is mild enough where my basement isn't that chilly to begin with.

mattmia2

You could put a 12 hour or so wind up timer in series with the thermostat.

AdmiralYoda

Out of curiosity...is there something like a SPDT switch that opens (or closes) at a certain temperature? I imagine it would be like an Aquastat but is in-line with the pipe.

mattmia2

Like a snap disc thermostat?

Long Beach Ed

AdmiralYoda said:

Something like:
If the boiler water temp is greater than 120F (or something reasonable), allow the circulator to turn on. If it is colder than that...I'm not going to get much heat out of the radiators anyways....so stay off.

If my boiler is essentially cold, chances are it is mild enough where my basement isn't that chilly to begin with.

I did exactly that many years ago to heat a basement shop.

And yes, there are clamp-on adjustable aquastats as well as those with probes you can install in a pipe tee. I used to find them cheaply on ebay out of season or remove them from scrap boilers, as they seem to last forever.

gfrbrookline

I have an oversized boiler in similar proportion to yours and was able to overcome the short cycling on pressure by upping the size of my gorton radiator vents and massing out my main vents with big mouths. My system rarely hits 1.2 on the pressure gauge now and my radiators get hot top to bottom left to right.

ethicalpaul

I put an aquastat on mine but I never even wired it up. I set up a smart outlet on my circ pump and I just run it a few times per day at times when we are in the house. Like you said, during the heating season, the boiler is always coming on periodically, so there is always hot water to circulate.

EBEBRATT-Ed

The basement rads on steam will warm the basement and the first floor so will probably use little xtra fuel