To replace ageing steam OIL boiler for steam GAS??

patrykrebisz · May 6

My ageing steam OIL boiler (which i have patched up with some steel plates last summer) is on its last legs. I'm considering to switch to GAS.

» I know the oil is more efficient.
» I have steel liner in my chimney already.
» Since my current gas is only heating up 50 gallon hot water tank, i should "I think" have enough margin for gas boiler.

I know my current boiler Burnham V8h5 (that delivers 512 sq ft of steam) is way oversized for my 2000ft house. (on 10F cold days, it was 15min on and 15min off). I'm thinking of swapping to something along 300 sq ft of steam (maybe SteamMax 125 or 150).

Now my question, how do i confirm if my gas company can deliver adequate supply? What other factors should i be considering? I'm very familiar with steam and oil but know very little about gas. (I'll be rouging in the boiler and the steam piping but will have licenses plumber connect the gas.)

pecmsg · May 6

1St get the proper size specs for the boiler. All radiators need to be measured and there EDR calculated.

Then choose a boiler closest to that EDR and look up the gas requirements.

Then contact the gas company and ask them.

Don't be surprised you if need a new meter and gas piping!

Steamhead · May 6

First off, we need to know how much radiator capacity you have. That's how we size steam boilers.

To switch to gas, you need to know what size boiler you need (see above) then see if the existing gas service line and meter will handle the load. Typically, gas suppliers will only talk to licensed gasfitters about this. And there may be a fee if upgrades are needed.

Where are you located? We might know someone who can help…………………

patrykrebisz · May 6

If we know that my current boiler is capable of 512sq ft and on a very cold (10F day) it is on 15 min and off 15 min (and keeping house nicely at 73F), why do we need to measure radiators? It i got a boiler half-that size it would be on 100% of time on the 10F day and still keep the house warm. Am i correct in my reasoning?

mattmia2 · May 6

is this one pipe or 2 pipe? one pipe will be very difficult to balance if you aren't making enough steam to come close to filling the whole system with steam.

there could be other reasons that your boiler is short cycling other than it being much larger than the system so the first step is to calculated the edr of the connected radiation.

ethicalpaul · May 6

https://forum.heatinghelp.com/discussion/comment/1895935#Comment_1895935

I don't argue with your reasoning, but measuring radiators is quite easy.

I'm one of the few in here who thinks there's no need to buy a boiler to match your oversized radiation (if your radiation is indeed oversized). You can do any balancing you need with venting and/or blankets/enclosures on radiators that get too hot on a long call for heat regardless of venting.

patrykrebisz · May 6

It's 1 pipe system. The system is tuned up to "perfection." (well vented; pressure doesn't raise too quickly; and then drops fast).

I want to get something that produces half-the steam my current boiler is + extra margin. Thus my reasoning is to go after something around 300 sq ft+.

I've done the calculations in the past but simple measuring radiators doesn't seem to make much sense as windows, insulation and few other unaccounted factors play as much role in how warm the space gets.

I don't want the conversation be derailed. i just want to see if i aim to go after 300sq ft steam boiler, is there a way by looking at my current gas pipes if the gas system will sustain the transition?

pecmsg · May 6

it’s not that difficult to take measurements and get the exact EDR that you need.

ethicalpaul · May 6

https://forum.heatinghelp.com/discussion/comment/1895940#Comment_1895940

Yes, there are charts that will tell you how much gas your current service can provide vs how much your appliances need.

But don't worry, your thread will 100% get derailed 😂

pecmsg · May 6

But don't worry, your thread will 100% get derailed
???

Jamie Hall · May 6

https://forum.heatinghelp.com/discussion/comment/1895935#Comment_1895935

No. Sorry. That tells me that your overall system — boiler plus radiators — is oversized for your load, but it tells me — and you — exactly nothing about how big a boiler you need to power the radiators.

There is one way, and only one way, to size a steam boiler: match it to the load it is powering — the radiators. As the rest of folks have said, add up the EDR or your radiators and select a boiler with the same EDR rating or, possibly, slightly less — but not more.

You may find, by the way, that in the longer term you may not save anything by switching to gas… and we don't do politics on The Wall.

EBEBRATT-Ed · 1:08AM

@patrykrebisz

As others have mentioned the only way to size the boiler is to measure the radiation.

If you want to downsize after that by reducing the pick-up factor have at it.

guessing is a mistake.

Seems like you mind is made up.

mattmia2 · 1:32AM

the gas pipe sizing in the house will probably be from the tables and method in the code for low pressure gas with 1/2" wc pressure drop. sizing the service will depend on the pressure in the street.

EdTheHeaterMan · 3:26AM

@patrykrebisz said: "I know that my boiler operates 15 minutes ON and 15 minutes OFF, so a boiler with half the energy input is the correct size regardless of any other rule you throw my way.

Now, my question is: how do I confirm whether my gas company can deliver an adequate supply? What other factors should I be considering? I’m very familiar with steam and oil, but I know very little about gas. (I’ll be roughing in the boiler and steam piping, but I’ll have a licensed plumber make the gas connection.)"

Well, I would say that you opened the door to proper sizing with this statement: “What other factors should I be considering?”

I have read several articles related to steam boiler sizing, and there was one in particular that discussed operating a boiler that is smaller than the connected EDR would normally suggest. It explained how the standard “sq. ft. of steam” rating already includes a pickup factor—traditionally about 33%—to account for heating cold piping and system losses.

The article also pointed out that, in some homes where all the steam mains and takeoffs are within the conditioned space, that “loss” is not truly lost heat. It also discussed how a slightly smaller boiler may take longer to recover from a satisfied thermostat condition because it has to warm all the piping more slowly, but that can sometimes improve overall efficiency by reducing short cycling.

As long as you don’t go too far with undersizing, you will probably be fine.

Since the discussion has already "been derailed", how difficult would it be to actually measure your radiators and determine the connected EDR? Once you know the true EDR, the decision becomes much easier.

If I had to guess, I would estimate that your system is probably somewhere around 400 sq. ft. EDR. The person who selected your Burnham V8H5 may have seen that the V8H4 was rated at only 396 sq. ft. of steam and decided to go one size larger to avoid making a mistake. In my opinion, that was a mistake, but back then "Bigger is better" was a "way of life"

If that estimate is correct, you could probably operate successfully with a boiler in the 350–400 sq. ft. steam range. The SteamMax 150 is rated for approximately 388 sq. ft. of steam, while the SteamMax 125 is rated for about 321 sq. ft. steam. Based on your description, I might lean toward recommending the SteamMax 150.

That said, if I were doing the installation as a contractor, I would still measure the existing radiator EDR myself just for my own confidence and verification.

Another point often made by steam experts is that steam systems must heat all the connected metal before they can effectively heat the space. If a boiler is undersized too much and ends up running for hours on mild days just to build enough steam to slightly warm the house, you may actually use more gas than you would with a properly sized boiler that cycles normally.

So I guess I partially agree with your thinking—but I would still do the homework and verify the actual EDR. You may find that your home truly has less than 400 sq. ft. EDR, and your Burnham oil fired was oversized by a lot.

Just some thoughts from an old fart in a wheelchair, what could he possibly know?

hot_rod · 3:40AM

I can’t imagine that the gas service wouldn’t handle a 150,000 boiler?

What size is the piping at the water heater location. What size does it start out as at the meter?

Numbers on the gas regulator or meter would get you some data.

Start with a call to the gas supplier, the info you need may be in there database.

bburd · 3:56AM

The meter capacity is printed on the nameplate. The connection to the main is probably adequate to supply the full rating of the meter.

The capacity of the piping after the meter will have to be checked, and it may well have to be enlarged between the meter and the boiler if it was not sized with gas fired central heating in mind.

To replace ageing steam OIL boiler for steam GAS??

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