Convert One Pipe Steam to Hot Water (?)

JC_6

Greetings folks. I'm a long time lurker here, first time poster, not a DIYer, not a professional. Just a homeowner trying to educate himself.

I'm contemplating whether it's "worth it" to convert from steam to hot water. Particulars are:

Relatively recent (maybe 10 years?) natural gas fired boiler
266 mBTU input,
212 mBTU Gross Rating,
I=B=R rating of 663 sq ft EDR (159 mBTU), per label on the boiler.

One pipe steam risers with wet return, beginning at end of the steam main, back to the boiler.

Connected radiation: 570 sq ft EDR, a mix of thin tube standing rads and Burnham recessed units, all CI.

The system is balanced and runs reasonably well, that is until all the rads fill with steam, when not surprizingly the boiler starts to short cycle. This tends to happen only when recovering from setback, or on particularly cold winter days. Steam mains are vented and insulated.

Now the "issues" :

1) Short cycling, as noted above, and the associated wear and tear on controls, components, etc.

2) Though the system is reasonably well balanced, there are 3 rooms that are particularly difficult to heat. The house can be quite warm, but these 3 rooms remain stubbornly chilly. Even though the house is well insulated, one of the 3 can do with better under-slab insulation. I'm hoping this will eliminate the problem there. But insulation in the other two is already maxed out. On a typical winter day (outdoor temp ~32 F), the house would be 68, with one of the problem rooms stubbornly hovering around a steady 62 and the other at either 78 (just when the heating cycle ends), or about 59 (just before the boiler fires again on a heat call from the thermostat). There are double paned windows throughout the house, all air-tight.

3) Above and beyond the waste of fuel that comes from having an oversized boiler, I also get the sense that I'm burning way too much fuel to heat up all that iron during the Fall / Spring shoulder season, just to take the chill off and warm the house by a few degrees.

4) When all the rads are hot all the way across, they begin to softly burble, letting out very small amounts of condensed steam. They don't spit; it's more the sound a baby would make blowing bubbles from his/her mouth. This despite the fact that the boiler is set to cut out at well under 1 lb pressure, and the rads are appropriately pitched.

5) I was spoiled by living some years ago in a house heated with a 1940s era hot water system. All Burnham recessed convectors with a low mass copper fin boiler. The system was silent as the night, and heated the house to a subtle perfection. I never knew winter could feel so good! Now, it seems I'm either chilly or sweating, depending on where the boiler is at in it's cycle, though I've checked and temps never range more than a degree or two (except for the 3 problem rooms noted above).

I've had multiple, well qualified professionals in to assess the burbling rads, and no one seems to have a solution. We've replaced air vents numerous times, with no change. Some of them noticed that the worst offenders were repiped at some point in the past (and the angles of take off from the main don't match other, original steam risers of the same diameter). On other rads, we saw copper pipe rising from the floor, connecting to the steam valve. The boiler itself, by all accounts, has been piped correctly. I didn't want to start ripping into walls to repipe rads until I evaluated all the alternatives.

As for the two chilly rooms, it seems the best idea would be a hot water loop from my boiler. But I'm told my boiler doesn't support that option, so that's out. And apparently the load would be too great for the standalone DHW heater to take on.

_____________________________

If I could wave my magic wand, I'd have a modulating, condensing boiler with outdoor reset hooked up to all my existing rads. I'd have TRVs on all the rads, with no thermostat. This would accomplish another goal which is apparently impossible with steam: the ability to "zone" each room individually. And there would be sufficient radiation for the system to run in condensing mode 90% of the time.

How crazy is this ? I understand it's possible to fish Pex/Al/Pex tubing through walls, but can that even be used to hook up to existing CI rads?

Which kind of emitters are better to use with a condensing boiler - low mass stainless steel or CI ? Can they be mixed ?

Bearing in mind that I haven't had a heat loss calc done yet, would any of you professionals venture a guess at how much fuel I might save by running a system like this vs the steam one I have now? I realize that it would probably take many years to recoup the investment, but for me hot water heat is the ultimate luxury in terms of comfort, so it's far from a question of just dollars and cents.

Any thoughts you have are most appreciated - Thanks!

Steamhead (in transit)

I wouldn't convert it

Those steam distribution problems can be fixed, and you can use TRVs designed for one-pipe steam in rooms you want to keep cooler. If you try to use existing piping or radiation in a conversion, it can leak and damage the house. I've seen this happen and it ain't pretty. Hot-water will run at over 10 times the pressure of steam.

You might be able to tune that boiler so it doesn't short-cycle so much. BTW, is that a Utica PEG-262 or Columbia CEG-262 series boiler?

The burbling sound comes from either badly installed piping, or the oversized boiler could cause this too.

Where are you located? Have you tried the Find a Professional page of this site?



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JC_6

Right on the money -

It's a Utica PEG-262. My initial reaction was to go after the problem rads and repipe them, too. After adding them up, I see it's just short of one third all radiation (by sq ft) is improperly connected.

But by the time I get finished with all the labor expense to repipe them, aren't I already halfway to the labor cost of piping in a completely new system anyhow?

Not to mention that I'd still be left with the same [oversized] boiler.

I have used more than one professional from this site, and they've proven to be as stumped by this situation as I am. Not one seemed to think it worthwhile to repipe the problem rads. I guess I'm just supposed to open windows.

TRVs were also held in low esteem. "They don't work". "Cost alot for no performance". Wanting to see for myself, I was able to find an ISTEC TRV. And guess what? It didn't work. It was just as unable to hold back the steam as the burbling airvents.

Steamhead (in transit)

\"aren't I already

halfway to the labor cost of piping in a completely new system anyhow?"

Not really. Remember in your present system, there is only one pipe to each radiator. With hot-water you would need two pipes to each rad and a completely new set of returns.

Did that TRV have a built-in vacuum breaker? If not, it won't be effective- as the steam condenses inside the rad, it pulls a vacuum that draws more steam into the rad. The vac breaker solves that problem.

Where are you located?

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Unknown

cost a lot and don't work?

Steamhead is right about the trv on steam radaitors, I have installed them and customers are very happy with them as they can control each room temp and seen lower fuel usage. Again, as Steamhead pointed out, the trv must have vaccum breaker which I learned from my first job as this rep didn't know the differnce( he's no longer there). Danfoss have them...