Greening 2 Pipe System

Ironman

@DanHolohan, @Jamie Hall, @Steamhead, @EzzyT and the rest of our steam experts:

We’re bidding on replacing the boiler in a 1929 mansion with a two pipe system that now has 3 motorized zone valves with about 1100-1200 EDR. About 300’ of that is in a ballroom with indirect rads in a crawl space that’s not easy to access, so that’s an estimate for those rads.

What I’d like to do is put TRVs on each standing rad, use a modulating or lo-hi-low gas burner, remove the zone valves, rebuild traps, replace vents and modify the ducting on the indirect rads so they draw conditioned air from the interior using a couple of small blowers.

Does anyone see anything wrong with this approach or anything to watch out for?

DanHolohan

 Your plan sounds good to me. 

Jamie Hall

One advantage of working on a system that size is that you probably can implement a modulating or at least low-high boiler -- at which point almost all of the problems with TRVs on steam disappear at a stroke. Since the boiler is, one might say, automatically right sized!

Be nice if you could find a true linear pressure sensor with say a 0 to 16 ounce range to control a true modulating boiler....

The only thing I'd look out for (other than routine maintenance type things) is making sure that the mains are adequately dripped and vented. I'd prefer crossover traps into dry returns -- since the dry returns have to be generously vented anyway.

Ironman

Some pics:

Ironman

I know that the header is wrong; that will be redone.

delcrossv

Jamie Hall said:

Be nice if you could find a true linear pressure sensor with say a 0 to 16 ounce range to control a true modulating boiler....

Here you go, priced accordingly: Still would need a PLC to convert to mA for the burner.

https://alliedelec.com/m/d/b6b6bd8d2a0003a2ab36a6438f87a166.pdf

EBEBRATT-Ed

Probably only going to find a lo-high fire boiler in that capacity looks like your around 300k

KC_Jones

http://www.midcointernational.com/pdf/8471-91.pdf

Not sure if it's available, but Mark S has a 250 version of that modulating burner on his boiler.

The 500 modulates down to 100.

Steamhead

Staying with oil, or switching to gas?

Ironman

Steamhead said:

Staying with oil, or switching to gas?

LP gas.

mattmia2

There is also the multiple boilers of varying sizes option too although that seems overly complicated for this situation.

nicholas bonham-carter

Matt’s idea is sound with 2 boilers in a tag-team arrangement, controlled by a vaporstat, and a two-stage thermostat.
Maybe a little natural vacuum wouldn’t hurt as well.—NBC

EBEBRATT-Ed

2 boilers is probably a budget breaker.

EBEBRATT-Ed

@Ironman

Peerless SC falls into the range you need. 6 section I think.Has CI push nipples (they do have other boilers with gaskets) available with Beckett, Power Flame, or Midco gas burners with on-off, L-H-O, L-H-L or full modulation.

Available knocked down or assembled

I am sure their are other options like Weil

Ironman

EBEBRATT-Ed said:

@Ironman Peerless SC falls into the range you need. 6 section I think.Has CI push nipples (they do have other boilers with gaskets) available with Beckett, Power Flame, or Midco gas burners with on-off, L-H-O, L-H-L or full modulation. Available knocked down or assembled I am sure their are other options like Weil

Thanks Ed,
that’s exactly one of the boiler/burner options that I have my Peerless distributor and rep looking into already.

Great minds work alike. Unfortunately, so do weak ones. 😂

Ironman

EBEBRATT-Ed said:

2 boilers is probably a budget breaker.

I’m not opposed to the idea of two boilers, we did that with two MegaSteams a few years ago. But my understanding was that unless they fired simultaneously, the water level in one would be off.

Someone help me there, please.

EBEBRATT-Ed

A lot more work and expense.

each boiler has to have a header then both boilers feed a common system header.

Idle boiler will fill with condensed steam off the header so you will need an overflow traps

probably need a boiler feed tank with pumps, pump controls on the boilers

It gets $$$$ quickly

As long as you can get two position firing or modulation i wouldn't consider 2 boilers at 1200 square feet.If you were up around a million input, yeah

pecmsg

Ironman said:

EBEBRATT-Ed said:

2 boilers is probably a budget breaker.

I’m not opposed to the idea of two boilers, we did that with two MegaSteams a few years ago. But my understanding was that unless they fired simultaneously, the water level in one would be off.

Someone help me there, please.

https://forum.heatinghelp.com/discussion/164296/where-is-the-savings-in-twinning-boilers-in-this-house

pecmsg

I also found this:
https://www.pmengineer.com/articles/87639-multiple-boiler-systems

EBEBRATT-Ed

Two boilers is a lot more work and expense. Each boiler needs a header then each boiler feeds a common system header.

The idle boiler will fill with condensate from the steam header. Then you need a boiler feed tank with pumps and overflow traps on the boilers boiler feed pump controls and wiring.

with modulation or two stage firing available I can't see two boilers with steam.

EBEBRATT-Ed

@pecmsg

That article is pretty much written for hot water

dopey27177

Firstly, if the zone valves are correctly sized as well as the radiators in each zone why remove the zone valves? Here you state that the steam traps need to be repaired or replaced. As shown it looks likes that you need to insulate all the steam piping.

What benefit will you get by removing the zone valves and installing TRVs.

In your two pipe steam system the zoned heated spaces must be set to operate at no more than 2 PSIG.
I do not know what the boiler operating pressure is or would be but a vaporstat down stream of the zone valves set to close at 2 psig or less and open at 1/2 PSIG will modulate the steam supply during the heating cycle.

Installing two boilers in a job so small is counter productive.
This is a small mansion and a small boiler as far as many mansions go.
The heating system does not have breast cancer, fix what needs to be fixed don't create a possible nightmare where you will live in this building for an entire winter.

Spell out what you are doing and why in each step especially the need for pipe insulation.

You do not have give the specifications of the new boiler other than it being a cast iron steam boiler with cast iron push nipples, the steam traps by size, the insulation being fiberglass 1" thick.

Jake

jumper

In the seventies boiler trains were operated by a building superintendent or custodian. Both feed and combustion exhaust were manually isolated when not running. I don't remember if they worried about steam getting into off line boilers. I do remember that safety authorities did worry about somebody firing up a boiled with combustion vent dampered.

With two pipe TRV I wonder if conventional traps are necessary? How often does steam close them?

The Steam Whisperer

First thing I'd add is avoid the SC boiler at all costs. All 3 we installed were burning up the natural gas burner heads 1- powerflame mod burner, 1- Midco mod burner and 1- Midco on/off burner. We replaced two of them with WM 80 series. The third we orificed the 2 pipe system it was in and down fired it significantly. Since downfiring, no more burner issues.

I would also orifice the radiators to the current heat load, which is usually about 60% of the radiation size, unless the system was sized using the really old SBI standards. You probably need only about 40% of the radiation capacity if it was sized to SBI. TCutting the boiler size about in half saves about the cost of the orificing work, but give you much better seasonal efficiency. This usually also means you can eliminate all the radiator steam traps.
If the building is maintained at a constant outdoor temperature we have found that direct outdoor reset of the burner works much better than outdoor pressure reset with orifices. Pressure reset requires much too fine of gradation in order to get actual reset of the burner output for most of the season with orifices. TRV's are the icing on the cake.

JUGHNE

Is the ballroom a zone that needs to be maintained with heating or is it maybe a one day a week usage?
Could it just directly piped on it's own boiler?
A little oversized for quick warm up as needed?

Ironman

JUGHNE said:

Is the ballroom a zone that needs to be maintained with heating or is it maybe a one day a week usage? Could it just directly piped on it's own boiler? A little oversized for quick warm up as needed?

It’s definitely a different zone. Repiping it is not an option that I’d wanna consider, nor would another boiler be.

Im already gonna be bidding against a company that doesn’t understand steam or hydronics and wants to convert it to hot water.

If our bid is severely higher (and it obviously will be to some extent), it’s gonna be difficult to convince a HO who knows nothing about this to go with us.

Ironman

Just for everyone’s info: the rads were originally sized for steam and come very close to matching the actual heat loss.

Jamie Hall

Good luck, @Ironman . Perhaps not the best time to remind them either of your signature or... I think it's @Charlie from wmass ? You get what you pay for...

Charlie from wmass

As small of a system as you are talking I would look into installing two separate boilers one large enough to cover 2/3 of the load and the other one around half of the load. And turn the boilers on and off by pressure or by the zones attached to them in series with the vaporstat. Just a thought.