TwinBoiler Schematic

vaporvac

We've finally finished a plan for the boiler install. These are two stage-fired Slantfin Intrepid TR50s paired with two Riello #G400 series .#C8554115 I'm looking for any feedback concerning the feasibility of this schematic and any changes or problems those experienced with their install can see.



This is for a two-pipe Trane VaporVacuum system.  The thinking with this layout is as follows:  with this design there is still only one steam main leading up to

the house supply. It allows us to have the two boilers close together

with the fronts facing.outwards and gives exactly identical

piping over to the main steam line.  We shouldn't need a condensate tank

because the boiler levels will even out because each has its own

condensate return with each boiler having a  Hartford loop and they are

both connected together through the condensate return and the level in

the condensate will even out in the two boilers.This will ensure

the system is a closed one allowing a vacuum to be pulled. With this we won't need a condensate tank or two separate boiler pumps with boiler

float level switches, both which would be difficult to seal and maintain

a vacuum not to mention the increase in cost and complexity.

The discussion on the consensate tank issue can be found here:  <a href="http://www.heatinghelp.com/forum-thread/146003/CondensateTank-Why">http://www.heatinghelp.com/forum-thread/146003/CondensateTank-Why</a>

The discussion of SFs piping diagrams as well as the diagrams themselves can be found here:

<a href="http://www.heatinghelp.com/forum-thread/146002/Drop-Header-Which-way-to-Go">http://www.heatinghelp.com/forum-thread/146002/Drop-Header-Which-way-to-Go</a>



I hope someone replies to this. I know it's late in the heating system, but we'll be working on this over the summer. Thank you everyone for the help thus far. Colleen

 

nicholas bonham-carter

twin boilers

would a Gifford loop, be better at keeping the boiler levels under control?--nbc

vaporvac

More research...

Thanks, NBC. I'm researching that today...reading through some old posts with queries from you as well as F. Gifford's site. I'd only associated the Gifford loop with one-pipe systems, but it looks like it can be used for two, as well.



Hopefully, folks can look at all this near boiler piping and compare it to that in my prior post to see what might work best. I have time to get this right . At the moment I'm just try to get good dimensions to pour the new pad.

gerry gill

I dont see any reason

Why what you sketched out shouldn't work just fine.

vaporvac

That's great news!

I'm really happy to hear you think this would work, Gerry. It's a little different from what I've generally seen, but WM had something similar for twinning their boilers.



Any thoughts on NBC's idea on using a Gifford loop vs. a Hartford loop?  I'm still not clear on how it's better, but if it's simpler or space conserving, I'm all for it.



Does it look like this design enables us to eliminate the condensate tank?

Dave in QCA

comments

Colleen,  This is looking pretty good but I have a couple comments.  Regarding the condensate tank, I think you mean the reservoir?  You won't know whether you will need that until you operate the system and see how slow you condensate comes back from the system and whether it causes a drop in your boiler water to the level that more water must be added, that eventually causes the boiler to be flooded when all of the water finally returns.



Regarding the piping, I think you have got this very close, and if you did the drawing.... I am impressed indeed!  The problem that I see is that when looking at this drawing, and you are view the boilers from the back, each boiler has 2 risers, a header and an equalizer.  This is all good.  Then, each boiler has a steam supply the goes up and then drops into a pipe that I'll call the building header.  This head drips down and connects to the return of the boiler on the left.  This will cause the left boiler to over fill over time.  I don't seen any piping that will allow the water level of the boilers to equalize.  It seems to me that the return piping of the left boiler should continue on over to the right boiler, so as to tie them both together.



I'm sure one of the pros, especially Dave Bunnell will jump in and comment on this if I am wrong.



On  a few other notes, I owe you a few emails and hope to catch up soon when I am back home at my own computer.

vaporvac

Piping,Reservoir tank

Just lost everything I wrote! Ok. Thanks all. So I did mean reservoir tank. Will the boiler still flood without an autofeed as I don't plan on having one, at least to begin with? How do I plan for one as in placement and ensuring it feed the boiler evenly?



Can I eliminate the returns coming off the mains since I already have equalizers on each boiler or should I just continue the line to the RH boiler. Concerning the condensate return line...would it be better to for a "T" between the two boiler to ensure they're fed evenly. I'm also just noticing I have the condensate going uphill at the end so I'll have to make sure it's head downhill instead.



Dave, I just thought you'd gone MIA now that the warmer weather is here! Hope this is all making sense. Thank you again.  Colleen

vaporvac

ready to pull the plug...

The new fireproof ceiling has been hung and the concrete pad will be poured on Thursday. Just thought i'd see if anyone had any last minute suggestions or comments concerning the piping diagram attached above, and the thinking leading to it.Se had tried to configure something with the boilers facing away from each other to have only one drop header feed, but couldn't figure out a take-off for the two equalizers or Hloops (although they may go gifford, the jury's still out on that). BTW these are two slantFin tr50s with Riello power gas burners, stage-fired.



Thanks ahead for any comments.

Dave in QCA

Simplification

Colleen, I have been wondering how your project was coming along. Glad to hear from you again!

I have made some edits to your drawing as a suggestion to simplify the piping. Also, I think when you compare it to the Slantin documents you will find that it is consistent with their recommendations.

vaporvac

Thank you, Dave!

A much too belated THANKs for that schematic. It really got us thinking in a new direction as I didn't realize each boiler didn't need its own equalizer. I've sent your drawing with some changes to SF for approval. We have to reorientate the boilers as there wasn't enough space for servicing them in the original plan. No biggie and will make it much nicer to access. Consequently, we'll be dropping the heading in the other direction OVER the boiler. At least we hadn't poured the pad.

SF is good in the tech dept, but it would have been nice if the piping diagrams for stage-fired boilers were a bit more explicit and easily found without have to fish around. Some diagrams aren't even on the site and nothing comes with the boilers. Probably the pros know their way around the system, but trying to design one is no cake walk. I guess that's why they're call PROs.

vaporvac

latest schematic, and hopefully last...

So after fiddling around with sizes we've changed a few things around using Dave's schematic as the base. SF liked that one and said it would allow for a stable water line. Thanks again, Dave..

These new ones have a few advantages and look more similar to SFs designs. Does anyone see any problems with either one? We're a little perplexed as to where to put the king valves to allow draining/cleaning so that's not set in stone. I'm also attaching a little scale drawing so you can see approximately where this fits into the scheme of the boiler room. 1sp=3".

The risers are 3" dropping into a 3 or maybe 4" header. I have lots of 4" ipe from the old install. We wont pipe down the equalizer until further down than shown. Thanks all for taking a look at this. Hopefully SF approves as well. Colleen

Dave in QCA

looks good

Colleen, the drawing both look good to me.

vaporvac

45degs

Thanks Mark. That's something i wouldn't have thought about. Just to be clear the drop is at SF's suggested 45deg angle, but it should work the same. I'm pondering the isolation valve...we just didn't want to screw with the original piping too much and wanted to maintain equal pressures and water lines. p.s. How's the midco working out?

Rod

Isolation Valves

Isolation valves-  Mark's comments got me thinking that if you ever needed to take one of the boilers completely off line but still operate the other, you could do so by using each boiler's King valve but would also need a valve on each boiler's individual return line off the common return pipe (see attachment) . As it's very easy to over complicate things by coming up with contingencies for scenarios that are unlikely to happen, the isolation valves may not be needed /desired. I just thought I would mention it in case it might be useful to you.

- Rod

vaporvac

Soon!!!

Thanks for your comments and edits. Good points all and easier to incorporate now than as a retrofit. No date set yet...still trying to get everyone's schedules to jive. It will be a joint project between the pipe-fitting, burner install, venting and controls. I still have to order the vaporstat and Tekmar control mentioned in my other post. That seemed the easiest solution. We're also having the asbestos removed from the old Ideal coal behemoth. It's too near the new boilers to risk bumping into it all the time. Better to do it now than later.



Did we ever get to see a pic of the installed Midco? I wasn't checking in as often over the summer. I have to live that dream vicariously!

Dave in QCA

I didn't mean to recommend

TEKMAR. I have a tekmar in my building and for various reasons it works great. But, it does not give you 2 stage control. if you only have vaporstats to control hi-lo, it will start out on hi an run on hi until you build pressure. So, that means every single cycle will run both boilers. Now, another way to do this, if you have your heart set on the Tekmar is to add a single pole double throw switch into the circuit. I did, because I need it. In the auto position it allows the vaporstat to run the high fire according to it setting. In the LO position, it does not allow hi fire to operate. In the HI position, it hold the burner in high fire as long as it is firing. Of course, it will quickly shut off on the controlling vaporstat.



Colleen, if I was hooking your system up I would do it the way Dave Bunnell did with a 2 stage thermostat. I simple 2 pole double throw switch can be used to switch boiler is lead and which is lag. It would just be wired in the thermostat wiring to reverse the connections with the flip of a switch.



If you leave your thermostat setting alone, the only time the second boiler will run is when one won't keep up. That is the best for efficiency. Of course, if you have the t stat turned down and turn it up, then they would both run in this scenario too, until the temperature is satisfied, then one would shut off.... then eventually the other.

vaporvac

Ooops! Taco, not Tekmar

This is what happens when i rush. Total brain cramp there...this is what I meant to write concerning the controls re: Jstar   He advised using the Vaporstats to control staged pressure, and a two-stage

thermostat coupled with a TACO 2-stage switching relay to control the

boilers. I meant to write TACO , not Tekmar!  Do you think that is a good choice to switch from on boiler to the other?

Eastman

Will steam find its way from

one unit into the other?

Dave in QCA

Lead/Lag

Ha ha ha. I know what you mean. Yes, while I am not familiar with the taco device, Jstar recommended it and he knows what he's doing. (understatement) I am sure it is a package device that allows you to switch which boiler is lead and which is lag.



Perfect!

JStar

TACO

Here's the TACO 2-stage switching relay.



http://www.taco-hvac.com/uploads/FileLibrary/102-418.pdf

vaporvac

Pressure Transmitter?

OK...I'm definitely interested in that  Vstat, but what the heck is a pressure transmitter? You have the coolest stuff!

Don't know how I missed those postings...a lot to see. I'll have to devote some some to that.  Again, the coolest stuff.

vaporvac

Taco says "No"!!!!??????

Jstar. I sent you an email.

JStar

TACO

I responded to your email, but I'll make my opinion public, too.



They would be fools to think that the control is only applicable to hot water systems. A relay is a relay is a relay. I don't care if it's running a pump, a boiler, or a hair dryer. If the electrical ratings are within spec, it'll work.



We have 2 of these relays in commission and working perfectly. If we always listened to the manufacturer, we would be stuck 50 years in the past.

vaporvac

Thank you for your public and private response

Thank you for your public and private response, but are you sure you weren't listening in on my conversation to Taco? Thanks for setting my mind at ease... it just didn't make sense what they were saying. However, I've had some folks refuse to believe that wet-based boilers can be used with a gas gun, even when the manufacturer says so!

I think it's steam that's the problem...so few companies want to deal with it. I don't understand why as it's not like the the mod/cons are a piece of cake to install or maintain either. In the end, the American manufacturer loses as we seem to end up importing our technology instead of being the innovators. OK...off my soapbox!