Boiler Piping

Ed_Wynhoff

I'm going to start from the beginning so please bear with me. Three years back my wife and I purchased an old Masonic Temple which had been partially converted to offices. The existing steam system was one of the scarrier things I have witnessed but that is another story. One of the contingencies was that the former owner install a new boiler system. I have 40 years in the trades as a carpenter and 3 years of hard knocks and learning about steam the hard way. When we went through owner training I asked about all the water hammer in the distribution header and I was told that this is normal for steam (the trainer was the owner of the installing company). As a wood tick who was I to argue with the expert. The pressurtrol was set at 10 lbs and some rooms were not getting heat. I consulted with another contractor and they said that we could try turning up the pressure a little (nothing about venting). The first year we went around and fixed leaks in the system but it didn't help with the rooms that were under heating. It should of dawned on me that the radiators that were leaking the most were also getting hottest, it was a venting problem not pressure. Being tired of the "Experts advice" I started to do some research myself and I ran on to the Wall. It didn't take much reading to find out that this is the place where the true Steam Experts hang out. The first thing I did was purchase Dan Holohan's book The Lost Art of Steam Heating (I wish I had it long ago).

After reading for about 2 hours I went over and turned down the Pressuretrol to 1.5 lbs. and it's a miricale suddenly there's heat to all the rooms. We had some problems with overheating and we installed the Danfoss TRV,s on the 2nd and 3rd Floor 1-pipe system. And the complaints are gone (mostly).

After reading Dan's book further I realized that the near boiler piping needs work. We still have water hammer in the distribution header, although it has been reduced considerably. Now's where the experts come in. The existing header is constructed as follows.
*Header constructed of 6" pipe (see pics)
* 3" takeoff to Second Floor radiators (1-pipe system), 2" takeoff to 1st Floor North zone and 1st Floor South zone (2-pipe system).
* All 3 zones have a motorized zone valve. I know that this isn't Ideal; but I don't know how to get away from this. The tenants in the offices are really particular and if the temperature varies by a couple of degrees I'm getting a phone call.
* The existing header doesn't provide a way for the condensate to get out other than fall back into the boiler with some collisions into the steam along the way.
* The cross header is welded and does not have swing or slip joints (see pics). I'm not sure if we should cut the elbow and tees out, rotate them 90 degrees and add elbows to allow for expansion? I think that the vertical leg would rotate on the unions. Are we flirting with disaster with the current piping configuration? Thoughts?
* There are 2 Dunkirk D248-400 boilers that are piped together before they go into the distribution header. Based on Mr. Holohan's book my thought is to seperate them and put them into the header individually(see sketch). We removed radiators to do some apartment build outs and no longer run the 2 boilers in tandem (the apartments are on seperate forced air systems). When we were running both boilers, one boiler would shut down and it would suck the water out of the other causing excess makeup water to flood the system and blow the excess out of the condensate pump reservoir. We have 875 sq. ft. of EDR left in the building heating 6,500 sq ft with the average ceiling height at 9' With the latest improvements the building heat is staying at the set thermostat temperature even on sub zero days.
* As currently constructed the 2 First Floor zones are on the same 2" takeoff. Would it be better to have 2 seperate takeoffs? The zone valves are located about 2' after the header and then are reduced to 1 1/2" after the zone valve. If we do 2 takeoffs for the Floor should we use 1 1/2" or 2" from the header to the zone valve?
* Should we install a vent to remove the air from the distribution header?
* Is the attached sketch for the new header on the right path to remove water hammer and provide dry steam? I truly appreciate all of the advice I get from all of you as I have gained more knowledge reading information on this site and Mr. Holohans book than by talking to the local "experts". I've tried to explain this to the best of my very limited knowledge hopefully there is enough information that you folks can make some sense of it all. THANK YOU All.

Jamie Hall

There is nothing fundamentally wrong... at least with the concepts! As to minor points -- I'd stay with 2" for the takeoffs for the two independent zones. The whole system would be happier with the two boiler feeds separated. The drop header arrangement in you sketches would give you the swing joints which would be really nice to have (you are saved by the fact that all the piping is iron, so the expansion stress isn't as much as it might be...).

I presume the condensate return tank is vented to the atmosphere -- hence the F&T traps. I also presume -- at least I hope -- that the two boilers have independent boiler feed pumps, controlled by the water level in their respective boilers, and that any makeup water is to the condensate return tank, controlled by its level. At least I hope... The drip you show from the end of the 6 inch header to the condensate tank -- with the F&T -- is essential.

The zone valves create a potential for problems, as I'm sure you are aware. On the one pipe part of the system, condensate will be trapped above the valve when it closes. Lots of it. You are proposing an F&T above that zone valve; it should be as close to the valve as possible; I can see a couple of ways to do it, but I'll leave that up to you an your pipe fitter! The other two zone valves also need the F&T's, and again -- as close as possible to the valves -- but they aren't quite as critical.

Are those zone valves full port?

MilanD

If your edr is trully 879 just one of those boilers will be enough to heat the building. Dunkirk d248 400 is rated 971 edr. If you are running them both together, you are waaaay oversized (double!).

As to 2 pipe part of the system, make sure all radiator traps are working. Those radiators should be easy to dial in the heat given the radiator traps are in working order. You won't need zone valve on that one ever. I wouldn't expect those rads to have any issues with heat, and can work on oz of pressure. 1.5 psi may still be too high and you may need a vaporstat.

As to 1 pipe, make sure wherever the last radiator riser is, that there is enough main venting, which I'm sure you are.

Zone valves you have there seem to already have f&t traps just above them so that's good. Again, unless you had them serviced, assume they need to be serviced, guts replaced or replace the entire cover assembly. Just make sure you have a few extra gaskets as you will need to stack a few to make a positive seal. I've used automotive soft non-hardening blue gasket dressing to help seal if there was a leak. A life saver.

As to redoing the header, get plenty of help a big pipe wrenches. Definitely do it over the summer.

Finally, if it's possible to 2 stage that boiler, I would recommend doing it. This will downsize the boiler when zones close which is what you want. I'm unsure if this is possible on this particular boiler.