Converting 2 pipe steam convector connections to hanging unit heater

JUGHNE

I have a 2 pipe system, dry pumped return, 2.25 PSI operating max pressure. Almost double boiler capacity for present connected EDR.
One convector location could be of better use if it were repiped to feed a hanging unit heater.
The existing convector is a 58 EDR.
Main in dead man tunnel directly under it is 3 1/2" fed by 4", this is now the first unit connection after boiler.
Horizontal runout is 30" of 11/4".
1" riser of about 30" to 1" angle rad valve.
Return is 1/2" dropping to 3/4" horizontal into 1 1/4" dry return.

I would like to use the 1" angle valve into the bull of a tee, drip & dirt leg the bottom run of the tee and use the top tee run to feed heater. There would be about a 10' riser to the top of the unit heater.
The drip would go into the 1/2" return drop.

For return of unit heater 3/4" drop to tee w/dirt leg & 1/2" trap w/cooling leg?? or not?? then into 1/2" return.

If I read charts right the 1" dripped riser could handle 150 EDR or 36,000 BTUH.
The proposed unit is a Reznor 23/33 rated at 138 EDR or 33,000 BTUH on high speed fan.

Questions: will the piping plan deliver the rated EDR?
Will 1/2" Hoffman 17C angle traps work for both drip and heater trap?
Is cooling leg at unit recommended or not? (there would be ample room 10' off floor)
There is very little room to gracefully add cooling leg for riser drip after angle valve.
Is any air vented needed at unit. (Dry return is open vented at cond pump, but it is 350' of pipe away)?

This is a school with about 12,000 Sq Ft on one floor. Has one T-stat. for building.
Would aquastat for fan only control be best on supply or return?
New unit would be in entry/hallway, not near class rooms.

EBEBRATT-Ed

I don't think you need an air vent. For control I usually see a strap on aquastat on the return. Piping looks a little undersized. 17C will handle 165edr@1 psi diff, 120edr @1/2psi diff. The 1" supply is probably ok. The 1/2" return I think is too small. Your going to get a lot of condensate when the fan comes on. 17C is ok for the drip. JMHO

JUGHNE

Thanks, EDEBRATT_Ed
I could go with a 3/4" 8C trap with 3/4" pipe return all the way to the riser thru the floor which is about a 16" long bottleneck of 1/2" pipe before increasing to the 3/4" in the tunnel. I want to avoid visiting the tunnel as it has asbestos and is a 100' crawl just to this pipe. There would be 8' of 3/4" vertical pipe above the "bottleneck" to give a little head/push (I'm hoping) to the condensate drain.

I was thinking about an air vent because the last 100' of 2" dry return may have a little sludge that impedes air venting and any air venting may help the entire system out.

How about cooling legs for the unit trap, any opinions?

Thanks for your time.

EBEBRATT-Ed

Lots of traps are installed without cooling legs. If you think you need an air vent you can put one on---can't hurt anything. Or just leave a tee and add it if you need it. Sounds like it will work ok.

JUGHNE

Thanks again! Now I just have to convince the school board that they need it done......prevent the draft from the new outside door location and use up steam that they already have.....also cut down a little bit on the short cycling of oversized boiler.

MikeJ

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