Hot water loop questions

jhewings

Hi I am setting up a hot water loop off my steam boiler. The loop will be 3/4" copper feeding two 1/2" hePEX loops and heat transfer plates under tile floors and a 1/2" hePEX feeding a cast iron radiator. The loop will return to the wet return of the 1-pipe steam system. My options for the supply boiler tapping are either a 1/2" tapping which Weil McLain describes as the lower tapping for a float LWCO. (The LWCOs are on the other side of the boiler) or the 3/4" drain tapping currently not in use.
My preference is the 1/2" tapping because it is higher and perhaps less likely to accumulate mud. I would have to use a 1/2" male npt 3/4" female npt adapter. Do you guys think this is OK? Or should I use the 3/4" drain tapping?
Should I use a wye strainer, maybe oversized with bushings?
For a pump I am looking at a 1/40hp Taco bronze. Should I get the Integral Flow Check version? Or use a separate flow control valve? The tile floors are a few inches above the boiler water line. I am planning to throttle the gpm with globe valves on the pex returns.
There will be a bypass line to reduce the temperature in the loop.
Thanks for reading.

Jamie Hall

I'd take the 1/2" tapping. The water level should never get down there, so that should work well. What I would do, though, is take the line down to near floor level and install the pump at that level. Then go back up to the radiant plates.

Which specific Taco are you planning to use? You have two different head loss numbers to consider: one, the one you want to match flow in the loop for, is the usual -- the total head loss in the loop. The other, though, is that on startup the pump will need to be able to provide at least some flow with that total head loss in the loop plus the elevation difference between the boiler water level and the elevation of the floor plates. Chances are it will -- but it's always worth checking the pump curves to be sure.

I would definitely use a wye strainer before the pump.

HVACNUT

Are these 3 loops all 1 zone? If so, the CI rad might not ever fully heat. I'm not familiar with transfer plates but under tile tells me you dont want 212° water under your tootsies. 
Also consider that there will be minimal pressure and that can cause problems by itself. 
Think about using a plate HX or even a small indirect water heater and pipe the hydronic side as you would a water boiler, with a pressure reducing valve to 12 psi, extrol, and 30 psi relief valve. Two zones. High temp for the rad and low temp for the floor. 

jhewings

Hi thanks for the comments. The Taco pump I'm looking at is 006-BC7-IFC at SupplyHouse.com. With the pump near the floor the head will be under 4ft. There are 2 Pex loops about 180ft each. I think the gpm for the pex should be about 1gpm. The pump curve says this pump can provide 6 gpm at 4ft head. One of the loops will be supplemental heat for a garden apartment. It has a steam radiator ceiling mount with a ceiling fan pushing heat towards the floor but the temperature in there is a few degrees lower than I want especially when outdoor temps are mild. The tile floor is about 20% of the floor in that small unit. It is is raised up and I can get under it. The rest of the floor in there I can't get under. The other tile floor is in an unheated hall at the base of the stairs and I'll take whatever heat I can get there. Not trying to get 68 degrees. The radiator would be near the boiler because with the new boiler and pipe insulation the boiler room is a bit chilly. Again I would take whatever heat there.

jhewings

Jamie I reread your comment. On startup the total head is 4ft plus about 6" or maybe 1ft difference between the boiler water line and the pex under floor. So using 5ft head, the pump can move 5 gpm. If I am understanding your comment.

Jamie Hall

Should work nicely.