Basic Advice

Dave Meers

I'm a DIY'r installing radiant heat in a new, well-insulated workshop. I'm referencing Dan's books - "Pumping Away", "Primary-Secondary Pumping Made Easy", "Hydronic Radiant Heating", "RadPad", and "Modern Hydronic Heating" (Siegenthaler, 1st edition ). The boiler is a Weil-McLain WGO-3 located next to the loop manifolds (short Primary loop). I prefer circulating pumps instead of zone valves but could still go either way. Primary loop and manifolds are not yet installed. Year round domestic hot water volume will be very small, needed mostly just to wash greasy hands. So, I'm figuring on just using a small point-of-use hot water heater rather than run the boiler all year round. I come up with a total building heat loss of about 46,000 BTUH which includes heat losses through the slab. The main floor is slab on grade (2,234 sq.ft.) with seven, 300' loops of 1/2" PEX embedded in the concrete. 2nd floor heated space is about 1,180 sq.ft., of which 200 sq.ft. is office space heated by a 220' loop of PEX under the plywood subfloor. The remaining 2nd floor space is for storage or workspace and will be heated with hydronic baseboard.

The advice in the books is invaluable but there still seems to be too many different ways to do this! I have the following concerns so far:

1. Primary Piping - 1 1/4" or 1" copper? It seems like 1" should provide enough flow to system (46,000/10,000=4.6 GPM) and I could save some $ on fittings, components, etc. but I don't want to undersize and wish I had used 1 1/4".

2. Zones - Should I do 3 zones - main floor, office, 2nd floor storage/workspace?

3. Copper Manifolds - Local dealer is suggesting prefabricated copper (1"main, 1/2" tees) with balancing valves on Supply and mini ball valve on Return.

4. Zone Temperature Control - I want to keep it simple and not too expensive. It's a workshop, not a residence. Don't need a Rolls Royce.

Thanks for any suggestions or comments.

Rich Lee

Alan(CaliforniaRadiant)Forbes

So far, So good.........

That 1" primary will take you up to 8 gpm no problem.

Zoning sounds OK; you want to make sure that rooms on the south side of the building are on a separate zone from rooms on the north side.

We use brass manifolds; copper ones work just as well.



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Mark Wolff

Heating

The 1 1/4" manifold will be better for the sole reason that 1" doesn't always distribute the water as evenly under full demand. I tend to shy away from circ pumps on every zone because they don't have a positive stop of water flow. Check valves only stop reverse flow, numerous seemingly small miscalculations can cause unwanted flow through zones that are supposed to be off. That is the benefit of zone valves. Also they are about half the price of circ pumps. Have one circ pump for the loops with the t-stats turning on a switching relay to that circ pump. 3 Way mixing valve or variable speed injection pump feeds that manifold with hot water.

Because you have three different heat requirements (slab infloor requires a lower temperature than staple-up infloor; both require lower temp than baseboard) you will actually be creating 3 different temperature manifolds, the baseboard line can come directly off the supply and return manifold on the boiler. See attached drawing for better understanding. Sorry in advance for the REALLY basic drawing, I normally make these in MS Visio but I doubt you have it on your computer. If you do, I can send you a real mechanical drawing plan for it.

S Davis

First some questions,
#1 How are you mixing down your water temps for your radiant floor?
#2 How is the tubing installed under the floor in the up-stairs?

S Davis

Dave Meers

#1 How are you mixing down your water temps for your radiant floor? - Probably a Honeywell Sparcomix which can be plumbed as a 3-way mixing or diverting valve.

#2 How is the tubing installed under the floor in the up-stairs? - with plastic "clic" clips screwed to the underside of the subfloor. They hold the tubing about 5/8" below the plywood surface. I've attached 1/2" foil-faced DOW TUFF-R foamboard to the joists for insulation and upward heat reflection.

Dave Meers

You've gone the extra mile! Thanx! Send the drawing if you don't mind. What version of MS Visio do you have? I can download a visio viewer.

Rich

Paul Rohrs_2

For the record.....

You can save your visio files as a JPEG and then attach them. Attached is a sample drawing.

Regards,

PR

S Davis

Has there been a heat loss calc. done? do you know what your design water temps are?
From your description it sounds like you will need at least two mixed water temps. and one high temp.
Usually Joist Bay heating requieres water temps some where between High temp and radiant floor(140-160) especialy a 4" slab installation wich usually has lower temp requirment(90-120) these are just ball parks to know for sure you need a proper heat loss with flow and temp requirements.

Dave Meers

Has there been a heat loss calc. done? - Infiltration losses are included:

The 1st floor(slab) space needs about 32,400 BTUH. I'll figure 110* into the concrete. Entire 2nd floor space needs about 13,100 BTUH. 200 sq.ft. of 2nd floor will be radiant. 140-160* supply seems higher than what I've been reading. Remaining 2nd floor is baseboard at 180*.

Paul Rohrs

Visio for Mark Wolff

Hope this helps. Let me know.

Paul