Save the Radiators! Diagram

Kevin O. Pulver

This is the ARCO gravity hot water system from an earlier thread today. Do you see anything wrong with the piping diagram? All advice or questions welcome! Any balancing valves necessary for the 2 and or 3 inch lines?
Thanks, Kevin

Brad White

A couple of things

Not knowing the BTU load especially to each side/branch, this is all conjecture but some general ideas, Kevin.

Not to be too fussy of course but to make sure the details are covered, I would avoid bullhead tees if you could, especially on the return. Probably more of an academic point, the flow velocity is going to be very low and pressure drops minimal.

Some instrumentation (thermometer wells) would be a nice way to assess performance on both supply and return.

At first I was going to suggest some kind of balancing device but if you are considering TRV's on the radiators that should not be necessary.

Also, is the piping pattern and expected flow rates at least proportional? If so, I would put in TRV's on the radiators and be done with it.

If you decide to install balancing valves, put them in both returns not just the large one. Pressure drops are so low in these systems that the presence of any small obstruction magnifies the pressure drop imposed.

Something else seems odd though, the relative size of the returns (1-1/2" per side) and the supplies (2" and 3" as noted). Just odd.... I mean the water returning is more dense but not that much... Was the system modified since it was built?

Dave Stroman

That is the way I would do it except I would not use bull head tees. The system pump can be a 007 or even a 005. Probably no need for any balancing valves, the water will almost flow without a pump. I use a strainer on the return to the boiler to keep the crud out of it. The green pumps seem to do better on dirty system than the red ones. Use plenty of isolation valves. And don't forget to cap off the expansion tank in the attic.

Dave in Denver

Steamhead (in transit)

The way you have it drawn

the system is the primary loop and the boiler is a secondary loop. It will work much better with a dedicated primary loop and circ, and the system and boiler as their own secondary loops with their own circs. That makes three loops. If you use an indirect, you'd have four loops.

If the boiler manufacturer says that only two loops are needed (as on the Solaia, pictured), the primary loop will run thru the boiler, and the system loop will tee off the primary loop as a secondary loop. The same would go for an indirect if you use one, then you'd have three loops.

Whichever method you use, the indirect should be the first to tee off the primary loop. This way it gets the hottest water, and you shouldn't need to prioritize it.

For sizing the system circ, go here:

http://www.heatinghelp.com/newsletter.cfm?Id=125

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Dave Stroman

Hi Steamhead. You know, I have done it both ways and I don't think it makes any difference.

Dave in Denver

Kevin Pulver

Thanks Brad

No bullhead tees, thermometer wells, balance BOTH returns or none.
I don't think it's ever been modified, and I didn't measure them exactly, but took notice that the returns into the boiler were smaller than the supplies going out. Now in my pictures, the left side looks almost the same size, but I'm almost certain the right return was smaller- but maybe just where it drops from the ceiling to the boiler? I'll need to go look.
I don't know about the piping being proportional. The main floor EDR is 356 and the 2nd floor 265. I suppose it was balanced right when new. I think TRVs sound like a good idea. Do you have any favorites? Kevin

Kevin O. Pulver

Does this look better?

I got rid of the bullhead tees and made the primary/boiler loop more dedicated I guess. Four thermometer wells for supply and return, and forget any balancing valves on return if I use TRVs. Add a "Y" strainer and plenty of isolation valves, Get rid of the open tank presumably in tha attic, size a new one, and what else? THanks, Kevin

Steamhead (in transit)

It's better

but the secondary tees should be close together, not more than a couple inches apart and with no elbows in between. Look at the Solaia pic again to see this.

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Kevin O. Pulver

You're right Steamhead.

I understand the concept of the closely spaced tees, but did illustrate it completely wrong. What do you like for TRVs? Kevin

Jim_65

TRV's

We have always had great success with Oventrop or Danfoss.