Radiant / baseboard mechanic room piping layout / design

gchristman

I'm building my first radiant system and I'm at the point where I'll be designing the piping layout for the mechanic room. (I have had professional heat loss / tubing design done and installed already)

A couple things,

1. I'm using a weil mclain gv90+6 manual page 20 http://www.weil-mclain.com/sites/default/files/field-file/gv90-manual_1.pdf
2. I'm considering zone valves for my small baseboard loops. The nook is supplement to the radiant due to heavy glass use and the office is also supplement to the radiant for additional quick heat. I could use circulator pumps if needed, but I was hoping to save some energy.

I'm a little confused with the primary loop off the boiler and the secondary loop that connects the zone loops. Is my layout correct? Please see image.

Also the boiler has 2 taco circulator pumps built into it, would I need an additional pump in what I'm calling my secondary loop?

Is a circulator pump needed for the DHW? or should that be put on the primary loop like shown on page 26 in the manual?

Lastly, would the zone switching relays be what's needed for the each zone?

Ironman

No the secondaries are not correct. They need to connect to the primary through closely spaced Tess, no jump across as you've drawn.

The higher temp emitters need to be the first things connected closer to the boiler. Then the lower temp emitters as you move farther away from the boiler on the supply line.

Your indirect should be piped directly to the boilers supply and return, not off of the secondary.

I would also use a manifold and one circulator for the radiant instead of all the individual connections that you've drawn.

gchristman

Thanks Bob for getting back to me. Just to reiterate, the only thing wrong with my drawing is I should have the baseboard first since it requires a higher heat load and the radiant last.

Return the heat sources directly to the supply line with a close T rather than jumping to the return side of the loop.

With the baseboard being on separate thermostats / zones, would this cause any problems when the zone is active verse off with the return water temperatures from the baseboard to the secondary loop varying down the line with the radiant mix valves? I'm not entirely sure if the mix valves are mechanically regulated or automatic.

The image you have circled, where the primary boiler loop meets the secondary loop, the distance between the return and supply should be a maximum of 1 1/4 x 4? The first image confuses me a bit when viewing that in comparison to the one you have circled.

Okay, DHW on the primary, zone valve or circulator?

All my radiant loops use uponor manifolds with separate thermostats all with approximately 200'/225' foot loops. Some of the manifolds are on the second floor supplied with 3/4 while others are in the basement near the mechanic room. Some also have varying temperatures, I have the following
2 6 loop
3 2 loop
1 4 loop
1 8 loop

Are you saying I should tie all them into one manifold in the mechanics room and use a single circulator? Would I still use the mix valves for each zone and a zone valve?

Thanks Bob.

gchristman

I found this diagram demonstrating how I could use a single circulator pump with multiple zones. Does it look correct? But the big question is how do you balance them considering the balance may shift when the zone valves are open and closed.

Zman

First off, I would not even consider that boiler for a radiant system. It's just an oddball Frankenstein contraption, not a condensing boiler not really a conventional boiler. What's the advantage?

Most modern firetube condensing boilers will give you far more control and much better efficiency.

I would run this system with a set up similar to page 43 in this manual http://www.lochinvar.com/_linefiles/KH-I-O_Rev D_100267332_2000508039.pdf

The boiler would be set up with out door reset to maximize efficiency.

The baseboard zones would not need a mixing valve and one circ would handle all zones.

All the radiant zones would run at lower temp with one circ and the mixing valve that would be controlled by the boiler.

The system would have a total of 4 circs, 1 mixing valve and as many zone valves as desired.

What you have is more complex than needed. Additionally the water will not flow very well through the baseboards as the path back the boiler is more appealing. There is an excellent chance that the some ghosting will occur through the mixing loops.
'

gchristman

The reason for using the gv90 is it simple and still maintains 91% efficiency with hot return water from the baseboard. I believe if I remember right, the radiant guy who sold me the boiler showed me some charts showing how high efficiency boilers only maintained their efficiency if the water was returned at a low temperature, but quickly loses it's efficiency once you introduced baseboard with hot water return above 120. The boiler has already been purchased and installed, so there will not be any changes to it.

Anyhow, from what I understand is the boilers internal pumps will handle the circulation of the primary loop which is where the DWH will be. Based on your diagram, a pump will be needed.

The secondary loop will have a pump.

Off the secondary loop there will be two additional loops each containing a pump.

Loop one would be the baseboard where there would be a pump and my three zones each containing zv's and the last zone being the end of that loop. My guess is the when ever one of those zv's are open, the pump will be activated.

Loop two would be the radiant with a single mix valve and a single pump and also with separate zv's for each zone. Again the last zone would be the end of the loop. The returns would be sent to the mix valve and back into the secondary loop. Now what happens when we have all the zv's open and I have a loop with much greater pressure than another loop, is that loop still going to get proper gpm?

Am I understanding this correctly?

Zman

OK, I understand.
With the constraints that you have, why not leave the DHW as drawn, then combine all the mixed zones together with one smart mixing valve and one circ. You can zone it after that.
I would do the same with the baseboard loops as they won't get any real flow the way it is drawn.
You could then eliminate the circ you have after the expansion tank and eliminate the big loop as it is redundant.

gchristman

Thanks zman, I met with the designer this morning and he had all the same suggestions you had except for a single circulator for all the radiant zones. He said there was to much head to get proper flow which would require independent pumps. Can you see anywhere else I could add some efficiency. He sold me 8 pumps this morning.

Canucker

8 pumps? For 225' radiant loops? What flow rate do you need for the heat loss? I didn't see it posted. Does the designer expect the return temp from the radiant to stay above 120F for much of the heating season as the reason for not using a high efficiency boiler?

gchristman

approximately 15gpm total. He designed it before we added a couple bedrooms and a small office to the plan and prior to that it was 10.1 gpm. We were originally going to heat the two bedrooms and office with baseboard, but opted to go all radiant. We need to supplement the nook with baseboard which I believe will just be a backup to the radiant due to the radiant not being able to put off enough btu's, the basement is heated with baseboard, and extra baseboard in the office to just quickly heat the air at a higher temp. All zones are supplied with 103 degree water except the nook where it's 139. I was hoping for less pumps to keep energy consumption down, but he seemed to believe the head loss would cause uneven flows between the different zones.

Zman

He is flat out incorrect about the 8 circulators. He likely uses mixing valves with very low CV ratings and needs to compensate by overpumping.

You can run well over a dozen loops with most typical circulators.

I would never run radiant heat with a fixed temp. Outdoor reset is King.

Now I am curious, what mixing valve did he sell you?

Ironman

You also don't need a mixing device on each loop. One, or two at the most, supply water temps should be more than sufficient for the radiant floor.

8 pumps is ridiculous . I've got jobs with 16 loops (no mixing valve) and one Grundfos 15-58 circ on medium speed is pushing them all with a 10 -12* delta T.

gchristman

Taco 5000 85-150
http://www.supplyhouse.com/Taco-5003-C3-3-4-Sweat-5003-Low-Lead-Mixing-Valve

gchristman

I just want to make sure I'm being clear, 7 zones 30 loops. And I agree it seems like over kill, but I'm no expert.