All my heat goes to first zone

Ryandiydc

Hi there, I built my closed loop 5 zone system with circulator pumps. The main loop in the boiler room is all 1” pipes to manifolds that connect to 1/2” pex. My problem is that a majority of the hot water goes to the first zone’s pump and each zone after that gets less and less (140,120,110,100,90). The first two zones are for my second floor and therefore have larger pumps but this was happening when I only had the first floor connected. I am thinking that maybe my primary loop should be downsized before the pump to reduce the volume of water being pulled by the first zones? Or is this all an issue with not bleeding the lines properly?

Snowmelt

Need a diagram of how you piped the system, Also some pictures of the system

GroundUp

Sounds like it's piped wrong, and you need to do some balancing. Please share photos of the system.

Ryandiydc

I am in the process of replacing the non-O2 barrier pex with copper so the pumps aren’t in the picture but here is a rough diagram of the central loop

hot_rod

Do you know the total gpm you need for the system? The 1” pex may be a bit small

Those white plastic caps are also used for balancing the loops

Ideally you would know how many gpm each loop requires, get them all flowing and balance each loop by turning those caps

It would be nice  to use a delta P type circulator that could adjust flow as zones turn off and on

Without some flow data it will be a hit and miss process.

Ryandiydc

I calculated 10gpm for the system (100,000 but/10,000) with 12 loops around 300 ft each.the boiler is in the basement, Zone 1 and 2 supply the 2nd floor and use Taco 0015 msf3. The other 3 supply the 1st floor and use the Taco 007 f5. I have used the valves to get all the loops flowing at ~.5gpm but the problem persisted. I really appreciate everyone’s help with this

GroundUp

It's piped wrong. The return is connected to the supply and they are mixing, with minimal flow actually getting through the boiler. The return needs to be disconnected from the supply down on the bottom left. That boiler needs a minimum of 3 GPM flow under any circumstances, so unless 3 zones are calling, it's not getting adequate flow. It should be repiped to a primary/secondary arrangement in order to work properly and retain factory warranty.

Also, you said above you calculated for 100k BTU. That MS series boiler only goes from 34k to 68k so there is not 100k to go around. 6.8 GPM with a 20* delta is .567 GPM per loop.

The 1" pex sizing is not an issue, and the white knobs are NOT for balancing. The flowmeters (supply/bottom manifold) are where flow is supposed to be adjusted.

Ryandiydc

Awesome, thanks for your help. That’s right, it’s the MS-20 with a 68k output. I should have waited till I was fully awake to post a response. I did consult with radiantec before ordering it and according to their calculations based on my cad drawings of the pex layout it should be enough to keep up. As far as the primary/secondary loops, would a check valve between the supply and return be functionally the same as separating them? And from what I’m reading I will need to add a primary loop pump as well, right? Here is a picture of what I think you are saying

mattmia2

If the boiler doesn't have a built in circulator than you need a boiler circulator. You have nothing to force flow though the boiler if there is no boiler ciruclator. The zones should connect through closely spaced tees, the supply and return should be next to each other for each zone in the primary loop. With your connections spaced apart like they are the primary circulators and the zone circulators will interact.

Another sort of old style solution would be to install the boiler circulator and install a differential bypass valve between the supply and return to guarantee a minimum flow through the boiler.

hot_rod

In the first drawing there is no need to have a boiler pump as long as the boiler gets adequate flow with the smallest zone calling. It looks like a basic electric boiler, really no pressure drop.

Looks like some two loop zones. So. Maybe 1 gpm in those zones.

If you do a primary secondary I would do a parallel, not series piping to assure all zones get the same temperature, like this example. Which does need a boiler pump.

GroundUp

Why am I not surprised that Radiantec would give the green light on that piping arrangement? I swear, nobody in that building has ever spent one minute in the field.

The check valve would not create hydraulic separation, you'd need to pipe it similarly to what Hot Rod shows in his attachment there with closely spaced tees or an actual hydraulic separator. I am a distributor for Electro and build a couple dozen of these systems per year- attached is a similar system I built recently using an MS-20, although this one is zoned by actuators instead of having so many circs

Ryandiydc

To be fair to Radiantec, they only approved the boiler size and pex layout, the plumbing mistakes were all me. Thank you so much for the picture groundup. Diagrams help but that really cleared things up. Here is a diagram of what I’m thinking will work. What’s another $400 in fittings at this point? lol

hot_rod

Not the best piping as the various zones are in series. So for example if zone 1 was seeing 130f, as return comes back it blends down temperature to reach successive zone. So the last set of tees will see a much lower temperature and will not heat adequately

The primary secondary I showed will give each zone the same temperature, always

Looks like Electro wants / gpm minimum in their manual, so you could just pipe direct, without primary secondary,  if your small zone allows 2 gpm

shat us going on to the right, where do those lines go??

GroundUp

Ryandiydc said:

To be fair to Radiantec, they only approved the boiler size and pex layout, the plumbing mistakes were all me. Thank you so much for the picture groundup. Diagrams help but that really cleared things up. Here is a diagram of what I’m thinking will work. What’s another $400 in fittings at this point? lol

That's also bad and you'll have the same problem. Every zone will get a lower supply temp than the previous zone that's calling. Pipe it as I or Hot Rod's diagram show. Anything else will be an issue. Also, there is a 0% chance that your smallest zone will flow 2 GPM- with that said, field experience says that 3 GPM is the absolute minimum to prevent spot boiling at the elements which causes damage to the boiler. P/S with a single set of close tees using your existing manifolds and headers will be the simplest and most cost effective. A couple fittings and an extra circ, you're all done.

Ryandiydc

Thank you all for your patience and expertise. I understand now (I hope). I think this is basically what Rod suggested just adapted to my setup. One close tee and a circ that allow a constant 3gpm to loop through boiler secondary loops that will pull hot water only when their pump is running. 

hot_rod

If the boiler has outdoor reset, use that also.

With any primary secondary piping there is a temperature blending. You may not get boiler temperature water to the zones, so if that boiler has a system sensor option, strap that just before the first distribution circulator. This way the boiler is trying to supply the temperature the ODR is requesting to the lods.

My favorite piping is with a hydraulic separator. Gives you air, dirt, magnetic, and hydraulic separation.

HomerJSmith

The low head loss common piping should be generous in size. The only reason you need larger pumps is to over come the pressure loss (head loss) at the required GPM.

GroundUp

Yes, that's much better. The MS-20 does not have an ODR function nor can it utilize a system sensor without external controls, but if you pipe it as you show there and properly balance the loops, your temp entering each zone should be within a couple degrees of what the boiler puts out. A 1" loop as shown with an 0015e should flow upward of 10 GPM through the boiler loop, so if you balance the loops to a lower flow than that under full load, the mixing should be pretty minimal. It'll take a little bit of finesse to dial in, but you're certainly on the right track now.

Ryandiydc

Thank you all again for your help, I will try to remember to report back the results. Hopefully this saves another DIY’er the same headaches I put myself through