Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Having trouble balancing WattsRadiant manifolds... showing 0 GPM

I'm new to this forum, so forgive a little ignorance on my part.  I'm a controls engineer (20+ years experience) that understands electronic things very well, but this hydraulic stuff is challenging my notion that I can figure anything out with time and the internet. 

OK, basics of my system... bear in mind I've installed all of this myself, no professional help.  I've got a 40x60 pole barn with concrete floor.  I used oxygen barrier PEX tubing, with 10 loops, each around 240-ish feet in length.  I just finished installing a HyrdoShark3 electric boiler, 122k BTU (36kW) size, with a HydroSmart integrator panel, the 120LT model.  It feeds 2 sets of 5-gang WattsRadiant stainless steel manifolds with regulator valves on the return and flow guages on the supply, for each individual circuit.  The integrator panel is setup for primary/secondary circuits, although I've noticed that the panel I have (pre-fab from supplier) came with the secondary pump at the return of the secondary loop, where all of their pics online show it at the supply of the secondary loop.  The engineer in me says it shouldn't matter other than the static operating pressure at the manifolds would be lower in my setup.  (All you hydraulics experts can insert insane laughter here :))

After going through the recommended fill/purge cycle, I had 1 of the 10 circuits that during the purge, stopped flowing the water/glycol mix from the outlet hose.  After opening and closing both supply and return valves on that circuit mutliple times, it finally started flowing again, and all circuits showed plenty of flow (visually out of the hose) at this step.  However, after all of the purging was completed, and I put the system into action, I noticed that all of the flow guages are reading 0.  I think it was like that even when filling the system, but I wasn't looking that closely at the gauges until after that part was complete.  The way those guages read, the plunger is all the way UP to read 0, and as the flow goes up (to 2), the plunger goes DOWN.

I initially setup the boiler to run at 140F, and noticed that the supply temp/pressure guage to the integrator panel was only showing about 110F.  My temp guage at the manifold supply inlet only showed around 80F.  I've tried multiple times to contact the HydroShark tech line, and spoke to a live person for about 3 minutes the first time, with promise to call me back after giving them my name/number.  I've tried 2 other times now and either get voicemail only, or had a person tell me everyone was in a mtg and they'd call me back... nothing.

Here's where I'm just floundering, and hoping maybe someone can help me figure this out.  The pumps are 3speed, and during the brief conversation with their tech person, they confirmed I may have too much flow, and recommended slowing the pumps to the middle speed.  After doing that, I saw about 120F on the panel inlet, but still lost about 30 deg to the manifold inlet.  On my own, I dropped the pumps to their slowest speed and can now get to almost 130F at the panel inlet, but still lose about 30F to the manifold.  The T-valve is open to allow pressure balancing between primary/secondary loops, as recommended, and verified with external thermocouples that my temp loss is at the T-valve.  On a whim, I closed the T-valve (in purge setup) and voila, I've got 130F coming into my manifold.

I still show 0GPM on every circuit, even with the T-valve closed to force all flow through the manifolds, but obviously still have flow since I'm moving enough water to kick the boiler on.  However, nothing I do on the regulators seems to change the flow guages at all.  The PEX tubes coming out of the supply manifolds are all getting hot, confirming I have some kind of flow there.  Could I have air trapped in the flow guages causing them to not read correctly?  Something else to look for?  I have a manifold purge valve on the return side (sits higher than supply manifolds), and have tried bleeding, but if the flow guages are capable of "trapping" air locally, the only way I could bleed that air would be to crack the mount nuts to let the air out, right?  I'm at a loss, but I can't get the guages to read to balance them, and don't know if my system has more issues because I don't know whether I'll still have such a high temp loss at the T-valve once its opened.  I tried the blind approach of letting the system just run like that, but found that with outside temps around 40F, my system struggles to keep 50F inside the building... although it had NO problem sucking down electricity like the Griswold house at Christmas time!

Anybody have ideas?


  • MNSteve
    MNSteve Member Posts: 10
    Pump problems...

    I would guess that the pump on your secondary loop is not large enough to overcome the head loss in your radiant system. The reason I suspect this is that you said when you close the "T-Valve" you then start the get flow. With this valve closed, the two pumps are essentially working together in series. With 10 loops at 240 ft each you are going to need a relatively large pump. Take a look at the secondary pump on your integrator panel and post the model number / specs.

  • paul_79
    paul_79 Member Posts: 91
    having trouble

    post some pictures of boiler and piping and of manifolds and mark supply and returns  would be helpful
  • NRT_Rob
    NRT_Rob Member Posts: 1,013

    1. first, anyone saying you have "too much flow" is completely unqualified to help you. Stop talking to them. while that might explain a temperature drop to a manifold it is not important... it's unlikely you actually need 130 degrees at the manifold.

    2. most likely problem is that you are pumping backwards. check the arrow/"suction bump" on your pump bodies. If not, ok, great, but it's fast to check.

    3. can you get a flow reading if you close all but, say, one loop on a manifold?

    you'll probably need to post a sketch of the system or some pics for much more diagnosis.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • MechTech_2
    MechTech_2 Member Posts: 84
    Power purging

    the Watts manifold through the supply manifold and draining on the return side can damage the flow gauges. With enough pressure the plastic stem can pierce right through the disc, and result in a false reading of 0 flow, and sometimes even jam the disc and actually prevent flow.  
  • BobAls
    BobAls Member Posts: 7
    Give this a try

    In the past I've had a few problems similar to yours when trying to get your Manifolds to flow. If you have Actuators screwed to the returns on the manifold, I would recommend to unscrew them temporarily (don't worry about the wires,leave them hooked up). Back out the adjusters so that you get a generous flow potential. Now, on the inlet side (side with the flow indicators) unscrew the flow gauge (counterclockwise) with the wrench provided. People forget to back the input side out after they have finished purging.If you follow the purge instructions, you actually shut off the inlets and the outlets for all the circuits that you're not purging at the time......................it's pretty easy to forget to open up the inlet (flow gauge) side.

    The reason I recommend you unscrew the actuators (if present) is that they can tend to not open (watch the little red indicators) and restrict the flow.

    Hope this is somewhat helpful.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    I would strongly recommend using

    a Taco 008 Delta T circlulator on the secondary loop that supplies the manifold. Set it at around a 10 deg DT and run as low water temps as possible. This will allow the slab to ramp up at max boiler output and will also help preventing slab overshoots, especally if you use an outdoor reset on the boiler. Keep in mind it takes a tremendous amout of BTU's to raise the slab temp to desired setpoint. If you give me the volume of the slab I can calculate how long it should take to reach setpoint. Also if you have oversized the boiler you can put it on a load control and take advantage of cheaper electric rates. The slab can act as your thermal mass contaner. I have done this and it works superbly.
  • Brew
    Brew Member Posts: 1
    edited October 2012
    Issue with flow indicators on watts manifold inlet

    The original thread was started last year but I have a similar issue and am wondering if original poster had resolution to the issue. I've had radiant floor system running for the past 5 years with very similar setup as the OP: flow indicators functioning last winter. When I turn on the system this year (pump and boiler) I see all indicators showing 0. Even after closing all but one zone still see no movement in the indicator to the one open zone. The pump is definitely running and all valves are open.

    Some observations: the piping on the inlet side of the pump (my setup is boiler -> pump -> manifold with about 2 feet of 3/4 copper in between each) does not get hot. The outlet side of the pump temperature does raise to boiler temp. Seems weird since the connection is boiler -> pump -> manifold. It would seem I don't have circulation but don't understand where the stoppage might be occurring. The only thing that seems plausible is the pressure valve that has is one directional that might also act as a backflow preventer and is stuck in closed position.

    Any suggestions would be appreciated.
This discussion has been closed.