Zone Trouble shooting help

Discussion in 'HVAC Heating & Cooling' started by JEM_1964, Apr 11, 2017.

  1. Stuff

    Stuff Well-Known Member

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    OP thinks system is air bound. If so wouldn't the head pressure matter until the system is bled properly?
     
  2. Dana

    Dana In the trades

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    Not really. The system pressure needs to be high enough to fill it to the top, independent of the head pressure of the pumps. In short, you can't/shouldn't rely on the pump to fill the system.
     
  3. JEM_1964

    JEM_1964 New Member

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    Thank you all,

    The Watt valve says its set to 14-17psi with a range of 10 to 25, which says to me it needs to be set to something and marked. I will carefully measure the verticle height, and then buy a gauge to to set the water pressure. I have never used this valve to purge air, I only moved the horizontal yellow handled valve shown on the left hand side of the top picture in post 12 to the off position and opened the blue handled faucet. I dumped many buckets of water but did not change anything - which led me to think that the yellow handled valve was bad. Once I set the pressure correctly, how should the auto fil valve be used to try and purge the air out of the system? Dana, my calculations say that the range of 14 to 17 psi would mean that there could be almost 7 feet of difference in vertical height the setting could support. the highest being 32.5ft. The max is not going to be far from the truth in my set up - but I will measure not guess at this. Is there a down side to rounding up to the next foot and setting the psi a little higher than the calculation or is too much as bad as too little?

    Thanks and best regards

    Jim
     
  4. Dana

    Dana In the trades

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    It usually takes WAY more than mere "many buckets" to purge air out of a system. It's more common to run a hose over to a sink with a drain (or outside) and let it run for many minutes as it chugs & burps, until it has been running clear for some time.

    I can't tell from this picture what that yellow handled ball valve you're turning off isolates, but I think it's between the pump & boiler (?), based on this picture:

    [​IMG]

    The white handled ball valve in this picture is what shuts off the potable supply to the autofill valve, and it needs to stay open while filling the system (as shown in this picture):

    [​IMG]

    If you flip the lever on the auto-fill to stand up straight, it maximizes the rate of flow into the system, which speeds up the air purging. When you have been opening up the blue valve it lowers the pressure on the system, and the auto-fill has only been opening up enough to re-pressurize the system, but the flow has been going straight across from the auto-fill valve to the hose, none flowing into the zones.

    If the Viridian happens to not have the check valve installed (pretty common with zone-valved systems) it looks like you can force flow through the zone by turning off the ball valve directly to the right of the blue handled hose tap, manually opening the zone valve to the air-locked zone, opening up the purge valve, then flipping the lever up on auto-fill and letting 'er rip.

    Once you have established clear flow through the zone with no burps & chugs, turn the purge valve down to a slow to moderate flow, flip the auto-fill valve's lever back so it regulates the system pressure to it's adjusted value, and turn off the purge valve completely. With any luck the zone will now work.

    If the check valve IS installed it will block the flow from spinning the Viridian back we'll have to come up with another strategy, but it's possible/likely that with the Viridian running, and the auto-fill lever flipped to full-on, opening the purge valve when the system is over-pressurized would get you there.

    An extra foot of head is only 0.43 psi, so yeah round up to the nearest foot, then add 3-4 psi to make sure that the pumping head of the air handler coil doesn't negatively pressurize the low pressure side of that coil relative to the room pressure. If you crank it to much more than 20 psi you may have to change out the pressure relief valve to something higher than a typical 30 psi version.

    When you change the system pressure, you also have to set the charge of the expansion tank to the new pressure, which has to be done when there is no system pressure on the expansion tank. This is going to require a bit more analysis of the isolating valves to figure out how to do that without introducing a huge amount of air into the system.
     
  5. JEM_1964

    JEM_1964 New Member

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    Boston, MA
    Hi Dana,
    It has taken a bit to get here, but I have determined that the Navien combi unit reports water pressure and it is 21.4psi for the heating and around 12psi for domestic HW. I need to take pictures of the whole set up as you have asked, but the "turning off the ball valve directly to the right of the blue handled hose tap" the valve you asked me to turn off I believe is broken and stays open all the time. I think I am never actually purging air out of the zone, but I don't know how the system would operate if that valve were always off or always on. I know that the handle is loose moving it from one position to the other and the other valves have resistance. I also was not expecting the system to be set for 21psi, would this valve position cause the system to work harder? According to your calcs, I should be able to run an air handler over 40 feet higher than my boiler and I know that is not my setup.
     
  6. Dana

    Dana In the trades

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    The pressure readings are only valid when there is no pumping going on, but at 21 psi it should be able to fill the system without pump-assist, as the purge port can be isolated from the fill valve except via a path that goes through the zone plumbing. It appears that with the yellow handled valve directly adjacent to the blue handled valve (which I believe is where you are draining the water?) that isolation is achieved. But if there's a check valve in the Viridian it will stop the fill water from flowing up, since it's the opposite direction of when the pump is running. It's very unlikely for a brand new (or nearly new) ball valve to be seized up to where it can't be closed but it can be pretty stiff, even if others like it on the system seem to swing freely.

    I don't understand how the potable water side can be 12 psi. That would be very low pressure for a potable supply from the city/county water system. It clearly isn't enough to pressurize the heating system up to the measured 21 psi, and isn't enough to lift water to the upstairs air handler. If there's an upstairs sink, bath or shower, does it have incredibly low (or no) flow?

    The blue handled tap in the middle lower part of the picture connected to the hose appears to be a ball valve in the off position, which is where it should be when not purging air. That ball valve doesn't block flow in the heating system, but it can drain the heating system. Turning it 90 degrees will open it, and water should flow into the hose.

    Where does that hose go?

    [​IMG]

    If your potable side is really 12 PSI the auto-fill valve will never fill the system, but if you have another hose tap somewhere not shown in the pictures it may be possible to fill the system using an exterior pump with sufficiently high pumping head.
     
  7. JEM_1964

    JEM_1964 New Member

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    Hi Dana,
    I think I am wrong about the 12psi statement, I will check that because my hand writing is awful (the 2 could be a 7). The right hand horizontal ball valve to the purge valve is the one I think is broken because I turn the handle with no resistance at all - all the others you have work to move the position off to on. If I were not able to turn the horizontal valve off or on, what would that do purge air process? I have no sinks or plumbing above my first floor yet, but I have full water pressure in my kitchen sink which is on the first floor. I have a gauge at the house that was left by the plumber for the rough inspections that were done- I think what you are saying is that the Navien can't be used to measure pressure because the zones should not be calling when I am trying to purge the air and the Navien doesn't dispaly zone information unless that mode is operational...
     
  8. Dana

    Dana In the trades

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    Try opening up your purge valve slightly, then cranking the no-resistance ball valve next to it. If the flow changes even slightly, it's working.

    If it's not working try spinning the keeper nut off the handle, see if it isn't just the handle that's stripped, or what else might be at issue. If you can grab the stem with a vice-grip without messing up the keeper nut threads, see if you can't get it to free up with a bit of wiggle.

    Are there any threaded fittings or unions near the air handler in question? Easing open a threaded connection a half to full turn near the top of the system open would allow air to escape, allowing the zone to fill. If it hisses & sputters a bit, it's probably going to get you there. If it dribbles water with no escaping air hiss/sputter it means it's already filled (at least up to that level), and something else may be the problem.
     
  9. JEM_1964

    JEM_1964 New Member

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    Hi Dana, I will try both your suggestions. The system is PEX, so although they had to cut in small sections to hook up to the upstairs unit - I don't believe there is anything threaded. However, based on what you are saying - I should have the plumber put in faucet connection to aid this process should it be needed in the future.

    It also sounds like you are saying that horizontal ball valve may be serviceable in place with out cutting it out and installing a new one. This would be awesome and I will try this right away. You have really gone above and beyond to help me so far - I really appreciate your insights and suggestions.

    Best regards

    Jim
     
  10. Dana

    Dana In the trades

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    If you're going to tap into the plumbing at or near the top of the system, just add add system-top air vent there. It doesn't have to be as big as a hose tap, since it only needs to bleed off the air, not flush the system.

    You would only need to have another hose tap if trying to purge air at the top of the system with higher pressure and high flow water injected from taps well below the top of the system.
     
  11. JEM_1964

    JEM_1964 New Member

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    Location:
    Boston, MA
    Hi Dana and everyone, I have been limping along with one zone since the last time I posted here and finally got professional help... It turns out that my two one inch lines feeding the two HVAC zones plus the one inch direct hot water feeds are all serviced by a 1 inch primary loop.

    The plumber separated the two zones with independent pumps and put a taco relay controller (removed the zone valves) and both heat zones started working but later at night my direct hot water got starved because of the primary loop install by my first plumber.

    I don't have the funds to completely rip out the primary loop and start over (at least professionally), but I want to ask a couple of questions here:

    1) If the two heat zones were sized at 5/8 or even 3/4 - the 1 inch main would be bigger diameter than these zones. Can I turn the ball valves in the two zones to restrict the water flow to effectively what a 3/4 inch line can carry?

    2) Is there a way to control the pump in the Navien boiler such that it is not drawing so rapidly from the main loop? I ask this because my plumber did manually tune the system once by turning the ball valve in the main loop down. He called it throttling the main pump.

    I ask this because before we made such great progress, the hot water always worked but only one heat zone could make it. Separating the two zones with individual pumps solved the heat zone completely but hot water can shut off because the primary loop can't send enough hot water to the indirect tank unless the primary valve is turned to restrict the water flow.

    Any thoughts would be much appreciated.
     
  12. Dana

    Dana In the trades

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    So if I understand what you're saying, it had all been pumped direct, not primary/secondary (despite the other pump in the picture.) Now the two hydro-air zones are on separate pumps as secondaries, but the indirect is still on the primary zone?

    This sounds like hack, not a design, but might still be made to work. Throttling back the flow to the air handlers decreases their output, but the air handler coils are (probably ridiculously) oversized for their loads. If that makes the indirect work, great. If it's not enough heat out of the air handlers you can raise the boiler temperatures.

    The system design is screwed up. Getting rid of the monster-0verkill pump on the primary should have been one of the first things to do. Pay close attention to the input to output delta-T across the boiler. If the primary flow is too low (probably isn't) the delta-T can go very high (over 50F) to the point of damaging the boiler. If the primary flow is too high (probably is) the delta-T could be quite low (under 4F), t00 low for great efficiency, but also an indicator that the flow could be high enough to cause erosion on the boiler's internal plumbing.
     
  13. JEM_1964

    JEM_1964 New Member

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    Hi Dana, The original "design" did have the heating zones on the secondary, but they shared one pump with two zone valves. They were all 1 inch pex with a main loop also sized at 1 inch. Only one heating zone worked along with the indirect water tank because the path of least resistance never allowed the attic zone to work. Separating the two zone with independent pumps solved the heating situation (I think we are likely over sized across the board). However the dual pump secondary are two 1 inch pipe loads on the 1 inch pipe primary loop and evidently that starves the indirect tank.
    Navien makes a primary loop installation kit with isolation valves for service, my original plumber didn't install that contains a 1.5inch pipe for its primary manifold - why this wasn't used I have no clue (it says it makes the installation easier for the plumber....) . It is working now the way it is for two days with 70 degree settings in the two zones and running the dishwasher, showers and laundry with 45 degree weather - don't know what will happen when its below zero though and I am worried. I found this offer on line for the install kit:

    https://gadgetsgo.com/Navien-NHB-Pr...MIuJWR2vG02gIViDaBCh3F-w7ZEAQYAyABEgLL4vD_BwE

    For 215 dollars this seems like a good idea to purchase so that I could leave all the valves open and be sure things will work. What do you think?

    Best regards,

    Jim
     
  14. Dana

    Dana In the trades

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    The pre-engineered hydraulic separation manifold makes it easier for a hack installer to not screw up the hydraulic separation, but there's no way you should be keeping the monster pump driving the primary. The original closely spaced tees hydraulic separator you have are a bit wider than the ideal, but not terrible (I've seen worse that still worked adequately.) Did that get ripped out?

    I'm not clear how that oversized primary pump could possibly drive any significant flow to the indirect if it's still plumbed with the tees. The indirect probably needs it's own pump, and the zone controller should give priority to the indirect, suppressing the calls for heat from the hydro-air zones until the indirect's aquastat is satisfied. Can you post some pictures of the current configuration?

    I also don't quite get why they used an indirect with the NCB-E150 combi-boiler. Is the indirect really just a buffer tank on the potable side of the NCB (which would automatically prioritize the hot water side.) The space heating side of the NCB-E150 is good for only 60,000 BTU/hr total, and either one of those air handlers would bring it to it's knees at a programmed 180F output, but it would still be able to deliver 120,000 BTU/hr of domestic hot water (enough for a full-flow shower) on the potable side.

    It's time for you to make the installation manual your bedtime reading, until you grasp how it SHOULD have been done and how it's SUPPOSED to work, rather than the hackery that has been delivered to date. Don't even think about buying the Navien manifold until & unless you know it's going to fix the basic problems with the system. It should have been workable with the zone valves on the secondary, but it might have needed more pump driving the secondary, less on the primary. I'm not convinced your second guy had any more of a clue about what he was up against than the idiot who installed it in the first place. (I don't suppose he had any Navien specific training in his credentials?)

    This whole thing is screaming for somebody who can do some of the basic math on it, but it's hard to even tell if it's basically hooked up correctly from the pictures & descriptions to date.
     
  15. JEM_1964

    JEM_1964 New Member

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    Hi Dana,
    I will take a picture of the current set up. The Navien unit is the NHB-150 combi boiler and the kit I posted was for that series. I do need to get a lot more educated than I am and appreciate the patience and help. The hot water can still run cold until I move that valve on the main pump and I can always get it to come back. The thing that I noticed about the install kit was that it had 1.5 inch pipe in its manifold and this install only has 1 inch line.
     
  16. Dana

    Dana In the trades

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    The NHB Series are not a combi boilers- the area straight-ahead (non-combi) condensing boilers. A combi boiler has separate heating and potable plumbing connections, and automatically prioritizes domestic hot water over space heating output.

    Calling it a combi boiler has made it confusing, leading to incorrect interpretations, for instance:

    It looks like they indeed specify a Taco 0013 F3 as the primary pump (see p.20 in the link in the first sentence), so that's not wrong, the way it would be if it were the NCB 150 combi- so stop calling it a combi boiler already!

    Again, the closely spaced tees hydraulic separator in the earlier pictures look well enough implemented that replacing it with the pre-fabbed manifold won't buy you ANYTHING. It is not related to of any of your issues, which are all on the secondary loop, and not much affected by the degree of hydraulic separation.

    See p.30 for the basic configuration with an indirect. Even though it's tapped off inside the primary loop, it needs it's own pump, and should not be pumped direct using the primary pump.

    There are DIP switch settings to check, as well as wiring connections to check to be sure it's been done per the manual. READ THE MANUAL! (and stop calling it a combi boiler! :- ) )

    At ~140BTU/hr of DOE output NHB-150 is ridiculously oversized for the space heating loads of 195 out of 200 houses in the US. But the HE-Z-70 air handlers are similarly ridiculously oversized. If you're running the boiler at at 165F output the air handlers will suck up all of the available burner capacity, leaving nothing for simultaneously running the indirect. The only sane thing is to operate the indirect as the priority zone, suppressing calls for heat by the air handlers whenever the indirect is calling. To get any condensing efficiency out of it for space heating you'll have to back off the boiler's output temp to under 140F - as low 125F would be even better, if the exit air at the registers isn't too tepid. Below 125F the savings from incremental improvements in combustion efficiency may well be canceled by the excess air handler power use of the longer calls for heat, since the heat rate out of the air handlers will be much lower.
     
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