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Zone Balancing, Boiler Protection, Buffer Piping/Control

2

Comments

  • D107
    D107 Member Posts: 1,849
    edited November 2019
    @SuperJ
    Re: throttling zone flow will be very difficult. Turbomax states that we need 5gpm to get the hot water yield; we will need at least the total 7gpm zone flow with all three zones calling based on what I have seen. Any less than 2gpm with the series-piped CI zones will see last rads in the zone short of heat. Two zones running would probably have the boiler at 4 or 5gpm. So if primary flow has to be more than secondary, maybe we have a problem with the whole primary-secondary/buffer concept with our system.

    Not sure if the $$ is the issue here. The installer is willing to make the corrections and has himself even mentioned a four way valve--though not sure why that's better for our application than a three-way. I was trying to keep it simple, but given the need for supply and return re-piping changes, going a little further with a valve would make sense--especially given what was already spent. And as long as we're doing all this, makes sense to me to go with the 2" short headers since they have to be changed anyway from 1.25" and I want to ensure this will actually work after all this effort.

    I'm trying to make sure of the detailed piping requirements first, then controls will follow.

    1. Supply piping: 2" header, move zone take-off closer to tank. As of now, there's no room between primary circ and tank to put the secondary heating circ. Suppose the zone takeoff is closer to the tank --tees right off the top of the tank--but the takeoff doubles back to the existing location via horizontal 90EL? That way, the current DHW circ which will be the prime circ--can stay where it is now as in photo below?


    2. For the return, see photo. Need to know if all this works. Probably have to upsize the flow control from the turbomax return to 2"...


    3. Not sure if the take off for the boiler protection line to the 3-way valve will also need a short fat header, but I'll leave that for another post.
  • SuperJ
    SuperJ Member Posts: 609
    Ideally you wouldn't have a bull headed tee above the tank, I would suggest keeping the 90, and putting a tee in the place of the horizontal nipple before the 90 to connect your secondary takeoff.

    Since you will be using the variable speed VT pump as your primary pump, you should be able to set your boiler flow with pump speed. I don't think an additional flow control would be necessary on your primary loop (thru the boiler and turbomax).

    For your secondary loops, your flow will be set by a combination of pressure setpoint on the VR pump, and by any flow controls on the loop in conjunction with the pressure drop across each zone. You really only need to restrict the flow on any zones that are flowing too much. A zone would be flowing too much if the return water temp is coming back without much of a temperature drop, and last radiators have more than enough heat. You can sometimes just use throttled ball valve to balance if the loops are close to begin with.

    Don't obsess about getting your primary flow set perfectly. If your tank gets depleted, the hydrostat can pause the secondary pump (when the turbomax aquastat calls) until the temperature is restored.

    If you go with a Taco i-series valve, the valve can ensure that your heating load doesn't interfere with DHW and give you boiler protection.

    A 3 way i-Series valve would work fine (no need for 4 way). http://www.taco-hvac.com/uploads/FileLibrary/102-145.pdf
    A way 4 gives you a bit better assurance of no unintended mixing. It wouldn't be wrong, I wouldn't have a problem deferring to whatever your installer is comfortable with. But a electronic mixing valve would be a value add that you should expect to pay for.

    When your primary and secondary loops are hydraulically decoupled or separated, you don't have to rely as heavily on flow controls.
    D107
  • D107
    D107 Member Posts: 1,849
    @SuperJ thanks. So it looks like we have a decent rough idea of how the piping will work except for the location of the 3-way valve and where the take-off is for that and I guess it will get teed into the return pipe close to the boiler and will be activated by a temp. sensor near that area.
  • SuperJ
    SuperJ Member Posts: 609
    The supply and return will be the same, the valve should be in between the primary loop connection and the secondary circulation (so above your turbomax). The only extra will be a bypass line connecting the A port to the secondary return line.

    C- secondary supply
    A-Secondary bypass to return
    B - Connection to primary loop



    Your turbo max would be the tiny piece of pipe between the tees.
  • hot_rod
    hot_rod Member Posts: 22,022
    A 3 way thermostatic for boiler return protection? Your tank would substitute for the hydro sep shown in this drawing, 2 not 4 piped.

    Mix valves for the distribution system could be thermostatic or electronic to give you more control with reset function.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Umm. Why not just turn the Circ hold off on the Hydrolevel and then come back to us with what happens? Are you utilizing the controls Outdoor Reset Function? I honestly think you have the wrong boiler for the application but its what's there so my first thought is.. Just turn the stupid hold function off... Then what happens and go from there.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
    D107
  • D107
    D107 Member Posts: 1,849
    @Chris_110 Thanks, yes someone else advised that. Is your reasoning that the 'hold' actually prolongs the time the cold return comes back into the boiler? We did not set up the Outdoor Reset with this, didn't feel we needed it. I'll remove the hold and report back.
  • D107
    D107 Member Posts: 1,849
    @Chris_110 Ps and maybe when I shut circ hold off, shall I put in a lo limit of 126 or so? RIght now it's cold start.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited November 2019
    Boiler should be cold start. You aren't trying to maintain water temp inside the boiler when neither the indirect or heating zones aren't calling.

    How is this wired? Are you utilizing the HydroStat I1/I2 for the Indirect and C1/C2 for the Htg Zone Circ call via the Zone Control End Switch to T/TV? If so is setting 4 in the HydroStat set to "C" Circulator operation on call from either? If so, did you turn "Off" the Economy Feature of the HydroStat that is factory set on?

    You're turning the Circ Hold Off as a troubleshooting tool. Not sure why you'd use this in your application anyway.

    While I love me some Johnny B not a fan of "Delta-T" pumping in a multi-zone application. In this application you have different emitters , different head and flow rate requirements. In Delta-T mode that pump takes about 3 minutes before fully reacting to what's actually going on in the system. Starts at the low end of the pump curve, gradually climbs to high speed and then does its Delta-T thing. Better off utilizing the Set Point mode. It will also provide you the boiler protection you seem to be looking for.




    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
    D107
  • CMadatMe
    CMadatMe Member Posts: 3,086
    gaabbee said:

    So I have been thinking a lot about your system but mainly because you have a lot of the same brand components as I do. If you are trying to avoid a re-pipe here is what I would do as long as the vr1816 and vt2218 are hydraulically separated. Not sure if I missed that part.

    Get rid of the zvc 403 and sr 501. Get a zvc 404 with priority. I would wire the 3 zone valves in slots 1,2, and 3, and then wire the turbomax aquastat on zone 4 as priority and use the jumper slots 3 and 4. The hydrosat will get connected to the "TT" end switch. Wire the vr1816 as the primary pump and the vt2218 as the secondary pump. This will allow the turbomax and boiler to never drop below the set low limit.

    In theory this should allow your boiler to perform like this. Turbomax set at a high of 160* low of 130*. Hydrostat high of 170* low at 0*. Pre-purge and circulator hold settings activated.

    If a DHW load lowers the turbomax temp to 130* the boiler will fire. Once the boiler water passes 126* the vr1816 will turn on until the turbomax reaches 160* then shut everything off.

    If a zone thermostat calls for heat the above will all happen the same except that now the vr1816 and vt2218 will both turn on. If the turbomax temps are between 130* and 160* already the pumps will purge down the water temps to 130* which then fires the boiler. Once temps hit 160* again the fire will turn off and the pumps will continue to purge down until the zone is satisfied or reaches 130* again.

    When a zone is calling for heat and a DHW call from the turbomax the priority setting will shut the vt2218 off and let the vr1816 continue to satisfy the turbomax. Then resume the zone heating.

    When it is all set up correctly it really is a thing of beautiful harmony. Just make sure those pumps are hydraulically separated.

    HydroStat provides DHW Priority no need to change out the Zone Control.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • CMadatMe
    CMadatMe Member Posts: 3,086
    D107 said:

    @SuperJ Things are in motion and we should have a plan soon. Like your suggestion that the Turbomax can be used as a buffer for two different purposes: for low return protection AND to be 'sipped' by the boiler to lessen the frequency of heating cycles.

    You mentioned 'placing the DHW sensor properly.' As far as I know the Turbomax has a single dedicated well--in the middle of the tank--for the aquastat. So not sure how that can be adjusted.

    Here are additional details I received from @gaabbee on how the controls could work.

    If you look at the wiring diagram (pdf attached) for the zvc404 the 4th zone would be the turbo max and have it’s aqua stat wired as the 4th zone thermostat and then jumper slots 3 and 4 for the circulator instead of a zone valve. There is a note about doing that.

    Your vr1816 would be wired directly to the zvc as the system pump. The vt2218 would be the secondary pump--or vice versa. There would not be any dhw pump. (Diagram in lower left corner) There’s a note again saying system pump turns on when any zone calls for heat. (Pumps hot water through the turbo max) The secondary pump turns on when any zone except priority calls. (Pulls hot water from the primary loop) This allows both pumps to run when a zone calls but turns off the vt2218 if the turbomax needs to catch up.

    The turbomax piping diagram from what I see doesn’t say anything about separation of the pumps."



    HydroStat provides DHW Priority, Zone Circ when ran in SetPoint mode will provide boiler protection providing he uses it's Supply/Return sensors.

    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited November 2019
    Is the ZVC403 end switch going back to T/TV on the HydroStat, the SR501 End Switch wired to I1/I2 and the Heating Zone Circ wired to C1/C2?

    I noticed in a post above you spoke to HydroLevel concerning the wiring. They want both pumps wired to the control b/c of its LWCO feature. Should it be activated it would turn power to the pumps off to protect them.





    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • D107
    D107 Member Posts: 1,849
    edited November 2019
    @Chris_110 said:
    How is this wired? Are you utilizing the HydroStat I1/I2 for the Indirect and C1/C2 for the Htg Zone Circ call via the Zone Control End Switch to T/TV? If so is setting 4 in the HydroStat set to "C" Circulator operation on call from either? If so, did you turn "Off" the Economy Feature of the HydroStat that is factory set on?

    See photos below. We are on DHW priority. My notes indicate circulator on I1/12 only --option B--on Hydrostat and Turbomax aquastat wired to SR501. Photos may indicate more than I can. Economy feature is off; VT2218 has temp sensors active, but last week I changed mode from ∆T to constant speed. Will look into setpoint.

    You're turning the Circ Hold Off as a troubleshooting tool. Not sure why you'd use this in your application anyway.

    With boiler temps on heating cycles rarely making it up to the 130s, and bouncing back and forth between 125 and 110 (Circ hold lower limit being 115) we felt it would limit condensation or boiler shock until we could determine a more solid mode of boiler protection. Currently there is no hydraulic separation; we've been discussing adding in those short fat headers at top and bottom of turbomax to achieve it.








  • CMadatMe
    CMadatMe Member Posts: 3,086
    There isn't a need for hydraulic separation. Is the Heating Zone pump wired to C1/C2 and if not what is powering it? I can't tell from your pic if C1/C2 have the HZ Pump wired to it.

    Heating zone pump should be wired to C1/C2 and operation mode should be set to "C" on the HydroStat. Now you'll have priority for the DHW. Now the Heating Zone Pump won't run on a DHW call.







    Set the VT2218 Htg Pump to SetPoint, add the supply/return sensors and the pump will give you the boiler protection you're trying to achieve.

    I really don't see any need for re-piping anything. It's the control strategy here that's all messed up. Get it all wired correctly, set the HydroStat up for Cold Start operation, set the high limit you want, turn off Economy and Circulator hold functions.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • D107
    D107 Member Posts: 1,849
    @Chris_110 I'll get more info about how it's wired, but Just to be clear:
    1-we have DHW priority already; the two circs never come on at once. There are usually multiple ways to achieve this, installer may have just wired it differently. The cold returns have nothing to do with heating and dhw circs running at the same time since they don't.
    2-We already have cold start, have the 160 hi limit, economy is off, and vt2218 supply/return sensors are in place.
    3-I hesitate on turning the Circ hold off for scenario like this:
    boiler is coming off a dhw cycle and hit the hi limit of 160º. heating cycle starts and brings temp down to circ hold low limit of 115º in a minute or two while boiler is firing. That's a 45 degree drop in a minute; my concern is with boiler shock.
    4-Hydraulic separation: as far as I've been advised, the only way to protect the boiler from the cold return water is to use the turbomax as a buffer with primary secondary piping. That is, switch the pumps; make the VT2218 the primary pump, and the VR1816 for the heating as secondary loop. In order to do that we need hydraulic separation so the two circ flows can act independently of each other and the buffer can inject some warmer water into the boiler return. as far as I've been advised, having the two circs run at the same time without the hydraulic separation would yield very uncertain results.
    5-I'm all for avoiding the buffer solution if possible. If Setpoint setting can solve the cold return issue that would be great. definitely something to look into.

    I will ascertain how the circ controls are wired.
  • SuperJ
    SuperJ Member Posts: 609
    edited November 2019
    I mostly agree with Chris except for the placement of the primary circulator. It should be located before the secondary pump takes off and run for both indirect and heating calls.

    The VT pump will not be able to protect the boiler in setpoint mode unless the primary circulator is running as well. You will just run with a high delta for a long time and have uneven heating on your radiators due to lack of flow.

    In setpoint mode it may not consistently give you the flow you need unless set to a overly high setpoint. It will throttle the pump down as the water comes up to and exceeds setpoint starving the last radiators.

    A bit a of hack that might work, in set point mode would be to place the RWT sensor on the boiler inlet and the SWT sensor in the secondary return and set the set point to something between 130 and 160f. That way the pump will throttle when boiler EWTs are low and then pump enough flow to bring the return water back hot enough to ensure the last radiators see some hot water.

    Whatever boiler protection strategy you go with, needs to be able to decouple the load when temperatures are too low. That’s a hard to do without some sort of mechanism to bypass hot boiler supply into the return keeping it 125f or higher.
    D107
  • D107
    D107 Member Posts: 1,849
    edited November 2019
    @hot_rod
    hot_rod said:

    A 3 way thermostatic for boiler return protection? Your tank would substitute for the hydro sep shown in this drawing, 2 not 4 piped.

    Mix valves for the distribution system could be thermostatic or electronic to give you more control with reset function.

    So your point is that thermostatic 3-ways--being cheaper I assume--are equally appropriate as electronic valves?
    Also, some primary-secondary questions:
    1. In most diagrams I see, the secondary circuit takeoff is at a right angle (tee) from the short fat header, not a 90EL from the end of the header. Is that the preference for both tank supply and return?
    2. In some buffer diagrams, it appears that the flow from the turbomax tank to the secondary comes from the bottom tank return port. True? I would have assumed it would come from the hotter top portion of the tank, but I guess that would require the water to move in two directions at once--into the tank from the primary pump and out of the tank from the secondary circ.
    3. I see some buffer systems put the primary circ near the end of the common return, just before the boiler instead of fairly close to just after the PONPC in the boiler supply piping. i'll assume this is no special preference as they are both after the PONPC.
    4. Is there a specified length for a short fat header? Maximum length? Must both be equal in length?
  • hot_rod
    hot_rod Member Posts: 22,022
    Doesn't matter how you pipe off the fat header pipe

    Supply from the top of the tank, always

    Some high pressure drop type boilers boilers prefer the pump flowing into the boiler, so pumping into the return. The HX in the boiler sees the delta P added by the circ.

    The header needs to be sized to handle all the combined flow (gpm) ideally with a low flow velocity. 2fps or less. Pipe sizing tables show flow velocity in various sized pipes at various flowrates.

    It's a low loss header, that short fat section, ideally very little flow velocity.

    This table give you an idea of sizing pipe by flow rate and flow velocity.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    D107
  • D107
    D107 Member Posts: 1,849
    @Hotrod You said, "Supply from the top of the tank always." I can see that's true for DHW, but here's the diagram on page 9 of the Turbomax for a Buffer Setup but the Primary Loop heads down through the tank top and exits the tank return and THEN takes off for the secondary (and then tertiary?) circuits. So secondary seems to be fed from bottom of tank.

    I'm going to have to find an Idronics that gets into buffer tanks. I think hydraulics IS rocket science.



    mikemac52
  • hot_rod
    hot_rod Member Posts: 22,022
    Ideally the tank will stratify, as such have more useable energy. So by supply from the top, I mean to say supply to the distribution from the top, hotter portion of the tank.

    here is the link to thermal storage Idronics 17

    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    D107
  • SuperJ
    SuperJ Member Posts: 609
    > @D107 said:
    > @Hotrod You said, "Supply from the top of the tank always." I can see that's true for DHW, but here's the diagram on page 9 of the Turbomax for a Buffer Setup but the Primary Loop heads down through the tank top and exits the tank return and THEN takes off for the secondary (and then tertiary?) circuits. So secondary seems to be fed from bottom of tank.
    >
    > I'm going to have to find an Idronics that gets into buffer tanks. I think hydraulics IS rocket science.


    I think it is necessary for the injection setup they reference in their drawing, because you don't want to dump cold zone return back into the top of your tank (and compromise your DHW generation capability). But if you takeoff your heating zones from the top and return them to the bottom you'll be ok.
  • hot_rod
    hot_rod Member Posts: 22,022
    One of the functions of a 2 pipe buffer is that the boiler output can go directly to the load without interfacing with the tank.
    Possibly on a design day the entire boiler output is going to the zones, so the boiler wants to pipe to the top where the distribution connections.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    D107Rich_49
  • D107
    D107 Member Posts: 1,849
    edited November 2019
    Not sure why an ESBE/Danfoss Thermic bypass valve has not been considered. Has three opening temps: 140º, 131º, 122º. With this, no balancing valves are needed. True, no buffer benefit but should solve the problem, yes? https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Danfoss-193B1700-Product-Overview.pdf

    Also the Caleffi 280. https://www.caleffi.com/usa/en-us/catalogue/thermoprotectm-thermostatic-mixing-valve-high-flow-sweat-280965a This unit has wider range and is more adjustable than the Danfoss. Has a 115º + 18 = 133º feature.

    I've been told that these might result in less even heating with our series piping; certainly this won't avail me of the 48 gallon Turbomax thermal mass.

    So far I've narrowed it down to Taco I-series 3-way electronic mixing valve with outdoor reset, thermostatic 3-way valve, and Danfoss thermic system bypass/Caleffi thermoprotec valve.

    Another thread on the subject: https://forum.heatinghelp.com/discussion/160451/will-a-danfoss-esbe-vtc-thermic-valve-used-to-control-return-temp-lock-up-the-system-flow
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    This is what I would recommend if you go with the Thermic/Thermoprotec. There are ways of cutting a valve in that are a bit easier but this will give you the best protection and balance. I would get the 130F element, but since there is a 18degF control band the 122F would likely work too.

    You would need to get the boiler protection valve (Caleffi/Danfoss/Taco i-Series), and the larger ZVC with DHW priority.


    D107
  • D107
    D107 Member Posts: 1,849
    edited November 2019
    Thanks much for the diagram. In this setup--with the Thermic System Bypass Valve by either Danfoss or the Caleffi 280-- I would hope to have the secondary take-off tee off the top of the 2" header from the top of the Turbomax and then double back to connect with the existing location of the heating circ. So while the circ is not as close to the tank as we'd like it, the take off would be, which I assume allows it to function as we'd like it.
    In this setup, I assume the heating circuit would be receiving flow from the top of the turbomax for not only boiler protection but also as a buffer to allow short heating cycles without the boiler firing?
  • SuperJ
    SuperJ Member Posts: 609
    You may be able to run off the buffer directly without the boiler. But you want to make sure the tank is maintained hot enough to have uninterrupted DHW.

    To do this you would use the tank aqua stat to fire the boiler. And just use the zone valve controller to start the secondary pump and open the valves. But you wouldn’t have DHW priority.

    If you want to run off the tank without the boiler. I would recommend the taco I series valve to control the secondary supply temperature in outdoor reset mode. It will draw down the tank slower on mild days and could be setup to throttle if your tank supply gets too cold giving you dhw priority using the boiler protect feature.

    I’ll try and draw a diagram for that, it would be a bit different.
    D107
  • D107
    D107 Member Posts: 1,849
    edited December 2019
    @SuperJ. Thanking you in advance for that alternate diagram. However based on your post, I'm not sure I'd want to give up DHW priority. The full buffer function seems to add complexity to the system. The boiler protection aspect is much higher on my priority list than having the turbomax avoid boiler firings on small loads.
    So perhaps the choice would be between a thermostatic valve or a electronic one and maybe a 3-way or 4-way valve. Perhaps the new diagram could show a 4-way valve since my installer had mentioned that. Presumably whether a valve is thermostatic or electronic the diagram would be the same.
    I assume that for the thermostatic bypass function, the turbomax thermal storage could be tapped. I don't have a sense of how to calculate, on a given firing cycle, how many turbomax gallons of its 48 would be needed to bring up the return temperature from an initial 66 (about the lowest it gets in the shoulder season when there's long intervals between firing cycles) up to 130-140. To do that I have come up with a more accurate estimate of the water volume of my CI rads and piping.
    The two largest living room rads are: US Radiator Triton, 50" long, 3 Column, 22”H, 9” wide, 20 sections @3sqft/sec = 60EDR. There are two --very rough--volume formulas I've seen:
    1. 14 liters (3.08gal) per kw (3412btu). @240btus per EDR x 60 = 14,400btus/3412btu = 4.22 x 3.08 gal = 13 gal.
    2. 1.5 pints per EDR. 60 EDR x 1.5 = 90 pints or 11 gallons. (I'll use this one.)
    3. I measured the parts of the largest radiator that contain water, and came up with 2720 cubic inches, which equals 11.8 gallons.
    This is much more volume than I or any tech had estimated. So for radiators and piping for main zone, estimated water volume is 46 gallons. All three zones rads, piping, near boiler larger piping, and boiler itself totals 85 gallons, not including 50 Turbomax gallons. So, worst case scenario if let's say all three zones hold estimated 85 gallons of cold 66º return water against 50 gallons of avg 150º turbomax water (maybe raise Turbomax high limit?) plus a firing 50kbtu net boiler, does that sound doable without lowering Turbomax temp to the point where it calls for DHW in the middle of the heating cycle? (Note the boiler takes about 10-15 minutes to bring up the Turbomax from 135 to 150. This new water volume figure of 85 gallons plus the 50 in the Turbomax, raises the total to 135gallons instead of the prior estimate of 75.)
    Also it gives me the nutty idea, that with constant heating circulation the entire system water volume could be treated as a buffer, kept at minimum of 100º so that a heating cycle would have to raise the return temp much much less.--but of course with an atmospheric boiler how you do that without condensing?
    It just strikes me that with so many Wall discussions on how most of the time nighttime setback doesn't save money, what I have is a huge setback on every cycle, where water is going from 130 back down to 65º and then has to go up again, so in theory keeping that water from getting that cold might be more economical than having to raise it to 130-140 every cycle. Or I could add another 50 gallon storage tank....nahh...
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    Here is another option (Taco iSeries 4 way). It doesn't let you run without the primary pump though, and I think outdoor reset may be of limited utility in your case since you need boiler protection, and the thermal mass of your system gives you an inherent reset based on off runtime to achive setpoint. It also only give boiler protection for your space heating loads, not DHW calls if the tank is depleted.

    The mass (as you've calculated) is likely high enough that you don't need try too hard to run off the buffer tank for space heating. In other words boiler protection and proper primary secondary pumping should be your main goals. The Caleffi or Danfoss 130F valves will give you boiler protection, and reworking the tank pump into a primary/tank pump will give you proper primary secondary pumping (so your radiator flow doesn't suffer while the boiler protection valve is active).

    You can setup a ZVC to give you DHW priority where you interrupt space heating if the turbomax's aquastat calls for DHW heating. Otherwise the space heating and DHW can work at the same time if the temperature is high enough.


    D107
  • D107
    D107 Member Posts: 1,849
    edited December 2019
    @SuperJ, thanks. Ok so let’s assume we’ve now narrowed the overall goal to boiler protection with primary-secondary piping and the valve choice to the Caleffi 280 ThermoProtec 3-way mixing valve 122º or 130º setting, or Taco I-Series 3-way electronic mixing valve. Given the install issues we've had I'm trying to ensure I understand the good advice that's being given:
    1. Thermostatic valve, while not as accurate as Electronic, seems simpler--doesn't need a separate return water temp sensor. (Caleffi also makes a '280 ThermoMix mixing valve' --not sure what the difference is from ThermoProtec.)
    2. Valve on boiler return close to boiler will be 1"-1.25” NPT size and supplied by 1"-1.25" black pipe Via tee off boiler supply.
    3. No check valve needed on Turbomax return, only on heat return.
    4. We Need the Taco ZVC 404 Relay with DHW Priority instead of current ZV403 and SR501.
    5. Primary Circ would be VT2218 fixed speed and run on either Heat or DHW call.
    6. Heating circ would be VR1816 on Constant Pressure setting and run only on heating call. (*Note that the Circ Setters' orientation--on the return--may have to be changed if thottling is required due to current location being right after a 90El which I believe results an intolerable roar with anything above minimum throttling. I think Caleffi wants 4-5 inches of straight pipe run before a circuit setter. See photo.)
    7. On a heat call, both circs would run (off of Hydrostat 3200+) and both boiler supply water and Turbomax hot water from tank top would go to Heat Load. (*I assume that during heating call hot water goes both out of the Turbomax top pulled by Heat Circ and from boiler pulled by Primary circ. When Turbomax tank temp falls below cut-in temp, then DHW call would interrupt heating cycle.
    8. After piping is fully clear, we can get back to @gaabbee 's control settings. I just want to be clear that given the total return water volume, the Turbomax and boiler will be able to produce enough hot water to handle the boiler protection without depleting the Turbomax so quickly that heating cycles are constantly interrupted as the boiler and Turbomax catch up. It appears that Hydrostat Circ Hold will still be in effect as an added safety.
    9. Re: Boiler-Turbomax Capacity. If all three heating zones call, total required GPM from boiler will be 10gpm, with about 7gpm to zones. Not sure how to visualize how many gpms would return for boiler protection, how many gpm would go on to heating load, and how many gpm would go to heating load from Turbomax. Or with primary required 5gpm speed, how will heating load get its 7gpm?
    10. Hopefully there's a way to calculate that the required de-coupled primary flow within the Turbomax for the heat call does not conflict with the required 5gpm flow into the Turbomax from the boiler for the DHW.





  • gaabbee
    gaabbee Member Posts: 43
    Based off my memory you have 48 gallons in the turbomax and maybe 5 gallons in the boiler? I think the boiler you said was 53k btu's?

    If the turbomax calls for heat and the secondary pump shuts down it will take your boiler to heat the 53 gallons of water from say 140* to 160* about 11 mins.
    D107
  • D107
    D107 Member Posts: 1,849
    edited December 2019
    @gaabbee Yes, 48 gal turbomax, 5 gallons boiler. no problem with heating up the turbomax, 11-15 minutes, yes. Issue is the rest of the heating CI rads and piping which contains 80 gallons. My last two posts speak to the issues. Boiler is 50mbh net, 70mbh firing rate.
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    Excellent, you're setup for success. The ZVC404 offers a bunch of flexibility on the controls side.

    Your flow setters will probably be much quieter with the delta P pump since the pump will only have to be set high enough to handle your highest pressure drop zone. The other two zones may have to be throttled a bit to avoid overflowing.

    Your primary pump should be set for probably somewhere around 7gpm. It would be good to roughly match your primary flow to your highest secondary flow, if it doesn't match exactly that's not a big deal since the difference will flow thru your tank. You can calculate this based on the temp delta across the boiler since it's fixed capacity.

    Don't worry about the capacity for boiler protection. The actual BTUs delivered won't be reduced, just delayed slightly while the boiler warms up. If the boiler keeps you house and hot water warm now, it will after. And since you will have primary secondary piping the zone flow won't be diminished during warmup.

    The secondary flow will be biased towards the tank during warmup. Worst case is your turbomax gets depleted during warmup, all that will happen is the secondary pump will be paused while the tank recovers. Once the tank recovers the secondary pump will be allows to run again. Even if this cycle repeats a couple times that's fine since the boiler should be running the whole time.

    Eventually the tank and house will get enough BTU's to be satisfied, while maintaining hot DHW throughout the process.

    D107
  • gaabbee
    gaabbee Member Posts: 43


    you can plug the numbers in here to find out the run and off times
    D107
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    To answer your questions about flow:
    If the zone flow exceeds the boiler flow.
    The difference will go thru the tank. So if your primary is 7gpm, and secondary 10. The tank will make up the difference of 3gpm. So the tank will be depleted at a rate of 3gpm. If the tank gets cold enough to trip the aquastat, then the secondary pump will stop, and the tank will get the full 7gpm until the aquastat satisfies. All is well.

    What if the primary flow is higher than single zone flow?

    The difference will charge the tank. The RWT boiler protection valve will ensure whatever water enters the tank is sufficiently hot to produce DHW. If the primary flow is 7gpm, and zone is 4gpm. The tank will get 3gpm of hot water from the boiler, slowly charging it during a heating call. All is well.

    What if only the tank is calling?
    If only the tank is calling (no zones), all 7gpm goes into the tank charging it up. All is well.

    What if the thermostatic valve is limiting primary flow on warmup?
    If the thermostatic valve is recircing (cold return), the same as above will happen but the primary flow rate will be reduced. This isn't a problem, but may make the tank call for heat sooner. The important thing is the DHW priority so if the tank gets too cold, space heating is stopped. The DHW will be heated. As the return comes up to temperature the GPM will rise from close to 0 up to a max of 7gpm. The period of low flow is not a concern, it is a transient condition.

    The thermostatic valve just moves the thermal equilibrium point to the boiler return, instead of letting the rads dictate it. No matter what combination of DHW and heating loads you get, the boiler will be protected, and the DHW will be prioritized.
    D107
  • D107
    D107 Member Posts: 1,849
    @SuperJ @gaabbee Thanks for the info and encouragement. My hope is to come up with a detailed piping diagram by tomorrow, post it here for approval and then write out controls scheme based on info in this thread, then compare notes with the installer who's been doing his own research. I think working off a diagram is very important to avoid surprises. A few points:
    1. Not sure why circuit setters will be quieter. With all the setters wide open, even with flow up to 15gpm in one zone--as it sometimes got when it was on the ∆T circ setting--there was no or little noise. Only noise comes from even a little throttling even at 2gpm. Do not circuit setters need a few pipe diameters of a straight pipe run to avoid that? Don't want to get this repipe done and find we have to go back and open 'er up again. With the ∆P pumping, as you say we may need to throttle even more than we do now. Noise would be intolerable.
    2. 3-way valve size: 1.25" or 1"; bypass from primary to return: 1.25" or 1"? Note near boiler piping is 1.25". Zone piping is 3/4".
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    Regarding the noise. I’m always in favour of the manufacturer’s recommendations. The noise will come from high velocities and pressure drop. If the pump is set not to produce excess pressure to begin with, you won't have to throttle as hard and it will stay quieter. But I meant that a delta p pump will throttle itself as the valves close and will likely be quieter than your previous setup. You only need the pump to produce enough pressure to get your design flow thru the worst zone. What flow is that?
    You might be able to swap your pumps now before doing any repiping if the flange you’re flange measurement is the same. And see if noise is an issue.
    Only 2 out of three zones should have any throttle on the flow setters. If you need to throttle all 3 then your pump is set too high. You may need to try constant pressure and proportional pressure to find a curve that works for any combination of zones.

    Regarding valve size, at the boiler flow rates your looking at a 1" valve would be fine, generally you want the Cv to be somewhat close to the expected flow rate. If the Cv is too high the valve won't be as stable, too low there will too much pressure drop across the valve.

    1" piping is fine for the near boiler piping (it will have a velocity of 2.9ft/s at 7.9gpm). But for the common/header piping near your tank where the secondary ties in 1.25" would work, but 1.5 would be better to stay under 2ft/sec. No need to go any higher with the sub 12gpm flow rates you have.
  • D107
    D107 Member Posts: 1,849
    @SuperJ As far as my observations go, when all three zones are calling in Fixed speed VT2218 mode, total boiler flow is 10gpm and the sum of all zones gpm is about 7gpm. When each of those zones calls individually, the gpm of each is at least 1/2 gpm more than its gpm when all are calling. I'll have to compare the two circs' pump curves. FWIW Taco's notes are that for the VR1816 constant pressure mode is best for operating with zone valves, but, I doubt that's written in stone.
  • D107
    D107 Member Posts: 1,849
    edited December 2019
    @SuperJ oh re: worst zone--on its own I have first floor I at 3.5 gpm, 2nd floor is 2+gpm, and basement 2. Ideally I won't have to throttle anything. But even if circ throttles itself as long as circ setters throttle anything, there will be noise. Those gpms I gave you are kind of ideal for my series, system--gets enough --if a little uneven --heat to the farthest rads. Heat is a little less at last rad--where T-stat is--but house heats nicely.
  • SuperJ
    SuperJ Member Posts: 609
    edited December 2019
    D107 said:

    @SuperJ oh re: worst zone--on its own I have first floor I at 3.5 gpm, 2nd floor is 2+gpm, and basement 2. Ideally I won't have to throttle anything.

    You may not have to "throttle", but you can and should fine tune the balance. You want all the rooms on each zone to heat evenly without excess flow. Too little flow and the first rad will get hot but the next ones will take too long and give you uneven heating. To much flow will dilute your buffer quickly, and possible cause other problems (like noise). You really want to have the min flow that gives you even heating. This will maximize the buffer capacity of the turbomax. Loop delta T's are a good indicator but not set in stone.

    It's fine if the GPM varies a bit depending not the combination. You can't constrain everything. The flow will float a bit.
  • SuperJ
    SuperJ Member Posts: 609
    D107 said:

    @SuperJ As far as my observations go, when all three zones are calling in Fixed speed VT2218 mode, total boiler flow is 10gpm and the sum of all zones gpm is about 7gpm. When each of those zones calls individually, the gpm of each is at least 1/2 gpm more than its gpm when all are calling. I'll have to compare the two circs' pump curves. FWIW Taco's notes are that for the VR1816 constant pressure mode is best for operating with zone valves, but, I doubt that's written in stone.


    As long as your common piping has a low pressure drop compared to the zones, constant pressure will work well. If you have more loses in your common piping, a proportional pressure curve can even things out.