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Greenstar Boiler with Indirect DHW with Zone valves - many questions

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dtlemoine
dtlemoine Member Posts: 13
All - first post here, but long time lurker. Many, many thanks for the pages upon pages of wisdom that I've consumed over the last ~18 months troubleshooting a flaky install of a Mod Con with Indirect DHW.

For some background, I have 5 heating zones plus the indirect DHW. A couple of the heating zones are bordering on micro-sized, but I can see why the original owners did it this way, a couple zones are dedicated for rooms that don't get much use and can be kept pretty chilly in the winter. Perhaps electric would have been a better choice for those rooms... But I digress.

The 5 heating zones are controlled by a Taco ZVC406 Zone Valve Controller and fed by a Taco 007e. The indirect DHW is a Mega Stor 40 gallon, fed by it's own Grundfos 15-58, currently set to high. Boiler is a Bosch/Greenstar KWB42-3. There are no check valves anywhere in the piping. The boiler is plumbed with the LLH removed. Boiler circ is also set to high currently.

Piping layout... Boiler LLH goes to 1" iron supply pipe to a tee for the indirect DHW. 1" iron pipe continues after the tee to the expansion tank & airscoop, changes to 1" copper, followed by Taco 007e, followed by 1" copper manifold with 5 zones of 3/4" copper, each with a ZV. All 5 zones plus the indirect DHW return via 3/4" copper to a 1" copper manifold, eventually changing to 1" iron back to the boiler's LLH.

The indirect is fed by a 3/4" copper to the grundfos circ, and return is also 3/4". The boiler controls the circulators, alternating between space heating and indirect, with indirect on priority at max output, while heating temp is handled by the outdoor reset.

I have a number of questions...

1) Do I need to swap out the 3/4" piping feeding the indirect DHW with 1"? Mega stor calls for 1", the tank has trouble keeping up with a single shower that isn't pulling more than 2.5 gal/min. The circ on the indirect seems plenty robust. I suspect the 3/4" is having trouble carrying all the BTUs to the Mega stor quickly enough.

2) I get phantom flow on whatever heating zones are calling, when the indirect kicks in. I can tell as the heating zones will get scalding hot, when the outdoor reset could have been calling for nice gentle heat. I think it's actually flowing backwards through those zones. Is it possible to wire the system in such a way the zone valves close when the system calls for DHW heating, even if the thermostats are calling for heat? If not, would it make sense to add check valves to each zone? We previously had a check valve in the Taco 007e but it was noisy as heck so the plumber removed it. Said not to worry about phantom flow...

3) I get a crazy amount of cycling. I've back-of-the-envelope calculated my heat loss at around 100k BTUs on design day. The boiler produces 151k BTU, but only has a 4.2:1 turndown so min fire is ~36k BTU. I'm well under 36k most of the year, so the system cycles, I get run times of 1-2 minutes typically, so obviously losing efficiency here. Aside from swapping out the boiler for a smaller unit, with better turndown ratio, is there anything I can do here? Buffer tank? If yes, I have a few more question on sizing and piping...

4) The installer didn't include an expansion tank for the DHW (cold water supply has a backflow preventer). How critical is the expansion tank? I plan to put one in, but wondering how quickly this needs to happen. He didn't pipe in a heat trap either, I can feel the hot water climbing towards the ceiling when not in use. I'll configure with a heat trap when I cut in to the piping to install the expansion tank...

5) Bonus question, for any Greenstar owners... Assuming for a moment the thermostats are calling for heat, and DWH is satisfied, the internal boiler circ and Taco 007e will periodically shut off. Like, all of the sudden, system goes silent. Stats are still calling for heat, but everything just shuts off. SyYstem sits silent for 4-5 minutes, then circulators fire right back up and system continues on it's merry way.

Any window folks can provide is extremely appreciated. I've long grown tired of going back and forth with the original installer, and the story above is much improved since the original install, at this point I'm hoping to just be tidying up the loose ends.

Happy to provide more details about the install, clarifications to anything I described poorly, and photos wherever helpful.

Cheers,
Dave
Framingham, MA
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Comments

  • dtlemoine
    dtlemoine Member Posts: 13
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    Here are some photos that may help provide context.






    Framingham, MA
  • mattmia2
    mattmia2 Member Posts: 9,734
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    1. The capacity of your HDW may be producing what it was designed for. Usually there is some way to look at the firing rate of the boiler. If it is firing at 100% when you are experiencing one of the calls where it runs out of hot water then it is a design issue, not a piping flow issue. It could be either. If you have particularly cold incoming water in the winter your tank could be undersized. There should be a first draw table in the manual for the indirect that will give how long the tank can supply hot water various flow rates with various boiler sizes and tank sizes.
    2. You would need a flow check in these zones to prevent phantom flow or to make the zone control close the zone valves during a dhw priority call (which I am not sure if it is possible). This is likely the cause of problem 1, you are still heating the heating zones when you need nearly all of the capacity of the boiler to keep up with the DHW demand. You could add a separate flow check in the common piping of the heating loops, others here can give you advice on which ones will be quiet.(a flow check requires some pressure to open it, it stops forward and reverse flow with the pump(s) off).
    3. Most mod con boilers have anti short cycle settings, you can give it something like a 10 degree or more difference between when the burner shuts off and when it turns back on during a domestic heat call, you can make it wait some amount of time, say 10 or 15 minutes before it fires again and my HTP has a feature called "step modulation" where it starts at the firing rate of the previous cycle and steps up the rate if it doesn't get the water up to temp in some period of time, this keeps it from heating the water at high fire rate up to the upper limit in a couple minutes, it makes heat more slowly to run longer cycles. Take a look at the manual to see what features the Bosch has.
    4. The expansion tank is pretty important, I am surprised you aren't getting dripping from the relief valve and a spurt of high pressure when you first open the hot water. Consider putting in a pressure gauge while you're at it.
    BillyO
  • Jamie Hall
    Jamie Hall Member Posts: 23,415
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    Take the easy one first. You need an expansion tank on that domestic hot water, like... yesterday. That is not an option or nice to have, and it's a bit of a wonder that the lack of one hasn't caused problems.

    It would be possible, with some wiring wizardry, to add relays to close any open zone valves when the DHW is calling. It would be easier, in my view, to add check valves to control the phantom flow. Check valves don't have to be noisy, if you use the right ones.

    It would be helpful to rearrange the location of the main pump and the heating expansion tank and air scoop so that you are pumping away from the tank, rather than towards it. The system probably works OK the way it is, but that's not to say it wouldn't work better pumping away.

    There are no magic bullets to control the cycling; your boiler is enough bigger than what you need (like half again...) that it will cycle, no matter what. However, while it won't stop it, a nice buffer tank will reduce the cycling to a much more manageable level. You would need another pump (one to circulate water from the boiler to the buffer, one to circulate water to the zones -- you have that one -- and one for the DHW -- you have that one, too).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,244
    edited March 2020
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    what temperature are you running the DHW tank? I see it has a thermostatic mix valve. As such 140F should be considered both for legionella protection and extending the drawdown. You should get around 60 gallons of usable DHW from that tank. Maybe define your DHW needs or wants.

    low flow shower head cold help extend that drawdown.

    The indirect circulator should have a check valve inside.

    Yes you need a DHW expansion tank or other means of expansion control, by code.

    Does it have a DHW recirculation system?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • dtlemoine
    dtlemoine Member Posts: 13
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    Thanks all! A bit of a rambling response, I think I've captured everyone's feedback and questions.

    The 40 gallon DWH tank in theory should cover our house's needs (2.7 gal/min at 77 deg rise, with 180 degree boiler water - theoretically sufficient for a shower that maxes out at 2.5 gal/min). Just the wife and I at home, no kids. The tank is set to heat to 140 deg, and we mix down to the mid 120s. Well water definitely colder in the winter, but even in the mid 40s, we should be able to get back up above 120 deg (in theory, of course). I suspect the phantom flow from the cooler heating zones cooling down the DHW supply water hurts us here. Check valves, or some fancy relay wiring - this has been added to the to-do list.

    I'll take another look through the Bosch paperwork to see if I can delay the calls for fire. The circ is humming along happily ~20 hours a day through the various zones, but the fire is a frequent on-off-on-off all day. Perhaps a buffer tank down the road to help the situation longer term.

    The pressure release on the DWH tank is 150psi, our well only cycles between 30-50psi, so either the release valve is fubar, or we're just not generating enough pressure even at the pump's max pressure to trip the valve. I will make adding an expansion tank my priority.

    Re: check valves in the zones: any concern that adding 5x 3/4" check valves would add too much head for the Taco 007 to keep up with, or is this a non-issue?

    "It would be helpful to rearrange the location of the main pump and the heating expansion tank and air scoop so that you are pumping away from the tank, rather than towards it. The system probably works OK the way it is, but that's not to say it wouldn't work better pumping away."
    - The pic may be deceptive, but we're pumping away from the airscoop and tank. Hot water flowing left to right towards the manifold, heating zones all departing to the house vertically above the zone valves. The one exception is the DHW supply coming from the tee in the iron pipe is located before the expansion tank, the 5 heating zones all come after.

    No water recirculation system in the house, so hot water only moves when a fixture is opened. The hot water climbs up the DWH supply pipe and therefore backwards through the mixing valve into the cold water supply when not being used, I think due to the lack of heat trap??
    Framingham, MA
  • hot_rod
    hot_rod Member Posts: 22,244
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    Correct the tank has a dump volume plus the ability to generate as you use it. Next I would calculate how much you use, or with a 5 gallon pail, how much you actually get before it drops to an un-useable temperature. Plenty of households get by with 40 gallon tanks, even slow recovery electric ones :)

    It is possible that the increase in pressure will not trip that 150 lb relief, especially if a hot water tap is opened frequantly.

    With 100% close zone valves you should not need checks on all the zones, unless you suspect circulation backwards up the return side? typically the indirect would work fine with just a check in that circulator.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 9,734
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    hot_rod said:


    With 100% close zone valves you should not need checks on all the zones, unless you suspect circulation backwards up the return side? typically the indirect would work fine with just a check in that circulator.

    The only caveat here is that the zone valves are open during a DHW priority call, it is just turning off that circulator, if I understand right. This could be taking enough heat away from the DHW call to make it fall behind. Because an indirect is controlled to run longer, less frequent cycles, it is heavily dependent on the full output of the boiler to make its first draw rating. A direct fired gas or electric water heater puts its thermostat at the bottom of the tank so it senses the draw quickly and fires the burner or element soon after a big drawdown begins and it may run a short cycle if that drawdown isn't very long. An indeirect positions the probe near the center of the tank to make it cycle less often but this means it has been adding cold water to the bottom of the tank for a while by the time the boiler fires and comes up to temperature so it needs that big 100,000 btu/hr+ output of the boiler to heat the incoming water and the water that has already been added to the tank. HTP has a nice chart of this in their Superstore manual, it might not be as commonly show in in other literature.
  • mattmia2
    mattmia2 Member Posts: 9,734
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    I suspect they are connecting the indirect and its pump to a built in controller in the boiler and have the zone valves connected to the zone controller with the zone controller connected to TT/DH of the boiler so the zone controller knows nothing of a DHW call and the DHW priority is handled in the boiler.

    If this is the case, one way to make the zone valves close on a DHW call would be to add a 120v coil relay in parallel with the DHW pump terminals on the boiler and connect the normally open terminals of that relay to a zone set up as DHW priority in the zone controller. That would be simpler than adding a check valve and would not have the slight hit to pump performance the check valve would have.
    egansenSuperTechSolid_Fuel_Man
  • hot_rod
    hot_rod Member Posts: 22,244
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    If everything wires to the Taco box, there should be a DSHW priority function, that alone may clear things up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2Grallert
  • fenkel
    fenkel Member Posts: 162
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    Go back and check all zone valves, take cover off and check.to make sure theyare opening and closing correctly.
    Are you using an fw200 controller?
  • fenkel
    fenkel Member Posts: 162
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    I would also pull all circulator pumps and check for ifcs...make you have them in...
    Turn your grundfos on indirect up as high as it will go.
    Next :Follow the flow of boiler hot water..
    Turn your heat controller(thermostate) to each zone off, then go over to wash machine tub and open hot valve, next run indirect tank down until it kicksthe boiler on, next place a hand on each zone to see if water is pushing back.. give it a while to run... you should only have the boiler hot supply only heading to indirect tank.
    A small indirect tank shoukd make almost unlimited water...
    We just installed a Bosch 131 with a 40gallon indirect tank and i believe the first hour return was 282 gallons per hour...almost 4.5 gallons per minute... we plumbed it per the manual. 16 gpms and head of 5.1...
    We did set tank at 140 and have a thermostat controller set at 118..
  • dtlemoine
    dtlemoine Member Posts: 13
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    "I suspect they are connecting the indirect and its pump to a built in controller in the boiler and have the zone valves connected to the zone controller with the zone controller connected to TT/DH of the boiler so the zone controller knows nothing of a DHW call and the DHW priority is handled in the boiler.

    If this is the case, one way to make the zone valves close on a DHW call would be to add a 120v coil relay in parallel with the DHW pump terminals on the boiler and connect the normally open terminals of that relay to a zone set up as DHW priority in the zone controller. That would be simpler than adding a check valve and would not have the slight hit to pump performance the check valve would have."


    This, this, this. Thank you - I think this is exactly what I'm looking for.

    You're spot on - both circulators are controlled by the boiler, the heating circ shuts down the same moment that the DWH circ fires up. The Taco ZVC knows nothing about the hot water call, so it sits there like a dummy, leaving the ZVs open that are calling for heat. I have one spare zone on the ZVC, the priority zone, so I will tinker to set up the relay as you describe. This seems like the ideal solution.

    The installer originally piped the DWH with a zone valve rather than circulator, as a priority zone on the Taco controller, this is why you see the 3/4" stub coming off the manifold. This was before I asked him why were installing an indirect DWH tank on a mod/con with an outdoor reset as just another zone. This is when I realized he wasn't planning to install an outdoor reset...

    Any other thoughts about the 3/4" piping on the indirect? Mega stor looks like they call for 1" or 1 1/4". Obviously I need to clean up the phantom flow from the heating zones cooling it's supply down, but is it worth changing out the pipes? The phantom flow seems to originate on the return side, I can feel the returns of the heating zones pull the 170-180 degree water backwards through the zones when the DHW fires, the supply sides on the heating zones eventually heat up enough to burn my hands if the DHW call is long enough.

    Thank you, thank you, thank you again for everyone's insight. I have learned so much from this awesome crowd over the last year, what an awesome place to turn for help.
    Framingham, MA
  • dtlemoine
    dtlemoine Member Posts: 13
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    No IFCs on either circulator - when the guy put the Taco in, he specifically said he never installs them, because he's never seem phantom flow cause an issue. I'm almost quoting verbatim.
    Framingham, MA
  • fenkel
    fenkel Member Posts: 162
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    How about the shirt cycling issue?
    Is the outdoir reset ab fw200 controller?
  • GW
    GW Member Posts: 4,699
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    You have a KWB and you have an indirect? I don’t follow, normally it’s a combination boiler and no tank, or a heating only boiler with a tank
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • mattmia2
    mattmia2 Member Posts: 9,734
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    These are a little more expensive but a cleaner way to just install it through a knockout instead of having to find someplace to mount a relay, thanks to I think @hot_rod :
    https://www.functionaldevices.com/products/building-automation/relays/#pilot
    dtlemoine said:

    Any other thoughts about the 3/4" piping on the indirect? Mega stor looks like they call for 1" or 1 1/4". Obviously I need to clean up the phantom flow from the heating zones cooling it's supply down, but is it worth changing out the pipes? The phantom flow seems to originate on the return side, I can feel the returns of the heating zones pull the 170-180 degree water backwards through the zones when the DHW fires, the supply sides on the heating zones eventually heat up enough to burn my hands if the DHW call is long enough.

    You can look at the firing rate of the boiler during a big dhw call (once you get the priority thing sorted out). If it is at 100% it is getting all the heat it can output in to the indirect tank water. If it is modulated down, it would benefit from bigger piping to increase the flow. You can film it with a cell phone to monitor what is happening during the cycle without having to stand there watching it.

  • dtlemoine
    dtlemoine Member Posts: 13
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    Gary - it's the KBR, not the KWB (floorstanding, not the wall mount).

    Fenkel - yep, FW200 controlling the temp. I've been slowly nudging down the reset curve to the point where the majority of zones are calling for heat 20+ hours a day. The short cycling I'm referring to is the boiler firing, that happens dozens (maybe more??) of times per day for 1-3 minutes when it's warmer out. It'll run for maybe 5-10 minutes in the coldest of weather. More fine tuning on the curve is necessary. I have high output baseboard everywhere in the house (the old spirotube, newly installed), nearly every foot of exterior walls, so we're able to run at lower than typical temps for baseboard, theoretically helping the efficiency by spending more time condensing.
    Framingham, MA
  • dtlemoine
    dtlemoine Member Posts: 13
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    Mattmia (Matt?) - good call. Just ran a test with the zone valves closed, opened a few hot water faucets... maxed out very briefly at 82% fire, then slowly settled down through the 70s stabilizing in the mid 60s. Boiler loop was at or above 180 as the supply for the indirect slowly worked its way up to 180. Seems like more pipe could help?
    Framingham, MA
  • fenkel
    fenkel Member Posts: 162
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    Have you given any consideration to turning down the btu output on heating cycles...
    I have done it on the last install.
    We built the system to supply 145 degrees supply for heating, but we had alot of short cycles...icalled tech support and the tech walked me thru turning the supply output down.. know in colder temps boiler will run 12 minutes on, then cycles for 10 to 12 minutes...
    Question what temp us your supply temp for heating set at...
    T he fw 200 controctor has a indorect hit water program in it, you need to attach the indirect pump to boiler, the set boiler to: water heater as a zone...when the call comes for hot water the boiler will heat the tank and the zones, but thete is a small issue, all zones will go the output supply temp for heating the tank..
    The issue you have is this, the zone controller you have will not teconize the indirect if i the indirect is hooked to boiler.. now if you have the indirect hooked to the zone controller it will only use the supply temp to heat the indirect..
    Do you have the installer manual???
  • fenkel
    fenkel Member Posts: 162
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    If youll like i could walk you thru the adjustment..its pretty easy...

    Here's how we set it up in.general:
    Let presume we did an acurate heat loss calculation.
    The net boiler btus per heat loss calculation is 85k
    Boiler btus is 100btus.
    We set the boiler output to 85%.
    Remember the indirect is still at a 100% to gives up lots more btus for water heating..
    Now we check to see how the boiler reacts at the 85% we set it at that, alot of times we can take out another 5% and we now have a boiler that no longer short cycles...but we have plenty of btus to heat up water...
    I emailes a guy on " the wall"
    Years back and he stated he'd.cut his output btus down to make his combi boiler give better hotwater, because he could use a bigger btu combi boiler and make it work..
  • mattmia2
    mattmia2 Member Posts: 9,734
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    dtlemoine said:

    Mattmia (Matt?) - good call. Just ran a test with the zone valves closed, opened a few hot water faucets... maxed out very briefly at 82% fire, then slowly settled down through the 70s stabilizing in the mid 60s. Boiler loop was at or above 180 as the supply for the indirect slowly worked its way up to 180. Seems like more pipe could help?

    I suppose you have to see if the tank temp is still falling and what the return temp is while it is modulating down. It could be a limit of the transfer of the coil but it is most likely lack of flow. ~140,000 btu/hr is a lot for the 4-6 gpm that you can push through 3/4 copper(4.5 gpm is recommended for 3/4). You would need a very high delta t to transfer that much through 3/4.
  • fenkel
    fenkel Member Posts: 162
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    Question, woukd you happen to know how many feet of heating tub you have in indirect...
    1 inch pipe would help, alot manufactures want gpms to be 16 or higher on some tanks...that with around 6 ft of head....thats a pretty good sized pump..
    The tank manual will have the gpms and head needed...that that information and head over to size a pump at grundfos website, you might be suprized that your pump might be too small..
    SuperTech
  • fenkel
    fenkel Member Posts: 162
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    Just read you last post to Matt, you need 100% to indirect tank...otherwise you will not get good hot water...
  • hot_rod
    hot_rod Member Posts: 22,244
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    with the control logic sorted out and priority working, why not see if the 3/4 lines to the indirect give you adequate DHW.

    The tank dump may cover your load, the smaller 3/4 will just slow the recovery to get the tank back to set point..
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2
  • dtlemoine
    dtlemoine Member Posts: 13
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    There is ~20 feet of 3/4" piping for the indirect, including 8x 90 deg elbows.

    The system is configured to modulate temp to the heating zones based on outdoor reset. Max supply temp is currently set to 154 deg F on design day (I think currently set to -4 deg F, suburb of Boston). Most of the time on a ~30 degree F day, I have supply temps for heating zones around 130 deg.

    When the indirect calls for heat, the system disregards the outdoor reset, and targets 180 deg supply. Last night I watched the boiler output during a call for the indirect, it started around 50%, climbed steadily to 82%, then tapered back down to the low 70%s. Supply temp slowly climbed to 180, but the boiler temp shot to 180+ very quickly. This leads me to believe that the indirect circulator can't pull the BTU's away from the boiler fast enough?? Am I reading that right?

    The Mega Stor II 40 gallon is looking for 8gpm minimum. The interior coil is rated at 2/8 ft water col of head, plus the ~20 feet of 3/4 piping above.
    Framingham, MA
  • hot_rod
    hot_rod Member Posts: 22,244
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    dtlemoine said:

    There is ~20 feet of 3/4" piping for the indirect, including 8x 90 deg elbows.

    The system is configured to modulate temp to the heating zones based on outdoor reset. Max supply temp is currently set to 154 deg F on design day (I think currently set to -4 deg F, suburb of Boston). Most of the time on a ~30 degree F day, I have supply temps for heating zones around 130 deg.

    When the indirect calls for heat, the system disregards the outdoor reset, and targets 180 deg supply. Last night I watched the boiler output during a call for the indirect, it started around 50%, climbed steadily to 82%, then tapered back down to the low 70%s. Supply temp slowly climbed to 180, but the boiler temp shot to 180+ very quickly. This leads me to believe that the indirect circulator can't pull the BTU's away from the boiler fast enough?? Am I reading that right?

    The Mega Stor II 40 gallon is looking for 8gpm minimum. The interior coil is rated at 2/8 ft water col of head, plus the ~20 feet of 3/4 piping above.

    Speed 3 on the indirect circ? If so that is about all you will get.
    Is it adequate? No harm done with the boiler ramping down if it cannot move the full DHW indirect load.

    Increasing the pipe size will increase the amount of BTUs you can move.

    If it supplies all the DHW you need, really no sense in scrapping all that tube and fittings to upsize?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2Solid_Fuel_Man
  • dtlemoine
    dtlemoine Member Posts: 13
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    Yep - the indirect is set to speed 3.

    Related but previously unasked question... What's the appropriate speed to set the boiler's internal pump to? It's also a 3-speed grundfos. Typically 2 or 3 of the 5 heat zones are calling at any given time throughout the winter being supplied by the Taco 007e. Also don't want to sacrifice DHW rebound.

    To maximize efficiency, my understanding is the fastest speed that doesn't outpace the secondary circ (so we don't suck heated water back in to the heat exchanger through the LLH).

    Here's the curve:


    Framingham, MA
  • fenkel
    fenkel Member Posts: 162
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    I might lower the speed on boiler pump... to two, but you might have zone temp problems....
    Question... do you have adequate hot water temp and amount to service your domestic needs??
    Many of our design temps are at 145 degrees and cold day temps of -20 degress..
    Close to your system design.. we still get cycle time of 7to10 minutes cycles all the time.. if you boiler is cycling every 3 minutes, something isnt correct.. your cycling to much..
    Whats your btu % set at?
    I think page 57 first section 1.e gives you that %. And how to adjust..
    Another question, whats your water quality???
    Do you use any chemicals?
    Do you use deminerized water?
    Dont use softened water for make up water..
    Water chemistry is as important as boiler cycling for longevity
  • dtlemoine
    dtlemoine Member Posts: 13
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    mattmia2 said:

    These are a little more expensive but a cleaner way to just install it through a knockout instead of having to find someplace to mount a relay, thanks to I think @hot_rod :
    https://www.functionaldevices.com/products/building-automation/relays/#pilot

    Quick question about using a relay to trick the Taco ZVC to close the heating zones when the DHW circ fires up... Am I correct in thinking this is the model I'd be looking for?

    https://www.supplyhouse.com/Functional-Devices-RIB2421C-Enclosed-Pilot-Relay-10-Amp-SPDT-1-HP-24-Vac-DC-120-277-Vac-Coil?gclid=Cj0KCQjw9ZzzBRCKARIsANwXaeLVYC8Dob6dnRDDnKAb1smPgL1f9AKJadRAvhs6KKWsEERZxbrjEgEaAs48EALw_wcB

    Would the relay be hooked up to the 120v in parallel to my circulator (circ black to relay wht/brn, circ white to relay wht/yel) then straight to the Taco (relay wht/blu to taco red input, relay yellow to taco white input)? Or have I totally bunged up my understanding of how this thing works?
    Framingham, MA
  • hot_rod
    hot_rod Member Posts: 22,244
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    The power for the indirect circulator comes from the boiler?

    So you could add the relay to that 120V line and power the taco box thru the NC wires on the RIB.

    However if for some reason the Indirect doesn't or cannot recover its load you will not have any heat. Homes have frozen with that glitch.

    When you feed the indirect thru the relay box it usually has a time out function. maybe the boiler has that included on the indirect pump output?

    Do you have a 6 zone relay box, or just 5 for the 5 zone valves?

    If you have a 6 zone box use the priority zone to power the indirect.

    Call for DHW comes to the relay box, powers the 24V valve connection, add the RIB there, white/yellow, white/blue for 24V, and power the 120V cir from the RIB, 120V hot to yellow, orange to circ. This may give you the time out function and run the entire system from one box.

    The installation manual for the Taco box should show how the priority function works.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • dtlemoine
    dtlemoine Member Posts: 13
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    hot_rod said:

    The power for the indirect circulator comes from the boiler?

    So you could add the relay to that 120V line and power the taco box thru the NC wires on the RIB.

    However if for some reason the Indirect doesn't or cannot recover its load you will not have any heat. Homes have frozen with that glitch.

    When you feed the indirect thru the relay box it usually has a time out function. maybe the boiler has that included on the indirect pump output?

    Do you have a 6 zone relay box, or just 5 for the 5 zone valves?

    If you have a 6 zone box use the priority zone to power the indirect.

    Call for DHW comes to the relay box, powers the 24V valve connection, add the RIB there, white/yellow, white/blue for 24V, and power the 120V cir from the RIB, 120V hot to yellow, orange to circ. This may give you the time out function and run the entire system from one box.

    The installation manual for the Taco box should show how the priority function works.

    Right now the power for the indirect circ comes directly from the boiler. It's a 6-zone ZVC, right now only 5 zones are connected. The call for heat to the indirect comes via a temperature sensor, rather than a thermostat, by way of the sensor reporting to the boiler the real time temp, and the boiler comparing to the set temp, and firing up the circ (and raising the temp to 180 supply, rather than outdoor reset temp).

    So effectively I'm looking to "trick" the ZVC into thinking it's part of the party. Need something that will send a 24v input to the ZVC on zone 6 when the indirect circ powers on with 120v from the boiler.
    Framingham, MA
  • hot_rod
    hot_rod Member Posts: 22,244
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    is this the relay box you have? it pretty much shows you how to do this on the installation manual.

    See that zone 6 is a priority, it will turn off all other zones when enabled.

    Terminal 1&2 at the bottom is 24V. So power the RIB
    White/yellow & white/blue. Be sure you are using the 24V leads, colors change on different RIB models.

    Now you need to put 120V onto the RIB contact "common" then take the N.O. orange I think, check on yours to the DHW circ.

    Really no "tricking" involved, this is the logic built into these relay boxes. :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Canucker
  • dtlemoine
    dtlemoine Member Posts: 13
    edited March 2020
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    hot_rod said:

    is this the relay box you have? it pretty much shows you how to do this on the installation manual.

    See that zone 6 is a priority, it will turn off all other zones when enabled.

    Terminal 1&2 at the bottom is 24V. So power the RIB
    White/yellow & white/blue. Be sure you are using the 24V leads, colors change on different RIB models.

    Now you need to put 120V onto the RIB contact "common" then take the N.O. orange I think, check on yours to the DHW circ.

    Really no "tricking" involved, this is the logic built into these relay boxes. :)

    [edit]

    removed previous comment

    [/edit]
    Framingham, MA
  • fenkel
    fenkel Member Posts: 162
    Options
    Try this:
    Take CH zone pump off the boiler and install it on taco zone controller..
    You'll no longer need to trick the system...
    Take a look at this section in fw200 controller manual..
    I believe you might have something not set correctly within the fw200 controller program..
    We set this program to run as a heat call..
    Which means heat zones can run at the same time as dwh..thats only when the heat zones call for heat..
    If the boiler is idle, a call for water heating will only activate the the pump to the indirect, but if a zone calls for heat during a call for hot water, it will get the same temp(180 degree) thru the heat cycle.

    Id also reset your % btu for CH to 65%..
    Id also look at your outdoor reset settings.
    When we went to factory training a few years back, they stated not to go crazy making changes to the reset curve , you could possible flatten out the curve and potential cause the boiler to work inefficiently.
    Fyi: alot of installers do not install outdoor resets with boilers..why?
    Like others will say.. keep it simple...
  • fenkel
    fenkel Member Posts: 162
    Options
    We have a work around for you...
    Take the pump circuit off boiler and install on taco controller.
    To do so: disconnect the incoming power to taco controller, ( might be from a from circuit breaker..)
    Next, on back of boiler , open the power junction box..this box will be the box where your pumps are hooked up.
    Take CH circulator offthat romax connector, next, install that pump on taco zone box as a pump, you might have to take a jumper out of zone controller.
    Next take a set of wires from the black romax colored connection in boiler to the taco zone controller incoming power.
    This will shut the zone off when a call for dhw calls. Pump will also shut off..
    Question... open the panel up,
    What does the display say currently..
    Should say this..
    Oitdoor temp on top line,under the line it should say, supply temp HC 1
    Then a temp,followed by time.
  • mattmia2
    mattmia2 Member Posts: 9,734
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    the boiler has a dhw contact closure to generate a dhw call with the taco zone controller? If i'm looking at it right, the dhw is controlled with a thermistor in the indirect connected to the boiler.
  • fenkel
    fenkel Member Posts: 162
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    You right on about the dhw being controller by a thermistor, but...dhw makes the call to boiler, boiler shuts down the pump to CH.
    Instead of pump attached to boiler power , the call now powers the taco zone controller. ( The pump is attached.to.zone controller).when dhw call is fulfilled the boiler will allow a call for CH and repower the taco zone controller.
    What you doing in short is poweing the zone controller from the boiler using the power that woild have run the CH pump..
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 9,734
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    Oh, i see. Almost.

    The dhw pump is still powered from the boiler

    How do you power the t-stats off the zone controller if you're cutting all power to the zone controller?
  • fenkel
    fenkel Member Posts: 162
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    We use battery power honeywell thermostates.
    Forcus pros 5000...these are non programmable units..
    mattmia2
  • fenkel
    fenkel Member Posts: 162
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    We are planning to try the new honeywell t4 pros,
    then the wifi versions asap..
    Some clients want to be able to monitor their systems will on vacation... but we have concerns w/ outdoor set programs in the newer thermostats...
    Its a learning curve w/technology.