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one circulator and using zone valve for dwh indirect (pic) ?

ron
ron Member Posts: 222
edited April 12 in THE MAIN WALL
Pondering a boiler update and piping... house with one zone of baseboard heat and I want to go with an indirect for domestic hot water, house is small (1000 sqft).

is using one VT2218 delta-T circulator and then using a zone valve on each loop (the one zone of baseboard heat and the indirect tank) a good or bad idea? Or using just one 3-way zone valve? Or should I go with the vt2218 on the baseboard heat and a separate circulator on the indirect loop? thanks.

will this work?


Comments

  • mattmia2
    mattmia2 Member Posts: 5,749
    Separate zone valves or put a flow check in both loops (it can be part if most circulators) and a separate circulator for the indirect. Make sure you size the zone valve and piping so you can get enough flow through the indirect.

    Is the boiler CI or a mod con?
  • Zman
    Zman Member Posts: 7,357
    Some details or pictures of your system would help.
    Generally, when you have only 2 zones and they have different flow characteristics, it is easier to have a circ for heating and a circ for the DHW. They will both need check valves.
    I see no reason to spend extra money on fancy circs, a simple fixed speed would work just fine (unless of course, you have been up late watching John Barba and have been convinced that every circ should be Delta T B) )
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Alan (California Radiant) ForbesMikeAmannEdTheHeaterMan
  • MikeAmann
    MikeAmann Member Posts: 435
    edited April 14
    K.I.S.S. - Use 2 separate circulators, the delta-T on the heating zone.
    You will need a "relay-in-a-box" to connect it.
    Zone valves can have high CV values (restriction).
    What do you have for an aquastat? A Hydrostat makes this setup really easy.
  • Robert_25
    Robert_25 Member Posts: 410
    Ron, it largely depends on what you choose for an indirect water heater. The flow requirements of the indirect might be considerably higher than your baseboard zone - and some indirect water heaters can be pretty restrictive. If that is the case a dedicated circ. for each zone would be the way to go.

    You may be able to use a zone valve with a low CV value on the indirect and run it that way, it just depends how the flow requirements for each circuit compare.
  • hot_rod
    hot_rod Member Posts: 16,566
    A typical spring return zone valve will b e 7-8 Cv. 9- 10 gpm easily through those valves.
    So unless you have 110K or larger boiler, a ZV if fine for indirect flows, 1" piping is a good idea.. One delta P circ, zone valves for heat and dhw.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rick in Alaska
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,342
    edited April 14
    Am I missing something? The diagram shows the supply from the boiler going direct to the DHW indirect. From what I see here, when ever there is a call for heat, the indirect will get full temperature hot water from the boiler flowing thru the HX. This will overheat the DHW in the indirect tank. I think maybe the simplest thing is to follow the manufacturers instructions on the DHW indirect tank.

    If you do choose Zone Valve to separate the heat zone from the DHW zone, then use a fast opening zone valve in order to keep the recover time from call for DHW to actual hot water from the boiler circulating thru the HX.
    Too many times I have had "Insufficient Hot Water" service call only to discover there is a 90 second delay from the call for DHW from the thermostat until the Taco 571 end switch deploys the circulator on the system. that will then circulate cold water to the DHW tank for the startup sequence of opening a vent damper or pre-purge of combustion fan, then a trial for ignition. then proof of ignition, them main burner then the boiler water, still circulating cool basement temperature water into the DHW tank, will start the increase in temperature. Then after main burner fires for about 3 or more minutes the boiler water actually is hot enough to start the heating of the DHW tank. This is a scenario that happens in the summer (non heating) season when the boiler can get to be basement or room temperature from sitting idle for hours. Also the Taco Actuator will be at its coldest operating condition making the time from call for heat to activating the end switch as long as 90 seconds in some cases.

    Since you can not do anything about the normal boiler startup sequence, You don't want to add more time to that delay in call for DHW to actually heating the water.

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    rick in Alaska
  • ron
    ron Member Posts: 222
    edited April 14
    thanks for the replies. Forgot to mention, I'm leaning towards using a Weil-Mclain WGO2 boiler with a 45gal Aquaplus2 indirect.

    The house being small, 1000 sqft and 1-zone of heating, I'm inclined to think the smallest boiler available (practically speaking a wgo2) at around 75k btu will still be somewhat oversized so always pumping though the indirect when the 1-zone calls for heat the indirect would act as a buffer tank and help with efficiency, was my thinking. Wanting to find the best piping setup for such a situation.

    The house will be getting a shower stall installed, it has just 1 bathroom and 1 person in it so hot water demand is probably as low as it could possibly be... not like there is multiple bathrooms and 2+ people showering at the same time so the smaller 35gal indirect I might even choose. Along with keeping in mind the eventuality of selling the house and selling value, so i want the install and setup to be A+.

    The indirect from weil website states 1.6 gpm head loss for their 35/34/55 gal indirects and all have 1" NPT boiler in/out sizing. And using a VT2218 delta-T circulator I am figuring there will basically be no worry about mis-sizing it'll just do it's thing and account for what little extra head the indirect and zone sentry value has which I figure will be well within the VT2218 pump curve - looking for validation on this.
    With 1 3-way zone valve, 1 circulator, and a hydrostat 3250 I am hoping it should all be pretty simple and solid.


    http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf
    3-way Cv (Kv) / Ft of pipe equivalent, at 4' per sec max residential flow rate
    3/4" sweat 3-way Z075C3 having Cv of 3.3 (2.8) / 82
    1" sweat 3-way Z100C3 having Cv of 3.0 (2.6) / 411
    I don't know how to read this

    assuming no typo on their part, supplyhouse lists
    Cv=3.3 for 3/4", and Cv=8.9 for 1", for sweat 3-way zone sentry's.
  • hot_rod
    hot_rod Member Posts: 16,566
    ron said:

    thanks for the replies. Forgot to mention, I'm leaning towards using a Weil-Mclain WGO2 boiler with a 45gal Aquaplus2 indirect.

    The house being small, 1000 sqft and 1-zone of heating, I'm inclined to think the smallest boiler available (practically speaking a wgo2) at around 75k btu will still be somewhat oversized so always pumping though the indirect when the 1-zone calls for heat the indirect would act as a buffer tank and help with efficiency, was my thinking. Wanting to find the best piping setup for such a situation.

    The house will be getting a shower stall installed, it has just 1 bathroom and 1 person in it so hot water demand is probably as low as it could possibly be... not like there is multiple bathrooms and 2+ people showering at the same time so the smaller 35gal indirect I might even choose. Along with keeping in mind the eventuality of selling the house and selling value, so i want the install and setup to be A+.

    The indirect from weil website states 1.6 gpm head loss for their 35/34/55 gal indirects and all have 1" NPT boiler in/out sizing. And using a VT2218 delta-T circulator I am figuring there will basically be no worry about mis-sizing it'll just do it's thing and account for what little extra head the indirect and zone sentry value has which I figure will be well within the VT2218 pump curve - looking for validation on this.
    With 1 3-way zone valve, 1 circulator, and a hydrostat 3250 I am hoping it should all be pretty simple and solid.


    http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf
    3-way Cv (Kv) / Ft of pipe equivalent, at 4' per sec max residential flow rate
    3/4" sweat 3-way Z075C3 having Cv of 3.3 (2.8) / 82
    1" sweat 3-way Z100C3 having Cv of 3.0 (2.6) / 411
    I don't know how to read this

    assuming no typo on their part, supplyhouse lists
    Cv=3.3 for 3/4", and Cv=8.9 for 1", for sweat 3-way zone sentry's.

    Looks like you have data on a 3 way zone valve? A two port valve is what you want.

    Know that a delta t circulator will limit heat transfer to a fixed delta. With zone valves a delta P cicr is a good fit.

    If you want to buffer the boiler a reverse indirect like a Thermo 2000 is a good option. A mix valve on the output if you maintain it at high temperature. You would need to make sure an ODR didn't allow the tank to run too cold and not give you adequate DHW.

    Although a mod con with an 8K low turndown output would solve a few problems. Better efficiency and less cycling.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Zman
  • hot_rod
    hot_rod Member Posts: 16,566

    Am I missing something? The diagram shows the supply from the boiler going direct to the DHW indirect. From what I see here, when ever there is a call for heat, the indirect will get full temperature hot water from the boiler flowing thru the HX. This will overheat the DHW in the indirect tank. I think maybe the simplest thing is to follow the manufacturers instructions on the DHW indirect tank.

    If you do choose Zone Valve to separate the heat zone from the DHW zone, then use a fast opening zone valve in order to keep the recover time from call for DHW to actual hot water from the boiler circulating thru the HX.

    Too many times I have had "Insufficient Hot Water" service call only to discover there is a 90 second delay from the call for DHW from the thermostat until the Taco 571 end switch deploys the circulator on the system. that will then circulate cold water to the DHW tank for the startup sequence of opening a vent damper or pre-purge of combustion fan, then a trial for ignition. then proof of ignition, them main burner then the boiler water, still circulating cool basement temperature water into the DHW tank, will start the increase in temperature. Then after main burner fires for about 3 or more minutes the boiler water actually is hot enough to start the heating of the DHW tank. This is a scenario that happens in the summer (non heating) season when the boiler can get to be basement or room temperature from sitting idle for hours. Also the Taco Actuator will be at its coldest operating condition making the time from call for heat to activating the end switch as long as 90 seconds in some cases.

    Since you can not do anything about the normal boiler startup sequence, You don't want to add more time to that delay in call for DHW to actually heating the water.

    why a flow check with zone valves?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ron
    ron Member Posts: 222
    edited April 14

    Am I missing something? The diagram shows...

    barring lunchtime diagram mistake in my diagram, I was always wanting to pump through the indirect to take advantage of it as a buffer tank given boiler size and small sqft of heating.

    The 3-way zone valve circuit that's always open runs the boiler+circulator+indirect loop. So whenever the indirect water heater calls for heat it gets it and there is no waiting for the zone valve. The closed side of the zone valve would prevent water flow through the baseboard heat, depicted by blue line. The only "call" for heat to operate the 3-way zone valve would be hallway thermostat for the 1-zone of baseboard heat.

    So a somewhat dhw priority inherently? I took that flow on/off directly from taco diagram, they had 4 examples for their 3-way valve. Running just hot water heater the 3-way zone valve is running on its normally open circuit so shouldn't be an issue. Occurring to me now running 1 zone of baseboard while someone takes a shower at 7 am in January in CT could be an issue?
  • mattmia2
    mattmia2 Member Posts: 5,749
    Was that diagram there when i commented...
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,342
    edited April 14
    I'm not sure you want to use a three way valve or the piping configuration you have drawn in your original diagram.
    1. Please follow the path of hot boiler water, and lets say that the Aquaplus-2 is full of 120° water.
    2. At that point in time the heating zone calls for the boiler to make heat and the boiler water goes to 180° limit temperature.
    3. How is the 180° water going to get to the 3/4" baseboard without leaving some of the 180° temperature in the 120° water tank?

    IT CAN'T !!!

    That 180° boiler water will pass thru the 120° water and some of that heat will make the DHW tank water hotter than 120° and the boiler water will leave the tank at something less than 170° in order to get to the room that baseboard is in.

    Let's say that the call for heat lasts for several hours during an extreme cold snap overnight, while you are sleeping. You may wake up the 160° or hotter DHW in the tank. Be careful taking that shower in the morning.

    Do you follow my logic here?

    You need a path from the boiler to the baseboard that does not got thru the Aquaplus-2 DHW tank.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    rick in Alaskahot_rodSolid_Fuel_Man
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,342
    edited April 14
    hot_rod said:


    why a flow check with zone valves?

    I stole that diagram off the internet, you would need to ask the original designer. It was probably already there on the artist's equipment and he never removed it. But I agree, not needed. I'll fix the diagram.

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • hot_rod
    hot_rod Member Posts: 16,566

    hot_rod said:


    why a flow check with zone valves?

    I stole that diagram off the internet, you would need to ask the original designer. It was probably already there on the artist's equipment and he never removed it. But I agree, not needed. I'll fix the diagram.

    throw an expansion tank in also, upstream of that return piped circ :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ron
    ron Member Posts: 222
    Ed convinced me, I am abandoning my original diagram because it'll heat the indirect water well over 140°F when zone heat calls.

    haha yes I stay up late at night


    Zman
  • ron
    ron Member Posts: 222
    So I think i am going to go the [traditional ?] route, shown below, since a new boiler comes with a 007 circ anyway might as well use it. Then, circulators come with built in check valves correct, so I wouldn't need a zone valve? Given pic below should the VT2218 (or other circ) be piped pulling before or after the 007 pushing the water heater?

    And I am stuck with oil heat... planning on a wgo2 boiler with hydrostat 3250.


  • Zman
    Zman Member Posts: 7,357
    Tie it in to the left of the DHW circ. You need a flow check on both circs. Most smaller circs are available with internal check valves.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Zman
    Zman Member Posts: 7,357
    If you control the circs with something like this, you can prioritize the DHW over heat.https://www.supplyhouse.com/Taco-SR502-4-2-Zone-Switching-Relay
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • pedmec
    pedmec Member Posts: 220
    ed, i'm late to reply but i was thinking the same thing. doesn't anybody notice they are piping thru the indirect and then into the heat loop. i thought i was crazy and i might be missing something lol.
  • hot_rod
    hot_rod Member Posts: 16,566
    edited April 14
    it could be this simple, delta P circ, two zone valves of your choice, Webstone purge ball valve at boiler return. Of course Caleffi components would be best :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MikeAmann
    MikeAmann Member Posts: 435
    I redid the diagrams from "Pumping Away". Feel free to use them.

    Zman