Boiler, Little wiring help

[Sponger76]

Hi all. New to messing with boilers and I am piecing an old baseboard system, to a newer tankless boiler and I read that you can remove zone valves and control the zones with circulators. Please, dont try to talk me out of this route because I have already replumbed my system taking out the old zone valves. My question is this.
I already have a Taco zvc403 zone valve controller and I would like to try to employ this to control my zone circulators. I understand how relays work for the most part and know just enough to fry some circuits, but I would like to avoid that if possible. I watched a video on wiring a circulator to the taco, which uses the onboarding n/o com n/c connection but that only sends power to the circulator and then that makes the power constant? I want to use the zvc to turn the circulator on for the zone demand as needed.
Am I stuck to order up a new controller designed for controlling zone circulators as the main way to control a zone vs a zone valve?
By the way, I have a Navien NHB 110 boiler with p/s manifold installed. The main circulator on the manifold is wired direct to the boiler slot on the boiler. There is a second 2a slot for another circulator and a 3rd slot for a dhw circulator. I dont believe with the zvc installed, that I need to use these extra slots for anything, especially the domestic hot water slot. Even if I could somehow use the 2nd circulator slot, I now have 3 circulators, which is why I prefer to use the zvc if I can for my application. I included a wiring schematic for my zvc to help. Thanks for any help you can give me.

 

[Phog]

I'm not sure I completely understand what you're asking. It seems like you are wondering whether you can wire circulator pumps directly to the Taco zone controller you have without using a relay. The answer is no. The circulator pump usually needs 120VAC power input and your zone controller outputs only 24VAC. You therefore need to have the zone controller switch a relay that has a 24VAC coil -- the relay then turns 120VAC to the circulator on/off.

 

[Sponsor]

 

[WorthFlorida]

I think what you're looking for is TACO SR503, up to SR506. This has a 120v input and relays 120v output for each zone to turn on the circulator for that zone, if you have three circulators. Each zone is controlled by it own thermostat. It's a very simple device.

If you have one circulator and wants zone control, you use your ZVR503, then you need zone valves that operate on 24v ac or do as Phog suggest.

 

[Sponger76]

Ok, that's kind of what I thought about the zvc I have. No, i didn't mean that i didn't want to use a relay, but it wasn't making sense to me that after you use the 1 relay, how you would link the thermostat to call it for heat. I am actually going to go with a navien controller for this. Thanks all

 

[Phog]

it wasn't making sense to me that after you use the 1 relay, how you would link the thermostat to call it for heat.

Your boiler should have an external input to call it and activate the burner/main circulator. This gets wired to the lower left terminals on your ZVC labeled "to circulator or boiler aquastat". Then your zone thermostats get wired to the 3 terminals across the top of the ZVC diagram. When any zone thermostat calls for heat, the ZVC both calls the main boiler/circulator & activates the zone output along the bottom of the ZVC diagram that corresponds to the calling thermostat input. You could use the ZVC you have and it would work fine. The only thing you need to do additionally in your situation is to add a relay in-between the ZVC and each zone circulator, as described above.

PS - If you have an indirect hot water tank you should make sure to hook it up to a priority/DHW zone in whatever control you end up using.

 

[Sponger76]

I have the navien nhb 110 with a hydraulic disconnect loop to suffice the p/s loops. The boiler circulator is hooked to the boiler circulator on the boilers motherboard. The t/t ch is wired to the zvc, which when it was zone valves, the thermostat would call for heat, kick on the boiler and then the boiler circulator would start spinning. The old system I am converting from, had a single circulator with 2 zone valves and I thought the 2 systems could be similarly joined up. Later I figured out why it needed the p/s loops. I spoke with a coworker who talked me out of the zone valves and into the circulators. I have read a few forums about the politics regarding zone valves vs circulators and I'm not looking to get into a discussion about that. To make things easier, I just bought the navien smart controller that links right up to the mother board with a specific wire. This thing is supposed to talk to the boiler and turn on based on the outside temp so pipes dont freeze. The smart controller gets the 110 supply from the breaker, then each feed spot delivers the needed 110 to each circulator
On a side note, I was discussing this with my father and had come to a similar conclusion regarding getting a stand alone type relay to make the current zvc work.

 

[Phog]

It sounds like you're on the right track, there is also debate on whether the hydraulic separator is necessary or not for p/s loops with circulators but that is another debate. (Personally I'm in favor and would do my own system exactly as you're describing). Good luck.

 

[Dana]

I have the navien nhb 110 with a hydraulic disconnect loop to suffice the p/s loops. The boiler circulator is hooked to the boiler circulator on the boilers motherboard. The t/t ch is wired to the zvc, which when it was zone valves, the thermostat would call for heat, kick on the boiler and then the boiler circulator would start spinning.

The NHB-110 is way oversized for 19 out of 20 houses in the US. Even at non-condensing temps it has enough output at high-fire to keep my sub-code 2400' house + 1600' of basement cozy even when it's -100F outside. (If it ever gets that cold at my house I'm moving!) Were it not for the 11:1 turn down ratio it might be crazy-oversized at minimum-fire for the zone radiation too, which can still be an issue at condensing temperatures.

Most houses in the US (and probably yours too) would do just fine with the NHB-55, which can modulate ~20% lower than the NHB-110, for longer cooler more comfortable & efficient burns. At temperatures low enough to deliver 95% efficiency it takes about 48' of typical ~8" tall fin-tube baseboard per zone to emit the full min-fire output of the NHB-110, but only 38' with the NHB-55 (and NHB-80).

Even though you're not going to swap it out it's still worth doing the napkin math heat load calculation, as well as the napkin math on the zone radiation at condensing temperatures to be able to find a good starting point to dial-in the outdoor reset curve.

Whether & when the system needs to be pumped primary/secondary or not is only a "debate" among people who don't do math (or can't read the fine print of the warranty ). The pumping needs & pumping head of the zones can be quite different from the pumping head of a water tube heat exchanger boilers such as the NHB series, but it doesn't take rocket science type math to get it right. Many systems could be pumped direct with an NHB if the zone's are roughly comparable and in the right range, but not all. If you're not doing the math setting it up primary/secondary is a lot safer. It's a lot easier to skip the hydraulic separation and still make it work reasonably well over a wide range of zone flows with low-head fire tube heat exchanger boilers (which also have the additional benefit of a modest amount of internal thermal mass if the zone radiation is insufficient and low-mass.)

 

[Taylorjm]

As someone else said, you would need a 24v ac relay that is activated when the zone calls for heat and completes the 120v circuit to power on the pumps. I did someone similar with a forced air system and had some duct booster fans to push the air up to the second story. I put a relay inside a double gang box when wiring up the 120v blowers so that they were activated when the zone board called for heat/ac for that particular room. It has worked for 10 years without a problem. With the price of the zone control boards, I would see about using the existing one you have only add the relays, but I'm pretty good with electronics and wiring. If your not comfortable with it, then don't risk it.

 

[Dana]

As someone else said, you would need a 24v ac relay that is activated when the zone calls for heat and completes the 120v circuit to power on the pumps. I did someone similar with a forced air system and had some duct booster fans to push the air up to the second story. I put a relay inside a double gang box when wiring up the 120v blowers so that they were activated when the zone board called for heat/ac for that particular room. It has worked for 10 years without a problem. With the price of the zone control boards, I would see about using the existing one you have only add the relays, but I'm pretty good with electronics and wiring. If your not comfortable with it, then don't risk it.

Even though it's not a major engineering project to build up a relay box, it's just a lot simpler and cleaner to install a zone controller designed for powering up circulators, and would give you the option of installing an indirect water heater and giving it priority over the spaced heating zones.

 

[Sponger76]

Thank you all. So when I chose the nhb-110, I did it in the least effect way. I have a 18-1900 sqft home. The previous boiler was a peerless purefire boiler that put out 89k btus. Taking on way more than I could handle, I sized it for the boiler based on 110k btu's with the option for 11:1 turn down ratio. I also figured that one day my dhw could be piped in and it could control both house functions and still have room for other things. I am in the process of converting a 3 season room into a 4 season extra room which may also get tied in (not certain yet). Anyway, the house is old and drafty so some actual math was going through my head when I made this purchase even if it was wrong. I have toyed with relays a bit in the past and did not, I repeat, did not burn the house down. I think that you are right in that I could just use what I already have, and yes, buying the circulator zone controller is a little wasteful, but I like the idea of having a circ zone controller that is meant for the actual boiler and the ease of just tying stuff in. That said, I appreciate all the knowledge you guys are sharing with me. All advice is being considered on my path forward.

 

[Sponger76]

I have a circulator question. If a circulator is installed, but not powered, will it free wheel when the boiler pump kicks on? I ask because I am curious just how much water will leak by a circulator pump when it is actually powered up and waiting for the thermostat to call.

 

[Phog]

I have a circulator question. If a circulator is installed, but not powered, will it free wheel when the boiler pump kicks on? I ask because I am curious just how much water will leak by a circulator pump when it is actually powered up and waiting for the thermostat to call.

The circulator won't stop flow through it, and this is exactly what the hydraulic separator is for. It provides a pressure break point between the boiler loop and the branches, thus preventing undesired flow through zones that are not calling for heat. In other words, you have already constructed your system in such a way that you won't see phantom flows.

 

[Dana]

If/when other zones are actively pumping it negatively pressurizes the supply manifold relative to the return manifold- if there is going to be any flow on the unpowered pump it will be a reverse-flow through the idle pump, not the forward direction. Many/most circulator pumps now come with a small plastic check valve to prevent that back flow, but it isn't necessarily pre-installed.

While a hydraulic separator will mitigate the amount of positive pressure the boiler pump flow puts on the supply manifold, preventing flow from idling zones is not it's purpose. It's purpose is to keep changes in zone flow from interacting with the amount of flow through the boiler, letting the boiler pump guarantee the correct amount of flow.

Even an old drafty uninsulated house in NY doesn't usually need as much output as the NHB-110 as long as it has glass in the windows and doors that shut. Putting a current code-minimum insulated addition onto an old drafty house often lowers the design heat load despite the increase in exterior surface area, since it's replacing leaky/lossy walls & window area with much tighter and better insulated wall & window area. A code min window loses less that 1/3 the amount of heat per square foot of a wood-sash single pane, a 2x6/R20 wall loses about 1/4 the amount of heat per square foot of an uninsulated 2x4 framed wall.

It's pretty common to find old cast-iron boilers that are 3x or more oversized for the house's heat load- far more common than finding a right-sized boiler (~1.4x oversized for the 99% load) , and too often they're also oversized even for the radiation (putting heat into the system faster than the radiation can even take it back out.) While replacing like-for-like on BTU output is a really common error, it almost always is an error, and not in the best interest of comfort or efficiency (or up-front cost.)

But with an NHB-110 there is a lot of flexibility, as long as place isn't micro-zoned to death. The smallest zone radiation that balances perfectly with the minimum fire output at condensing temperatures is would be 45-50' of fin-tube (or equivalent), but with some care in the programming and set up you may be able to get away with as little as 35', or using higher mass radiation (even flat panel rads have substantially more than fin-tube) to suppress short cycling.

It's almost never necessary or desirable to up-size the boiler for delivering domestic hot water. Simply giving the indirect water heater zone priority would be the "right" solution in 99 out of 100 cases. (In most zone controllers there is at least one zone that has a priority option. The instructions on how to set up the priority zone is in the manual.)

 

[Sponger76]

Ok wow, thank you Dana. I might have to reread that a few times. Tons of info there. As for the nhb 110, at this point I just gotta make it work. Plus, I should have done a btu calculation based on sqft with how many doors and windows I have. A little too late, but good to figure out and know and that might also help me fine tune what I have because I will have a goal.

 

[Phog]

Sponger, here is an article you may find helpful:

https://www.hpacmag.com/features/siegenthaler-hydronic-piping-layout/

 

[Sponger76]

Thank you for this article. I dont think this will be a great issue for me once the 2and circulator is actually wired up. Currently I have zone 1 hooked in to the boiler at the secondary ch located, primary being the boiler ch location. Once I recieve the ch controller, I will be finally installing the manifold for the p/s loops. Without the p/s installed and having the entire system loop through the boiler circulator, I'm bound to get improper pressure at each of the zone circulators. I know that this is incorrect and will correcting it once I get the controller. I dont have a way to pump the zone 2 loop as it sits now and bleed-by is actually maintaining a reasonable temperature for zone 2, believe it or not.
Included is a crude drawing of my finished product once I add the manifold. Nothing glorious, and there are a few tributaries that feed off of a header that is not included in this drawing, but I dont think in the end that I have a morphed system. Well, not yet anyway.

 

[Sponger76]

I have a head cold that woke me up and I began thinking about my system because that's what I do. Anywho, I was thinking about the morphing in that article and it lead me to thinking about my common return piping. If i have not decoupled hydraulically with a p/s, I would imagine with not just 1, but 2 positive pressure ch's, I am probably pressurizing zone 2 and feeding water backward through the common return header. Sorry if this was already mentioned, but I am exhausted and just journaling my thoughts at 2am when I should be sleeping. If it's not feeding backward, then it still may be feeding past the zone 2 ch under the same theory (positive pressure without a decouple). Once I have the controller in place and the p/s, hopefully problem solved. If that doesnt work, I am gonna have to breakdown and get a professional.

 

[Dana]

I have a head cold that woke me up and I began thinking about my system because that's what I do. Anywho, I was thinking about the morphing in that article and it lead me to thinking about my common return piping. If i have not decoupled hydraulically with a p/s, I would imagine with not just 1, but 2 positive pressure ch's, I am probably pressurizing zone 2 and feeding water backward through the common return header.

You're not creating a reverse flow if the integrated check valves that they're shipped with are installed on the zone pumps (recommended). With or without primary/secondary piping at the boiler those reverse flows on the inactive zones would still happen if there aren't check valves. Without primary/secondary and no check valves that reverse flow through the idle zone would lower the flow through the boiler.

With primary/secondary pipe the flows through the boiler aren't much affected by which or how many zones are running. Whether the total zone flows are 1 gpm or 10 gpm the flow through the boiler won't change very much, which is important with high pumping head water tube heat exchangers. Without the the primary/secondary hydraulic separation it's important to do the math and get it right to make sure the boiler is neither under or over pumped.

You have the P/S manifold installed- leave it there. If you want to tweak things do it after it's all up and running, but you're likely to break something if you try to pump direct using two zone pumps unless you did the math ahead of time. I'm pretty sure Navien isn't going to honor the warranty if it's gets destroyed when pumped direct with a seat of the pants design.

 

[Sponger76]

Ok that makes sense as well. I do not have the manifold installed yet, as I was waiting for the circulator controller before I messed with it again.
Funny because when I read the install manual, I felt like it suggested to use 4 different circulators and if not, make sure that the circulators had check valves. Now to me, that makes me believe that the 4 listed as suggested circulators, would have a check valve. That said, I am including a picture of a circulator flange and if you didn't mind, can you tell me if this will work for what you are talking about? Thanks, Bob

Oh, p.s: the circulators I have are the wilo star S 21 F