Help: Blew my transformer and the 120v part of a ZVC

SENorthEast1895er

I tried installing a ZVC, realized it wouldn't work for my purpose, tried to revert, blew my 24v transformer, tried to go back to the ZVC (it would work until I could get a replacement transformer), and then my ZVC lights stopped working and functions stopped. It still has 24v across the fuse (failure correlated with when I was screwing in the electrical box cover, but that might just be a fluke)

I didn't take good enough pictures in the process of installing the ZVC, so I'm wondering if I got something wrong here. Here's a drawing of how the 120v is currently wired (grounds not shown):



When using the Transformer, I had wired the zone valves as follows:



When using the ZVC, it was wired to spec. I've tested it isolated from the heating system (using an old computer power chord), and I get no green light then, either.

What happened?

(more in-depth of what I did)
Thought I would be able to use the Munchkin Vision 1 system with my 1-circulator system with a ZVC. Talked to HTP Tech support, they said it would work (use the end switch on the zone valves to call either the central heat or direct hot water).

Installed it and realized turning the boiler on via the Zone Valves and controlling the circulator via the ZVC meant that the boiler would continue to run after the circulator was turned off.

Called HTP to see if this was a problem, got elevated to Level Two tech support, and they said yes, that would be a problem.

109A_5

Hello @SENorthEast1895er,
The sketches looked reasonable.
Either way what controlled the circulator before ? I'm kind of at a loss why the change was needed.



https://www.htproducts.com/literature/lp-102.pdf

109A_5

Hello @SENorthEast1895er,

SENorthEast1895er said:

It still has 24v across the fuse

Usually good fuses have nearly zero voltage across them. When they are open or blown they have the system voltage across them.

With a blown fuse, with one meter lead on the common or neutral wire, the blown fuse would have system voltage on one side and zero voltage on the other.

The actual ZVC make / model may help since with a TACO ZVC the 120 Volt part is only the primary of the transformer and the relay contacts.

SENorthEast1895er

ok, going to get new T-stat wire and a fuse. A lot of this old stuff is in terrible shape, and I just reused the 3-strand wire. From other places, wondering if moving things around made a short somewhere.

@109A_5

Transformer controlled it. ZVC 403.

there’s a little blurb about it why in the bottom of my post, but only makes sense if you know about that make/model.

I have a mon/con boiler that’s able to do ODR with a different temp for and indirect DHW, all from the control board.

However, it’s been running w/o either for 20 yrs (just set at 185, when I can probably heat with 140 or lower central heat temps) and I wanted to get the efficiency and comfort of an ODR.

However, my boiler expects P/S piping and two circs to do so. My boiler is not piped P/S and has only one circ (but is piped in a way that’s acceptable for non-ODR use). In that system, the primary circ shuts off when the hot water calls and my (non-existent) circ for the hot water loop is turned on.

I thought I could get around this by using a ZVC to control the circ and taking the TT off the zone valves to control the boiler. Boiler manufacturer tech support gave this the thumbs up.

This worked when installed. However, it resulted in the following scenario: when the t-stat turned was satisfied, the ZVC would shut off the circ but the boiler would continue to run without any circ running, resulting in spiking temps.

This I didn’t like, so I called up the boiler manufacturer and asked them about it. They elevated me to level 2 tech support, where they told me it was a no-go.

SENorthEast1895er

ok, pulled out my multimeter for some continuity tests. The T-stat wire is old and was zip-tied to the pipes, so insulation is in terrible shape. There’s continuity between green and red on my DHW zone valve wire when disconnected from the zone valve.

I’m guessing that’s my problem. Maybe the zone valve opened, closed the TT circuit right as I was screwing in the electrical box, and blew the fuse, leading to a false concern about the 120v wiring.

Connection shown in violet. On closer inspection, insulation is visibly torn right where the jacket ends. Likely in such bad shape that it just pulled apart there when I clipped and re-stripped the ends.

On the Taco 403-4, I’m 24v across the fuse (guess I’m just bypassing the fuse here), no continuity, and no voltage from either side to common.

So, if I’m lucky, a simple fuse will fix this thing?

109A_5

Hello @SENorthEast1895er,
OK, I think I understand what you were trying to accomplish. I think I would have set up the ODR and just bridged the two pump outputs from the control board, maybe with a relay or two if needed. So if the control board wanted to activate the CH or the DHW pump the only pump you have would be turned on.

SENorthEast1895er said:

On the Taco 403-4, I’m 24v across the fuse (guess I’m just bypassing the fuse here), no continuity, and no voltage from either side to common.

This does not make sense to me, like your meter was not connected to the ZVC common during that measurement.

I would replace the dilapidated wiring and replace the fuse and go from there.

SENorthEast1895er

@109A_5 I was testing off the 120v common (white); should I have been using the 24v common?

In any case, the fuse is definitely blown. In better lighting, the telltale carbon deposit (i assume that’s what it is) is inside the glass.

The relay seems promising, but I’m too inexperienced to figure out the following:

The DHW wires need to go to the boiler to tell it to fire at a higher temp, but they’re also needed at the ZVC/relay to tell it to open a valve/ start a circ.

Honestly, I’m a bit confused about the difference between the ZVC and a relay. Seems like both just connect to the t-stat and tell the circulator to start. The ZVC just adds the ability to control zone valves (and the SR501-EXP-4 adds all sortsa nice features like post-purge, etc)

109A_5

Hello @SENorthEast1895er,

SENorthEast1895er said:

@109A_5 I was testing off the 120v common (white); should I have been using the 24v common?

Well if you are testing on the 24 VAC side of things I would use that common. Since that 24 VAC common may not be bonded to the buildings equipment ground which should be bonded to the 120/240 neutral you were apparently using. So that makes sense why you were not seeing 24 VAC on one side of the fuse.

The relay seems promising, but I’m too inexperienced to figure out the following:

The DHW wires need to go to the boiler to tell it to fire at a higher temp, but they’re also needed at the ZVC/relay to tell it to open a valve/ start a circ.

Honestly, I’m a bit confused about the difference between the ZVC and a relay. Seems like both just connect to the t-stat and tell the circulator to start. The ZVC just adds the ability to control zone valves (and the SR501-EXP-4 adds all sortsa nice features like post-purge, etc)

The ZVC does have relays in it. However it (in my opinion) does not have the logic or communications to your boiler to work correctly and in concert with your boiler. Your boiler has the means to correctly control the circulator pump(s) as needed with a CH call and/ or a DHW call.

To try to do it with a ZVC may become awkward as you are finding out. You would need a XX for the CH and another independent XX for the DHW to control your boiler, the ZVC does not provide both. I don't know if I would bother to use a ZVC 403-4 for one CH zone.

The ZVC also is used to clean up (or avoid) the mess of wires that multiple CH zone valves and transformers can make, also provide 24 VAC for the zone valves and system status indication.


You maybe able to use the Orange connections for the DHW control. However you still need to have the boiler turn on your only circulator with either a CH and/or DHW call. And this is very atypical, may confuse others in the future.

SENorthEast1895er

@109A_5

re: zvc. I was wondering if that sort of setup would “work”. It’s certianly better than my original idea, as that would only turn the boiler on once the zone valve was open (assuming taco 3 or 4 wire valves).

But yes, Id much rather have the boiler control the circulator, as I worry about post purge and things. I assume that’s what you’re talking about when you say “logic to talk in concert with the boiler”


Of course, I’d much rather have the boiler control the circ. However, I don’t see how a switching relay (which is the only kind I know about) does that, as the TT wires still go into it, are used to trigger the circ (via the relay), and then send a TT to the boiler aquastat.

To “trick” my boiler into running one circ for both, I would think the bridging idea works best, but I don’t know how to do that. I also need to think through any ramifications of doing that (worst I can think is that the circ would end up cycling on and off a lot)

I’m going to keep the 403 around, as I’m leaning more and more towards a a repipe at some point in the future that would end up with 2 zones + DHW. Also might be the easiest way for me to see what’s going on with boiler calls and any potential trial short cycling

HomerJSmith

Look, your wiring is wrong. The ZVC has a transformer and the boiler 925 board has a transformer. You just can't wire two transformers together like your drawing shows.
You can use the ZVC which is a safe way to wire it if done correctly. You only have one pump. No auxiliary transformer needed. Wiring this way, the ZVC transformer and boiler transformer are isolated from each other. You have no ODR or other benefits of Mod/Con. The boiler will run at the programed 160 deg setting.

mattmia2

If the munchkin doesn't have a setting or terminal for a boiler circualtor that runs on any call you can connect a relay (lie a RIB relay in a box that jsut mounts in a knockout with flying leads with a 120vac coil and contacts) separately to the dh and dhw circulator connections and connect the contacts in parallel, You could also probably just connect the circulator to both the DH and DHW hot connections but I would check with HTP about that.

If you connect the transformers together at the shared terminal on the zone valve you have to be careful if both transformers have one end bonded to ground (the transformer for the zone valves and the transformer in the boiler) that the side bonded to ground from both is connected to the shared terminal or the side not bonded to ground is connected to the shared terminal from both or it will short out through the grounding system.

EdTheHeaterMan

Here is a simple way to get what you want. It involves purchasing 2 inexpensive relays. BUT the wiring is a little tricky. That is because you will be introducing a common from 2 transformers to several common terminals in your system. Here is the relays you will need https://www.supplyhouse.com/MARS-92341-DPST-120v-Relay. You can source them locally, you want a relay with a 120VAC coil and a set of normally open contacts

The wiring on the HTC boiler is not designed to be able to make the common wire apparent Let me explain:

When using a switch that has no load involved with the switch operation you have 2 legs. When a wire comes bundled with only 2 conductors there is usually a white and a black or a white and a red on low voltage. That is because most wires are connected to some power source and some load that uses the power. The switch is usually placed on the power side (the black or red wire) and the neutral is unswitched (the white wire) but the wires that go to the switch should both be black (or red on low voltage). But they don't make the wire that way. So we are supposed to already know that a switch leg that has white insulation around it is actually a black wire. And to make it more clear we should put a black or red tape around that white wire on roughing in that wiring.

The wires on your boiler are the same color for both the switch legs to devices like the CH thermostat is 2 gray wires and the DHW thermostat is connected to 2 light blue wires. However when you add that extra transformer for operating the zone valves, and there is a common terminal (#2 on the Taco 571 is common to the end switch and the heat motor) you need to keep both the transformers in phase so as not to let the factory smoke out of one of the transformers. So it is important to notice the #3 wire from each zone valve MUST go to the proper wire in the 20 pin connector. Even though it does not matter when using thermostats, it does matter when using zone valves so not to cross the wires and cause a series 48 volt wiring setup that will short out the control wires.

That was a lot to say make sure the #3 goes to the proper wire on the 20 pin connector and #2 goes to the common on the 10 pin connector plug. Look at the detail on the diagram where all the blue wires go to the same three pins on the 10 pin connector.

Sounds complicated but it is actually quite simple if you do it one step at a time.

So open the file to look at the diagram. Zoom in to see the details

109A_5

Hello @SENorthEast1895er,
If I understand your situation correctly you want to have the CH and DHW control separated so you can use ODR and have the DHW at a normal temperature for DHW. The issue is you only have one circulator pump. Maybe not optimum and not what the boiler manufacture intended, however it seems to work for you.
If the boiler's control of the circulator pump is not supervised on the load side of the relay(s) on the control board.
If the neutral wired to each pump is not switched.
Maybe you can connect the Pink and the Orange wires together so that if the boiler wants either circulator pump on CH or DHW the only pump you have will run.
The Red annotation is of the concept, if that will work I would make the actual connection at the end of the Pink and Orange wires.
Otherwise you would need a relay to buffer the boiler's two circulator outputs to control one circulator.



You could sneak a relay in like this if it only needs the Hot switched. The DHW has priority control.

SENorthEast1895er

@HomerJSmith @mattmia

Could you clarify? I’m really unclear about this second transformer that you’re both talking about trying in to. At no point were both the externally mounted transformer and the zvc both on my system. The only place either of these tied into the boiler when in use was at TT.

As far as I could figure, TT just looks for closure; it doesn’t send voltage.

The ZVC was working when I initially installed it. and only went bad after I took it off, put the old transformer back on and promptly blew it. Then I put the ZVC back and and it went kaput. (I thought from shorted out t-stat wire; I think the insulation tore near the sheath when I clipped and stripped it to rewire it as needed for the transformer (after removing the ZVC))

Please let me know if there is something I’m missing. I’d like to install this replacement transformer tomorrow.

EDIT: seems like I was right; t-stat wires were shorting. Replaced them and put in a replacement transformer and it’s going strong.

109A_5

Hello @SENorthEast1895er,
Your sketch looked like this classic circuit, I was happy with it.

SENorthEast1895er

thanks @109A_5 . My best guess is that Boiler TT in my sketch is being confused for boiler transformer.

SENorthEast1895er

@109A_5 Alright, have the new transformer wired in. seems to be working fine; n\been watching it for about 20 mins.

@EdTheHeaterMan Perfect, thanks for that mock-up.

@mattmia2 given that HTP ok’d the used of a ZVC (Level 1 technical support) and firing the boiler via the 2&3 terminals, then rescinded that when I called them back and asked them about what I thought might be a problem (circ shuts off when 1&2 circuit opens. then, I presume it takes 1-2 mins for the 2&3 to open, same as it does to close. This means that the boiler will be firing with the zone valve shut and the circ off for some amount of time. While negligible, I was also concerned about what a stuck-open zone valve would mean; a boiler continuously firing without a circ running. they elevated me to level 2 technical support for that one).

So, while I’ll call and ask, I also want to think through things for myself and ask the experts here.

I really don’t know why they wouldn’t design it to handle this situation. It seems like such a minor change to the programing logic (if domestic hot water circuit is not connected, use the other circ). Makes me concerned that it’ll really screw up my boiler.

109A_5

Hello @SENorthEast1895er,

SENorthEast1895er said:

I really don’t know why they wouldn’t design it to handle this situation. It seems like such a minor change to the programing logic (if domestic hot water circuit is not connected, use the other circ). Makes me concerned that it’ll really screw up my boiler.

I would think with any of the three circulator control methods described above the boiler would be happy as long as a zone valve does not restrict all flow through the boiler.

I think the logic will accommodate either as long as it is set up per the manual, in your case your are doing both CH and DHW and missing a circulator and the normal accompanying piping. Using the zone valve for the DHW makes the fluid flow logic awkward.

SENorthEast1895er

@109A_5 To clarify: Do you mean using the zone valve to trigger DHW temps makes the fluid flow awkward? I assume so; I would describe them as bad or problematic (and that’s why I shied away from it).

109A_5

Hello @SENorthEast1895er,
I believe your system uses zone valve to steer the water, either CH and/or DHW and just uses one circulator. When all the calls are satisfied and the zone valves close does the boiler shut down instantly and shut off the circulator ? If not is there still water flow through the boiler with the zone valves closed ?

SENorthEast1895er

@109A_5 Yes, as it’s currently wired and as I’ve observed, the boiler turns off as soon as t-stat is turned off.

The only concern I have in that regard is short cycle protection, which I believe would be the only instance where the boiler would run w/o a t-stat call. Need to read the manual and observe.

If that’s the case, then the advice of @hot_rod to close the bypass valve must be used very cautiously (from my post about reverse flow; that thread contains picture of piping).

However, a quick look through the 925 and vision 1 manuals (using pdf search for “short”)that short-cycling protection is done via supply/return delta-T rather than a timer (timer seemed to be the easy/intuitive solution for this, but delta-t makes waay more sense with a little bit of thought).

I’m not crazy about that bypass valve because I think it contributes to short cycling (delta T rises very fast), but it’s better than firing with no flow.

Good news is that I just did a manual reset and was able to keep the house warm w/ 100 degree water and outside temps of 30 degrees (design temp for my area:14). So I likely can stay in condensing mode 100% of the time, even with that bypass valve cracked.

(the reverse flow issue means my t-stat is rendered ineffective, so I figured I’d try just running all night long at a low water temp, as zine been told that the idea of “always on at minimum temps” is more efficient than on-off cycling. Need to keep the place reasonably warm, as we have tenants on the third floor. I just turned the hot water t-stat off overnight).

109A_5

Hello @SENorthEast1895er,
OK, as long as you have a workable plan that you like.

HomerJSmith

As far as I could figure, TT just looks for closure; it doesn’t send voltage.

The TT is just a switch connection. When the switch (thermostat) closes it has voltage and passes current. The ZVC has a transformer and the boiler has a transformer. Wire the ZVC to the boiler by my diagram and you will be fine.

I thought from shorted out t-stat wire; I think the insulation tore near the sheath when I clipped and stripped it to rewire it as needed for the transformer

For the wire to blow a transformer, the secondary (24V) wires must be a direct short. Stripping two thermostat wires and touching them together won't blow the transformer. It just acts as a closed switch sending current to a load such as a relay. If the thermostat wires that you touched is from the transformer, yes. If from the thermostat, no.
Using a ball valve as a bypass valve is a poor choice as the valve is or 75% closed before it starts to regulate.
You will always get flow if the pump is running whether or not the bypass valve is open or closed. If the valve is closed the flow thru the HX will be too slow and the boiler water will reach high limit temp and cycle. If the valve is open hotter water will enter the boiler and you will reach boiler setpoint (160 degs) faster and cycle. With a bypass you will have flow thru the HX, but sys flows thru the sys and indirect will be problematic.

I've already discussed that a Taco 007 pump is too small a pump for a 140M. A 007 is ok for a 80M, but you realize the Munchkin manual gives those recommendations for the boiler heat exchanger and not for the sys piping pressure losses. So, using a smaller pump + sys losses, your flow may be marginal at best. The solution is not a bypass, but to correct your installation errors.

SENorthEast1895er

@HomerJSmith ah, thanks! that clarifies some things. I didn’t install this and didn’t catch the recommendations for sizing of the pump when looking through the manual.

SENorthEast1895er

@HomerJSmith @hot_rod

A test (DH circuit running):

 bypass valve open: boiler cycles on/off inlets than a minute

bypass valve closed: it ran for 10 minutes straight before I had to leave. 

From what I understand, the circulator seems to be moving  enough to keep the heat exchanger in a happy place (maybe HTPs 0010 recommendation assumes P/S and/or more head than my retrofit gravity system). 

I guess, with the bypass valve closed, the heat exchanger would slowly overheat (over more than 10 mins) and that this (presumably higher) temp could be more damaging to the boiler than the short cycling.  

I also suspect that this boiler is comically oversized. If I’m actually only using the few few modulation stages, my effective boiler BTU output would be much less, and the 007 would be less problematic, correct (obviously, this is a bad way to plan things; mostly I just want to make sure I understand things correctly). 

I didn’t test with DHW, so that situation may be different.

Is there anything I’m missing and/or misunderstanding?

SENorthEast1895er

@109A_5
Using the ZVC as you described mostly works. However, there is one situation I’m concerned about. 

When there is a DH call and the DHW calls, the boiler and circulator keep running until the DH zone is shut (the DHW zone valve won’t open for another minute). 

I don’t understand why this is happening. It does Not happen in reverse (when DH is still calling and DHW shuts off).

 However, if I’m remembering my basic zone valve wiring correctly, this behavior happens there, too (TT call is active until zone valve 100% closed).   

Note that I didn’t jumper 3 & 4 on priority as 1) I have a 3 wire zone Valve going into it. My understanding is that jumping those two simply tells the ZVC that a two-wire zv (or no zone valve) is “open”. My 3-wire already does that. 

109A_5

Hello @SENorthEast1895er,
I suspect you are seeing the warm up time for the wax motor in the zone valve for CH zone. Maybe if it is an issue and you have enough boiler capacity just shut off the priority switch in the ZVC 403.

The boiler keeps running since there is still a call for heat present from the other zone (in that scenario). Its just that the zone valves take time to warm up.

In all the illustrations in the manual the water flow can not be totally cut off by zone valves. I suspect the way your system is set up that is not totally true.

It probably does not happen in reverse due to the DHW priority logic.

109A_5

Hello @SENorthEast1895er,

Or there is a built in delay in the ZVC 403 or the boiler's logic.

109A_5

Hello @SENorthEast1895er,
Possibly the wax motor cool down time until the end switch opens has an influence on the ZVC 403 priority logic.

109A_5

Hello @SENorthEast1895er,

SENorthEast1895er said:

(the DHW zone valve won’t open for another minute).

In a way this makes no sense since the DHW call is from an aquastat or the thermostat in the indirect. If the thermostat controls a go through the ZVC 403, I would think the ZVC 403 is adding the delay. Maybe shut the priority off and see if it makes a difference.

SENorthEast1895er

@109A_5

I’ll test some of this stuff out later. It should be noted that, as soon as priority calls, the non-priority zone lights go off. I would expect that to kill the call to the boiler. 

However, there’s the call to the boiler through the indirect “circulator” circuit. But that shouldn’t activate until priority zone valve is open. 

The only time I see this behavior is with the priority override. All other boiler/circ calls end as soon as the T-stat closes. 

(Not clear from your diagram: the ZVC is controlling my single circ). 

I don’t know how long the wax cool-down time is. That being said, I don’t think boiler shut-off is tied to a delay on the ZVC. I put my multimeter on terminals 2 & 3 to test for a closed circuit. As soon the circuit opened, the boiler shut off. 

My system is setup so that water flow is always possible; there’s a bypass valve. I’ve been advised by @hot_rod to close it and see how the boiler takes it. 

Well, with it open, the boiler with cycle on and off within 30 seconds. 

With it closed, I walked away after 10 minutes of continuous firing. 

I’m just not sure what all to look for to ensure I’m not damaging the unit, other than monitoring inlet and outlet temps (in this situation we’re talking about, outlet temps only rose a few degrees. And, given that the circ was running and the valve was at least partially open, I assume those are accurate. So maybe I just shouldn’t worry about it). 

I have enough capacity for both zones simultaneously (it was wired to work that way from install 20 yrs ago), so I’m just going to go turn off priority (and open my bypass a bit) until after Christmas, so I can enjoy my holiday without having to try to figure this out ASAP. 

If I got one of those new-fangled, fast-acting zone valves for the indirect, this would be less of an issue. 

Note: I can’t test the behavior by switching off priority because it only happens when priority is activated (zone 1 calls boiler until ZV is closed). Doesn’t happen any other time. 

hot_rod

The Caleffi ZSR have 3 sets of TT connection. One set is for priority which controls zone 1 pump.
There are 3 pump out puts, priority, primary, and zone pump.
You can configure the relays with dip switch.

So if you need only one pump to run for DHW, or if you need an indirect and primary, you can select to couple two relays. So you have more customization options.

Here is some info and piping examples

EdTheHeaterMan

SENorthEast1895er said:

@109A_5 Alright, have the new transformer wired in. seems to be working fine; n\been watching it for about 20 mins.

@EdTheHeaterMan Perfect, thanks for that mock-up.

@mattmia2 given that HTP ok’d the used of a ZVC (Level 1 technical support) and firing the boiler via the 2&3 terminals, then rescinded that when I called them back and asked them about what I thought might be a problem (circ shuts off when 1&2 circuit opens. then, I presume it takes 1-2 mins for the 2&3 to open, same as it does to close. This means that the boiler will be firing with the zone valve shut and the circ off for some amount of time. While negligible, I was also concerned about what a stuck-open zone valve would mean; a boiler continuously firing without a circ running. they elevated me to level 2 technical support for that one).

So, while I’ll call and ask, I also want to think through things for myself and ask the experts here.

I really don’t know why they wouldn’t design it to handle this situation. It seems like such a minor change to the programing logic (if domestic hot water circuit is not connected, use the other circ). Makes me concerned that it’ll really screw up my boiler.

The delay on the Taco 571 on start up and on shut down, will not be a problem if you use the diagram I mocked up. That is because the end switch of the DHW zone valve or the CH zone valve will not be closed (connected) to operate the burner and pump if the valve is closed. The valve opens before the end switch closes, and the end switch opens before the valve closes. With other designs, that may not bew the case.

109A_5

Hello @SENorthEast1895er,

SENorthEast1895er said:

I’ll test some of this stuff out later. It should be noted that, as soon as priority calls, the non-priority zone lights go off. I would expect that to kill the call to the boiler. 

However, there’s the call to the boiler through the indirect “circulator” circuit. But that shouldn’t activate until priority zone valve is open. 

The only time I see this behavior is with the priority override. All other boiler/circ calls end as soon as the T-stat closes. 

If disabling the priority with the switch changes the behavior it probably is the ZVC 403 logic. Just the way they control the pumps.

(Not clear from your diagram: the ZVC is controlling my single circ).

Which one there was two. The first just bridges the control boards two pump outputs, (assuming a common, un-switched Neutral) without seeing the board it may work or not as previously explained.

The second uses a single relay to select the appropriate Hot wire for the selected pump and the DHW pump Hot wire has priority and also assumes a common, un-switched Neutral for both pumps.

Enjoy your Holiday.

SENorthEast1895er

@EdTheHeaterMan

 Thanks for that clarification. However, I see now that I misspoke. 

With the current setup using a ZVC (assuming priority is set), the circulation and boiler do not run with zone valves closed, as I previously stated.  

However, they do run while the zone valve is closing. This only happens when switching from zone 1 to priority (during the closure of zone 1 valve). 

If I’m understanding correctly, your wiring would also run while the zone valves are closing (and, indeed, before all of this, my boiler ran while the zone valves were closing). 

Is this correct?   

HomerJSmith

@SENorthEast1895er, you have so many post going that I am getting confused. To reiterate, what is your problem and what do you want.
To be blunt, your sys is piped wrong for a Munchkin. Your pump is under powered and your flow is unbalanced. You cannot use a Vision 1 ODR with a DHW with a single pump, PERIOD! I guess you can, but your left wondering where your domestic hot water disappeared to. (Your first post.) I guess you can program in your WWSD to over 100 degs.
You have been given a lot of advice, what changes have you made other than replacing a transformer (in the ZVC, I assume).
Re-reading your posts, I'm just not getting it. Probably my lack of a formal edjication.

HomerJSmith

A further consideration regarding the slow responding 570 ZVs. If you are going to use the Taco ZVC and you are having a problem with the boiler firing and the ZV is not opening fast enough, do the following.
You can have the ZVC fire the boiler and pump with the ZVC TT connections or the ZV's #2 & #3 connections to the Munchkin TT. That problem is solved by having the ZV's #2 & #3 connections fire the boiler and pump. Forget the TT connection on the ZVC. Both ZVs are connected together at the #2 & #3 connections and then connected to the Munchkin TT. That way the ZV will be fully open when the boiler starts. The wall thermostat opens the CH valve and the aquastat opens the DWH valve. The ZVs can operate singly or together depending on the call for heat. With both valves open, you have flow problems.

The saying in hydronics is: The flow is the conveyor belt that moves heat energy from the heating plant to the heat emitters.
Merry Christmas to all!

EdTheHeaterMan

SENorthEast1895er said:

@EdTheHeaterMan

 Thanks for that clarification. However, I see now that I misspoke. 

With the current setup using a ZVC (assuming priority is set), the circulation and boiler do not run with zone valves closed, as I previously stated.  

However, they do run while the zone valve is closing. This only happens when switching from zone 1 to priority (during the closure of zone 1 valve). 

If I’m understanding correctly, your wiring would also run while the zone valves are closing (and, indeed, before all of this, my boiler ran while the zone valves were closing). 

Is this correct?   

Yes. While the valves are taking their good ole' time closing (but before they close all the way) the end switch is also on a cam that is eventually going to open the contacts. The end switch will open (turn off) before the valve closes all the way, so the burner and circulator WILL stop before the valve closes all the way. That is acceptable operation in most cases.

SENorthEast1895er

Alright, had this system setup for about 2 months now and haven't had any major problems thus far. I do have one current problem, though, and was hoping I could get some help with it. As @HomerJSmith pointed out, I had a ton of problems and had them split between a few posts, so I'll consolidate here instead.

The Current Problem

There seems to be a substantial amount of air trapped in the system; I've done about 8 or more bleeding sessions over the past few months and still haven't gotten water out of my bleed valves, despite having sufficient PSI. I'm not sure where the air keeps coming from. (system was drained to hook up a new radiator in the fall).

(one possibility; air has gotten into the DHW loop, which doesn't have any bleed valves on it)

Unfortunately, the only rads with air in them are upstairs in the tenants area, so I can't access them as often as I'd like.

Previous Problems Unresolved

Thankfully, there are only two issues from before that still concern me; neither of them particularly urgent.

My Hacky ODR with an Improperly Piped Munchkin
I've used a ZVC to "hack" the Munckin to be able to use the ODR. That's working well. Obviously, as @HomerJSmith has mentioned, my system isn't piped as Munckin intended for this purpose, and you've warned me about this.

However, my system is piped for a retrofit per the Munckin manual. And, as far as I can tell, there are only 2 differences between how it ran before and how it runs now. First, it has different set points for the DHW and Heating Circuits. Second, it is no longer possible for both the CH and DHW circuits to be open at the same time.

Other than that, I don't see any change. And, while I understand it's not in the manual, I don't understand how that would damage my furnace any more or less than its previous, retrofit arrangement (the manufacturer, HCP? gave me the go-ahead on using a ZVC a while ago).


Backflowing Circuit
One of the two CH circuits was back flowing after the boiler would run for some time. (the two central heating circuits are both controlled by the same valve). However, that no longer appears to be an issue, likely due to running at a much, much lower setpoint (-40 degrees at design temp, if I recall correctly). I suspect it never reaches the critical point that @EdTheHeaterMan explained.

However, I would like to know if I could expect efficiency gains if I installed a check valve.

General Curiosity
The piping in the system is a mess. I'm curious if there are simple and easy things I can do to improve the system (install some check valve. replace expansion tank with compression tank. install an air separator. I think I have some broken valves; replacing with ZVC if head pressure, etc is ok. replacing 007 with 0010, per @HomerJSmith letting me know it's undersized).

I'm also just generally curious if there are medium-sized jobs I could do to prep for a repipe when the time comes (I'm tempted to repipe the first floor as a zone in a way that would make it easy to pipe it into a P/S or similar system).

And, in a final note; Overall, my heating bills are about the same as last year, despite the fact that last year, 1/3rd of my house had the radiators basically closed off (3rd floor was being rennovated, so I tried to just keep a trickle flowing through the rads). So I'll call that a win.

Also, I'm running much, much colder temps (old: 180 all the time. New: I think I set it at 140 for design temp. Maybe lower) and am semi-excited to see what my actual heat loss for the house is. I suspect I can heat the house with a much, much smaller boiler when the time comes to replace this one.

HomerJSmith

I'm going dizzy re-reading all these posts and I'm not even a Blonde. I'm so confused so I will summarize your sys operation.

1) The Muchkin controls the ODR with the ODR curve that you can plot. It is the temperatures that you put into that plot curve. That is going into the Vision 1 program access and making temp adjustments to steps #8 thru 11. Then the Muchkin will adjust the boiler temp based upon your reset curve.
2) The Munchkin controls the DHW indirect tank temp, the heating priority, and time between the DHW needs and the space heating needs. It does this with a sensor (Vision 1) in the indirect tank well or with an aquastat on the indirect tank. If it is an aquastat, you set the tank temp with the aquastat and the aquastat turns on and fires the boiler. If a sensor, the Munchkin programing set the indirect temp and turns on the boiler.
3) The only thing that the Taco ZCV does is operate the zone valves, PERIOD. It doesn't turn on the boiler. It doesn't do priority zoning for an indirect tank unless you have a priority switch in the ZVC and the indirect tank ZV is connected to that terminal. So, don't expect the TT connection on the ZCV to turn on the boiler.
4) The Taco 571 zone valves open each circuit to the flow (terminal #1 & 2) and turns on the boiler (terminal #2 & 3). Terminal #1 & 2 are connected to the thermostat or aquastat thru the ZVC transformer. Terminal #2 & 3 is connected to the TT wires in the Munchkin. The ZVC should be able to power 3 ZVs. The reason that you want the ZVs to turn on the Munchkin is that the ZVs are slow acting valves and when the valves open they turn on the Munchkin pump. The ZVC will turn on the pump quickly maybe before the ZV opens.

Flow is the conveyor belt that move heat energy to where you want it to go. The flow thru the sys is dependent upon the size of the pump (head produced) which overcomes the resistance of the piping at the desired flow. An undersized pump on a boiler may cause short cycling of the boiler. It may also limit the BTUs the boiler is capable of producing to the heating elements in the sys, I think. A 140M boiler is capable of producing 140,000 BTUs/hr with 14 GPM thru the boiler's heat exchanger. An undersized pump may not have the power to move that much water. I think I got this right. I hope this is a clarification.

EdTheHeaterMan

@SENorthEast1895er said

The Current Problem

There seems to be a substantial amount of air trapped in the system;

I needed to see this on paper to get it clear in my head. Your air problem will be ongoing as a result of the piping design of the system. (I like this kind of paper.. I call it Screen Paper)


This is what I have come up with to the best of my ability, to see your system on paper. I could not help but to see one of the biggest problems in the industry, that goes overlooked on a regular basis. Placing the expansion tank on the discharge side of the pump and the auto fill on the inlet side of the pump. This is a recipe for air problems. You are making Boyle’s law work against you and the pressure reducing valve work against you.

Let’s start with Boyle’s Law of dissolved gasses. There is air dissolved in liquid. Just like there is water vapor dissolved in air. (the latter we call humidity) So if there are air molecules dissolved in the water that we put in the boiler, how does Boyle's Law affect that air? There are two things that determine the amount of air that can stay dissolved in water.

Pressure and temperature.

The higher the temperature the lower the amount of air that can be dissolved
When you lower the temperature the water can absorb more air
Pressure is opposite
The higher the pressure, the more air can be dissolved in the water
Lower the pressure and the dissolved air is released out of the water

Now think about the circulator pump and how it moves the water. Higher pressure fluid comes out of the pump, as lower pressure flows into the pump. So there is a definite change in pressure in this system.

There is also a flame involved in the boiler and that changes the temperature of the water higher, while all those radiators lower the water temperature. So there's definitely temperature changing.

Now if you can design a system that has a lowest pressure and highest pressure in the same location, then you will have an area where dissolved air explodes out of the water and becomes actual AIR that can be removed from the system and placed where you want it to be in the expansion tank. (The air does not really explode out of the water but it makes millions and millions of micro bubbles) But you don’t have a place like that in your system
Your system is more like the “Common Mistakes” illustration where the pump is between the fill valve and the expansion tank. So your system can actually take the air from the expansion and absorb it into the water in the expansion tank, since that water is colder than the water that is in the connecting pipe it is actually heavier so it can fall down the pipe into the hot water that is rushing by that tee fitting. Since the water in the pipe is hotter than the water in the tank it is lighter and will migrate up that same pipe that the cold water is migrating down . Yep the water can go 2 directions in the same pipe at the same time. Think of it like a lava lamp where you see the hotter fluid rise to the top and get cooled off and the cooled water drops down to get heated up.

The problem is that the cool water in the tank has absorbed some of that air in the top of the tank and when it hits that hot stream of water flowing to the radiators, that cold water gets hot pretty fast and releases the dissolved air. And since those microbubbles of air are already headed to the radiators then when it gets there those microbubbles will settle in the radiator and the water has less dissolved air returns to the boiler to get reheated and goes past that expansion tank to rise up into the tank to replace the water that's falling out of the tank and eventually all the expansion tank air ends up in the radiators after a month or two. Now you have a waterlogged tank and air in the radiators.

There is another problem with the pressure in the system, and if you look at the illustration you can almost see it.

Cold system's fill pressure according to the information you provided is 15 PSI at the feed valve. That will cause the air in the expansion tank to compress to 15 PSI with the rest of the system is filled and the radiators purged of all air. The expansion tank now becomes the point of no pressure change. (you need to look that up yourself) As long as there is nothing added or subtracted the air cushion in that tank will be 15 PSI. See the illustration on the left.

Now start the pump and it will have a difference in pressure between the inlet and the discharge openings. And for this example it will be 7 PSI Since the tank will always be 15 psi then the outlet of the pump must be the same as the air cushion plus any friction loss that may be in the system between the tank and the pump. In this case I will say it is 1 PSI friction loss. That means the pump outlet must be 16 PSI. Since the inlet must be 7 PSI lower than 16 PSI at the outlet, it will drop to 9 PSI. See the top right illustration.

But that will affect the pressure reducing valve because it is at the inlet of the pump that is set at 15 PSI and is connected to a 9 PSI pipe. What will that be, you ask? Maybe the fill valve will add water to bring the pressure up to 15 PSI. add that to the outlet of the pump and you get 22 PSI. and since we added water to the system the expansion tank air will need to compress to 21 PSI because there is more water in the system and it needs a place to go since all the radiators are full of water. See the bottom right illustration.

Since it is only 22 PSI in this case, the relief valve is not going to discharge any time soon. But with the other problem listed above it will not be long before the air in the tank is reduced to the point where you no longer have enough room for the heated water to expand without increasing the pressure to 30 PSI and you will have air problems with radiators and a leaking relief valve.