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

HomerJSmith

Ed Young, I am taken-aback by your post. Your post is amazing. The graphics and explanation must have taken a lot of time and effort on your part. You are my hero of the day.

SENorthEast1895er

@HomerJSmith

Ok, thanks. I think using the ZVC "incorrectly", as I am, avoids the problems you've brought up (until someone else works on the system, at which point they won't understand what's going on).

1) I'm pretty damn sure the ZVC doesn't turn on the boiler or the circ until the ZVs are open (it's been a few months, but I did a ton of testing on it). That's why I'm running all 3 wires from the ZV into the ZVC.
2) TT will, unfortunately, will close regardless of whether it's a DHW or CH call. This is why I'm using the ZVC "incorrectly", described below.
3) ZVC does have priority zone.

Per someone's recommendation on here, I used the secondary zone circulator end switch (unenergized, of course) as the TT call for the DHW.

This means that, when DHW is called, the ZVC energizes the DHW ZV, waits for it to open, and then simultaneously sends calls to CH (via TT) and DHW (via secondary-circ used as TT. The primary circ is also called; this end switch is used as intended). Obviously, the Munchkin overrides the CH call.

Behavior is the same if both zones are calling. All I need to do is make sure the ZVC and the Munchkin have the same max-override timeout (60 minutes), which I've done.

@EdTheHeaterMan
As always, thanks for the thorough explanation. I read one of Dan's books; enough to have a passing familiarity with the Point of No Pressure Change (and bidirectional flow inside a single pipe). I suspected it had something to do with the Expansion tank. That expansion tank is also on the circuit that is back-flowing; maybe it's contributing to it.

So I guess I'm stuck just bleeding for months on end until I fix the piping. Bah humbug.

docbar99

@SENorthEast1895er - Thank you for your suggestion- I like the idea, it may bean easier solution and it looks like that unit is not that expensive. Where would be the correct place to install that device?
Many have suggested that the circulator should be moved to the supply side. If that is the case, would it be north of the circulator?


Also- do these devices have to be cleaned out periodically? Does the rust in the water clog it up over time?

SENorthEast1895er

I'm back here to post as I might need to eat some serious crow. Smelled some gas by the exhaust vent this morning and yesterday (no gas detected inside); gas company came out and said my boiler may be misfiring.

Not sure if I could've created this problem somehow with my ZVC setup as described in my previous post. But this this is seriously overdue for a servicing. (I don't know if this boiler has ever been serviced. Not in the 2 yrs we owned it, not in the 7 yrs the previous owner owned it) .

I should note that the gas small seems to dissipate very quickly and may be just associated with firing-up the boiler. Not sure if that's super concerning; this post says that's "the only acceptable gas smell"https://forum.heatinghelp.com/discussion/113973/munchkin-gas-smell.

Regardless, this boiler needs some servicing. Looking for advice on how to find a qualified service tech. My gas company offers a parts and service plan; could I trust that?

I've heard some bangs that I thought maybe came from my basement (thought it might've been a water pressure issue somewhere, as I was having some water hammer issues until I replaced a toilet); I wonder if I've got an issues similar to this guy: https://forum.heatinghelp.com/discussion/134372/munchkin-backfiring-problem. But I haven't been getting any errors.

@dcobar99 I will not comment on someone else's system as I am not a professional.

pedmec

Time to call in a tech. I installed munchkin boilers and they are not set up to work without primary/secondary piping if your trying to accomplish ODR. This is one of the reasons that munchkins got a bad rap (among other things). The 925 did not have the ability to be told that it is not piped primary secondary. The primary circulator shuts down when you hit warm weather shutdown (WWSD). this will cause you to have no hot water in the summer. I would take the supply for the indirect hot water tank and move it below the existing circulator. Then remove the zone valve and add a circulator. this will allow the 925 to control the circulator for the indirect and allow for it to operate in the summer months. You can add a sensor or aquastat in the indirect well. it auto detects if its a sensor. same for the ODR sensor. Remove the zone valve for the heat as you no longer need it and replace it with a flow check. Now your thermostat/aquastat con go directly to the 925 control board. simple.

this is based on how you have it drawn

Steamhead

@SENorthEast1895er , try the Find a Contractor page of this site to locate someone who can help you. Go here:

https://heatinghelp.com/find-a-contractor/

SENorthEast1895er

Thanks for the insight, @pedmec. I ended up doing what 109A_5 recommended with their annotated version of the ZVC board layout (use an un-energized circulator relay to call the DHW). I talked to HTP tech support level 2, and they said that should work fine.

So it goes like so: Hot Water stat call goes to ZVC, which opens the Zone Valve. Once the zone valve is open, the ZVC turns closes both the primary and secondary circulator switches. The primary circulator switch goes to the circulator. The secondary circulator (unenergized) switch goes to the the HW switch on the 925. The 925 hot water time-out is set to the same as the ZVC's (60 mins).

From your post, I assume that there are mod-cons that will work without primary secondary piping. This gives me hope that I don't need to repipe my entire house to have an efficient boiler and outoor reset.

Jamie Hall

Just a thought. Primary/secondary piping should be a pretty simple task, and doesn't mean repiping much of anything beyond the manifold right next to the boiler.

SENorthEast1895er

Thanks for the info, @Jamie Hall. Not sure it applies, as I don’t have a manifold right next to the boiler. Just an old gravity fed system in a 135 yr old house. Never been repiped.

Jamie Hall

Not a big deal to put a manifold in — pre made or built yourself (probably easier in some ways) from an assortment of fittings and nipples and so on. Basically one loop with the primary pump on it, with the expansion tank and automatic feed (if used) and air removal just before the pump, of fairly or relatively big pipe which runs from the boiler outlet back to the boiler inlet. Take a straight section — long enough — and each secondary zone taps off that with a T and a pump, and then at the other end of the straight pip taps its return back in with a T. Or you can have one secondary tap off that loop, with a single secondary pump and zone valves. You can get a lot fancier and have individual temperature control on each zone…

SENorthEast1895er

Ok, back again. Had a guy come and service the boiler; not having any issues anymore. Said the boiler was in excellent shape for it’s age, so that’s nice. And he caught another install error; the exhaust pipe was below the intake pipe (outside the house), so likely drawing in low-O2 air.

If someone could look over this report and tell me if there’s anything concerning, I’d appreciate it. Just want to confirm that the boiler is in decent shape and there isn’t anything concerning going on. To get this report, we turned up the water heater, so no ODR running for this; water temp was something like 180.

@EdTheHeaterMan regarding my expansion tank (and air) issues due to misplaced points of low pressure/temperature (which you explained in detail earlier in this thread): I was kinda hoping that I could run the circulator with the boiler off and get the high-oxygen air flowing out of my expansion tank before firing up the boiler for the season. However, after reading through your post (and trying to understand it), it doesn’t seem like that’ll do anything because there will be neither a pressure nor temperature differential at the T for the expansion tank, which means nothing will flow in/out of the expansion tank. Is this correct and is there anything I can do before the season starts to expedite the incredibly-slow bleeding process necessitated by the lousy install job someone did on this boiler?

EdTheHeaterMan

You are correct about nothing flowing in or out od the expansion tank at that Tee fitting regardless of the type of tank (pre-charged or old school compression tank type) This is the definition of the concept of Point Of No Pressure Change (PONPC). In a closed system. nothing will flow into or out of that tee fitting unless you add pressure or reduce pressure in the system somewhere. By turning on the circulator, you will change the pressure at the circulator. The outlet side will become higher that the inlet side of that pump. based on the location of the circulator pump, that will determine weather the outlet increases the pressure to the discharge side or if the pressure on the inlet side decreases, or if a combination of both happens.

SENorthEast1895er

Looking for help and advice on this on this, yet again.

The basic questions are 2:

• What would cause a Taco ZVC to have both the Central Heat and DHW calling at the same time?
• What would cause a Munchkin (or circulator) to produce a high-pitched whining noise (I assume a pump or fan working overtime) when both CH and DHW are being called for (I assume that the DHW override time limit has been exceeded)
  • There was a lot of air in the system; I don't think there is a leak, the system is piped poorly and it may have come from expansion tank.

The system has been working well-enough for the past year since I implemented the hacky Taco ZVC solution from @109A_5. I had it serviced this year, and the serviceman said that it was in very good shape for it's age with no immediate concerns.

However, twice in the past year, including just a few minutes ago, I've gone downstairs and the ZVC (wired as @109A_5 recommended on the previous page) has indicated both DHW and CH calling for heat, with zone valves open. I have both the boiler and the Vision 1 system to have DHW override for 1 hr. My understanding was that, after 60 mins, the ZVC would revert to a Central Heating. However, I don't know what happens next (if the hot water isn't satisfied).

Just now, I went to check on the boiler because it (or the circulator) was making a high-pitched whining sound. Like a pump or fan working overtime. As stated already, both DHW and CH were all lit-up on the ZVC. I turned the hot water t-stat down, and the whining stopped immediately.

There was a ton of air circulating through the system; my first thought was this was causing a fan or pump to work overtime (due to inadequate cooling). However, this may not explain why the noise stopped immediately after turning off the hot water (unless the boiler instantly turned off due to water temp being higher than the CH set point, which it was).

My first concern was that there was a leak. However, pressure is constant and the auto-fill isn't on. My next thought was that having both zone valves open had somehow released a lot of the air trapped in my compression/expansion tank (I forget which it is) (because my system is piped very poorly, @EdTheHeaterMan explained it pretty well above).

I've since turned of CH and turned on the DHW, and, after a bit of "clearing out", there's less air audibly going through the system. No whining noise at all. However, I seem to have misplaced all my radiator keys, so I'm off to Home Depot to get some more and test the theory that air was somehow released from the expansion tank.

Another thought I had is that the 60 min DHW timeouts of the ZVC and the Vision 1 are not perfectly aligned. If the Vision 1 timeout happens first, then colder water would be sent to the DHW, cooling the tank and creating a vicious cycle.

Thanks

EdTheHeaterMan

@SENorthEast1895er asked:

What would cause a Taco ZVC to have both the Central Heat and DHW calling at the same time?

the CH thermostat and the aquastat on the indirect water heater will at times both call for DHW Since you are not using the ZVC to operate the circulator pump and the ZVC is only opening the zone valves, If you set the priority switch to OFF then both will register as calling for heat and both zone valves will open. both amber and red LED will indicate that there is a call for heat and the the end switch is closed (turned on).

If the ZVC is set for priprity ON then both amber lights may light but the DHW red light may light indicating that the DHW ens switch is closed (turned on) and the CH red LED will be off indicating that the CH zone valve is not open and the end switch is not closed (turned OFF)

EdTheHeaterMan

@SENorthEast1895er asked:

What would cause a Munchkin (or circulator) to produce a high-pitched whining noise (I assume a pump or fan working overtime) when both CH and DHW are being called for (I assume that the DHW override time limit has been exceeded)

There was a lot of air in the system; I don't think there is a leak, the system is piped poorly and it may have come from expansion tank.

In order to understand the Whining noise I would need to hear it. Can you post a video of the boiler while it is making the noise? Pump impellers can make noise, Combustion fan can be out of alignment and make a noise. With so many items that are in need of attention, it is not easy to say where to start without actually heating the noise ad possible the source of the noise (where the noise is the loudest)

SENorthEast1895er

EDIT: woke up at 4am and caught the noise. see next post.

thanks for getting back to me so quick, @EdTheHeaterMan

It should be said that, since turning down the indirect t-stat and fiddling a little bit, I’ve heard nothing outside of the normal quiet hum that I expect.

I haven’t been able to recreate the noise; however, I also haven’t recreated the exact conditions.

I assume that, at the time I heard the noise, the indirect hot water was calling for <60 mins. Per the the Taco 403-4 manual, if indirect is calling for >60 mins, other zones will be given power.

I would expect pump impellers and fans to be more constantly problematic (present with only 1 zone calling), rather than something brought out by some sort of zone priority issue. Please let me know if and how ill-informed I am on that front.

Google says that trapped air can make a whining noise. Not sure if I trust it, but I do have air problems and I heard a ton of it moving through the pipes right by the boiler (inside the boiler?) as soon as I turned down the indirect tstat. So I’m hoping that’s it. Although I can’t figure out why turning of 1 t-stat call instantly stopped the noise (the indirect t-stat was what I turned off).

If I recall correctly, I set the Muchkin to also have a 60 minute priority for DHW. I was thinking that this would “match” the ZVC. However, now I realize I’m wrong. The ZVC handles the priority and prevents the Munchkin from seeing simultaneous CH and HW calls for the first 60 minutes. If the HW is still unsatisfied after that time, the ZVC would then send both calls to the boiler and the boiler would start its own timer.

As far as I can tell, it just creates a situation where the actual priority = ZVC priority + Munchkin priority.

The ZVC does control the primary (and only) circulator.

In the meantime, I’ve (slowly, over the course of the day) increased my indirect t-stat from 50% to 75% of full t-stat value (there’s a mixing valve; I swear it’s the only part of this install that was done right… and it was added 10 yrs after install) to hopefully decrease the likelihood of 60+min indirect calls.

SENorthEast1895er

Hi @EdTheHeaterMan Here’s video. Not the circulator. Was unclear to my ear whether it was coming from the front or back of boiler, but, in the video, it sounds a little louder at the back. To my ear, it also sounds like something is sucking air (something I didn’t notice before).

Also took a video of turning off the water heater and noise stopping. However, noise is quieter in the video than I expected, so it’s not that audible.

As you can see from the shorter video, both circuits are calling for heat. According to the Taco ZVC manual, that means that the indirect hot water heater has been calling for heat for 60+ minutes.

This happened at 4am. I had to turn the HW thermostat from 75% (where the scalding warning begins)down to 50% (where it switches from blue to red) for it to shut-off.

While we have tenants, and they sometimes shower late, I don’t think they were running the hot water that low at 4am. Note that I used to run the water at about 50-55% termostat setting. EDIT: I think I partially figured this out. Once the hot water tank calls for more than 60 minutes, the ZVC sends both HW and CH calls to the boiler. The Munchkin alternates between HW and CH temps, but the ZVC is controlling flow to zones. In this state, all zones are open, so the hot water tank is getting sent 120 degree water every 30 mins or so.

However, while this explains why I had to turn down the t-stat so far for it to open, it doesn’t explain why the hot water tank is calling for water for 60+ mins at 4am.

And I don’t know how all that air is getting in. Pressure is constant (18 psi when hot; drops to 16 once the circ kicks on, due to gauge placement. My guestimate for static pressure needed is minimum 14 to cover guesstimated 33 feet from pressure gauge to top of last radiator); filling valve is closed. My best guess is a third-floor radiator bleed valve is stuck a little bit open (it feels like the threads are stripped, and I’ve never been able to get water out of the third floor radiators, So I assume it’s closed. As you may recall, I have a terribly-piped system).

I’m tempted to run out to the plumbing supply (before we get hit with snow) and grab an auto-bleed valve to throw on the radiator that seems to catch 99% of the air. I’m just worried it’ll cause me to miss other problems.

But, back to the problem at hand. I’m just confused all-around.

• What’s the noise?
  • How bad/dangerous is it?
• Why all the air in the system?
• Why isn’t the HW getting satisfied?

Boiler Noise (I don’t know why, but you have to click on this one):

https://youtube.com/shorts/ApSXibUg3Gw?feature=shared

Turning off the HW; burner stops, noise stops. Lots of gurgles:

https://youtu.be/9vY381okh_0?feature=shared

Central Heat firing alone a few minutes later. No “whirring noise”, no gurgles. (but plenty of buzzing from some faulty florescent light ballasts)

https://youtu.be/QeIhvECNdVc?feature=shared

EdTheHeaterMan

I listened to the noise and heard it stop. I find nothing unusual about the noise. that noise sounds like my boiler when it is operating. I have an oil fired boiler. you can not heat that noise when the burner is operating. once the boiler reaches 180°F the high limit will stop the burner from operating. then I can hear the noise that I heard in your video. That is the noise of the pump operating. If the call for heat stops when the burner is off, then I also hear the pump operating noise stop just like your video. Being that I believe that your noise is normal I have these all important questions…. Are you cold? Is the heater not able to keep the home at the desired temperature? Are you getting cold showers? Is the heater unable to produce enough DHW?

I will follow up with this comment "If it Ain't broke… Don't fix it!"

SENorthEast1895er

@EdTheHeaterMan

I think you only watched the videos showing the issue wasn’t constant. For some reason, the video with the actual problem was only showing up as a link in my previous post. I thought it might get missed. Here’s a link; I don’t know why it’s not embedding into the post automatically.

oh, hey, look at that. it worked this time (I had to fiddle with some setting over on youtube).

Talked to the retired plumber of record for the neighborhood. He used to service this system. His guess was flash-boiling, which makes all the gurgling that immediately follows make a lot of sense.

My pressure gauge is reading 18 psi (hot); yet I haven’t gotten water out of the top radiators. He advised me to 1) not trust the gauge too much and 2) power down, open valves, run the circulator, and add water until I get water out of the top.

I had assumed I was slowly bleeding air out of the expansion tank, due to the lousy setup here.

https://youtu.be/ApSXibUg3Gw