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.