Taco zone valve help needed.

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Old 01-25-14, 12:06 AM
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Taco zone valve help needed.

Really odd issues I'm hoping an expert can help out with. I have an on-demand boiler for heat and hot water. The heat system contains two zones for forced hot water baseboard heating. About a week ago, the upstairs zone (zone 1) started staying on, putting the temp up to the 80s. I did a bit of research and found that this was likely either the zone valve itself, or the easily replacable power head. To try and troubleshoot the problem, I tried swapping the two heads.

I wish I could easily recall everything I tried, but among them, I attempted to cleanup the nest of wiring and eventually picked up a new power head. Within minutes of connecting the new head, it "popped" giving a fried electronic smell and showed a distict coppery spray from an internal component and actually started smoking. I quickly turned it back off and did my best to follow a diagram to rewire everything again. Neither zone worked on it's own but could operate if I pulled both manual levers down. The head for zone 1 was staying fairly warm and I still noticed a faint smell but was unsure if it was remnants of the one that blew/smoked. Today I installed two new power heads and fired it back up.

The second floor appears to be working fine now, but the first floor (zone 2) won't turn on without pulling the lever down to manually bypass the head. The basement also has a distinct "burnt electronic" smell again today after swapping the heads. I have some pictures to illustrate how it's currently wired:

Power source



Here, the green wire connects to both a green lead headed to the boiler and a green headed to zone 1, the white wire runs towards zone 1, and the red wire to/from the boiler heads to zone 1.

Zone 1 valve



Here, the green and red from the first pic connect to terminal 2 & 3 respectively. The white line connects to one side of the thermostat, and the other side connected to terminal 1. Note that a new wire here also feeds from the white line, and terminals 2 & 3 headed towards zone 2.

Zone 2 valve



Much like the first valve, the green lead connects to terminal 2, the red to terminal 3, and the white goes to one end of the t-stat. The other end of the t-stat is connected to terminal 1.

Thanks in advance for all the help!
 

Last edited by NJT; 01-25-14 at 07:12 AM.
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Old 01-25-14, 07:15 AM
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Hi Mike, I pasted the images into your message... it's best to use a PUBLIC album on photobucket so we can scroll through the images and not have to open and close... but they're here now so no problem.

I'm going to try and sketch out a wiring diagram from the photos... let me think about this for a bit.

Tell us what control that terminals 2 & 3 are wired to on the boiler.
 
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Old 01-25-14, 07:44 AM
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Wiring seems to agree with this... I wonder if this drawing was what you worked from? Even wire colors seem to agree... this is old drawing from 'back in the day'. I believe that this was an 'as-built' drawing of someone's wiring. I would have used different wire colors, but the electrons don't care what color the wires are as long as they go where they are supposed to:



Mike haz multimeter?

Meter set for AC volts on terminals 1 & 2 of zone 1, no call for heat, zero volts. Call for heat, 24 VAC.

Ditto for zone 2.

Meter on T T at boiler, no call for heat, 24 VAC, call for heat from EITHER zone valve, ZERO volts.
 
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Old 01-25-14, 10:12 AM
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Thank you soooo much for your help. I just grabbed a new 24v transformer on my way home from work just in case but after running your tests, I don't think that's the problem. (like an idiot, i was trying to test voltage using DC yesterday and thought either my miltimeter or transformer was screwed up).

Anyways, here's the results.
The transformer is reading 24v.
Zone 1 (the one that works) is reading 24v when heat is on and 0v when it's off.
Zone 2 is reading 0v in both cases. Then with both heats on, I checked:
Zone 2 Terminal 1 to Zone 1 Terminal 2: 0v
Zone 1 Terminal 1 to Zone 2 Terminal 2: 24v

This is telling me that the circuit isn't completing for the Zone 2 thermostat. That should narrow it down to a short in the wires (you can see they're very old with rope casing instead of plastic), or the thermostat. The t-stat is only a few years old but could I have blown it out while messing around? I may just got get the stuff to replace both unless someone has another possible cause.
 
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Old 01-25-14, 10:23 AM
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more good news, I disconnected the two t-stat wires at zone 2 and connected them and at the t-stat I have continuity. Seems like a blown t-stat?
 
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Old 01-25-14, 10:40 AM
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Zone 2 Terminal 1 to Zone 1 Terminal 2: 0v
Zone 1 Terminal 1 to Zone 2 Terminal 2: 24v
This isn't telling you anything special really... not sure why you are 'crossing' between zones 1 and 2.

Terminal 2 is connected together anyway...

So from EITHER terminal two to Z1 T1 or Z2 T1 will give you the same data.

I disconnected the two t-stat wires at zone 2 and connected them and at the t-stat I have continuity. Seems like a blown t-stat?
Mike, yer cornfuzin me!

If you disconnect the thermostat wires and connect your meter set to read ohms to the two thermostat wires, you should read OPEN (INFINITE) when the stat is NOT calling, and ZERO (SHORT) when the stat IS calling for heat.
 
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Old 01-25-14, 10:46 AM
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Zone 2 is reading 0v in both cases.
Yes... this is saying that the Z2 t'stat isn't calling for heat, not 'making' the circuit, and it's very possible that you fried it when you fried the zone valve by passing humongous current through it.
 
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Old 01-25-14, 10:51 AM
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Sorry for the confusion, I was 'crossing zones' to rule out that there was a short in the lines connecting them together.

Regarding continuity, I tied both feeds from the t-stat together at the zone to test that current fed all the way from on wire at the t-stat to the other (which it did). I'm off to grab some lunch and a new t-stat, I'll let you know how it goes. Thanks again!
 
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Old 01-25-14, 10:58 AM
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I still don't get it... I'm thick sometimes though...

If you go to the T'STAT (NOT at the zone) and connect the two wires together there, and the valve opens, that tells you that the wiring and the zone valve is GOOD, and the t'stat is bad.

If you connect the wires that go to the T'STAT together AT THE ZONE VALVE, the zone valve should open and boiler fire. This will tell you that the zone valve is good, but leaves question regarding the wiring to the t'stat.

While yer out, I like mine with lettuce and tomato, Heinz 57 and french fried potato, big kosher pickle and a cold draft beer, good God almighty which way do I steer?
 
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Old 01-25-14, 01:05 PM
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This damn problem won't end. So I hooked up the new thermostat, fired it back up and boom, Zone 2 worked perfectly! I turned that thermostat back off and fired up the thermostat for Zone 1... and nothing happened. I checked the voltage between 1-2 and got 24v, that seemed fine... then checked voltage between 2-3 and it showed about 3-4v. Seemed odd. Then I checked the voltage between 1-3, about 27-28v... as if the voltage for 1-2 and 2-3 were being added together. I turned it back off, waited a min and turned it back in again... still not kicking in.

I waited about 10 mins and checked again. By now 1-3 was all the way up over 50 volts, so I immediately shut it down. Does this sound normal? or is this maybe back to the original transformer theory?

I also followed the line that runs to the boiler and it feeds into a Taco SR 501 switching relay. The green line that connects to the transformer and both terminal 2s is connected to a connector labeled "R" on top and "T" on bottom. The red line that connects to both terminal 3s is connected to a connector labeled "W" on top and "T" on bottom.
 
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Old 01-25-14, 01:28 PM
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Well, for starters don't worry about the voltage between 1 and 3, it is meaningless.

Not going to go into why it's meaningless, that would cause information overload... just trust me on this!

as if the voltage for 1-2 and 2-3 were being added together
hint: they ARE. But it doesn't mean anything!


then checked voltage between 2-3 and it showed about 3-4v.
This means that zone 1 head has a dirty endswitch if all the wiring connections are tight.
 
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Old 01-25-14, 02:12 PM
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It's a simple series circuit.

From the transformer to one side of t-stat
From t-stat to #1 on zv
#2 on zv back to transformer.
That completes the t-stat circuit
From #2 and #3 on zv to TT on boiler.
That completes the burner circuit.

Duplicate that for both zone valves.

Why are you using a switching relay when you are using a separate transformer. Why not go right to the TT on the aquastat.
 
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Old 01-25-14, 02:49 PM
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Why are you using a switching relay when you are using a separate transformer. Why not go right to the TT on the aquastat.
I was kinda wondering the same thing myself, but I know that we've worked on this system before and sorta kinda remember that there was a reason for that relay... just don't remember what that reason was.

I'm pretty sure it's running the pump... and the other relay pole is firing the boiler...

But the specifics I can't recall...

Maybe for some reason an isolation relay was needed?

Mike, do tell what the reason for the 501 was again?

(not that it makes any difference to the operation of the valves though................._)
 
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Old 01-25-14, 03:47 PM
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I'm not exactly sure why the relay is needed. I know that the water line has a Taco circulator as well so could that be the reason? It's a pretty crazy setup from about 4 years ago when federal tax credits made on-demand heat/hot water boilers become very attractive. The brand is quiet side if that helps.

On to an update:

Seems like I finally got everything working! I'm sure it was a combination of a few things but the last thing I had to do (and probably the initial cause) was take the head plate off zone 1 and clean both the plate and the valve with penetrating oil/steel wool. It kept getting wedged on the plate and likely was the cause for sometimes staying on/sometimes staying off. It's actually working now even with the original head. Doesn't quite slide as smooth as I'd like but it's pretty close. If it starts up again, I'll likely have a plumber come out and solder in a whole new valve. FYI, I did shut off all the water valves at the boiler while working on the valve, not sure if that was necessary but I didn't want to risk a shot of 175 water in the face lol.

I'm guessing I actually fried the head/thermostat on zone 2 when I was trying to troubleshoot it. In the end, those ended up being my only material costs (about $100 for both) as I can return the second head and the transformer.

Thanks again for all the help!!! If you're ever in Rhode Island, you got one with lettuce and tomato, Heinz 57 and french fried potato, big kosher pickle and a cold draft beer with your name on it!
 
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