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Melted 3 Taco zone valves on Boilermate zone

redrocket
redrocket Member Posts: 5
Hi, 
I have a 1977 New Yorker oil fired boiler with a Taco 6 zone controller using 5 zones, with the gold Taco zone valves.  The controller has  2 transformers, and my Boilermate is on the 6th zone, which has priority. 
A couple of months ago I had to replace the oil burner control, because my boiler was turning on and off repeatedly and also one zone valve head, on the bedroom zone, because it stopped working. 
In the past month, I have burned up 3 more Taco zone valve heads, all on the Boilermate zone. Two of them filled the house with an electrical burning smell, the 3rd, I caught early. They all had drips of melted wax running out of them. This is the only zone I’m having difficulty with, now. It ran for 7 years with no problems. The Boilermate was used when I installed it in 2015. This is the first time I’ve had trouble with it.
I have not been able to find any information on how to test the aquastat in the Boilermate. When it calls for heat the zone valve reads 24.04-24.08 V between terminals 1&2. But, the valve doesn't open. It gets hot and smelly, though. Inside the Taco zone control, the terminals read over 26V. And when I checked the other zone valves that were calling for heat, they read over 26V until they got heat, then they fluctuate between 23-26V. 
I’m wondering if it’s possible that 24.04-24.08V is causing my zone valves to burn up and it is all caused by the aquastat for the Boilermate? But I don’t know how to test it. And I don’t want to put another new zone valve head on there and burn it up. It’s starting to get expensive. Or could it be something else entirely? The valve itself?
I would appreciate any insight that you may have. 
Thank you in advance,
Alana 

Comments

  • Zman
    Zman Member Posts: 7,295
    I think it is very likely the valve itself. If the isolation valves above and below are operational, you should be able to rebuild the guts without draining the system or soldering.

    I am always curious what the system water looks like and how the chemistry is when you see things like this.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Jamie Hall
    Jamie Hall Member Posts: 18,699
    Is there more than one transformer on this system? And, if so, what is hooked into what?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Zman
    Zman Member Posts: 7,295

    Is there more than one transformer on this system? And, if so, what is hooked into what?

    This was my first thought. The pictures of the wiring are so clean that it does not seem probable.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,983
    edited May 9
    The sequence of operation of a Taco Zone Valve Actuator is designed to open the circuit to the actuator heating element once the piston reaches the maximum opening. Once the circuit is opened the wax in the piston will cool and the piston will move to the closed position and the contacts for the heating element will close and the wax will heat up and cause the piston to open until the contacts open. The movement of the piston in and out is very small and the cycle of opening and closing the heater coil contacts continues until the call for heat is completed. (Side note: this is the reason this zone valve needs an isolation relay if used with the Nest thermostat) @Zman has the answer. if the valve is stuck and does not allow the piston to move freely to the full open position, the heating element will never open to allow for the cooling of the wax inside the hydraulic chamber. Since the electric heater stays energized longer than it is designed to be on, the Hydraulic pressure builds up enough to cause the seal to fail and the wax leaks out.


    Hard to find diagram of the inter workings of the Taco zone valve actuator. Pretty cool design, but not my favorite valve to use. I have never opened one up the repair as @Zman suggests, but its worth a try.

    Mr.Ed


    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    mattmia2Solid_Fuel_Man
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,900
    Take the actuator off the valve and see if you can move the valve stem up or down. Try it on one of your good valves so you can see the difference. The valve is probably rusted in position and the actuator can't move it
    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,983

    Take the actuator off the valve and see if you can move the valve stem up or down. Try it on one of your good valves so you can see the difference. The valve is probably rusted in position and the actuator can't move it

    Those valve springs are really tough to open. You will need a large pair of offset pliers (often called Channellock pliers even if manufactured by others).

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    Solid_Fuel_Man
  • mattmia2
    mattmia2 Member Posts: 5,279
    I don't get this series zone valve. they are slow, they are expensive, they are complex. It is like you put all the disadvantages of all the other designs in one valve.
  • redrocket
    redrocket Member Posts: 5
    Thank you so much for all the great advice!

    I think you guys are right on the money. I squeezed the valve stem with a pair of water pump pliers and it does move, but it was crunchy in the beginning and it doesn’t go all the way flush with the plate. Then I tried one of my good ones and it does go all the way flush to the plate. 

    The fellow I get my parts from is totally in agreement with you guys, too. So, I brought home a new valve and I am going to try to switch the guts out and see what happens. It might be a couple of days before I have time, but I will let you know how I make out.

    I have 3 transformers, all together. 2 in the Taco zone controller and 1 on the side of my 200 amp service panel. Not absolutely sure how they’re wired up, though or how many of them are actually being used.

    I’ve read a lot of bad things about the Taco zone valves, lately. And having just burned out 3 of them, you'd think that I would be a hater by now. But, I have to give credit where it is due. I moved into this house almost 30 years ago, and this year is the first time I’ve had to replace any of them. 

    Thanks again, 
    Alana 
    Solid_Fuel_Man
  • redrocket
    redrocket Member Posts: 5
    Woo hoo!!! That was the ticket! Thank you so much to everybody who offered advice!

    The old valve guts were plastic and warped. The new ones were brass, I have high hopes for its longevity. I may have warped it when I  sweated it in 7 years ago....didn't know it was so easy to take apart. 

    I am always curious what the system water looks like and how the chemistry is when you see things like this.
    The water was pretty clear, no noticeable discoloration or anything.

    Thank you again!
    Alana 
    Solid_Fuel_Man
  • mattmia2
    mattmia2 Member Posts: 5,279
    That looks pretty crusty. What kind of radiators and piping does the system use?
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,445
    The wax motor valves have the advantage of having very few parts which actually move. Those parts that actually move, move very little comparatively to a spring return zone valve. 

    The slow movement can be an advantage. 

    That said, I always use Caleffi Z-One or Erie zone valves. 

    But, as you said there are many of those old Taco heat motor valves which have been in service for 40+ years. They just fail in strange ways, which makes some people not like them. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • mattmia2
    mattmia2 Member Posts: 5,279
    The end switch not being isolated from the control can be an issue in some installations as well.
    Solid_Fuel_Man
  • Steamhead
    Steamhead Member Posts: 15,263
    mattmia2 said:

    The end switch not being isolated from the control can be an issue in some installations as well.

    That's why I always install isolation relays when using these valves.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • redrocket
    redrocket Member Posts: 5
    That looks pretty crusty. What kind of radiators and piping does the system use?
    Mostly radiant floors. Copper in slab, circa 1947. Kitchen addition has a couple of slant fin radiators with all copper piping and another addition has Pex in slab. 

    The end switch not being isolated from the control can be an issue in some installations as well.
    That's why I always install isolation relays when using these valves. 
    Would you fellas mind explaining this concept in more detail for dummies, like me, please? Maybe some diagrams? 

  • Zman
    Zman Member Posts: 7,295
    edited May 12
    The Taco zone controller serves as an isolation relay.
    Your system has very nice low voltage wiring.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Solid_Fuel_Man
  • hot_rod
    hot_rod Member Posts: 16,118
    Older style thermal actuators can consume a bit of transformer power, on that model, call it 1 amp. So count the number of valves at 1A.
    Doing the math, 5 valves would be 5 X 24V= 120Va transformer required. That valve cycles about every 17 seconds, so they have a fairly consistent power requirement.
    If you add power hungry t-stats like some Nest versions that can pull an amp, you need to assure you have enough transformer for the occasions where everything is running at once, design day, perhaps.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • redrocket
    redrocket Member Posts: 5
    Ok. Thank you. You had me worried for a bit. Thought I might have needed to make some changes...
    You fellas have been extremely helpful! Thank you so much! 
    Alana