My boiler is short-cycling


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Old 01-24-10, 10:34 AM
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My boiler is short-cycling

I have a SlantFin VictoryII Model VHS-150EP boiler system with 5 TACO zone valves (24V; Type E; N/C) including one for domestic hot water, that I installed seven years ago. Recently and intermittently whenever a thermostat calls for heat, the boiler will cycle on, the light on the zone valve flickers, and then the boiler shuts off again. It will do this over and over again.
The water temperature usually is below what it should be or even cold. I usually shut the whole system off, wait half an hour, then fire it up again and it works okay. No wind is blowing outside when this happens. Any ideas?? Thanks.
 
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Old 01-24-10, 12:06 PM
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Any and every zone acts the same way?

Sounds like a loose wire connection somewhere...
 
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Old 01-24-10, 12:54 PM
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Are the zone valves and t-stats all wired into a controller box ? (is this where the light is ?).
 
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Old 01-24-10, 01:40 PM
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The zone valves are all wired in series; no control box. The light is on each zone valve. When activated the light initially blinks, then stays on while the zone valve opens, then when no more hot water is needed, the valve closes and the light goes off.
I've noticed that the short-cycling seems to occur only when Zone #3 is calling for heat. Thanks.
 
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Old 01-24-10, 02:02 PM
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I would suggest you have a bad zone valve. It possibly could be the thermostat but I would guess the zone valve. You could try moving it to another zone and if the problem moves it is the zone valve, if it does not it is the thermostat or a loose wire.
 
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Old 01-24-10, 06:58 PM
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Its a pain chasing down an intermittent problem sometimes.. good thing if you already seem to have it narrowed down to the one circuit. Since you're already aware that the tstat and zone valve are wired in series across the 24v supply, it should be fairly easy to follow the wire connections (give em a tug or even remake the connection just to be sure) along the route. Its possible that your tstat is bad also. Or, a drywall screw/etc may have hit the tstat wire way back when and now its starting to corrode apart.

@rbeck.. Im not familiar with those zone actuators with the lights on em.. is this just a simple light across the input wires ? Sounds like a handy thing to have actually (I might mount some 24v lights across my wirsbo mva's..)
 
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Old 01-24-10, 07:41 PM
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I can't recall having seen a Taco ZV with lights on 'em either... maybe older models ... 'type E' ? ...
 
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Old 01-24-10, 11:55 PM
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I believe what you have are Taco ESP zone valves. Black
power head, plug in quick connects. If so, years ago I
unfortunately installed a lot of these and now I'm cutting
them all out and replacing them with a different brand.
Taco no longer manufactures these valves. They have
many design flaws. Suggest you replace ALL of your zone
valves if you expect any reliability. I use W/R 1311 series,
with a PAM-1 relay for two wire applications. You could use
the 1361 series, but I can buy the 1311 with a PAM-1 cheaper.
I use these zone valves because they are power open/close,
and they are full port.
 
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Old 01-25-10, 04:48 AM
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Whoa SuperSteve....you may have had some issues which they had early on, but that has been long resolved. The valve is still in production. There is no reason to tear them ail out and start over. They changed the name when the valve was re-introduced with the upgrades. The newer valve has been operating just fine. One would have to do more research but I also believe it mounts on the same valve body.
The problem you have I have encountered with the heat motors where the end switch does not make and hold upon opening. Once it holds everything works OK.
Here is a link to the new valves
http://www.taco-hvac.com/uploads/Fil...102-111new.pdf
 
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Old 01-25-10, 10:55 PM
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RBECK-My bad. Going on info fed to me by suppliers as to
availability of ESP/EBV valves. There were many "revisions"
made to this product. I have replaced, on my own time, all
power heads that fell within the date code warranty that I
installed. Most of the replacement powerheads I have
changed out because they were malfuntioning too. All
the techs I talk to hate them. (yes, I know, hate is a strong
word) My suppliers probably got tired of warranting powerheads, so they stopped stocking them. I'm still going to
cut out all that I have installed, and replace them with tried,
tested, and true because I like to walk away from my work
knowing that I have done everything possible to provide my
customer with a safe, reliable, and efficient system.

I know what you're talking about with the heat motor type
valve, but it doesn't apply here.

Here's a link that theDokeys can go to so we can verify that
we are indeed dealing with a Taco EBV.
TACO - HVAC
 
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Old 01-26-10, 01:47 PM
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Thank you, SuperSteve2000, for the information. My valves exactly match the one in the link you provided. As I said earlier, I installed this system seven years ago and in that time I have had numerous problems with the TACO zone valves, like not closing completely when no more heat is needed or not opening when heat is called for. At one point, the vendor sent me all new zone valves because we determined the old ones had failed and were still under warranty. Two year later I replaced all five heads for similar problems this time at my expense. Now it seems that zone valve failure may be the cause of my short-cycling boiler. My plan is to replace my five existing TACO zone valves with complete new Honeywell #V8043E1012 zone valves ($51.45 each from PexSupply.com) Does that seem like a reliable alternative? Thank you again.
 
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Old 01-26-10, 08:30 PM
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No really- Thank you! That's exactly what I'm talking about
with those infernal Tacos!
The Honeywell is a good, economic zone valve. They are closed
by a spring, so in certain circumstances they can cause water
hammer. I would consider installing the V8043E-1061. It has
a flow rating of 8Cv, versus 3.5Cv with the 1012. Also, just for
serviceability, make sure you have isolation valves on both
sides of the zone valve. Pay attention to flow direction when
installing. RTFM! (read the fubarin' manual)
Once again, thanks- and good luck.
 
 

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