stuck valve?


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Old 03-08-07, 10:04 AM
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Question stuck valve?

Hi I'm new to post here but I've been looking at back posts to troubleshoot my problem.

I have BBHW with 2 zones. I have heat on first floor no prob. 2nd floor no heat. The trouble seems to be at the zone valve for the 2nd floor. Pipes on both sides of the valve are cold. I swapped out the power heads to prove those. I thought I had it because it worked with the head from 1st floor.

I when out and bought a new power head and it worked for a bit, but now the trouble seems to be back. I have swapped around the power heads and all work on 1st floor zone. I have tested out the thermostats by swapping them around. With the head off and the thermo calling for heat, I can push the valve plunger down, but pipes do not get hot.

The zone valves are Taco 571-2.

Could the valve be stuck closed?

With no heat running through that zone could the pipes possibly be frozen?
What to look for?


Thanks
 
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Old 03-08-07, 12:49 PM
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Taco Zone Valve

Try checking the voltages with a voltage tester; if you don't have one, there's an excellent GE unit for $10 at Wal-Mart.

Turn up the T-stat to 80 degrees to close the contacts & clean the contacts with a white envelope.

Check the voltage on the xformer supplying the zone valves; you should get ~40V AC.; check all screw contacts for tightness, with no wire strands shorting any of the adjacent terminals.

You should get at least 24V AC between terminals 1 & 2; and also at least 24V AC between terminals 2 & 3 of the zone valve when the system is calling for heat..

Also check to see that the wiring of the zones is correct; a wiring diagram comes in the box with the power head; you can Google Taco to get a copy on the internet.

There is a common wire that goes from the transformer to #2 terminal of both zone valves; the hot side of the xformer goes to the t-stat.

When the t-stat is calling for heat (closed) 24V AC is applied to terminals 1 & 2 of the zone valve, if it's good, it will open within 40 sec.; this will close a switch between terminals 2 & 3 (end switch) to energize either the "T" terminals on the aquastat (intermittant operating pump), or to the circulator (continuously operating pump).

In either case, the boiler should fire or the circulator should come on within 40 sec.
 
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Old 03-08-07, 01:46 PM
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Jack
OK this is starting to defy logic to me. I turned up the t-stat to 80 just like you said. Checked the voltage to the valve terminals 1+2= 21.5VAC. Between 2+3=21.5VAC also. Once the boiler fired 1+2 stayed the same 2+3=0VAC

I checked the voltages at the xformer =-26VAC before and after firing.
Blaser Electric is the manufacturer and the label says .24v

BTW the heat is working through that zone now!?!

I guess I will monitor it for now

Intermittent troubles are never fun.

Any ideas?
 
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Old 03-08-07, 06:16 PM
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Stuck Valve?

The problem could be in the thermostat. Taco zone valves draw a good bit of current compared to valves with electro-mechanical motors. What kind of stat do you have?
 
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Old 03-08-07, 09:00 PM
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Grady-Hunter Set and Save 1, 5-1-1 programmable model number 42204

http://www.hunterfanhq.com/hiw-prod/orderinv/frames/ps_frame.htm

And the battery is new.
 
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Old 03-08-07, 09:32 PM
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Taco Zone Valves

Grady is correct; Taco's have problems working with some programmable t-stats; if there is an adjustable heat anticipator on the Hunter it has to be set to .9.

Since the 1st floor t-stat is the same, see if you can find a difference in the settings of the 2 t-stats that would account for the 2nd floor not functioning.

Try disconnecting the leads to the t-stat & shorting them to see if that restores normal zone valve & heat cycle operation; if it does, the t-stat is the problem.

A testing procedure for 570 series Tacos is included in the site below, starting with "My home oil burner serves two zones..."

Corrections: the AC on the xformer & across terminals #1 & #2 needs to be 24 VAC; the valve takes 90 sec. to open on a call for heat.

They also describe a way to check the internal valve heat motor for defects by removing wire #1 & checking for ~22 ohms between #1 & #2; also check for dark brown hardened wax at the base of the piston to verify heat motor failure.

http://www.taco-hvac.com/en/products.html?current_category=66&show_faqs=1&PHPSESSID=62dfc864dd283aa3945
 

Last edited by jack horner; 03-08-07 at 10:33 PM.
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Old 03-08-07, 10:06 PM
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Taco

If the Taco link doesn't work, Google the phrase "my home oil burner serves two zones" (with the quotes) to get a procedure for testing the 570 series Taco valves.
 

Last edited by jack horner; 03-08-07 at 10:36 PM.
  #8  
Old 03-09-07, 01:48 AM
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Thanks for the leg work. I will check out the site and double check that the t-stat is set up correct. I will also have to check for the brown wax.

BTW don't you sleep?
 
 

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