Let's say house is at 60, boiler has not run for a few hours so she is cold. Set thermostat to 70 in Zone 1. Valve opens, but hard to tell if water is cycling or not. Lights on Taco controller indicate the zone has Asked for heat and the valve has opened. Boiler does not fire. Turn thermostat up on Zone 2, boiler fires, feeling pipes at boiler indicates both zones are now circulating hot water. If I do not turn another Zone up, Zone 1 will be lit up on controller, but house will not heat and boiler will not fire.

Have tried a different thermostat on Zone 1, no change In behavior. Bad controller? Bad valve? Appreciate any thoughts!

 

Hi Doug,

It sounds like the problem is with your electric zone valve's ENDSWITCH.

What type of valves ? make/model

 

Thanks Trooper!

These are Honeywell v8043s. Entire system is only about seven years old.

 

Just some other info:

When I turn zone 1 up, the yellow LED on the Taco lights (request for heat), the red LED lights (opened valve) but only half brightness until I turn on another zone. Also, if I just turn up Zone 1, I will often hear the relay in the boiler loudly click quickly several times, but again, it will not fire.

 

There are two basic varieties of the 8043, one has screw terminals on the end plate, the other has one pair of yellow wires, and one pair of red wires. Below I'm going to assume you have the wired version...

A little about how and why first...

The Taco panel when activated by a thermostat should activate a relay and send 24VAC to the YELLOW wires, which turn on a motor inside the valve head.

This motor then opens the valve, and inside the valve head is a 'microswitch' (the ENDSWITCH) with a lever on it that gets pushed when the valve is fully open.

When the endswitch makes contact, it sends this signal back to the Taco panel which activates another relay in the Taco panel that sends a signal to the boiler to turn on.

There is also a relay in the control box (the aquastat) on the boiler that will make a 'click' when it is activated.

That's how it's supposed to work.

The fact that the LED only glows half bright is probably telling us that perhaps the problem is not with the valve head, but with the relay in the Taco panel.

Are all the 'channels' in your panel being used? If not, pull the relay (they should be 'plug-ins') from an unused channel and swap it with the bad one.

If all channels are used, swap the relays between two channels and see if the problem follows the relay. (might be a good idea to make a mark on the suspected 'bad' one first).

Try that and let us know... I'll be in and out doing stuff around the house... will check back during the day.

 

If the problem does not move when you swap relays, the problem is certainly with the zone valve head, and the endswitch in it.

At this point, you could swap the wiring for two of the valves and see if the problem follows the valve head. My bet is that it will.

OR, do you have a multimeter and know how to use it?

 

Hey NJ.

I DO have a multi and know how to use it.
This has been happening for about two weeks now, but never with enough consistency for me to nail it down. For instance, if the boiler is already hot, the valve opens and hot water moves, so there appears to be no issue. Or if Zone 1 requests heat, and so is another zone, then that other zone trips the boiler on, and again, heat flows. It has only been recently that I have noticed if I just try to run Zone 1, things don't work as they should.
When I pull the cover from my 8043, I have two red wires, and a yellow and orange appear to be what controls the valve opening and closing, so I imagine the 24 v must run down the reds.
I did swap on the Taco, zone 1 with 4 (4 is normally my HW), and yes, the problem was still there (boiler will not kick on if needed).
if I need to replace the 8043 (looking likely), can one just swap the electrical portion of the switch? I am good at wiring, not good at plumbing!
You say when the zone opens, it feeds 24v to the aquastat. Always? Even if the boiler has enough hot water already?

Thanks for the help!

 

Are your valves 8043 'E' or 'F' ? the E models have the wires coming out of the valve, and there will be two RED and two YELLOW. The 'F' models have screw terminals on one side panel... not sure if the wires inside will always follow the same color code... which do you have?

If the REDs that you are referring to are in fact the ENDSWITCH wires, they are a simple SWITCH. No voltage is fed to these wires from the zone valve. If there is voltage on them, it is coming from the Taco panel.

Yes, if there are two screws holding the valve head to the valve, you can very simply replace the head. If there are FOUR SCREWS holding it on, you will need to drain the system in order to change. Chances are that your valves are the newer variety with two screws.

The E model with 18" wire leads:
40003916-026 - Honeywell 40003916-026 - Replacement Head for V8043E Zone Valves

The F model with terminal screws:
40003916-048 - Honeywell 40003916-048 - Replacement Head for V8043F Zone Valves

Do NOT go by the picture, they are both the same.

Not exactly what I said... I said it sends a SIGNAL... but NOT 24VAC... the signal is a DRY CONTACT CLOSURE, a SWITCH. And that signal is sent to the Taco panel. The Taco panel then in turn takes this signal and sends it on to the aquastat.

 

The control on the boiler (aquastat) is what controls the burner depending on the water temp.

So the short answer is that when there is a call for heat, the Taco panel will ALWAYS tell the boiler that the home wants heat. The boiler control will tell the circ to run, and MAY, or MAY NOT fire the burner as needed.

 

Hey NJ, I have model F. I will probably go to my Plumbing/Heating store and see if they have the replacement head and start there. My system used to be hooked up with a power vent, which added this extra bit of complexity to the whole system (i.e., zone calls for heat, boiler needs to heat water, sends request to power vent, power vent turns on makes sure it is venting properly, sends clearance to boiler to turn on). We got rid of the power vent and put in a stack, but the wiring is still a little confusing to some!!

In my testing, Zone 2 is the zone that is my problem, even though throughout this thread I kept saying Zone 1 (my bad). So here's what i did:

Assume the "channel" on the Taco is bad. Move Tsat2 (Tstat for Zone 2) and Valve 2 to Channel 1. Request heat. No firing of boiler, red LED is half lit.

Assume bad thermostat. Move Valve2 to Channel 1 with Tstat1. Request heat. Boiler does not fire. (When I did this after another hour or so, before I was writing down all my testing, the boiler DID fire. This is what is just confusing the heck out of me. If it is a bad zone valve, then it is doing something weird sporadically, not all the time).

I have done some other testing, but like I said, it seems too "hit and miss". Since you said the microswitch is simply a closure, I get what you might be implying is for me to request heat, then check the ohms going across the red lines? If it's closed it should be zero. In doing this, if I request heat on Zone 1, across the red is 0 ohms (or damned near it!). The same with Zone 2 produces nothing, basically an open.

Your thoughts? If I am correct in assuming what you are saying about the dry closure, then it would definitely seem to be that Zone 2's microswitch is malfunctioning.
Thanks very much for the help!

 

It IS possible for an endswitch with dirty contacts to be intermittent.

Very astute! You is one step ahaid'o'me ! Good on ya!

I agree... and the cause doesn't have to be the microswitch itself, it could be a bad motor, or worn gears... not fully opening, not tripping the switch... but the chances are that it's the switch, it's a fairly common problem.

You can expect to pay about $80 for the head if you purchase locally...

 

Thanks NJ Trooper! I am going to get the new head tomorrow and try it out and report back. If I get real bored, I may swap the head from one lightly used zone valve (family room in finished basement) and see what happens! That's only if I get bored though.

Thanks mightily for the help!

 

Doug, let us know the outcome... good luck!

 

It's always a distinct pleasure to come back to a place like this and drop the bomb: don't give up your day job honey, cause you were so wrong it's scary!

Unfortunately, that's not gonna happen here (or fortunately from the perspective of my wallet). Found the replacement head at my local P&H store, about $60. Replacing was a snap (note to self, wire it up first, it's so much easier)! Let the boiler get cold, turn up the zone and the boiler fires up. Nice, especially after getting up this morning and finding the downstairs was about 63F, and not heating.

Thanks Trooper, your help was much appreciated!

 

Glad ya got it all fixed up and didn't have to drop the bomb! Thanks for lettin' us know the outcome.

Good Luck!