I have a Burnham Series 2 boiler with two zones (upstairs and downstairs), controlled by Taco ESP zone valves. I have a thermostat downstairs (Hunter 44110) that works fine. Upstairs, I've tried two programmable thermostats (a Honeywell and last week another Hunter 44110) but neither upstairs thermostats effectively controls the boiler.

The downstairs thermostat seems to work ok but the upstairs one keeps resetting itself to 85 degrees, regardless of what I do. Hunter tells me they don't have a multi-zone thermostat and that is my problem. Does this behavior sound like I need to replace both thermostats with multi-zoned thermostats? If so, why is it that the downstairs one works ok?

Thanks for any ideas.

 

Hi Hollywood, how ya been?

That's a line of BS. You don't need a 'multi-zone' thermostat.

No, absolutely not.

Have you checked to see if the zone valve is opening when the thermostat is calling for heat?

What does the LED on the valve do when the thermostat calls for heat? (have a helper turn t'stat up as you observe the valve)

Are these thermostats for HEAT ONLY? i.e. only two wires to each thermostat?

 

Sounds like you've got some chilly Poltergeist in the home...

All the thermostats do this? this is very weird...

 

Hey Trooper, Nice to hear from you and thanks for the response. Yes, this is a heat only system. I hooked up the two wires exactly the same on both downstairs and upstairs (RH and W terminals). Sometimes the upstairs thermostat will work exactly as its supposed to----I turn the temp up beyond the ambient temp and the zone valves turn on along with the LED light. When I go away (this is an empty rental house I've been working on) and come back the next day, upstairs will be blazing hot and the t-stat will show 85 degrees as its setting. I reset the thing again and make all the heat and cold settings to be 50 degrees and again, it all works ok for some hours. There's no one else working in the house except for me so I can't explain why this is happening.

I know the upstairs thermostat I just installed is ok as I just took it out of my own house.

When I bought this rental house 5 years ago it had the old round, Honeywell thermostats (the old ones with a mercury switch inside) and I assume the previous owner didn't have these issues. Back then, I replaced the downstairs one with the new Hunter programmable but just got around to replacing the upstairs one during this current vacancy. I've tried two new t-stats now upstairs---a new Honeywell and the Hunter and both are doing these very odd things.

I am going up there again tomorrow and can test it out more fully and carefully note the odd behaviors.

 

I know that if you look at the reviews on the net for the Hunter t'stats, they all seem good, but I personally don't care for them.

But you are saying that BOTH the Honeywell AND the Hunter are resetting themselves? That is almost an impossibility. You say this home is vacant? Are you sure? Seriously, I wonder if someone is getting in there and messing with you...

Are you absolutely certain that the SETPOINT is changing to 85 ? and not just that possibly the zone valve is sticking open somehow and the ROOM TEMP is at 85 ?

Are the Taco valves new? that model (now called the 'Zone Sentry' I believe) has not been out all that long.

Do you still have the old Honeywell rounds?

 

Your question about setpoint reminded me of something I noticed last week----the zone valve for upstairs was stuck at the midway point between being fully open and fully closed (with the power on). It stayed that way for hours without any movement or LED lights. Eventually, I turned the breaker to the boiler off, waited a bit and flipped the power back on and the valve started working again.

The zone valves are Taco ESP (ESPO75C2-2 08-04).

I wonder if the zone valve for upstairs is defective and is intermittently working.

I never fully noted the behavior of the newer Honeywell other than it got hot upstairs when it shouldn't have. It wasn't until I tried the new Hunter last week that I started noting things more carefully. I was pretty certain it was the setpoint that was at 85---I don't think the room temp ever got above the upper 70's. I will double-check that tomorrow and do a more full report. Yes, I do still have the old mercury Honeywell thermostat. I will take that along and see how it compares to the newer ones.

I have the Taco instruction sheet for the zone valves. How would I check the upstairs one to make sure it's ok? (the sheet is dated 2003 so this hydronic system must have been installed just a few years before my purchase).

Anything else I might look for that might be causing this?

Thanks Trooper!

 

It does sound like the upstairs valve is 'sticking' open... and if that happens, you will get heat upstairs when the downstairs zone calls, in addition to when itself calls. Add to that the gravity flow which would likely occur.

I have no explanation for the thermostat setting itself to max... except a defective thermostat. (but you did say it was working in your own home, yes?)

Other than observe it's operation, I can't think of anything. If you've noticed it sticking open, then don't expect that to be a 'one time deal'. It may be doing this often, or all the time.

 

Today, when I arrived I turned on the circuit breaker to the furnace and made sure the upstairs thermostat was set to 60. The temp got to 66 upstairs after a while but the stat was still set to 60. The thermostat never changed its setting so maybe I was seeing things the other day when I noticed it was set to 85 (I am getting older!). But, as I was testing the upstairs thermostat, the Taco valve for upstairs clearly got stuck in the halfway position again while trying to shut off---I had to push it down to manually turn it to the closed position. So, I'm thinking the valve must be the problem. At least its a place to start. I'll read up on how to replace that valve----hopefully I don't have to drain the whole system. Is it possible to take the motorized plastic housing off and clean inside without replacing the whole thing?

One other thing I noticed that is important---that upstairs zone valve make a lot of noise when it operates---far more than the identical valve for the downtairs. All the more evidence that there is probably something wrong with that upstairs valve.

I'm not sure why the boiler would keep running though just because the zone valve isn't working. I thought the thermostat controlled when to fire the boiler.

 

It does... but through a 'middle-man' who happens to be your zone valves.

Thermostat signals the zone valve to open, when open, the ENDSWITCH in the zone valve signals the boiler to fire up.

So if the zone valve hangs open, it could still signal the boiler to fire even in the absence of a t'stat calling. But usually it would have to hang ALL THE WAY open to keep the endswitch engaged.

If it's hanging only halfway, you will get flow through that zone when the other zone calls, and also you would get GRAVITY FLOW even when no zones were calling.

I've never seen one of these valves... but I'm quite sure that the power head operator can be simply removed and replaced without having to drain anything, and it's usually the operator and not the valve itself that is the problem.

 

It's been a few weeks but I now have a new Taco operator on the upstairs zone valve. But, things are still not correct. This is what's happening with that upstairs zone:

When I turn the upstairs thermostat to a temperature lower than the room temperature, the green light on the zone valve operator turns OFF and the boiler turns ON. To turn the boiler off, I have to set the thermostat to a temperature higher than the room temperature (which makes the green light on the zone valve turn on). It's just the reverse of what should happen.

The downstairs zone works fine - a thermostat call for heat turns the zone valve light ON and the boiler fires ON.

When installing this new Taco operator on the upstairs valve, I had to flip the wire connectors upside-down in order to push into the slots on the operator. So, I thought that might be causing this so I took the wires out and reversed them so they were just like the old downstairs operator. But, that didn't change anything.

Any ideas on what's going on?

 

What is the make/model of the thermostat?

Are you sure you don't have it set to the 'cooling' mode? Or have the wiring on the cooling terminals?

What is the part number on the box for the new power head?

 

Hi Trooper, I was hoping you'd reply!

The thermostat is a Hunter 44110----same one I have on the downstairs zone.

The new Taco zone valve operator ("Actuator Head" is what Taco calls it) is model ZA024Q4A1. Taco told me that was the replacement for the original one (ESP075C2-2)----this is also the model number for the downstairs zone actuator head that I did not replace (the one on the left in the photo below).

I'll double-check my wiring at the thermostat when I'm there tomorrow.

Here is a photo of the two zone valves and their operators. You can see the green light on for the new operator on the right (the upstairs zone). So, that means the boiler is OFF when I took the photo.

 

This is weird... looking at all the documentation I can find at the Taco site, it is apparent that there are 'normally closed' and 'normally open' versions of this valve actuator, but I don't think it should reverse the action of the end switch... just the valve opening and closing.

How can this be?

Is it possible that the relative positions of the two plugs on the heads are 'swapped' ? and that the plugs are reversed? (one would think that they would make it impossible to do this, but who knows?) I just looked at the sheets again, and it appears that they are the same... in your photo, the motor connections are the yellow and white on the top, and the red/green is the end switch to the boiler.

Try this... to get the thermostat out of the picture, disconnect it. Make and break the connection by touching and un-touching the wires. This will tell you if the problem is the thermostat or the valve head (or wiring).

 

Just got back from the rental house and did the test as you suggested Trooper.

Before doing this test, I made sure the downstairs thermostat was set to lower than the room temperature. The downstairs works fine so wanted to remove it from the equation.

I then removed the upstairs thermostat. I then turned on the circuit breaker to the boiler and the boiler immediately fired on. I then touched the thermostat wires together. The Taco valve's green light turned on and the boiler shut off. If I keep the wires separated from each other, the valve's green light stays off but the boiler runs constantly and only shuts off when the aquastat tells it to. This explains why the upstairs was staying in the 80's all the time a few weeks ago when I first discovered this problem.

So, the upstairs thermostat seems to be fine and the valve itself is doing what it's supposed to---it lights up when the thermostat wires are connected but the boiler itself is doing just the opposite of what it should do---its turning off when there is a call for heat and turning on when there is not a call for heat.

The downstairs thermostat and zone valve work fine so I think that means its unlikely to be anything wrong with the boiler.

I'm puzzled.

 

I've searched and read just about everything I could find on these valves... other than a malfunctioning actuator, I can't find a single reason that makes any sense at all why it would be acting this way.

One other remote possibility... that actuator is actually a 'normally open' part, and is mislabeled.

Are the part numbers you gave the FULL numbers?

Somehow, some way, the endswitch has gotten out of synch with the controller in the head. Thing is, even if it get outta whack, the valve is supposed to automatically 're-index' itself upon power up.

I suggest that you contact Taco directly.

 

And you are absolutely positively certain beyond a shadow of a doubt that you do not have:

ZB024Q4A1

 

I should have taken a closeup photo of the new valve. I did get an email from PexSupply this morning asking me to rate my purchase and it was the ZA024Q4A1 that they listed me as purchasing. So, it's unlikely the unit inside the box was something different. I'll double-check the unit itself next time I'm over there in a couple of days.

Even with the old Taco valve that I replaced (with the ZA024Q4A1), the upstairs zone was behaving this same odd way so it must be something that is not related to the zone valve.

I'll call Taco tomorrow and see what they say but I imagine they will tell me it's the boiler that is at-fault.

 

Pull the plugs from the old valve and let them hang out and try it again...

 

I will report back when I go up there again, probably Wednesday.

Thanks Trooper.

 

OK, I'm just back from the rental house for the first time in a week. I did the test you suggested Trooper. I unplugged both the 24v and endswitch plugs from the downstairs valve (the older one that works ok).

The upstairs thermostat showed the room at 41 degrees and I picked a setpoint of 50 degrees. I flipped the circuit breaker on, the upstairs zone valve started flashing green, the vent started to open, the boiler started to fire and then immediately stopped as the zone valve turned clockwise 90 degrees. The vent then closed. I turned the circuit breaker off and the zone valve turned 90 degrees counter-clockwise.

Here is my bigger finding----the valve that I ordered from PexSupply and the label on the box is for model ZA024Q4A1. That is what Taco told me was the replacement for the older model I had. But, look at the photo below and you will see your assumption was correct Trooper. The valve inside the box had that other model number: ZB024Q4A1.

Do you think this incorrect valve is causing the problems I'm seeing? I think I needed a "normally closed" valve and I assume this ZB model is "normally open" though I'm not sure what those terms mean exactly.

 

Yes Sir, that is exactly the problem. They stuck the wrong valve in the box.

Normally CLOSED means that when the thermostat is NOT calling, the valve is CLOSED and the endswitch is OPEN (not calling).

Normally OPEN means that when the thermostat is NOT calling, the valve is OPEN and the endswitch is CLOSED (calling.)

Where would one intentionally use a normally OPEN zone valve? hmmmm... possible a heat dump circuit for a wood stove ? If there were a power failure, the valve would OPEN and allow gravity flow to the dump zone... in which case, the endswitch would probably not be wired to anything anyway, so is irrelevant. Or, perhaps the endswitch might be wired to a battery backed up alarm system to alert the condition... I'm sure there are other examples...

I guarantee if you put the correct head on there it will work properly. Hopefully PS will correct the mistake...

 

I installed the correct valve yesterday and everything now works as it should. Amazing what using the right part does!

Thanks Trooper for figuring this out for me. I would never have known to look closely at the label on the valve without your assistance. I ordered the correct part and the box it came it had the correct number. Somewhere along the line though, someone slipped the wrong valve into that box. They both look identical so without your help, I would never have solved this puzzle. Even Taco customer service didn't think to ask me to look at what model number I had installed----they said I had a "wiring problem" that I'd need to figure out.

I'm glad to finally be able to use the heat again.

Thanks very much Trooper. You're a real asset to this forum!

 

I learned a long time ago to question the parts. I once replaced a clutch in one of my cars. Got it all back together and it wouldn't disengage enough to shift. Took it all apart, examined everything, put it all back together... TWICE! (got real good at pullin' that tranny!).

And the parts LOOKED identical to the eye. Finally brought the stuff back to the store and said WTF?

Turns out that the clutch disc he gave me was a 5055, and the one I needed was a 5505. Damn Dylsexia! Worked like a champ with the right parts.

Thanks for the kudos! 'preciate it!