Hello,

I have 3 zones (1 for each floor). Everything worked fine up until 3 days ago. The heating for the top and basement floors (zones 1 & 3) work fine. The problem is, the valve for zone 2 is always open and on, and even though there is a programmable thermostat calling for a 68 degrees temperature, for the past 3 days the temperature on the main floor (zone 2) has been up around 74 or 75 degrees, regardless of what the thermostat on that floor is set to. It mysteriously gets as low as 71 degrees, but all the time the programmable thermostat is set between 60 degrees and 68 degrees.

For what it’s worth, when I installed the programmable thermostat 10 years ago, an HVAC person had to come over to install some type of relay (?) in between the new programmable thermostat and the zone valve in order for the programmable thermostat to work. I see this device connects to terminal #1. I only mention this because it is another mechanical/electrical device that is in the mix on this zone only (zone’s 1 and 3 are the legacy style thermostats and are not programmable).

Troubleshooting:
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1) I wanted to make sure it wasn’t the I disconnected the thermostat for this zone 2, so the red and white wires are dangling open in the thermostat location, not connected to anything… and the problem persists.

2) I called a local HVAC person who came over and said it was the zone valve and replaced it. He changed the zone valve for this faulty zone 2, and the problem persists. He said the zone valve is still malfunctioning and should be replaced anyway, so he left me with a $225 bill and nothing resolved.

He helped set me up with an appointment with someone more electrically knowledgeable about HVAC and they are coming over tomorrow. I don’t want to spend another $200 and not know what is really wrong…

Lastly, when the motor is running, when I disconnected terminal 3 the motor stops. Don’t know if that is significant but figured I would add it in.

Any ideas here?

Thank you!

 

You stil have the new valve? I'd call the owner/manager, and say he did not fix anything, and I think you shouldn't have to keep that part since the issue is still there.

Motor on the valve or the pump?

What happens you undo all the wire on the valve itself? Does it close?

I also going to move you over to the boiler section since the guys there knows more about the zone valve than I do.

 

Thank you for the response. Well, after doing nothing but waiting for 2 hours after posting my note, I decided to wire back up the thermostat and try again, and now everything is working fine. The furnace only came on when the thermostat was set higher than the actual temperature, and it turned off when it reached the temperature. Now it is 5:30am the next morning, and the temp is down to 64 (which it OK as the stat is set at 60 overnight), but the heating is on and the temp is rising as expected. I am hoping it is not an intermittent problem, so unless it is, I think we can close this one out. Thanks!

 

It is possible that when the new zone vale was replaced, the tech had a loose wire and when you disconnected and reconnected them, you may have possibly solved the problem.

Did the tech replace the zone valve head or the complete zone valve?

All it takes is a piece of dirt to cause a zone valve to stay stuck open and produce gravity heat or circulated heat when another zone is calling. Did he flush the zone with water? Sometimes you can flush the dirt through the system by purging it with the zone valve in the manually open possition

 

I hate to say it, but although the zone heating worked fine according to the stat all last night and this morning until we left for work, when I came home tonight the zone was stuck open and the temp was at 76 degrees. I took the stat off again and it stayed on. Coincidentally, a couple hours later I disconnected the wires from the new zone valve and then re-connected them back again (he only replaced the head and he didn't flush the zone with water) and a couple minutes later the pump turned off. It has been off for an hour and I'm sure if I hook up my stat again now, it will work fine again tonight.

The one thing I mentioned in my original note is that for this zone only, I have a nice Honeywell programmable stat, and when I installed it 10 years ago and replaced the standard honeywell circular dial type stat, it didn't work. The plumber/electrician said I needed a White-Rogers "enclosed fan relay", and he installed model 90-293Q in between the stat and this particular zone valve, and that has worked fine for 10 years. I only mention this because it is also "in-line".

For what it's worth, when the pump is on, if I unhook the blue wire connected to terminal #3 of the Taco 555-050RP zone valve, the pump shuts off. When I connect this same blue wire back up to terminal #3, the pump starts.

Thanks for all your help so far! Any more thoughts?

 

What brand zone valve are you using?

 

Taco 555-050RP zone valve.

 

First of all I think you have the wrong zone valve head

Is your system all hot water or is it combined with warm air fan coil units?

 

Here is the Taco page I am getting my info from

http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf

I think you should have a model 570 series valve. A 550 series valve is designed for high head conditions, which most homes will not have. Are the othe valves the same model number?

 

The new Taco valve zone head looks identical to the one it replaced, and identical to the other 2 Taco valve heads that run the other 2 zones (floors) in my home.

As far as your question - Is your system all hot water or is it combined with warm air fan coil units? ... The system is all hot water and there is baseboard radiators. I'm not sure what the "warm air fan coil units" refers to...

 

If you look at the Taco page I sent you, both the 570 and 555 look alike, but there may be differences on the inside. I have never known anyone to use a 555 valve so I cannot tell you for sure if there is a difference at this point.

If you take off the wires to screws number 1 and 2, you will disable the valve electrically and every thing should remain off for that zone. If not, try removing the head. that should mechanically make the valve close. If it closes properly, the problem is in the head.

 

OK, the pump was NOT on at the time. SO, I removed wires to #1 and #2, and set the stat for 1 degree higher than the current temp is, and the stat said 'heat on', and the pump never turned on. However 1 minute after I reconnected both #1 and #2, the pump came on after 30 seconds. Then as soon as I disconnected both #1 and #2, the pump immediately turned off. I think this means 'everything is OFF for the zone' when #1 and #2 were both disconnected.

Now, having said that, although I cannot see any model number on the zone valve head, I do see on the base of each of the 3 zones it says "571". So I think you are right - I have the incorrect zone valve head. I could test this. My basement zone does not really need to be on. I can disconnect it's zone head and put it on the zone base that is giving me problems and monitor. That way I know I will have a good 571 zone head on this base. Does that make sense?

 

To follow up on my previous note from last night, last night I took off the suspect 555 Taco valve head and replaced it with one of the other two existing 571 valve heads from the other zone, and now everything has been working fine for the past 9 hours - each time I turned the stat up the pump came on, and each time I turned the stat down the pump went off. I have done this about 20 times so I am hoping this is it.

I will keep an eye on this, as yesterday morning I thought it was resolved also even though the (wrong) 555 valve head was on the 571 valve base which, as it turns out, worked intermittently.

One note - I just noticed that on the box for the replacement 555 valve head, it does list that 555 model as a valid replacement power head for the 571 zone valve. So supposedly the 555 model should have worked?

 

So it sounds like it was a defective zone valve head.

I tried to find some info on the zone valve heads, but all I got was info on the complete valves. This is the reason I suggested that there may be a difference in the heads also. I have never seen a 550 series valve so I cannot say firsthand what types of differences, if any there are from the 570 series valves.

 

Hello, it's me again.

Everything worked fine for 1 year since my last post. Then about a 10 days ago, the symptoms came back. I came back from work and the temperature on the main floor (zone #2) was at 78 degrees with the prog. stat. set to 68 as normal. I then did nothing more than verify the 3 wires were connected to the zone valve tightly (which they were), and then (for no particular reason) I slid the valve stick from 'auto' to 'open', and then back again to 'auto', and then sure enough, a minute later the pump turned off. It had probably been on for 5 hours straight to bring the temp to 78 when it is ~30 outside. Then, two days later this same thing occurred and I "resolved" it the same way. It has been a week with no problems since. I do not know what triggers this problem (it was a lot colder outside a few weeks ago and no problems).

So, to re-cap from last year, I have placed different heads on, and the problem has reoccurred with different heads and with the thermostat not connected.

It is obviously very infrequently, and I wonder if the White-Rogers "enclosed fan relay" is somehow sending the signal to stay on and then resets its' signal when the valve stick is set from auto to open and then back to auto? It is the only "piece" I see in the loop that is different. The other two zones in my house do NOT have this relay (as they have older traditional non-programmable thermostats) and those zones have always worked correctly and do not have problems when zone 2 does.

Again, everything has been fine for a week (in 30 degree weather outside so the zone is coming on and off all the time), but I would really like to resolve this because who knows the next time it will come on for good and if I am on vacation no one will be there to notice it and get it to "reset" zo it may continuosly call for heat forever.

Any more ideas please? Thank you!

 

Has anyone determined if the "complete" zone valve has been replaced or if just the head has been changed? As mentioned in my earlier posts, the problem could be from foreign material, (solder, dirt, scale, wise potato chip bag, etc), don't laugh, I found one in a system that was operating for 5 years with no problems as the bag made its way through the system until it clogged a valve. So if the valve body has never been replaced, you may want to look there.

 

It was just the head that was replaced. If I understand you, you are suggesting that I have the pipe cut above and below the actual valve, and replace the "complete zone valve body" as an idea that could possibly resolve this? OK, thank you.