Zone Valve Taco Powerhead

heatingdude

Hi guys,

I have a boiler with three zones therefore three thermostats. One of the thermostats is a nest and reads there’s no power to Rh. I took of the thermostat and tested Rh to W and got 0 volts so I went down to the zone valve. I tested from terminal two to ground and got 0V while the other zone valves read 24V to ground. I decided to just turn on the other two to make sure they work and they kicked in. However they took a while to kick in and when I took off the thermostat (to the ones that were working) and tested Rh to W I got 0V which confused me. Is it possible that all three zone valves are going bad? 

Attached below is the wiring diagram 
if someone could help it would be much appreciated. 

EBEBRATT-Ed

The zone valves that worked are ok. The valve actuators have a wax element that takes 60-90 sesonds to heat up and work.

You won't get voltage between R & W in most cases the thermostat is just a switch.

A nest thermostat will not work dependably without a "C" or common wire. Your going to need some rewiring and a 3 wire cable to the Nest to make it work

pedmec

how about that maybe you wired it wrong. thermostat transformer should be wired 1-2. system transformer should be 2-3. common tap is #2. move blue to #2

heatingdude

EBEBRATT-Ed said:

The zone valves that worked are ok. The valve actuators have a wax element that takes 60-90 sesonds to heat up and work. You won't get voltage between R & W in most cases the thermostat is just a switch. A nest thermostat will not work dependably without a "C" or common wire. Your going to need some rewiring and a 3 wire cable to the Nest to make it work

So I won’t get 24V from Rh to W when the thermostat is off the wall unless I wait? 

heatingdude

pedmec said:

how about that maybe you wired it wrong. thermostat transformer should be wired 1-2. system transformer should be 2-3. common tap is #2. move blue to #2

I didn’t wire the system. And it’s been working for 5+ years. They added the nest thermostat afterwards 

109A_5

Hello @heatingdude,

Did you start at the secondary of the transformer (Brown and Pink) and verify your meter works correctly and you have it set to a AC (Alternating Current) Voltage range above 24 VAC. If it is set on DC (Direct Current) it may read zero Volts.
Also I agree with @pedmec the wiring looks odd, maybe 1 and 2 on the Zone Valve are reversed on the drawing.

heatingdude

109A_5 said:

Hello @heatingdude, Did you start at the secondary of the transformer (Brown and Pink) and verify your meter works correctly and you have it set to a AC (Alternating Current) Voltage range above 24 VAC. If it is set on DC (Direct Current) it may read zero Volts. Also I agree with @pedmec the wiring looks odd, maybe 1 and 2 on the Zone Valve are reversed on the drawing.

Well there was 24V between terminals so didn’t figure the transformer was bad and the boiler had been working for years so didn’t check DC either. As far as wiring it’s been working for years so it had to have worked. And 2 is definitely the red wire from the thermostat so I figured they just wired the thermostat after the motor.  

109A_5

Hello @heatingdude,
Obviously the transformer is probably good, since the system mostly works. What you wrote is your meter reads zero with every measurement you made.

The meter at the transformer is to VERIFY THE METER AC Volts operation, not the transformer and not to measure DC. Your wiring diagram is not typical, however if it is factual it may work with your boiler.

If you are using defective test equipment or test equipment set up wrong you will be confused.

pedmec

powerhead takes roughly two minutes to open and for the end switch (2-3) to make which initiate call for the boiler to come on.

you should have two transformers in this system although after looking at the drawing it looks like they are using the (1) system transformer to power the boiler and powerheads. Because of the way its wired you won't read 24 volts if the heater switch, which is located in the powerhead, is failed in the open position. measure from 1 and 2 at the zone valve with the thermostat closed and you should get 24 volts.

pedmec

If you have voltage at the powerhead as described then your powerhead is defective.

heatingdude

pedmec said:

If you have voltage at the powerhead as described then your powerhead is

defective.

Yes I had voltage between the two which is why I initially thought it was the power head but then I started looking at the wiring and it confused me insanely to see it wired like that so I thought it may be the nest thermostat doing something funky. But I figured since I have 24V coming to the 1terminal then there should be 24V to the 2. when I checked there was 24V between 1-2 and 0V between 2 and ground so I figured it must have been the power head. 

109A_5

Hello @heatingdude,
Keep in mind there is a switch to keep the Wax Motor from overheating. See red circle in picture. This switch may make the NEST unhappy and give you unexpected voltage readings depending on the state of the Zone Valve.

heatingdude

109A_5 said:

Hello @heatingdude, Keep in mind there is a switch to keep the Wax Motor from overheating. See red circle in picture. This switch may make the NEST unhappy and give you unexpected voltage readings depending on the state of the Zone Valve.

Hmm ok I’m probably going to change the thermostat first and then try it. And then I’ll change the zone valve 

109A_5

Hello @heatingdude,

Sounds like the expensive way to maybe fix it. As others stated I probably just needs a C wire to make the NEST happy.

Red oval in pic shows the switch.

109A_5

Hello @heatingdude,

HomerJSmith

The first thing that you need to determine is whether you have two wires at the old thermostat or three or more wires in the cable from the new Nest thermo to the zone valve.

The two transformers in 109A-5's diagram is the power transformer to the Nest and the other transformer is in the aquastat on the boiler.

heatingdude

109A_5 said:

Hello @heatingdude, Sounds like the expensive way to maybe fix it. As others stated I probably just needs a C wire to make the NEST happy. Red oval in pic shows the switch.

I don’t have another wire for the C and they don’t like the nest anyways 

pedmec

Regardless of whether you have a c wire if you measure between r and w at the thermostat and you have no voltage then you have a break in the path of circuitry. Because of how it is wired the only other controlled break is at the heater, as 109a_s has circled in the drawing.

heatingdude

pedmec said:

Regardless of whether you have a c wire if you measure between r and w at the thermostat and you have no voltage then you have a break in the path of circuitry. Because of how it is wired the only other controlled break is at the heater, as 109a_s has circled in the drawing.

Right. So my confusion came when I tested the thermostats (the ones that I was told were working) and I got 0V between Rh and W but then they came on (a century later) when I turned them on. 

109A_5

Hello @heatingdude,

OK, you are going to replace the NEST with an inexpensive Non-NEST thermostat. That makes sense to me. When you said "change the thermostat" I thought you meant with another NEST.

Joe Mattiello

Looks like you have a lot of help with wiring nest thermostat. It does take 1.5 min to open ZV, and make endswitch close to fire boiler. 

If you continue to have problems. 

Call Taco tech support at 401-942-8000 and ask for tech support.
they can walk you through it.

SteveSan

@heatingdude Please see the wiring diagram attached page 6, showing how to wire in a 570 series heat motor zone valve to your Nest. As Joe Mat suggested you can always call into Taco Technical Services during normal business hours 8am-5pm est. Mon-Fri and just ask for Technical Services.

heatingdude

SteveSan said:

@heatingdude Please see the wiring diagram attached page 6, showing how to wire in a 570 series heat motor zone valve to your Nest. As Joe Mat suggested you can always call into Taco Technical Services during normal business hours 8am-5pm est. Mon-Fri and just ask for Technical Services.

Appreciate the diagram. This system is wired very differently. 

109A_5

Hello @heatingdude,

Keep in mind the TACO diagram assumes two transformers, one shown in the diagram and one internal to the boiler to power the boiler's equipment when the TT is closed (Zone Valve End Switch closure). And that method is what most are probably used to seeing.

I suspect your system only has one transformer and that is the reason it is wired the way it was.

EdTheHeaterMan

Sorry I did not see this until today. There is a very simple solution. When wiring a 2 wire thermstat to a taco zone valve there is no problem wiring thermostat W to #2 and transformer C to number 1. and the punk wire on the transformer to the R on the thermostat. that is because W and R on the thermostat could also be labeled T and T. There is not difference between the ends of a switch. Electric is colorblind and cant read.
Both diagrams will work with only 2 wires



When you introduce a thermostat that requires a C to operate then T T no longer applies. that is because one of the T terminals must be R and the other T terminal is then the W on the thermostat. The wire that becomes R on the thermostat must be powered from the R on the transformer. The W on the thermostat then must go to #1 on the zone valve (Not 2 as shown). On your Control system the R must be the Brown wire on the transformer. That makes the C on your control system transformer the pink wire. That is attached to the Red wire and attached to the Blue wire in your diagram. Since the C wire (Pink) from the transformer must be connected to the common wire of the zone valve (that is the #2 post on the zone valve) and needs to be connected to the C on the thermostat, then the only option for the W on the thermostat must be connected W to #1 on the zone valve.

EdTheHeaterMan

Try this

HomerJSmith

If you only have 2 conductors to the Nest, you need an adapter that Nest sells. With a Honeywell T9 WIFI thermostat the adapter come with it. Recently on this site there were after market adapters that work with a 2 wire sys. Wifi thermos need a C wire to function properly.