Zone not activating main circulator

wirsbozo

Hi, all. Had a new manifold installed for my family room hydronic heating zone a couple weeks ago. All seemed, OK, but I noted to the technician that the temp seemed to oscillate over time. Came to realize that the family room zone (call it zone 5) would only get warm if the basement zone (call it zone 6) was on. When the thermostat for zone 5 calls for heat, the relevant zone circulators run, but the main circulator for from the boiler does not. The corresponding red LED on the Taco relay box does not turn on. The tech (and I) were initially fooled because we tested it while zone 6 was also calling for heat. When both zones were calling, zone 5 is also able to pull hot water. When zone 6 is not calling, zone 5 is unable to pull hot water.

I've included a couple pictures of the system. Appreciate any thoughts on where to start. Thank you!

hot_rod

When I come across a wiring rats nest like that, I remove all the wires and start over

You have pumps and at least 1 zone valve that I can see. Two relay boxes and one add on relay between them. Without a wiring schematic it is tough to know what is controlling what?

Seems like a lot of wire nuts inside the relay boxes, usually every wire that enters has a terminal to land on.

It sounds like two pumps are wired to one thermostat or relay in the box. Sometimes when a relay in the box fails a wire is moved to another relay until it can be replaced. See if somehow two pumps are wired together.

I'd start with determining how many thermostat and how many pumps, do you have the same number? Then one at a time turn on a thermostat and see which relay kicks in. Then what does that relay feed.

wirsbozo

Thanks, hot rod. I traced the wires a little more thoroughly and will outline that below. I had a tech here earlier this week who tried to trouble shoot. What he came up with was that either the motorized zone valve for this zone was bad or the relay for the zone was bad. While I waited for the estimate for that work, I just swapped a known functioning zone valve (honeywell mzv) with the "bad" one -- this did not change anything.

I also swapped the relay for this zone (24v hartland controls relay with DPDT) with a new one, with no luck.

Of note, this zone does not have a relay in the taco box itself like the other zones. It's wired through the big 24v relay in the middle of the two boxes on the left (see pictures) below).



- 24vac port on the upper taco box is wired to a red switch wire on the valve; the "com" port on the Taco box is wired to the relay via blue wire; I traced the t-stat wires down to the lower Argo relay box - they run the the t1 port and loop back to the yellow "motor" wires of the motorized valve.


When I call for heat, the relay buzzes, but it does not sound right. Not a clean click, but a rattling buzz, like when a transformer is shorting.

I also swapped with a known correctly operating thermostat just to be sure.

Green led on the lower argo box lights up, and two secondary water circulators get energized; however, the trouble seems to lay with the separate relay and the signal to the high power wires going to the main pump and back to the boiler.

Any thoughts on what to consider next?

EBEBRATT-Ed

@wirsbozo

This applies to the big relay in the middle picture if that is the one you think is not working do this.

Take a flash light and look carefully at that relay. If you look closely you will see a wiring diagram on the relay itself. Stare at it it's hard to see. Then shut the power off.

That relay has a NO (normally open) & a NC (normally closed contact.

With the power off move the wire from the NO contact to the NC contact. Turn the power on & see if the circulator runs and should now heat.

Check the power on the 2 small wires at the top you should have 24 volts when the thermostat calls for heat. If the pump runs when you move the wire but not when the stat calls replace that relay

You or someone now or next summer should rip the wiring apart and clean it up and rewire it. You will save yourself a lot of time in the future

bucksnort

How do you get away with running bare Romex instead of BX sheathed for the 120?

Jamie Hall

bucksnort said:

How do you get away with running bare Romex instead of BX sheathed for the 120?

Entirely legal in many jursidictions.

On the relays -- also make sure that the coil is really getting 24 volts when it is supposed to be energized. A buzzing relay is sometimes caused by low voltage, which should be caused by a poor connection anywhere in the wiring.

neilc

were any power stealing thermostats added ?

wirsbozo

Thanks, all. I'm back after not being able to focus on this for a bit. Voltage at the green 24vac wire on the switch board when the thermostat is calling for heat is about 5V. Voltage for the blue com wire on the board is about 27V. At the relay, it's the same: 5v for the green and 27V for the blue. Should it be 24V across both sides of the relay if working correctly? Should it be 24V for the com and 24VAC port terminals on the board?

Blue com wire goes directly to the relay, and the green 24vac wire goes from the board to the zone valve then from zone valve to the relay.

I had replaced the 90304 relay with a new one before writing my initial post. Moving the NO wire to the NC contact saw no change in operation.

No power stealing thermostats were added.

Appreciate any thoughts from here!

EBEBRATT-Ed said:

@wirsbozo

This applies to the big relay in the middle picture if that is the one you think is not working do this.

Take a flash light and look carefully at that relay. If you look closely you will see a wiring diagram on the relay itself. Stare at it it's hard to see. Then shut the power off.

That relay has a NO (normally open) & a NC (normally closed contact.

With the power off move the wire from the NO contact to the NC contact. Turn the power on & see if the circulator runs and should now heat.

Check the power on the 2 small wires at the top you should have 24 volts when the thermostat calls for heat. If the pump runs when you move the wire but not when the stat calls replace that relay

You or someone now or next summer should rip the wiring apart and clean it up and rewire it. You will save yourself a lot of time in the future

Jamie Hall

What you are really interested in is not so much the voltage measured to a ground somewhere, but the voltage across a coil or contact.

Consider a bog simple circuit: there is a 24 VAC transformer. One wire goes to a thermostat -- let's say the R terminal for argument. Then a wire goes from the other terminal of the thermostat -- let's say W -- to one terminal of a relay coil. Then a last wire goes from the other terminal oof the relay coil back to the thermostat. Now --what are the voltages? Well, between the two terminals of the thermostat it will be about 24 volts AC. Between either terminal and a ground it could be anything, depending on how the thermostat is built and wired. If the thermostat is NOT calling for heat, the voltage between the two terminals on the thermostat will be 24 volts. The voltage between the two terminals on the relay coil will usually be low, but variable -- ideally zero, but it might not be. Now it the thermostat switches to call for heat, the voltage between its two terminals will be zero, and the voltage across the relay coil terminals will be 24 volts.

Note that in all cases the voltage from any given terminal to ground is quite irrelevant, and could be almost anything.

wirsbozo

Thanks, Jamie. When calling for heat, the voltage across the RH and W terminals is .065V and the voltage across the relay coil terminals is 23.7V. When not calling for heat, voltage across thermostat terminals is 27V and at the relay coil it's 0V.