Boiler coming on

heatamateur

My heat started coming on at 6pm every day. It continues to stay on even after pulling the t-stat off the wall. The online tech said it was the switching relay (taco sr501), but I have my suspicions. What else could cause the relay to come on the past 3 days at 6pm?
Had a HVAC tech come by and for 175 bucks, he told me everything was working fine.
Heat came back on again at about 6pm, remained on again after unplugging/pulling t stat
I temporarily disconnected the red lead from tstat to the pump switch relay but want to know where I can start trouble shooting.

Jamie Hall

Somewhere else that red lead is getting power. You will need to trace out the wiring to find what is feeding it when the thermostat is really completely disconnected. I know it sounds blindingly obvious, but... there are no other thermostats?

JUGHNE

Does your boiler heat your domestic (faucet-sink-shower) hot water as well. Or a separate water heater tank?

heatamateur

Jamie: no other thermostats, i checked inside box behind thermostats and there didn't seem to be any shorts but i guess that does not limit out problems elsewhere. We use the same thermostat for central air and heat it's a hard wired honeywell.

JUGHNE:Boiler is a navien ch210. It is an on-demand combination for domestic hot water and boiler

GroundUp

It doesn't run with the red 24v wire disconnected at the relay, but it does run with the same red wire disconnected at the other end? Hmmm

heatamateur

> @GroundUp said:
> It doesn't run with the red 24v wire disconnected at the relay, but it does run with the same red wire disconnected at the other end? Hmmm

Yup, its gotta be a short right?

lchmb

but if it's a short why would it ever shut off? it wouldnt do it at an exact time every day...

Jamie Hall

Shorts don't -- usually -- pay much attention to the time of day...

But something is powering that red wire. How, exactly, is that red wire routed? Does it go directly to the thermostat? Does it go to some other control or relay and then to the thermostat? You need to trace that puppy and find out what is switching power onto that wire at about 6:00 PM...

RomanP

One way to know for sure If it’s a thermostat issue is to disconnect all thermostat wiring from your taco box and see if it ever turns on at 6 again. I never wired hydronic heating and forced air systems to same thermostat, always use separate thermostats.
Is it possible that your thermostat is getting juice from HVAC furnace?

delta T

What happens at 6pm? Laundry? Dishes? Showers? I feel like the DHW may come into play....only way is to start tracing where you have power and what is causing the relay to pull in.....

Leonard

Maybe 6pm is when the mice or chipmunks come home to their nest and sit on wire they chewed insulation off of, moving wires together and shorting them ???

Grallert

I'm not familiar with the Navien products but does this have a three way valve that's activated when there is a domestic call? I've seen a few time on other boilers the valve stick a bit and fail to close off one side or the other of that valve. Goes unnoticed in the heating season usually.

EBEBRATT-Ed

If the same stat runs your ac you may be getting a back feed from the ac system sum how

Solid_Fuel_Man

Take a picture of the thermostat base without the thermostat on it. R and Rc should both have separate wires and no jumpers.