1st floor heat on but not getting hot

ns6bk

Hello all. Amateur here and I'm coming to you for some guidance.
New to this forum but been lurking for a while. Tried searching for help but my issue sounds to be somewhat unique and I'm not certain of the issue.

Normally my 1st floor thermostat would sit at 68 degrees overnight and in the morning, it is scheduled to warm up to 70 degrees.
Recently my 1st floor thermostat would just sit at 68 degrees even though I have it set to 70 degrees every morning. What I noticed is that when I call for heat on the 1st floor, the pump would turn on but the boiler would not fire. From what it looks like, the vent damper is not opening which is why the boiler is not firing. When I call for heat on the 2nd floor, the pump turns on, the vent damper opens and the boiler fires. In the past, I know that the 1st floor follows the same.
Another thing I noticed is that my pump is make a relatively loud humming noise which I can hear on the floor above. This only happens when I call for heat with the 1st floor. The 2nd floor does not make the same loud humming noise. Is this part of the initial problem or separate problem?

I picked up a Taco SR501 to see if replacing the switch would solve the problem but I am unsure of which wires go where. The wiring diagram for the Taco is somewhat helpful but I am unsure of how to wire the #4 wire that is being jumped from #1.


I will try my best to explain what I have:

2 Thermostats - 1st floor and 2nd floor
Burnham stage 2 gas boiler
Single pump
1st floor thermostat connected to Honeywell R845a
2nd floor thermostat connected to Honeywell RA832A

JUGHNE

I would guess that the 1st floor zone valve is not opening, perhaps that is why the pump sounds loud.
Find your zone valves, assuming you have 2 of them, there may be a lever to manually open the water zone valve.

Usually when the zone valve opens there is an end switch that starts the boiler and pump.
The manual operation lever may not engage the end switch.

Pictures of the piping and valves might tell us more.

ns6bk

Jughne,

Thanks for the quick response. I've attached 2 images of the system. Hope it helps.

JUGHNE

If you have 2 tstats that means you have 2 zones.
The zones are controlled by each having a zone valve or each having a separate pump.

Your picture shows neither of these.
You need to back up and show all of the components connected to the boiler.
Zone valves would have wires connected as would pumps.
I see no relays of any sort either.

ns6bk

Yeh, kind of confusing. I was looking for the zon valves but don't have any. I attached some additional pics. The only relays I have are the switching relays. Could that not be the issue?

Thanks again for the help.

JUGHNE

You have 2 pumps, one for each zone.
When you run the working zone which pump gets the pipes hot?
The red one or the black one?

From the looks of the rear red pump you have had no one work on this boiler for years.
I suggest you call for service from a competent company.
I think you are in over your head.

SuperTech

@tommay if the problem was the flue damper it would happen regardless of which zone is calling for heating. It sure sounds like the problem is one zone not functioning. Most likely it's the one with the red B&G 100 circulator that appears neglected and probably hasn't been oiled in ages.

JUGHNE

The red B&G pump may need replacing by now.

The ceiling mounted controls need to be brought down and wall mounted.
The electromechanical relays, in that orientation, have to overcome gravity in order to close.

Obviously one of them is not working.

Opening the vent damper and setting it to "manual" operation would only allow the boiler to fire....if it was getting a call for heat....which it apparently is not.
As the other zone works.

The white wire could be part of a switch leg/loop, not necessarily a neutral.

I still stand firm that the OP/HO needs to call in a pro.
There is evidence on the service sticker on the door that someone was there to oil the pump in 2010.....could have been the last time.

ns6bk

So it looks like the red pump needed to be oiled. After it was oiled, 1st floor is now getting to the temps that the thermostat is calling for.
Lesson definitely learned to keep an eye on the boiler.

Thanks for all the help.