3 zone system, one zone doesn't turn on boiler

TJack303

Hello,

For some background, I have a 3 zone hydronic heating system with a natural gas boiler. Each zone has a honeywell zone valve. 2 zones are in-floor heat, 1 for the basement and 1 for the garage. The 3rd zone, and the one that is causing issues, is upstairs and controls hydronic baseboard heaters.

When I turn up the thermostat upstairs the boiler doesn't turn on, I even bypassed the thermostat and spliced the 2 wires together. Still nothing. If one of the other 2 zones are on I will get heat upstairs, so the zone valve is working but for some reason it's not sending the signal to the boiler to fire up. I rewired the entire control circuit and still same issue. I even swapped the zone valve heads for the upstairs and the garage, thinking maybe it was a bad end switch, still same issue. 

Any thoughts on what else I can try before calling a heating company to come take a look at it? I'm an electrician by trade so I thought I'd be able to figure it out but I'm stumped. 

mattmia2

Short the end switch wires and see if the boiler fires. I bet it won't. Find out where they are broken or fell out of a connection.

TJack303

mattmia2 said:

Short the end switch wires and see if the boiler fires. I bet it won't. Find out where they are broken or fell out of a connection.

Should have mentioned, I did short the end switch and the boiler fires. That's why I thought I just had a bad valve head(not sure if that's the right terminology) so I swapped them. When I swapped the garage one still worked like normal but the upstairs didn't. It makes no sense, and I'm just not sure what else the issue could be

TJack303

I also did a continuity test on the thermostat wires to verify it was a complete circuit to the valve head and the wires are good. 

Zman

The motor and/or end switch on those valves wear out over time and fail to prove.
I would just replace the whole power head. https://www.supplyhouse.com/Honeywell-Home-40003916-026-Replacement-Head-for-V8043E-Zone-Valves

TJack303

Zman said:

The motor and/or end switch on those valves wear out over time and fail to prove. I would just replace the whole power head. https://www.supplyhouse.com/Honeywell-Home-40003916-026-Replacement-Head-for-V8043E-Zone-Valves

I switched valve heads between the upstairs and the garage and the upstairs still doesn't work and the garage still does work. Seems like the valve isn't the issue. Do you recommend I still swap them? Also if I do buy a new one, I currently have a honeywell V8043F1036 is that interchangeable with the V8034E?

Jamie Hall

No. If swapping the valve heads doesn't fix the problem, they are not the problem. The problem is, as @mattmia2 said, somewhere in the wiring from the end switch to the boiler. Bad connection, broken wire... a variety of possibilities.

TJack303

Jamie Hall said:

No. If swapping the valve heads doesn't fix the problem, they are not the problem. The problem is, as @mattmia2 said, somewhere in the wiring from the end switch to the boiler. Bad connection, broken wire... a variety of possibilities.

Not that either. I completely rewired the control circuit. All 3 end switches are daisy chained together, the valve in question is the first one in the line, coming straight off the boiler controller. The other 2 are downstream from that and both of those work as they should. 

TJack303

Its wired exactly like this, only with 3 zones instead of 5. Also the fact that I can jumper the end switch on the valve and the boiler fires up rules that out. 

Alan (California Radiant) Forbes

Did you ever say that the zone valve opens when the thermostat calls for heat?

mattmia2

The valve is binding so the motor doesn't open all the way and close the end switch if switching actuators doesn't fix it but shorting the wires does. Try it with the actuator disconnected from the valve body.

EDIT: Or the valve isn't getting powered because of a problem in the thermostat circuit. Is the valve opening at all like @Alan (California Radiant) Forbes asked?

TJack303

Alan (California Radiant) Forbes said:

Did you ever say that the zone valve opens when the thermostat calls for heat?

I just found out that was the culprit. I assumed it did open because I got hot water flowing upstairs to the baseboard heaters earlier.  I had the thermostat upstairs set to 80 for a couple hours just to see if it would eventually fire. I just went downstairs to double check the valve and noticed the motor was really hot for that zone, like it was trying to open the valve but couldn't. So I turned off power and took the head off and exercised the valve itself a few times then turned power back on, without reinstalling the head. The boiler fired. So I put the head back on the valve and turned the thermostat off and on again and it's working now. I'm thinking maybe the valve got stuck slightly open so hot water was able to flow before, but it didn't fully open allowing the end switch to fire the boiler. 

TJack303

mattmia2 said:

The valve is binding so the motor doesn't open all the way and close the end switch if switching actuators doesn't fix it but shorting the wires does. Try it with the actuator disconnected from the valve body.

Yup that was exactly what it was. Thanks so much for the help!

Steamhead

Honeywell makes a repair kit for the valve body- I believe the part number is 40003918-006. It's also a conversion kit for older models, and may be described that way.