HELLO!!
This is my first post here, what a great site!! This might be more detailed than needed (or wanted), so if it is, please let me know

Issue:
One zone in my two zone home is currently not heating

Background:
I have lived in this home for two winters. This has happened both years. When it gets REALLY cold outside, my zone 1 (Living Room, Dining Room, and Kitchen) stops heating. Most of the season both zones work correctly, only when it get bitterly cold out that zone 1 stops working. Once the temp outside gets a little warmer, zone 1 will start functioning again.

Climate/Home Construction:
East Central Iowa (North Liberty). Currently outside it is wind-chill warnings ect, so it is very cold out. The home is a slab built (no basement) with a 4 ft crawl space underneath. Underside insulation on home has fallen down completely, pipes for heating are copper and they run in the crawlspace. The pipes are not insulated.

Heating System:
Gas fired, two zone, hot water baseboard heating. The boiler is burnham, the expansion pot is Amtrol, The zone valves are Synchron (V8043F 1036), and an Honeywell Aquastat Relay (L8148E)

What I can tell about the issue:
-Zone 1 thermostat is telling the valve to open, I can see the spring move when the thermostat tells it to. I cannot tell if the inner workings of the valve are functioning properly, but when I use the manual open on the valve there is still no resulting heat to zone 1.
-When I opened the box to the aquastat, I noticed one side of the square relay thingy (sorry, girl talk) was broken. The unit is still making some contact on both sides. I tried holding it in place for fuller contact, and using electrical tape to do same, but no resulting heat to zone 1.
-When the valve on Zone 2 opens, the water “drops” (I know that is not the correct term but not sure what to call it) and about a second or two later the boiler fires. When zone 1 valve opens, the boiler never fires.

Any ideas? I am seriously baffled by this heating system. But, as a plus, I have learned a great deal about hot water heat systems

Here are some links to photos of the system, and water flow ect.


Valves

Overall System


Zone 2 on left, Zone 1 valve on Right (closest to camera)


Aquastat Relay

 

No problem! The more info the better... GREAT presentation!

I think this is the key:

Inside the valves, see that little dark brown thingy (boy talk!) with the two red wires on it? That is called an 'ENDSWITCH', and it's purpose is to tell the boiler that a thermostat has called for heat, and the valve has opened. Those switches fail...

Before digging into that part though, take a look at the terminals where the wires are connected. They are labeled: TH-TR , TR , TH , and variations of ES or simply ENDSWITCH.

Don't worry about any of the 'T' terminals for now, if the valve is opening, those wires are fine. But do look closely at the wires on the endswitch terminals. Both endswitches on the two valves should be wired in parallel, and those two wires go to the aquastat terminals T and TV. Check to make sure that none of those wires are broken... it could be as simple as that. It's obvious that the one valve is working, so the wires to the aquastat are fine, but the wires BETWEEN the two valves are the ones in question.

Next thing... if the wires are fine, it's likely that the endswitch in the zone valve is not making contact. If you have a small piece of wire handy, you can prove this by temporarily touching the wire to the ENDSWITCH terminals on the bad zone. (do this while the thermostat is calling for heat). Be careful not to touch any of the 'T' terminals... there's no real danger there, it's all low 24 Volt wiring... when you touch the two endswitch terminals together, the aquastat should 'click', and the pump run, and the burner fire.

If this happens, then you have to think about repairing the zone valve... and this gets more complicated, because I can see from the pictures that you have the 'old style' valves that have FOUR screws holding the 'powerhead' onto the valve.

The NEWER valves only have TWO screws, and those newer units can have the powerhead replaced without having to drain the system... the old one just comes off, and the new one on... takes maybe a half hour or less... but unfortunately, you don't seem to have the newer valves.

There IS an 'adaptor kit' to fit the new style powerheads to the old style valves, but it doesn't help you because you still have to drain the system to install the adaptor kit...

Honeywell part number for the kit is 40003918-006 and can be purchased:

Zone valve conversion kit

Here's a data sheet on Honey's zone valves that may be useful:

Zone valve data sheet

The persons who installed your system did you a HUGE favor though... they installed shutoff valves above and below your zone valves. By closing those, you won't have to actually drain the system... you can isolate the valves to work on them. You may still get some dripping if the valves don't close 100%, but it sure beats draining the system!

more...

 

There is one other test which you can do... just to be sure we aren't looking at something like a frozen pipe or something...

Turn BOTH thermostats up a bunch to force a call for heat.

IF the cold zone valve IS opening, and the pipes are not frozen, with the OTHER zone ALSO calling for heat, you should get heat in the cold zone as well.

IF you find that you get heat in both zones, you can lock the bad valve in the open position, and turn down that thermostat and let the other thermostat control the whole house for the time being. The reason that I say to turn down the bad zone thermostat is because if it calls for heat when the valve is manually opened, it will reset the valve to automatic, automatically.

Try that first actually... then back up to the previous post.

 

SO...
I THINK that the mystery has been solved
I did as you suggested, and cranked the heat on both zones and waited (with baited breath) for the heat to start flowing to zone 1. Boiler kicked on, thought I “might” be feeling a bit of warmth, all seemed to be peachy, so I walked away. (Was going to give zone 1 time. just in case this really was going to work) when I remembered to check on the "Heat Situation" as I was calling it. I noticed that the boiler was not kicking on, and I was starting to get a tad chilly in the house. Swear, the first thought that went through my head was, "OMG, he is going to KILL me!! He told me to leave it alone, but ohhhhh no, I couldn’t"
So I tucked my tail between my legs and went to inform the husband. I decided to busy myself with other, girly type chores, as to stay out of his way (and avoid the butt chewing that I was sure to come). When I noticed as I was feeding the cat, that the carpet was wet under the window in the kitchen. dum, dum, dum (scary music)
Pipe under the window was frozen. When I cranked the stats, the iceberg melted, and voila, a river runs through it. I’m guessing that last year we had a smaller pin hole, and I just went undetected, as that is not a heavily traveled part of the house, I just recently relocated the cat’s food there.
Thank you SOOOOOOO very much for your help!!! And for speaking in my language

Cheers!!

 

Oh no... that's not what I wanted to hear!

I have a theory... the REASON that pipe froze is because that zone valve isn't firing the boiler. And, a contributing factor could be the insulation issues underneath... you said it all fell down...

I'm sorry it turned out this way, but please do keep us posted on the repairs. If we can help, offer advice, etc, just say so!