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mikestorm5 11-24-2012 02:24 PM

RESOLVED: Zone valve opens but doesn't fire boiler
I posted two weeks ago regarding this issue, but further testing revealed I didn't have all the facts the first time around.

Four zone heating system. Three of the zones each independently open and call for heat. One additional zone opens, but does not call for heat.

If I set the temp on the malfunctioning zone above ambient temp to fire the boiler, nothing happens UNLESS I do the same with any other zone. Then and only then does heat come to the malfunctioning zone along with the second zone.

I checked the wiring in the junction box that houses the zone/transformer/boiler wiring. Nothing loose.

4 zone gas / baseboard radiators
Burnham Series 2 Model B Gas Boiler
Taco Circulator 007-F5
Honeywell Hydronic Zone Valves (4) V8043E1012
Valve head 40004850-001 Rev. A

I'm leaning towards zone valve malfunction (end switch). Hoping for some corroboration and guidance as to whether I should attempt replacing the head myself. Many thanks.

how 11-24-2012 04:13 PM

Open the cover of the zone valve and compare the operation of the faulty one with an operating one. You will see an arm mechanically swinging across to press in the end switch. Does the faulty one actually press that switch in far enough to operate it? You should be able to press that switch in with a finger tip to get the boiler to fire.
Sometimes the arm doesn't travel far enough because the linkage is wearing out/ the switch is loose because of holding screw thats backed out / or the switch is faulty/
The end switch ( if faulty) is really cheap to replace but is often a bit finicky depending on the zone valve access.

mikestorm5 11-24-2012 04:48 PM

How, I'm way ahead of you. Finished doing just that.

Four zones. Turns out two are fully functional and two are not.

For two that are fully functional. Call for heat triggers mechanical arm and switch is depressed. Switch triggers ONE click from the boiler and it fires.

Faulty zone 1: Call for heat triggers mechanical arm and switch is depressed. Nothing happens (no sound of any kind). I manually depressed switch with screwdriver to see if perhaps switch was seated incorrectly. No go.

I turned off power, fully disassembled zone, pried open switch, sprayed switch with contact cleaner, reassembled, rechecked connections, turned power back on, and no change.

Faulty zone 2: call for heat triggers mechanical arm and switch is depressed. Boiler clicks a bunch of times. Nothing happens. Didn't bother cleaning this switch just yet as I saw your post.

Again, for two faulty zones. The valves appear to work as they receive heat if one of the two good zones causes boiler to fire.

Does this help?

EDIT: Switch Part # V5C010SB3X147 (if it helps)

how 11-24-2012 04:59 PM

Follow those two (red?) lines from the zone switches back to their source. There are often marretted or crimped connections inbetween that are loose. Jumpering those lines at the switches or using an electrical meter to check for 24V will tell you what the problem is.

mikestorm5 11-24-2012 05:09 PM

Followed two red wires for faulty zone 1 back to a junction box. Opening junction box reveals rats nest of zone/transformer/boiler wiring.

Six wire inputs are flagged as 'boiler', 'transformer', 'zone 1', 'zone 2', 'zone 3', and 'zone 4'.

Checked both connections and they look good. Casual inspection suggest they seemed to be spliced to a bunch of other red wires that most likely lead back to the other three zones.

ONE red wire from each switch in each zone are spliced together along with RED wire from wire input marked 'boiler'
THE OTHER red wire from each switch in each zone are spliced together along with WHITE wire from wire input marked 'boiler'

how 11-24-2012 05:18 PM

Can you jumper(pigtail) the switch when it's removed from the zone valve to confirm its a faulty switch?

mikestorm5 11-24-2012 05:39 PM

1. That was scary as hell. LOL.
2. It's the switch.

I fashioned a 3" wire and connected it to one of the connections right AT the switch. I turned on the power and used pliers to touch the other end of the 3" wire to the other connection right at the switch and the boiler fired.

I'll do the same with the other faulty zone tomorrow but in the iterim, here's the million dollar question: Where do I find a replacement switch? I googled the Part number and came up empty.

By they way How, there's no way I could have done this without you. THANK YOU.

how 11-24-2012 06:34 PM

Give your address area. I've always just gone to the local HVAC supply outlet to buy mine. You probably want to phone first to see if they will sell to non trades.
If your away from a big city then perhaps someone more used to online ordering of HVAC parts can chime in.

mikestorm5 11-24-2012 06:39 PM

Part number: V5C010SB3X147.

I live 30 mins outside of Boston. There's an HVAC supply store the next town over. Of course it's closed tomorrow. Will look around. Thanks again how.

mikestorm5 11-25-2012 07:09 AM

mJust wanted to post a small update for future generations who stumble upon this thread with the same issue.

After 30 minutes of googling the above part number V5C010SB3X147 and coming up empty, I 'dumbed down' my googling and tried searching for "8043E end switch" and came upon THIS PAGE

The part number is 272744B, BUT if you zoom in on the picture, you'll see V5C010SB3X147 clearly embossed on the switch. Apparently the switch comes with the leadwires soldered on (I'm just going to cut off the excess and splice to the already run wire) along with the paper insulator and two screws for mounting. I'm thinking the switch isn't sold by itself and the 272744B part number probably refers to the kit as a whole.

Searching for "Honeywell 272744B" yields much better results, and I bought 3 (2 to fix my two zones and one extra) from for $34 shipped. Will update thread again to confirm these are the right parts.

These switches are really worth around $4, so $8.50 per switch is pricey from a magnitude standpoint, but from an absolute price standpoint ($4.50 markup per part) who cares.

Thanks to Google AdSense Analytics trolling threads for keywords (part numbers) if you scroll up from this very thread, the banner add should link you directly to pexsupply and the proper part.

mikestorm5 11-28-2012 08:57 AM

Last entry to this thread. I received the end switches from Pex Supply yesterday and installed one last night when I got home from work. Zone call for heat now fires boiler. Will install the second end switch this weekend for the remaining faulty (not a priorty as it's in a part of the house we don't really use).

Thanks again to How. Your expertize saved me a couple of hundred dollars easy.

Fixed it 09-22-2015 06:37 AM

Honeywell End switch discontinued
I tried to find the Honeywell 272744B End Switch which isn't what is on the switch but V5C010SB3X147. it is discontinued. Sprayed some CRC contact cleaner in the two open slots on the switch and it works beautifully now. Be careful though since the contact cleaner is highly flammable.

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