Electro-Zone to Taco Zone Valves Conversion Question (HydroTherm Boiler)

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Old 02-24-14, 12:57 PM
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Electro-Zone to Taco Zone Valves Conversion Question (HydroTherm Boiler)

Hi, I have an early 1970's Hydrotherm HC-125 Gas HW boiler with the old 20Vdc Electrozone Electropak (zone box with 2 zone valves) with the circulator connected to and driven by the zonepak.

I have already purchased a taco ZVC404 Zone controller and two Taco 571 zone valves to replace the above since the valves and circulator will readily connect to the controller (24Vac).

My question is that the Hydrotherm boiler has an unmarked connection on the back of the boiler for two leads from where the ElectroPak connects to it and
drives the Gas Valve (which is an old Honeywell VS8279A1034-2 that is a millivolt system).

Can I directly wire the two leads from the taco ZVC404 to the back of the boiler and expect it to run the gas valve seamlessly or will the Taco fry the gas valve???

I did put a meter on those boiler inputs from the electopak and with the boiler fired up, I got a reading of 6.9 with the meter set at 200m DCV.

Thanks in Advance, John T.
 
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Old 02-24-14, 03:12 PM
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the Hydrotherm boiler has an unmarked connection on the back of the boiler for two leads from where the ElectroPak connects to it
This is a small terminal strip, yes?

Can you post a picture or two so we are certain we're talking about the same thing?

The Taco panel 'endswitch' or ' X X ' terminals are DRY CONTACTS, meaning they don't feed any voltage to the boiler. Those are the ones that should be connected to that terminal strip.
 
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Old 02-24-14, 03:35 PM
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Hi NJ Trooper,

I believe you are correct, it is a brown plastic strip with two screws that the Electrozone is connected to. That brown strip looks to be factory attached on the boiler jacket.

Its located on the upper right-hand corner of the BACK of the boiler. FYI, that brown strip is NOT part of an externally attached aquastat, relay or similar item.
I'm pretty sure we are talking about the same thing, But do let me know if you
still want to see a pic or two.

BTW, On my 2nd boiler (its a 2 family home) which is a smaller unzoned hydrotherm HC-65, that same strip in same location is marked X1 and X2. Being unzoned with only one thermostat, its obviously wired differently with an Aquastat hanging off of the back of that boiler to control the pump.

Best,
Johnt-NJ
 
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Old 02-24-14, 03:41 PM
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On the other system, being one zone, the thermostat would normally wire directly to X1 and X2. I'm not sure why the extra aquastat controlling the pump though.

That terminal strip is where you will wire the endswitch wires from the Taco panel.
 
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Old 02-24-14, 03:55 PM
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NJ TROOPER, You are DA MAN!

to your question, yes I would have thought so to, but the thermostat wires connect directly to the gas valve, been like that for as long as we've owned the house (30+ years). I think the original contractor ran out of bell wire and couldnt those connection with what he had left... LOL

One last question, I did just recently purchase two taco 571-2 valves from the big Orange box store, so would just like your expert opinion if I should go with these (reading about beeswax problems) or return them and go with the Honeywell V8043E1012's instead? THX, JTNJ
 
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Old 02-24-14, 04:03 PM
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Smile

Just reread your post.
There isnt an "Extra" aquastat on my 2nd boiler as it doesnt have a zone system.

Its a stand-alone 65K BTU boiler with gas valve, factory LS-50 aquastat, B&G 100 pump and small expansion tank.
 
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Old 02-24-14, 05:23 PM
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Can I directly wire the two leads from the taco ZVC404 to the back of the boiler and expect it to run the gas valve seamlessly or will the Taco fry the gas valve???
I dont think so.. The zone valves go to tt in the electropack... Then XX goes from the electropack to that terminal strip..

That terminal strip is just a satellite point. There is a wire from there to the gas valve internal inside the boiler jacket..

One of those wires after it comes back out the jacket to the gas valve go to the aquastat and one to the gas valve. The other side of the aquastat goes to the other gas valve terminal...


The Taco panel 'endswitch' or ' X X ' terminals are DRY CONTACTS, meaning they don't feed any voltage to the boiler. Those are the ones that should be connected to that terminal strip.

You sure you dont need to go to TT in the circ panel? ( Electropack?)
 
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Old 02-24-14, 06:15 PM
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You sure you dont need to go to TT in the circ panel? ( Electropack?)
My understanding is that the electropak stuff is all coming out?

Maybe the question should be

What is currently running the pump ?
 
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Old 02-24-14, 06:32 PM
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Question

Lawrosa, thanks for the info, I'm looking to eliminate the Electro-zone system completely from my boiler, so nothing Electrozone once I convert to Taco.

NJ-Trooper, I found some of the original documentation (circa 1971) that came with the Hydrotherm Boiler. The brown strip on the back is/was referred to by Hydrotherm as the "Terminal Board".

The 2 most basic wiring setups with just a thermostat directly attached to the terminal board is the constant-running circulator setup and an Aquastat-controlled circulator setup. BOTH of these show a POWERPILE Thermostat in their diagrams.

Your question regarding why my non-zoned boiler has the tstat wired directly to the gas valve and not to the terminal board might be because the tstat is a fairly recent Honeywell programmable t'stat.

The remaining four wiring diagrams show low voltage tstats wired to either an ElectrozonePak, RTS-20 relay, RT-20 Relay or T-20 relay,,, and each one of these are then wired into the lovely brown terminal board!

So with now knowing a little more about the old Hydrotherm HC Boilers (which btw, HC means "Hydrotherm Convertible") I beg to re-ask the question of whether the output signal from the Taco ZVC404 End switch would still properly drive the Hydrotherm Boiler as-is or do I need a switch/relay that will convert the zvc404's output signal to that of a powerpile Tstat..

Regards,
Johnt-NJ
 
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Old 02-24-14, 06:37 PM
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NJ-Trooper, to your questions,

Electrozone totally out of the loop.

and, The pump is being driven by the Electrozone box today, Taco ZVC404 will be doing the same when installed.
 
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Old 02-24-14, 06:45 PM
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thermostat directly attached to the terminal board is the constant-running circulator setup and an Aquastat-controlled circulator setup.

Those aquastats on the old hydrotherms, (not all of them) Had a hold off circ feature which held the circ off until the boiler reached 140F or so..

In regards to post #7 thats how my 2 zone HC 85 is wired with the power pile..



Here are pics of someone elses boiler from an older post..

Boiler-relay Photos by rviger | Photobucket
 
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Old 02-24-14, 06:57 PM
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You need a circ relay that isolates the 24volts from the millivolt... I dont know my part# . Its from 1984...LOL

XXXremoved wrong part #XXXX
 

Last edited by lawrosa; 02-24-14 at 07:14 PM. Reason: Removed wrong info..
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Old 02-24-14, 07:02 PM
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The pump is being driven by the Electrozone box today, Taco ZVC404 will be doing the same when installed.
The ZVC will only control the zone valves...
 
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Old 02-24-14, 07:12 PM
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Troop knows this stuff...But this is the relay I believe. Its same as mine but mine is 30 years old...

RA832A1066 - Honeywell RA832A1066 - 2 Zone 120V Switching Relay with Dpst switching
 
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Old 02-24-14, 07:17 PM
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Lawrosa, thanks for the RA832A relay info. Lets see what Troop has to say.

also, the taco zvc403 thru 406 zone controllers do have a pump end switch on them, heres the link to their wiring diagram and scroll down to page 28 which shows the zvc40X's with a system pump setup.

http://www.taco-hvac.com/uploads/FileLibrary/100-92.pdf
 
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Old 02-24-14, 07:33 PM
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Yes I see... I dont think I ever hooked it up that way...Interesting... My buddy uses the argo controls since they are cheaper...

I dont really retro fit stuff anymore...



http://r.search.yahoo.com/r/_ylt=A0L...ry/102-090.pdf
 
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Old 02-24-14, 07:49 PM
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Yes, you can run the pump with the Taco panel.

If you have the pump hold off aquastat, you can wire it in series with the relay outputs of the Taco panel to the pump.
 
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Old 02-24-14, 08:10 PM
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Gentlemen, I dont think I see any problems with running the system circulator directly off of the ZVC404's extra end switch.

My concern is whether the Main end switch can talk to the boiler in powerpile(millivolt) mode as-is or do I need a relay/switch to do that.
 
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Old 02-24-14, 08:13 PM
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My concern is whether the Main end switch can talk to the boiler in powerpile(millivolt) mode as-is or do I need a relay/switch to do that.
That will be fine John. The endswitches are dry contacts, no voltage, just a simple switch.
 
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Old 02-24-14, 09:00 PM
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Thanks Troop!, I was starting to think I needed a honeywell RS832A relay or equivalent, so I will keep you all posted and let you know how things go after the winter is over (unless the electropak fails before then). I have to say that as old as both of my hydrotherm 20Vdc/millivolt boilers are (now 40+ yrs) theyve been very dependable with only having changed out 2 circulators, 2 air exp. tanks and a thermocouple along with a few pressure relief valves and...the afue rating on both units is about 80%, so even their efficiency is still pretty respectible.

Regards,
Johnt-NJ
 
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