Wiring L8148E Aquastat, 3 Taco 571-2 ZV's, AT175F1023 Xfrmr & 3 RTH6580WF1001's

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Old 07-29-14, 11:16 AM
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Wiring L8148E Aquastat, 3 Taco 571-2 ZV's, AT175F1023 Xfrmr & 3 RTH6580WF1001's

Hello everyone! First I want to thank everyone that contributes to this forum and provides feedback and insight to those that need a helping hand! I've been reading posts on this site and have numerous questions answered since I bought my house back in March - so thank you.

My heating system consists of the following:

Burnham P207 NG boiler with Honeywell L8148E Aquastat
3 Zones (Taco 571-2 Zone Valves)
3 Thermostats

Now down to my problem...I want to replace my old round mercury-filled thermostats with wifi thermostats (Honeywell RTH6580WF1001). From what I’ve read online these thermostats are called “power robbing” thermostats and usually require an additional transformer and the dreadful "C" wire, of which most older setups that have the 2-wire system do not have. So I replaced the current red/white 2-wire with red/white/green 3 wire and purchased an additional 75VA transformer (Honeywell AT175F1023 75VA).

I wired in the additional transformer then turned on the switch at the boiler to turn on power. *This switch is actually very convenient as it provides a way to cut power to the aquastat and additional transformer*. Once I had power I went upstairs and prior to installing the thermostat I measured voltage. I had the following voltages:

R to W = 24VAC
C to W = 48-50VAC …..?????

Rather than doing things the right way I decided to try the thermostat… so I pressed it into the mounted housing on the wall and it powered up. Once the thermostat powered up I turned up the heat and went back down to the basement. Everything seemed to be working as the boiler fired and started to heat up.

Rather than burning something up I turned off the switch at the boiler and haven’t touched anything since.

Has someone wired up something like this? Or has anyone encountered this problem?

Obviously my main concern is not cooking the thermostats with the 50VAC, so I need to correct my wiring.

Can someone please provide a schematic or simple drawing that I can follow? I’m thinking the thermostats should be powered from the additional transformer and the rest of the system (aquastat and zone valves) be powered by the aquastat’s 40VAC transformer. I don’t think the transformers should be wired together in series or parallel and I believe that’s where my problem is. How in the world would I do this since there are only 3 wires? Do I need to add an additional wire?

Sorry this is so long

Thanks in advance,
Bill
 
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Old 07-29-14, 02:02 PM
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Hi Bill, welcome!

Were the zone valves originally powered by the transformer in the aquastat? You don't have yet another transformer anywhere in sight?

If so, and since you now have a 75VA transformer, my recommendation would be to 'off load' the zone valves from the aquastat transformer and wire them up to the new transformer.

I do not like loading aquastat transformers down with zone valves... With three valves it's likely that the transformer is already overloaded.

An alternative (but spending another 100 bucks or so) would be to install a Taco ZVC control panel. This would have built in transformers for the valves and thermostats, a terminal to 'land' the C wire on, etc, etc... It's a fairly simple job to wire up a ZVC panel. (and LOTS neater looking too!)
 
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Old 07-29-14, 02:08 PM
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I wanted to check the specs on the L8148E regarding powering zone valves...

Honeywell recommends not more than TWO of their V8043 series valves be used, and only ONE if the ambient temperature is above like 77F.

I believe that the Taco valves are MORE power hungry than the Honeywells, so if you are powering the valves off your aquastat, you've got a transformer failure waiting to happen.
 
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Old 07-29-14, 08:06 PM
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NJ Trooper, thanks for taking the time to respond. I definitely need to take some time and look at the zone control panel route. It sounds like it might be the best way to go.

My current setup is also using the aquastat's 40VA transformer to power the taco valves. I looked at the aquastat manual and you're right it only recommends to use only 2 zone valves with the 40VA transformer.

So if I order the taco zvc control panel would I still utilize the aquastat 40VA and additional 75VA transformer? I have no problem ordering the control panel, just want to make sure it will cover everything I need. Dumb question.... What zvc do I need?
 
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Old 07-29-14, 09:40 PM
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Your aquastat would stay, but the wiring would change a little. You'll only have 2 wires coming from the 'endswitch' in the taco panel to the two thermostat terminals ( T and TV ) in the aquastat. You won't have that 'third wire' coming off and going to the zone valves. The transformer in the aquastat would still be powering the aquastat itself.

No, you won't need the new transformer.

I would recommend you get the 4 'channel' panel, that way you'll have a 'spare' channel in case one goes out on you. Just move the wires over. Also one for expansion if that is in the future. The price diff between the 3 and the 4 is about $15.

ZVC404-4 - Taco ZVC404-4 - 4 Zone Valve Control Module with Priority

Click the 'Manuals' tab to have a look at the installation manual.

If you want to stick with what you've got, it's not that difficult to rewire and I may already have a drawing done for that. I'll take a look tomorrow, or you may find something if you "Search Forum" because I've probably posted it in the past...
 
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Old 07-30-14, 06:25 AM
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Is this how you've got it wired now? (with on more zone)

 

Last edited by NJT; 07-30-14 at 07:09 AM.
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Old 07-30-14, 07:01 AM
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In a nut shell, yes. That was the previous configuration before I added the additional transformer and wiring. If I get a chance today I'll draw up a quick sketch of my system wiring.

I also just order the ZVC panel that you recommended. I ended up buying the 406-4 panel to accommodate additional zones in the very near future. I plan on having a mix of my current baseboards upstairs and in-floor heating on the first floor. I know there are a lot more components that I need to purchase in the future for the in-floor heating, so this 6 zone panel is a start.
 
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Old 07-30-14, 07:08 AM
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You'll like the Taco panel.

Yes, combining hi temp baseboard and lo temp in floor gets complicated.
 
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Old 07-31-14, 07:12 AM
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Should get it by Friday and hopefully be running Saturday sometime. Dumb question...should I disconnect the circulator pump from the aquastat box and connect it to the zone panel? I'm assuming the answer is yes but I just wanted to be sure.

I was reviewing the schematic for the zone panel and noticed separate connections for the aquastat and circulator pump. Currently the circulator pump connection is within the aquastat box.
 
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Old 07-31-14, 09:51 AM
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No, you won't NEED to move the pump over.

That's the nice thing about those panels, their versatility... you CAN move the pump wiring, but you don't HAVE to.

The aquastat will still turn the pump on when there is a signal on the T and TV wires from the ENDSWITCH of the Taco panel.

No need to make extra work!
 
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Old 08-07-14, 05:03 AM
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NJ Trooper....Thanks for your help so far! It’s greatly appreciated….now just one more problem…

Long story short...the house had a new central ac system installed just before we bought it...lennox 4 ton unit I believe with the air handlers in the attic. It is controlled by a White Rodgers (battery operated) thermostat that also controls zone 2 heat.

I installed the Taco Zone Valve control panel and let me tell you it was well worth the money...absolutely fantastic. I've installed all 3 Honeywell wifi thermostats and they all work just fine for turning on each zone for heat. The problem is zone 2 thermostat will not power on once the AC system is wired in.

There are 3 wires coming from the AC unit....Y, G & Rc. From looking at the white/rodgers tstat: Y is cooling, G is Fan, Rc is 24v from the AC unit's transformer. Here’s what my connections are to the thermostat:

*Removed jumper from R & Rc
R 24v for heat (Taco zone valve panel)
W Heating call (Taco zone valve panel
C Common (Taco zone valve panel)
Rc 24v from AC transformer
Y Cooling call
G Fan from AC
W2 NC (no connection)
Y2 NC
K NC

Honestly I’m beside myself. I’m not an expert at anything but have experience in a lot of things, especially wiring and for whatever reason I just can’t figure out this dang wiring. The only thing that makes sense would be to bring a return wire from the AC transformer but I’m not sure where I would connect it on the thermostat.
I’m sure the problem has to do with 2 transformers…but just can’t seem to figure it out. I just read on Thermostat signals and wiring - Transwiki that the Fan (G) terminal is usually connected to Rc when Rc exists on the thermostat. Um…why?

Thanks again,
Bill
 
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Old 08-07-14, 06:29 AM
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This quote from that linked page probably tells the story...

The following information may have errors; It is not permissible to be read by anyone who has ever met a lawyer.
Use is confined to Engineers with more than 370 course hours of electronic engineering for theoretical studies
I'm going to look that article over later.

In the meantime, I know that you know enough to not 'experiment' with the wiring!

I do think that you may need a 'C' wire from the A/C as well... but let me think on it for a while. You might also head over to the 'thermostat' forum as there are folks there that know thermostat wiring well.
 
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Old 08-07-14, 06:52 AM
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That article is in fact, IMHO, poorly written.

Their use of the words 'connected to' are easily misinterpreted, and in this case, has been...

The Fan (G) terminal

The Fan (G) terminal is usually connected to Rc when Rc exists on the thermostat.
When they say 'connected to', what they are trying to say is that when the thermostat calls for the fan to run during a cooling call, that the G terminal is energized, and that energy is sourced from the Rc terminal.

If it was a RELAY inside the thermostat, one terminal of the relay contacts would be connected to Rc, the other to the G terminal.

When the relay 'makes', the G terminal is in effect "connected to" the Rc terminal.

They do NOT mean to connect the G terminal to the Rc wire!

I might have to chastise them on their ambiguous use of the English language!
 
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Old 08-07-14, 06:55 AM
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Electronic thermostats need power to operate and it would like both a hot and a common terminal to get power or both ends of the transformer secondary need to be available to the thermostat.
Good grief... WTH are they trying to say in this sentence?

"Never anthropomorpize inanimate objects. They don't like it"
 
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Old 08-07-14, 08:44 AM
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Haha, I didn't spend much time on that wiki page, it was something I found in a quick search. It sure as hell didnt make much sense to me either. And now taking a look at the page it's poorly written thats for sure.

The C wire provides additional power for the thermostat and is currently coming from the control panel. If I add another C wire from the A/C...where would it land on the tstat terminal block? Maybe I should remove the C wire that's currently connected and add a C wire coming from the A/C?

If I swap the Rc (24v from A/C) and R (24v from zvc panel) wires on the tstat terminal block the tstat will power up but none of the A/C controls work. It calls for cooling but the tstat never "clicks-in" if that makes sense. I tried turning the fan on from the tstat and that doesnt work either.
 
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Old 08-07-14, 11:44 AM
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where would it land on the tstat terminal block?
On the C terminal with the other C from the Taco:


image courtesy derekscomputer.com
 
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Old 08-07-14, 12:06 PM
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Sorry NJ Trooper...I need to spend more time researching than asking questions on here.

So I need to add a "C" from the A/C 24v transformer and land it on the "C" wire on the tstat with the other "C" from the Taco panel. I'll try it this evening and let you know.

My apologies again. Guess I was just extremely frustrated with this entire system with all the problems I've had. I really do appreciate you taking the time to help me out through this entire process.

Thanks yet again.

V/R,
Bill
 
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