Relay to Aquastat

Jim_46

I have a Kerr Boiler with a Honeywell Aquastat L8124L that controls the T-stat and circulator for the main radiator system Zone 1 in our home. I am now piped into that system (not electrically)for a Zone 2 radiant floor.This zone two has a Danfoss MTD T-stat wired to a 24V transformer, a FEME ZPD8 relay to a Astro 30B circulator. I have attached drawings of both the Zone 2 wiring schematics and the inside of the Aquastat on the boiler. I have been in the middle of setting up the zone 2 and it is going fine when my boiler has just been on for heating zone 1 and there is hot water to draw from. But when the system has been down for awhile the new zone 1 has no hot water to draw from. In other words I need to tie in electrically from this new T-stat-transformer-relay-pump schematics to the aquastat on the boiler in order to turn on the boiler when the new zone needs heat. By looking at my drwaings can anyone tell me what to disconnect/connect in order to accomplish this? I did do the orginal wiring but I was only following those schematics. Thanks much JE

Jim_46

Relay to Aquastat

I have a Kerr Boiler with a Honeywell Aquastat L8124L that controls the T-stat and circulator for the main radiator system Zone 1 in our home. I am now piped into that system (not electrically)for a Zone 2 radiant floor.This zone two has a Danfoss MTD T-stat wired to a 24V transformer, a Carlo Gavazzi RCP8 relay to a Astro 30B circulator. I have attached drawings of both the Zone 2 wiring schematics and the inside of the Aquastat on the boiler. I have been in the middle of setting up the zone 2 and it is going fine when my boiler has just been on for heating zone 1 and there is hot water to draw from. But when the system has been down for awhile the new zone 1 has no hot water to draw from. In other words I need to tie in electrically from this new T-stat-transformer-relay-pump schematics to the aquastat on the boiler in order to turn on the boiler when the new zone needs heat. By looking at my drawings can anyone tell me what to disconnect/connect in order to accomplish this? I did do the original wiring but I was only following those schematics. Thanks much JE

superMARKet

The Magic of ZC and ZR, Explained

You don't show any ZC or ZR connections in your schematics. Those are what you need to make this work properly.

ZC is a line-voltage output from the aquastat. It will give you 120V when the water temperature is over the low limit. You only want your circulator to run when the water temperature is over the low limit, so you use ZC to feed the circulator relay. (The water temperature will almost always be over the low limit anyway, since this isn't a cold-start system.) Mnemonic: ZC feeds zone circulators.

ZR is a line-voltage input. You feed it 120V whenever you want the water temperature at the high limit. You want the water temperature to rise to the high limit during a call from heat, so you power ZR when you power the circulator. Note that although ZR is conceptually an input, you can't connect just anything to it without taking care; any time something puts 120V into ZR, something else can take that 120V away from it. You need to respect ZR as an output too, and be aware that it can provide 120V whenever anything is calling for heat. Mnemonic: ZR is fed by zone relays.

So, looking at your diagram, remove the existing connection between relay terminal 1 and connect it straight to ZC. That makes sure the circulator will only come on when the water is at the low limit temperature. You're halfway there.

Now you need to get 120V into ZR whenever zone 2 calls for heat. You can't just connect the relay to ZR like you connected it to the circulator, because then the circulator itself would be connected to ZR. You'd find the zone 2 circulator running whenever either zone calls for heat (remember, the aquastat can put 120V on ZR). What you need is another pair of dry contacts on your relay (a DPST relay). I've never heard of the relay you're using, so I don't know whether or not it's got another pair or what terminals they'd be. Let's pretend they're terminals 3 and 4. You would connect terminal 3 to L1 (hot 120V) and terminal 4 to ZR.

superMARKet

The Magic of ZC and ZR, Explained

You don't show any ZC or ZR connections in your schematics. Those are what you need to make this work properly.

ZC is a line-voltage output from the aquastat. It will give you 120V when the water temperature is over the low limit. You only want your circulator to run when the water temperature is over the low limit, so you use ZC to feed the circulator relay. (The water temperature will almost always be over the low limit anyway, since this isn't a cold-start system.) Mnemonic: ZC feeds zone circulators.

ZR is a line-voltage input. You feed it 120V whenever you want the water temperature at the high limit. You want the water temperature to rise to the high limit during a call from heat, so you power ZR when you power the circulator. Note that although ZR is conceptually an input, you can't connect just anything to it without taking care; any time something puts 120V into ZR, something else can take that 120V away from it. You need to respect ZR as an output too, and be aware that it can provide 120V whenever anything is calling for heat. Mnemonic: ZR is fed by zone relays.

So, looking at your diagram, remove the existing connection between relay terminal 1 and connect it straight to ZC. That makes sure the circulator will only come on when the water is at the low limit temperature. You're halfway there.

Now you need to get 120V into ZR whenever zone 2 calls for heat. You can't just connect the relay to ZR like you connected it to the circulator, because then the circulator itself would be connected to ZR. You'd find the zone 2 circulator running whenever either zone calls for heat (remember, the aquastat can put 120V on ZR). What you need is another pair of dry contacts on your relay (a DPST relay). I've never heard of the relay you're using, so I don't know whether or not it's got another pair or what terminals they'd be. Let's pretend they're terminals 3 and 4. You would connect terminal 3 to L1 (hot 120V) and terminal 4 to ZR.

superMARKet

The Magic of ZC and ZR, Explained

You don't show any ZC or ZR connections in your schematics. Those are what you need to make this work properly.

ZC is a line-voltage output from the aquastat. It will give you 120V when the water temperature is over the low limit. You only want your circulator to run when the water temperature is over the low limit, so you use ZC to feed the circulator relay. (The water temperature will almost always be over the low limit anyway, since this isn't a cold-start system.) Mnemonic: ZC feeds zone circulators.

ZR is a line-voltage input. You feed it 120V whenever you want the water temperature at the high limit. You want the water temperature to rise to the high limit during a call from heat, so you power ZR when you power the circulator. Note that although ZR is conceptually an input, you can't connect just anything to it without taking care; any time something puts 120V into ZR, something else can take that 120V away from it. You need to respect ZR as an output too, and be aware that it can provide 120V whenever anything is calling for heat. Mnemonic: ZR is fed by zone relays.

So, looking at your diagram, remove the existing connection between relay terminal 1 and connect it straight to ZC. That makes sure the circulator will only come on when the water is at the low limit temperature. You're halfway there.

Now you need to get 120V into ZR whenever zone 2 calls for heat. You can't just connect the relay to ZR like you connected it to the circulator, because then the circulator itself would be connected to ZR. You'd find the zone 2 circulator running whenever either zone calls for heat and even when the water temperature is below the low limit (remember, the aquastat can put 120V on ZR). What you need is another pair of dry contacts on your relay (a DPST relay). I've never heard of the relay you're using, so I don't know whether or not it's got another pair or what terminals they'd be. Let's pretend they're terminals 3 and 4. You would connect terminal 3 to L1 (hot 120V) and terminal 4 to ZR.

superMARKet

The Magic of ZC and ZR, Explained

You don't show any ZC or ZR connections in your schematics. Those are what you need to make this work properly.

ZC is a line-voltage output from the aquastat. It will give you 120V when the water temperature is over the low limit. You only want your circulator to run when the water temperature is over the low limit, so you use ZC to feed the circulator relay. (The water temperature will almost always be over the low limit anyway, since this isn't a cold-start system.) Mnemonic: ZC feeds zone circulators.

ZR is a line-voltage input. You feed it 120V whenever you want the water temperature at the high limit. You want the water temperature to rise to the high limit during a call from heat, so you power ZR when you power the circulator. Note that although ZR is conceptually an input, you can't connect just anything to it without exercising care; any time something puts 120V into ZR, something else can take that 120V away from it. You need to respect ZR as an output too, and be aware that it can provide 120V whenever anything is calling for heat. Mnemonic: ZR is fed by zone relays.

So, looking at your diagram, remove the existing connection between relay terminal 1 and L1/hot and instead connect the relay straight to ZC. That makes sure the circulator will only come on when the water temperature is at or above the low limit. You're halfway there.

Now you need to get 120V into ZR whenever zone 2 calls for heat. You can't just connect the relay to ZR like you connected it to the circulator, because then the circulator itself would be connected to ZR. You'd find the zone 2 circulator running whenever either zone calls for heat or even when the water temperature is below the low limit (remember, the aquastat can put 120V on ZR). What you need is another pair of dry contacts on your relay (a DPST relay). I've never heard of the relay you're using, so I don't know whether or not it's got another pair or what terminals they'd be. Let's pretend they're terminals 3 and 4. You would connect terminal 3 to L1/hot and terminal 4 to ZR. Bingo. Now, whenever the thermostat calls for heat, the relay claps closed and you put 120V onto ZR. If the water temperature is below the high limit, the burner comes on. Excellent.

You can add as many DPST relays as you like as you add zones to the system, making the same connections to ZC and ZR, or you can get a prefab control panel that provides ready-to-use ZC and ZR connections for you.

superMARKet

The Magic of ZC and ZR, Explained

You don't show any ZC or ZR connections in your schematics. Those are what you need to make this work properly.

ZC is a line-voltage output from the aquastat. It will give you 120V when the water temperature is over the low limit. You only want your circulator to run when the water temperature is over the low limit, so you use ZC to feed the circulator relay. (The water temperature will almost always be over the low limit anyway, since this isn't a cold-start system.) Mnemonic: ZC feeds zone circulators.

ZR is a line-voltage input. You feed it 120V whenever you want the water temperature at the high limit. You want the water temperature to rise to the high limit during a call from heat, so you power ZR when you power the circulator. Note that although ZR is conceptually an input, you can't connect just anything to it without exercising care; any time something puts 120V into ZR, something else can take that 120V away from it. You need to respect ZR as an output too, and be aware that it can provide 120V whenever anything is calling for heat. Mnemonic: ZR is fed by zone relays.

So, looking at your diagram, remove the existing connection between relay terminal 1 and L1/hot and instead connect the relay straight to ZC. That makes sure the circulator will only come on when the water temperature is at or above the low limit. You're halfway there.

Now you need to get 120V into ZR whenever zone 2 calls for heat. You can't just connect the relay to ZR like you connected it to the circulator, because then the circulator itself would be connected to ZR. You'd find the zone 2 circulator running whenever either zone calls for heat or even when the water temperature is below the low limit (remember, the aquastat can put 120V on ZR). What you need is another pair of dry contacts on your relay (a DPST relay). I've never heard of the relay you're using, so I don't know whether or not it's got another pair or what terminals they'd be. Let's pretend they're terminals 3 and 4. You would connect terminal 3 to L1/hot and terminal 4 to ZR. Bingo. Now, whenever the thermostat calls for heat, the relay claps closed and you put 120V onto ZR. If the water temperature is below the high limit, the burner comes on. Excellent.

You can add as many DPST relays as you like as you add zones to the system, making the same connections to ZC and ZR, or you can get a prefab zone control panel that provides ready-to-use ZC and ZR connections for you.

Jim_46

Thanks very much Mark, I will put your excellent explanation to use. Also to anyone else reading my question, there actually is a diagram of the inside of the Aquastat with the ZC & ZR connections. It comes up on its own with my question but it is very very slow. Thanks again. JE

eleft_4

Aquastat

Try this.

H I H',

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eleft_4

Answers for Aquastat??

Jim_46

I changed it

Okay, I think I got it thanks to Marks great explanation. I did have a second switch ( #6 & #8 )on the relay and I have a new wiring drawing for your approval. Thanks much JE

superMARKet

Couple of things

Jim-

I sent this to you in an e-mail, but I'll repost it here for the benefit of anyone else following along.

First, let me make a correction. For ZR, you need to use terminals 5 and 8, not 5 and 6. I just noticed that you sent me the RCP specifications. The wiring diagram shows that 8-5 is normally closed, and 8-6 is normally open. I would put 120V into 8 and connect ZR to 6.

You need to bring the 120V connection to the relay through the same emergency switch as the aquastat and the other boiler controls. If the relay takes 120V from another source, you'll wind up putting 120V right back into ZR any time zone 2 calls for heat, even if the emergency switch is off. As it turns out, this is enough to run the burner. Kinda defeats the purpose of the emergency switch. The burner MUST NOT run when the emergency switch is off, so bypassing the emergency switch even for the relay won't cut it.

If you don't have easy access to the line switched by the emergency switch, you can take it from terminals 1 and 2 on the aquastat. Use a pigtail and wire nut for any splices you make inside the aquastat. Don't try connecting two wires directly to the same terminal. Make another run of 14/2 alongside the run you make for ZC and ZR, and use that as hot and neutral instead of the new line. It's not strictly necessary to keep the 24V transformer connected through the emergency switch, but it's a good idea. People servicing the system in the future might expect it, and could be in for a nasty surprise if they try replacing the transformer.

You can use a single run of 14/4 in place of two 14/2s if you like. I'd avoid using 14/3 plus the existing neutral connection, although I bet a lot of folks would suggest it. That kind of wiring is sloppy, difficult to troubleshoot, and depending on what else is connected to that neutral, hazardous.

Sorry if this is wordy, I want to make sure not just that you can make the right connections, but also that you see what's happening and why. This is especially important where safety is concerned!

Good luck, and let me know if you've got any other questions.

Einsiedler_2

back to t'stat

why not just connect the TV & T terminals (24V Tstat) thru #8 & #6 on relay...

then zone 2 call for heat triggers same way as Zone1 ?

EIN