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DHW Priority Question
sgall
Member Posts: 37
2 Years ago we switched our house (north of Boston) to gas and installed a Burnham Alpine 80 and a Superstor 60 for DHW. The heating system was a monoflow with cast iron radiators - each of the three floors with its own circulator and basement loop. At the time the system was installed, I assumed that it was setup to give priority to a DHW call so that the heating zone circulators would be shut off until the DHW call was satisfied. During the past year, we have been renovating our first floor and the monoflow system has been removed and runs of pex to the cast iron radiators from manifolds installed. Last weekend, when I was using the heat for the first time, I noticed the radiators were a lot hotter than it seemed they should have been given that it wasn't very cold outside. Upon checking the system in the basement it seemed that both the DHW and 3rd floor circulator were simultaneously running. I went over all the boiler menu choices which seemed to be correct. I am thinking that the system wasn't wired properly but both the Alpine manual and the Taco SR504 documentation are a bit cryptic. I was wondering if someone could take a look at the attached photo and point me in the right direction. Do I need to remove the jumper between ZC and ZR or is a another wire required? Thanks
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Comments
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Look at the zone priority switch. Zone 4 is supposed to be the zone that feeds the indirect DHW tank. The Priority switch must be set to OFF and when the Priority zone (#4) gets a call, the other zones will stop. Its difficult when Sparky uses all one color (pink) as the feeds for all the circulators and is so rude as to not mark the wires with those little cheap tags that the good guys use.
Remember, Cast Iron radiators take longer to heat up and longer to cool off.
I'm not familiar with Burnham Alpine boilers. They were never sold where I work. But I think that they can make DHW a priority and the heating on ODR and work with separate temperatures. If that is the case, the controls are probably not wired for optimum efficiency. You may need to find someone with good control strategy understanding.
The fact that someone changed a whole Monoflow Zone to PEX Spaghetti Home Runs, can create cross connections if not careful. What may be wrong if something is wrong, usually takes an "Eye On" consultation and repair.
Was there a good reason for changing the Monoflow zone?0 -
Sorry, Ice, maybe you just had a typo, but the priority switch must be turned to ON for that zone 4 to have priority. But there are other wiring considerations besides the Taco priority switch and my guess is that you are somewhat "miswired" as to control of the boiler, zones and DHW. Can you tell me what you have for woring on the terminal strip in the boiler? Thanks, Gary0
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Ice Sailor, we removed the 3 monoflow zones because we are opening up the entire first floor (1st floor is getting radiant ) and the house is a structural nightmare - pex runs were really the only cost effective way to repipe.
Gary Jansen, On TB2 we have the following:
Red Wire from Taco SR504 X (end switch) - Heating T Stat
White wire from taco SR504 X (end switch) - Heating T Stat
Red wire from Superstor aquastat - DHW Temp Switch
White wire from Superstor aquastat - DHW Temp Switch
Outdoor Reset Red wire - Outdoor Sensor
Outdoor Reset White wire - Outdoor Sensor
the rest are empty.
On TB1:
Empty - GND
Red wire - L1
White wire - L2
Empty - System Circulator
Empty - System Circulator
Red Wire - Boiler Circulator
White wire - Boiler Circulator
Red Wire - DHW Circulator
Empty - DHW Circulator
Thanks0 -
can you show me a piping schematic? I can then tell you what to do to straighten out the wiring. I believe you will have to add a relay. Pretty simple. Thanks, Gary0
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Gary J. , Here is the piping schematic from the Alpine manual - I had my plumber follow this exactly. If you would rather a picture i can do that too. thanks.0
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Never did like that piping diagram.It makes priority a little tough. You will need to add a relay.
Gary, what did you have in mind?
Is the the DHW wired as a switch or a sensor on that one?
Easiest thing might be a 120 volt DPDT that would close the 4th zone tt's on the taco whenever the dhw circ is energized?
Carl"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
If it is what I think it is, the boiler is controlling the hot water pump not the Taco Box. The way it is wired now...the Taco box has no way of knowing when the hot water is running. It receives a signal for heat, runs the proper zone pump and tells the boiler to run. It is not getting a signal from the boiler telling it to wait.
If the boiler has priority in it, then the system pump terminals will open when hot water is running. That is what has to tell the taco box to shut off the pumps.
The way I wire Knight boilers, we run a wire from the system pump terminal (120 volts) to the Taco box. Remove the jumper in the taco box between ZC and ZR. Using a multi meter, test ZC and ZR for power, it is on one of the terminals but I forget which one. Which ever terminal DOES NOT have power either ZC or ZR it will now be powered from the system pump terminal in the boiler, which opens (looses power) when the hot water zone calls. ZC and ZR are for tankless boilers to maintain temp, but can be used in this application as well. They both need power for the Taco box fed pumps to run.
You can't just connect TT terminals for hot water at both the boiler and on the priority zone on the Taco Box, it doesn't work right.
Hopefull not too confusing...0 -
Eric, Thank you. Do you think if I connect a wire from the Sys Circ post on "Boiler Terminal Strip [TB1]" to ZC on the 504 and remove the jumper that will do it? I think that is what you mean. See attached from Alpine Install Manual.0
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Yes, the system circulator terminal will power ZC or ZR whichever does not have power on i, and remove the jumper. Let us know how it works. That's how I wire Lochinvar Knight boilers
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Eric,
I like your solution. The only caution would be to verify that the boiler can handle the amperage of all the attached circulators. If it did, you could add a relay.
Carl"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
Considering the way you have it piped and the way it's wired right now, you do not have a system circulator to work with. If you have given me the proper info you have zone circulators and a DHW circulator. The easiest way to work around what you have its to add a 120 relay in parallel, not series, with your DHW circulator. Take the Common and N/O terminals of the relay (dry contacts) and connect them to TT on Zone 4 of the Taco box. Set priority switch to ON. On a DHW call, the relay will make along with the DHW pump, the boiler outdoor reset will be disabled internally in the boiler, the dry contact on zone 4 will close the priority relay, preventing your zone pumps from running, and the boiler, if programmed properly, will go to high fire. After DHW is satisfied, relay opens, DHW call stops, boiler goes back to it's operating curve and zone pumps are enabled. Something like a little RIBS enclosed relay with 120 volt coil will do the trick.1
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never mind...
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
I really get into this stuff
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I will give the jumper removal/wire addition a try in the next few days when i can get to it and report back. thanks everyone.0
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I believe ZC pulls in a relay in the multi box and the pumps are actually powered from L1/ L2, but I am not sure.....
There is a different thread in Oil Heating and Joe from Taco responded in it regarding ZR/ZC and cold start..... I commented to see what he has to say on it.
Stay tuned...0 -
Eric,
I think you are right. I wish they would publish a simple ladder diagram,,,,
The relay to TT4 may be a better options"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
I ran the wire from the boiler to the ZC terminal and removed the jumper. I checked it today while my daughter was showering and it seemed to work perfectly. I turned on the Zone 2 thermostat and when I got to the basement the 504 zone 2 light was on. Towards the end of the shower the boiler went to full fire and boiler switched from Central Heat Priority to DHW and 504 zone 2 light went off. At the end of the DHW call zone 2 came on again.0
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Nice... glad it worked for you!!0
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So did you just run a single hot wire from the boiler system pump hot terminal to ZC? Do you need to run neutral or ground at all?Eric said:If it is what I think it is, the boiler is controlling the hot water pump not the Taco Box. The way it is wired now...the Taco box has no way of knowing when the hot water is running. It receives a signal for heat, runs the proper zone pump and tells the boiler to run. It is not getting a signal from the boiler telling it to wait.
If the boiler has priority in it, then the system pump terminals will open when hot water is running. That is what has to tell the taco box to shut off the pumps.
The way I wire Knight boilers, we run a wire from the system pump terminal (120 volts) to the Taco box. Remove the jumper in the taco box between ZC and ZR. Using a multi meter, test ZC and ZR for power, it is on one of the terminals but I forget which one. Which ever terminal DOES NOT have power either ZC or ZR it will now be powered from the system pump terminal in the boiler, which opens (looses power) when the hot water zone calls. ZC and ZR are for tankless boilers to maintain temp, but can be used in this application as well. They both need power for the Taco box fed pumps to run.
You can't just connect TT terminals for hot water at both the boiler and on the priority zone on the Taco Box, it doesn't work right.
Hopefull not too confusing...0
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