How to add Zone Valve to Prevent “Ghost Flow”
I converted an old gravity radiator system in a four unit house to a central mod-con boiler then added two new zones for a total of SIX zones, each with its own pump. I use a Taco SR506-4 Switching Relay Controller. It works great.
The original cast iron piping and radiators in the four apartments was largely untouched and is 100 years old, no leaks, works great and the separate zoning works fine. The original apartments each had their own cast iron boiler. Replacing it with one mod con is amazing and it has worked great for a few years now. The original installer retired, so I’m on my own now.
The two largest zones, however, do have some ghost flow of heat. When all the Zones are heating, it overheats the Zone Two, a middle floor apartment. The only way to prevent that is to shut off the full port valve near the Zone Two pump by hand, which prevents the cross flow which is really backflow and the resulting “ghost heat”. If we don’t shut off the valve, the apartment can heat up to the low 80s. Awful. But once it’s shut off, eventually, that Zone Two gets cold. Fact is, Zone Two seldom has to run its heat all that much because the other surrounding units keep it pretty warm. I called the original installer and he suspects the old radiator return piping in the building is the culprit and we cannot fix that.
He offered a solution. He recommended installing two Taco Sentry Zone Valves, one on each of the Zone One and Zone Two, just ahead of each Circulator for Zone Two and Zone One, the largest zones. That way, the “ghost flow” of heat stops. Zone Two won’t call for heating that often, but it also won’t overheat if the zone valve is normally closed. And when it calls for heating that, the zone valve will open when the circulator is running. Swell.
So how do I wire in a zone valve on this switching relay? Can I? I assume I will have to add a transformer to power it? We have six smart thermostats on the SR506, so there isn’t enough 24v power or amps to run two zone valves. The SR506-4 Switching Relay Controller doesn’t have enough 24 volt amps to run all this. No zone valve terminals or end switches….
Can I power the zone valves with adding a transformer and connect it to the thermostat terminals on the SR506? If so, how and where do I connect the end switches? Any suggestions? How do I wire this? In fact, I’d appreciate comments on this solution.
Comments
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You have your Taco 5064 which now starts the circ pump. You want the thermostat to open the zone valve and then the end switch on the zone valve will start the circulator.
From your 120 volt supply install a new 120/24 volt transformer. From this transformer run a common wire to each of the two zone valves to power one side of the zone valve actuator.
Then the other side of the transformer (the 24 volt hot wire goes to "r" on both of your thermostats for those two zones. "W" from each thermostat will power its respective zone valve.
The take the two zone valve end switch wires and connect them to the Taco zone control and connect them to where the thermostat wires are now connected.
Just keep in mind with those zone valves closed you could cause Ghost flow in other zones.
This assumes your using 24 volt zone valves with and end switch.
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If it is truly a back flow situation, some circulators come with or you can add a check valve, you could also add an external check valve.
If you have your Heart set on a zone valve solution I would add a small 120 VAC to 24 VAC transformer, a relay and a 24 VAC zone valve to each zone with the ghost flow.
The transformer's primary runs off the switched SR506 circulator power (N & H). This provides an easy switched 24 VAC source to activate the zone valve only when needed.
Once the zone valve is fully open the zone valve's end switch closes, energizing the relay.
The energized relay then turns on the circulator.
At the end of the zone call the SR506 shuts off its circulator output (N & H) so the circulator and the transformer are shut off and the relay drops out and the zone valve closes.
There are certainly other ways to do this. This way may be a bit odd switching the transformer's primary but it uses minimal new parts, minimal wiring and you are not messing with the smart thermostats on the input side of the SR506.
You could use a 120 VAC zone valve(s) and forget the transformer(s), I'd still use the relay to switch the circulator since the zone valve's end switch may not be up to the challenge of the circulator's load. In this case I'd make sure the end switch is rated for 120 VAC service, and the relay coil would be 120 VAC.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
If you add a zone valve, make sure Flow Capacity (Cv) is adequate for your system.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
If it is truly a back flow situation, some circulators come with or you can add a check valve, you could also add an external check valve.
^^^^^^^^^^^^
THIS
Why would you want to bother with adding zone valves when they make check valves for this exact problem!!!
As 109A noted, you can probably add the check right in the pump!!
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in some cases the ghost is going up the return side, large diameter vertical piping can encourage that
So you might need to check both sides
Use a soft seat spring type conical check for good flow and silent operation
A serviceable type is nice if you have old iron piping. Rust and scale can hold them open a little
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Another vote for make sure you have functioning check valve. One at the zone2 circulator may be enough. If not, add an online check valve on the return side of zone 2. Theoretically that's all you need, nothing electronic necessary.
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What circulator do you have? Most them can easily accept an IFC, integral flow check.
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ALL my circulators have the plastic check valve in the top of the pump. The two zones in question are grundfos 26/99 pumps (oversized in my opinion, but they work). The first thing I did was replace the check valves with brand new check valves. This had no effect on the ghost flow. I think it's because the problem is on the return end—I looked at old photographs of the piping after installation, and The Old Guy who installed this otherwise solid system piped the two large zones with 1.25" individual feeds to each of the two large zones, but then combined the returns into one big 2" pipe going into the manifold, instead of individual pipes going into the manifold. Also the other four zones are piped 3/4" supply and 3/4" return. My guess is that the primary/secondary flow and flow rates are messed up because of that.
Hey, if you have another solution to this, I'm open. I thought zone valves were the answer because The Old Guy recommended it. I considered swing valves, but my supply and returns are vertical, not horizontal. I have nowhere to put a horizontal swing valve.0 -
See my other answer. Check valves was the first "go to" I tried, and this had no effect. I had check valves. I replaced them with brand new ones just to make sure. Nothing changed.
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The two large zones have Grundfos 26-99 pumps, the other four zones have Grundfos Alpha 15-55 pumps. All the pumps have plastic cartridge check valves. The ghost flow comes from the return back up to the supply—whether the pump is on or off—so the check valve in the pump wouldn't make a difference as it checks only flow coming back DOWN, and the ghost flow is coming from the manifold below, in the same direction of normal pumping/flow. It's flow coming back from the return manifold. At least, I think it is.
All I can say for sure is that when the other pumps are heating, the Zone 2 problem zone has a hot pipe, even when it's thermostat is OFF and the pump is OFF. Only a closed valve stops flow.
BTW, this boiler is in the basement, and three of the four units are upstairs up flow Only one zone travels horizontally, and that's about 120 feet back to the rear carriage house/same level.0 -
Ok check valves are not helping. Install the appropriate zone valve and wire it up. The first two responses provide wiring methods, pick the one you like. Each has advantages and disadvantages.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
if a check after the circ did not solve it, a zone valve after the circ may not either, if the ghost flow is a piping issue, or “rear end” return side Thermo siphoning
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Piping into a system which uses tees , the returns need to be teed back into the system …
There was an error rendering this rich post.
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RobinInCali stated " The only way to prevent that is to shut off the full port valve near the Zone Two pump by hand, which prevents the cross flow which is really backflow and the resulting “ghost heat”. "
So I would think a zone valve may work. I'm thinking there is a slight flow through the circulator in the normal direction causing the issue.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
I appreciate the diagram. I have always used Taco Sentry Zone Valves, which have terminals with a C and a W/Y on one side, then the end switches on the other side. I can certainly make sense with this diagram. But I do have a question. Am I wrong, or doesn't the SR506 already have dedicated terminals for controlling thermostats and zone valves, including an end switch to signal the boiler? Could you help me understand why an external relay is needed here? Would the SR506 terminals not serve the same purpose? THANK YOU THANK YOU THANK YOU
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Referring to this image below. The R & W terminals along the top are zone inputs. A contact closure (the thermostat) activates the associated zone. The X-X Isolated End Switch is a contact closure (an output) that tells the boiler that one or more zone is calling for heat (start the boiler). The N & H (Neutral and Hot) along the bottom are just switched 120 VAC outputs to power the circulator for each zone.
" Am I wrong, or doesn't the SR506 already have dedicated terminals for controlling thermostats and zone valves, including an end switch to signal the boiler? "
The thermostat activates the zone input on the SR506 not the other way around. The SR506 does not have any zone valve activation outputs like a the Taco ZVC series does, just switched outputs to power circulator(s).
The relay is two fold, the zone valve end switch may not be robust enough for the circulator load and may not be rated for 120 VAC service. Also the relay in concert with the Zone Valve's End Switch proves the zone valve is actually open before the circulator is energized.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
Just to be clear. With the method EBEBRATT-Ed posted above, that is probably the most common way (especially if you only have zone valves and no controller or circulators and there are wiring diagrams all over this site for that method and its variants.
Since " We have six smart thermostats on the SR506 ". Smart thermostats and their associated wiring with zone valves always seem to give folks issues for various reasons, and you are only adding a zone valve or two, and probably need to power that equipment from another isolated transformer anyway. The wiring can get messy and confusing for some.
Since your six smart thermostats and the SR506 are apparently playing nicely together, I decided to post an alternative method that does not touch the input side of the SR506. Use whichever method you are comfortable with and makes the most sense to you, since you will be maintaining it.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
Is this the right kind of relay?
https://www.supplyhouse.com/Functional-Devices-RIB2401B-Enclosed-Relay-20-Amp-SPDT-with-24-VAC-DC-120-VAC-Coil0 -
Yes that would work as long as your circulator is not over 1 HP.
If you like the RIB style for the money I would probably use this one since the switch provides more diagnostic functionality and you don't need the NC contact.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Ok, giving an update on all your excellent suggestions and help. I installed a zone valve on each of the problem Zones. The basic wiring to the transformer and control board/thermostat worked fine. This reduced the ghost heat by about 60%. I then tinkered with the pumps speeds for balance and flow reasons, Lowering pump speed on some, increasing others. That helped about 10%. I lowered the SWT 10 degrees, and that helped about 10%.
So it's 80% better, 80% less ghost heat! The Problem Zone averages 69/73 degrees all the time, whenever any of the other zones are firing and pumping heat in the building, which is mostly all day. This zone and its pump very rarely fires anymore, it just enjoys passive heat from the other zones, I guess. Maybe it might have a call for heat in the middle of the night for 10-30 minutes. That's it.
I consider this a success. The other options were to tear out walls and redo return piping, or redo the manifold, but frankly, this is good enough. Those wiring diagrams were priceless. Thanks.
Thanks you for all your suggestions.
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Excellent, glad to hear it provided a worthwhile improvement.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Not sure if anybody is paying attention anymore, but we have had a cold snap in San Francisco, with the heavy winter rains. The ghost heat issue re-occured. My new question is, is it possible that trapped air in the system is causing this issue? The top floor has bleeder valves on their radiators. The middle floor does not.
Again, to recap the main issue: When the middle floor turns on its heat, ghost heat migrates to the upper floor and the upper floor overheats. One data point that might help is that this is a new problem. We ran the system for three years without this problem, although surely, there probably was a little bit of cross flow up into the upper floor. But nothing like this.
What do I do? Purge the whole system with a hose starting from bottom floor to top? Shouldn't the bleed valves on the top floor get rid of all air because air rises?
Any more suggestions are welcome. Thanks.0 -
you have flow checks on each zone, right? seems like that would be number one in your recap to mention that.
you may need flow checks on the supply and the return, sometimes it is possible to get 2 way gravity flow within the same pipe, especially if the popes are bigger than they need to be for the needed heat output to each zone.
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if you have a flow check on the supply and a zone valve on the return and you are still getting overheating it is likely the anticipator in the thermostat isn't shutting it off early enough and everything is just still hot.
maybe there is some piping that is cross connected between the floors up in the building somewhere. maybe you removed some air that was stopping the cross flow.
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Can you post photo of your supply and return piping including circulators?
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Either you have a mis-piped system or thermosiphon up the return. You should never need a zone valve after a circulator on a single loop circuit. A flow check or hydronic spring check will work.
Forward or reverse thermosiphon are know causes of over-heating.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0
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