No zone valves on my system

bentz69

I have oil heat with 3 zones/3 thermostats (basement, 1st/2nd floor) using baseboards. The 3 thermostats are 110v line voltage units that operate the 3 circulator pumps. There are no zone valves on this system. I would like to install 3 Nest thermostats to replace these old line voltage units.

My plan is to install three 3 zone valves. I will re-use the current wiring (no plans on running new wires through the walls) to give the Nest's the 24v it needs by having the power supplied by a transformer. The Nest's will operate the zone valves and I will wire the micro switches in the zone valve to the circulator pumps to supply the pumps 110v to operate. Ive seen several systems that use the Nest which don't have a dedicated C wire and they work fine with no power lose over long term periods of non-usage.

Looking for input. Thanks

Robert O'Brien

Has to be Long Island!

John Ruhnke

You don't need the zone valves. You just need to add a three zone pump relay and change the wires around to make it work.

bentz69

Robert O'Brien said:

Has to be Long Island!

Why?

John Ruhnke said:

You don't need the zone valves. You just need to add a three zone pump relay and change the wires around to make it work.

I was adding zone valves because of the constant thermosiphon effect throughout the winter. I will get tremendous amounts of heat specifically on the 2nd floor when the thermostats are off

Intplm.

@bentz69 Adding zone valves will be helpful. But !
When you say you get a tremendous amount heat on the second floor when the thermostats are off is a result of thermodynamic law that says "hot goes to cold always."
This can be corrected by installing flow control valves on your system. This should stop the heat from going to the second floor as you describe.

Robert O'Brien

> @bentz69 said:
> (Quote)
> Why?(Quote)
> I was adding zone valves because of the constant thermosiphon effect throughout the winter. I will get tremendous amounts of heat specifically on the 2nd floor when the thermostats are off

Only place line voltage thermostats are used on Hydronic systems

HVACNUT

If the end switches on the zone valves are going to power the circulators directly, then the boiler won't maintain a minimum temperature. If it's a cast iron boiler, then the circulators should hold off until the boiler temp is above 140° to prevent condensing of the flue gasses. What aquastat is on the boiler now? L4081B? It can probably be done with minimal rewiring.

Dave H_2

Sounds like you are getting gravity flow in your system when the boiler is hot and the zones stop calling for heat.
Hot water rises, cold water falls.
Adding Zone Valves would definitely stop the gravity flow but would be adding more components to a system than is needed.

You could add check valves to the circulators to the stop that gravity flow.
I am not sure about other brands of pumps, but if they are Taco's and manufactured after 2006, you could easily add the check valve. All circs manufactured since then were machined to accept a check valve. You should be able to see the manufacturing date on the electrical box.

bentz69

I forgot to mention from the start that my boiler is for hot water AND heat.

I can see how the 3 zone pump relay would work but I would still need to install flow control valves as well. Whether it be a 3 zone pump relay with flow control valves or zone valves with a transformer I still need cut pipe either way.

I have 2 taco pumps and 1 astro pump. The astro pump is for the 2nd floor and the internal check valve is not installed. When I called astro they recommended the check valve not be used in hot water applications.

Intplm. said:

@bentz69 Adding zone valves will be helpful. But !
When you say you get a tremendous amount heat on the second floor when the thermostats are off is a result of thermodynamic law that says "hot goes to cold always."
This can be corrected by installing flow control valves on your system. This should stop the heat from going to the second floor as you describe.

I understand what your saying but I still need to convert the 110 to 24v to make the nest work correctly

HVACNUT said:

If the end switches on the zone valves are going to power the circulators directly, then the boiler won't maintain a minimum temperature. If it's a cast iron boiler, then the circulators should hold off until the boiler temp is above 140° to prevent condensing of the flue gasses. What aquastat is on the boiler now? L4081B? It can probably be done with minimal rewiring.

As I said above, I forgot to mention my boiler is for hot water as well

Dave H_2 said:

Sounds like you are getting gravity flow in your system when the boiler is hot and the zones stop calling for heat.
Hot water rises, cold water falls.
Adding Zone Valves would definitely stop the gravity flow but would be adding more components to a system than is needed.

You could add check valves to the circulators to the stop that gravity flow.
I am not sure about other brands of pumps, but if they are Taco's and manufactured after 2006, you could easily add the check valve. All circs manufactured since then were machined to accept a check valve. You should be able to see the manufacturing date on the electrical box.

I have 2 taco pumps that honestly look like they are the original pumps from when this system was built in 1986. The 1 astro pump is much newer. I dont have much information because I moved in last year. But I do know the astro pump does not have the check valve installed because I found it sitting on top of the boiler when I moved in. As I mentioned above, when I called astro they recommended not using the check valve on hot water applications because of the possibility of the check valve deteriorating

Dave H_2

This system is not an "open" system. The boiler may make hot water for the house as well as heat, but the water in the boiler is closed and the does not flush out.
Adding zone valves to a zone pump system is like wearing a belt and suspenders. You just dont need to do it.

By the looks of things, if you were cutting into the system; for about the same cost; I would change the circulators and add the ifc check valves to the new circs

Dave H

HVACNUT

Which zone is causing the heat rise? The first floor zone has a spring check above the circulator already.

John Ruhnke

I agree with Dave on this one. It is much easier unbolting the pumps then cutting into the lines. The new pumps are cheaper than zone valves so that is better too.

@bentz69 You said "As I mentioned above, when I called astro they recommended not using the check valve on hot water applications because of the possibility of the check valve deteriorating."

I think there is some misunderstanding of how hydronics work here. When the rep mentioned Hot Water, he meant Bathing Hot Water. The domestic water we drink and bath in has a lot of oxygen in it. This oxygen eats steal components up really fast. Everything has to be rust resistant to prevent this. It is all brass and copper piping on the domestic hot water system. That Astro pump is installed in the heating system. It is a closed loop heating system and no added oxygen can enter unless there is a problem or design flaw. I see black steel fittings on the hydronic side. So adding that check valve to the pump is fine. On the heating side the check valve has some steel components and that is perfectly fine in your situation.

Go ahead and install that check valve in the Astro Pump.

bentz69

I wont sit here and pretend I know much about boilers since this is my first home (moved in last year) but I am trying to learn

Dave H_2 said:

This system is not an "open" system. The boiler may make hot water for the house as well as heat, but the water in the boiler is closed and the does not flush out.
Adding zone valves to a zone pump system is like wearing a belt and suspenders. You just dont need to do it.

By the looks of things, if you were cutting into the system; for about the same cost; I would change the circulators and add the ifc check valves to the new circs

Dave H

So your suggestion is to replace the pumps with new ones, add the check valves to all the pumps and disregard the zone valves? I guess you agree with the others who suggested the 3 zone relay to power the nest thermostats and pumps?

Since I have 2 wire line voltage thermostats can anyone tell me how the 3 zone relay works with 120v pumps that now need 24v to the nest? Will this relay do the job or will I need a seperate transformer?

This?
https://www.supplyhouse.com/Taco-SR503-4-3-Zone-Switching-Relay

HVACNUT said:

Which zone is causing the heat rise? The first floor zone has a spring check above the circulator already.

The baseboards on both the 1st floor and 2nd floor get hot when the system is thermostats are off. I see what your referring to right above the basement pump. I did not know that was some type of check valve. In that case the 2nd floor has one as well right above the red pump. The basement has a flow valve in a different location and not directly above the pump. At this point Im guessing the spring check valves are stuck? A few taps might loosen them up but I wont know until it actually gets cold outside and the heat is off right? Is there another way to verify they are operating correctly?

Is it safe to assume that since there is a spring check valve directly above the red pump that is likely the reason why the internal check valve was not installed on the red pump?

John Ruhnke said:

I think there is some misunderstanding of how hydronics work here. When the rep mentioned Hot Water, he meant Bathing Hot Water. The domestic water we drink and bath in has a lot of oxygen in it. This oxygen eats steal components up really fast. Everything has to be rust resistant to prevent this. It is all brass and copper piping on the domestic hot water system. That Astro pump is installed in the heating system. It is a closed loop heating system and no added oxygen can enter unless there is a problem or design flaw. I see black steel fittings on the hydronic side. So adding that check valve to the pump is fine. On the heating side the check valve has some steel components and that is perfectly fine in your situation.

Go ahead and install that check valve in the Astro Pump.

Makes sense I understand.

John Ruhnke

The basement has a flowcheck in the line. If the flow stops when the pump stops in that zone then just leave it. Both spring checks on the other two zones failed. So use the internal check you have on the Astro. Now you only need to buy one pump for the third floor with an internal check valve. That Taco relay you picked out looks good.

HVACNUT

The three zone switching relay will work. You still won't have 24v supplied to the Nests, but that's ok. Ask Nest if they can send you resistors instead of using their transformer.
Can you get the model of the aquastat? L4006A or L6006A.
It should be the L6006A so it opens the circuit to the circulators on temperature drop. The wiring for the zone board will be atypical with that aquastat but it can be done.
Can an IFC circulator be mounted facing down? Anyone? Are the 1st and 2nd floor flo valves the same as the basement? Post a pic. You may be able to "bounce" the loops and clear debris from the seats of the flow valves. Or maybe just replace the inserts.

HomerJSmith

My two cents worth. This sys has been neglected, I hate seeing that happen.

The pumps--replace the Taco pumps with Grundfos UPS 15-58 pumps and put in the IFC (Integral Flow Check) valves as pictured by HVACNUT. Replace the IFC in the Astro. When the water is out of the sys check the air pressure in the Extrol Expansion Tank, it should be the same as the sys fill valve pressure setting. The tire pressure valve is under the blue cap on the Extrol, about 15 psi.


It looks like you have spring check valves on 2 of the pumps, I would remove those. Of course, if it were me, I would do some re-piping.

The 110V thermostats have probably #14-2/wg NMB wire with the connections in a J-box. I would use the wire going to the thermostats as a 24V connection with the black & white going to the R & W connections on the nest and the bare ground wire connected to the C connection on the nest. Since it is a bare wire you have to take precautions against shorting. Then you would have the charge circuit.

I would add 2 more J-boxes and wire 110V to each one and use three Fan Control Centers with DPDT relays. Wire it up as a DPST normally open. Use one pole to turn the circulator on the other pole to turn the boiler on. Run each nest wire to each box controlling that zone's pump. Connect #18/3 or 4 thermostat cable to the #14-2/wg on each end to make connections to the nest and transformer. Sound complicated, but it will work. Maybe you need a diagram. A cheap way to go.

https://www.supplyhouse.com/Packard-FC90112-Fan-Centers-DPDT-Relay-120-VAC-Primary-24-VAC-Secondary

HomerJSmith

HVACNUT, of course you can put a IFC in the down position. It is just there to stop ghost flow thru the pump side. Since, water flows from high pressure to low pressure, a pump operating on a manifold could push water thru an inoperative pump forcing backward flow which a IFC would stop, I think.

bentz69

Appreciate all the advice and suggestions I received. I will be replacing those 2 old tacos with new tacos working in conjunction with the 3 zone taco relay. Taco has a direct replacement newer model for what I already have and also an option for a internal check valve model which is only $5 more.

I have been advised that since my system already has spring check valves I should just replace them and disregard the internal check on the pump. After measuring the to Spring checks one is 2.25 and one is 2.75 in length. Supply house has a spring check at 2.5 inches for only $10 compared to 50$ at a local plumbing store. That's the only length that they have. Is it safe to assume that there should be enough thread on that pipe to accommodate a 2.5 in check in both sections?

John Ruhnke

As long as the spring checks stay in the open position I would just leave them alone or cut them out permanently. Do the eternal check valve in the pumps. That way if the eternal check ever fails it is easy to fix by unbolting the pump and replacing.