I have to replace my boiler zone valves- Should I use 2 wire or 3 wire?

DenverDude

I have a Raypak boiler, with 2 zone valves (upstairs/downstairs).  One of the zone valves went out, and the other one is 25 years old, so I figured I would replace both at the same time.  They are 3-wire, and my thermostats are old 3-wire.

I got a quote of $800 to replace the 2 zone valves with 3-wire White Rogers ones.  And a quote of $950 to replace the 2 zone valves with 2-wire Honeywell ones.

The 2-wire ones would require me to buy 2 new thermostats- but I kind of wanted new programmable thermostats anyway.  My understanding is that programmable thermostats are expensive for 3-wire systems.

What should I do?  Are there any advantages to 2-wire vs. 3-wire?  It will cost me a couple hundred bucks more to go 2-wire, but at the same time I don't want to get stuck with 3-wire and never be able to add a programmable thermostat.

But my main question is:  which system is more reliable/better?

Mark Eatherton

2 wire for sure...

Honeywell for sure as well.



The 3 wire stats you have will work with a 2 wire zone valve. You just have to figure out which 2 wires you have to use.



3 wire ZV's (White-Rodgers) are a royal PITA. Too many moving parts, and two many switches, and if one of them fails the valve fails.



With the Honeywell valve, you can replace the switch and motor gear (wear items) without having to break into the water side of the system.





ME

Plumdog_2

Any way you want

I just got done writing about the virtues of the old-school zone valves, and the whole piece just vanished. I like them. They flow about 4 times as much as most other types, can be installed without regard to direction, and are really very durable. You can use your 3-wire stats for 2-wire ZV's; just omit the power-closed wire. You can also control 3-wire ZV's with some programable stats (just look in the "compatibility" chart, they have to be OK with Hot Water Heat, Power Open/ Power Close 3-wire Zone Valves. (You can also use a N/O N/C relay to power a 3-wire ZV with any regular stat). You can also switch the 3-wire powerheads to the 2-wire powerheads without even letting water out. But watch out for the wiring; anybody familiar with these animals has a complete collection of burned out transformers to prove it. I see White-Rogers zone valves that are thirty years old  daily. Some still work. None of the other brands last as long.  

Plumdog_2

Any way you want

I just got done writing about the virtues of the old-school zone valves, and the whole piece just vanished. I like them. They flow about 4 times as much as most other types, can be installed without regard to direction, and are really very durable. You can use your 3-wire stats for 2-wire ZV's; just omit the power-closed wire. You can also control 3-wire ZV's with some programable stats (just look in the "compatibility" chart, they have to be OK with Hot Water Heat, Power Open/ Power Close 3-wire Zone Valves. (You can also use a N/O N/C relay to power a 3-wire ZV with any regular stat). You can also switch the 3-wire powerheads to the 2-wire powerheads without even letting water out. But watch out for the wiring; anybody familiar with these animals has a complete collection of burned out transformers to prove it. I see White-Rogers zone valves that are thirty years old  daily. Some still work. None of the other brands last as long.  

DenverDude

OK so that is one vote for each...

Anyone else care to weigh in?

DenverDude

what do you mean by "4 times the flow"?

Do you mean the flow of water to the zone?

Plumdog_2

Friction, or Resistance

All these valves and fittings and devices are rated as to how much fluid will pass thru at any given pressure. One model of 3/4 Honeywell zone valve is rated at 3CV, while another 3/4 valve is rated at 8CV. The White Rogers 1311 series is rated at (I think) 24CV. Look down the barrel of an open valve and compare. Mark can explain what that "CV" rating is and how it is arrived at. For most practical purposes, it doesn't matter that much. But if you have a lot of Baseboard on one loop, or an exceptionally long loop, or you want to maximize flow thru a Raypak, it could be a benefit. 

Mark Eatherton

Cv explanation...

Cv stands for flow coefficient. It is expressed as the flow through any given device to create a 1 PSI differential across the device. It is kind of like a MPG rating that the EPA gives for cars. Kinda.



In hydronics, a relatively unknown fact is that the control valve should represent 1/4 to 1/3 of the pressure drop for the circuit. If not, flow will vary significantly when all zones are on, basically causing the flow to "hunt" (per Robert Bean).



ME

DenverDude

Thanks guys- so...

I am leaning toward sticking with the 3 wire-  It is a little less expensive because he doesn't have to re-do the actual valves on the pipes, just switch out the control valves themselves.  The 2 current 3-wire ones are dated 1981 and 1989, so they DID last 30 years...

And my kids bedroom is at the far end of the downstairs loop and after reading your comments on Cv, I am concerned about getting enough flow there.

If I go with 3-wire, can you guys recommend a good 3-wire programmable thermostat for less than about $80?  And would I have to stick with White Rogers for that or could I go another brand like Honeywell?

I am looking at the Honeywell RTH6400D online, but how do I know if it is compatable with the 3-wire?  I don't have AC, just the boiler heat with 2 zones.

Slimpickins

they both suck but

since you already have W/R valves, I would use the existing bodies and pop in new heads. The newer W/R valves have better wiring connections than the old push in type. My personal choice are Oventrop electro thermal actuators or Caleffi if they aren't available. They're way more compact and use little power.

Plumdog_2

Go with two-wire

Get the 1361 2-wire valves. They will go right on the valve bodies you already have. Two screws thru the back. Use any stat you like. If the old ones are leaking around the rotating "stem" then have him replace the bodies as well.(gotta let the water out in that case)

DenverDude

Thanks- No they are not leaking. Is this a repair (switching out the zone valves) something I could do myself?

 I am a pretty smart guy, but not much experience and not a lot of tools, but I have the basic stuff.  They want to charge me $400 a peice for parts and labor.

Tim McElwain

Here in New England

we have had very good luck with White Rodgers ZV's.



The power to open power to close concept has worked very well. They have a much greater flow capacity than most valves I believe it is around 23 Cv at a 1 PSI drop.



They also only need .4 amps to operate. The three wire 1311 uses a SPDT thermostat and if the valve is replaced with a two wire the thermostat must be changed to a two wire thermostat, it will work with a three wire but you will not have the anticipator in the circuit which would perhaps affect the cycling aspect of the system.



The two wire 1361 have all the same capabilities.



The valves are easy to change just the heads but make sure when you do remove the two screws holding the head in place and not the bi-metal clip which holds the head to the valve, remove the head that way and you will get wet.



One thing that creates problems with these valves is that they should only be placed in a horizontal position, otherwise they eventually leak water around the rubber grommet attached to the paddle wheel.



They are easy to troubleshoot (I have a step by step procedure in my Hydronic Controls manual).



White Rodgers lists compatible thermostats for the ZV's in their catalog.

DenverDude

OK, after much back and forth I am having them install Honeywell V8043 2-wire zone valves

And the guy is putting in new valve bodies as well.  Tonight I am going to Home Depot to purchase new 2-wire programable thermostats.

I hope the system works!  Cold here in Denver today

tim smith

RE: WR zone valves

We have worked with these for 30+ yrs. The wiring diagrams for them are still the worst ones ever made! In multiple zv wire up, you have to pay attention or you will have zone valves constantly turning, The warp switch in them is a interesting little item. They are as other said very reliable and great CV rating. We replace power heads and seal assembly's all the time as needed. Not all are guys get the wire up so we have one guy who works on them more than the others. Good luck, Tim

Tim McElwain

Tim I have a little

system I came up with years ago. Here it is:



Any zone valves that use numbers instead of TH, TR. END SWITCH Example Honeywell  (Those are easy). They go this way



Three terminals is a three wire - power is 1 & 2  (1 breaks through the thermostat to get to terminal 1) - end switch 2 & 3. (TACO)



Four Wire- 1 & 3 Power  2 & 4 end switch (DOLE)



Five Wire - Series 80 two wire 24 volts - SPST T'Stat WR 1361-102  ! & 2 power - 2 &  3 end switch  4 & 5 TSTAT (5 & 2 are common on some of these)



Six Wire -  1 & 2 Power - 2 & 3 end switch SPDT 4 & 5 power to open 5 to 6 power to close.



If you notice there is a pattern here  ! & 2 are always 24 volt power (exception is DOLE) 2 & 3 are always the end switch. The rest is T'Stat wiring.



I have a series of very easy to follow wiring diagrams (Seven Pages) showing all different replacement wiring sequences.



An interesting bit of trivia, one community here in RI has a number of Six wire White Rodgers 1311 zone valves. Now up here in TACO land that is unusual. The interesting thing is that is also were John White lives.