Zone valve vs circulators

Unknown

really needed on most applications ? Just looking at the Taco IFCs we use , the check looks like it impedes the flow more than if we used a regular circ and Honeywell zone valves . Even a flowcheck looks pretty restrictive . We've had a discussion in the past about zone valves and indirect tanks and you said it might not be the best choice . I guess my question is about the amount of flow using both methods .

[Deleted User]

Zone valves vs circulators?

I am replacing an old oil-fired boiler that drives hot water through baseboard convectors. Total square footage is around 2300, and the calculated heat loss is around 60,000 btu. There are 3 heating zones and one zone for an indirect water heater. Two different plumbers have proposed Munchkin 80's, but one recommends a single pump and zone valves, and one recommends four circulators. The first guy says circulators will push the water too fast and possibly miss my 2 toekick heaters; the second guy says circulators will maintain constant velocity no matter what the demand. This is probably an old boring question to you pro's out there but a search of old posts didn't reveal an answer - can you give me some feedback on these two points of view?

Joe Brix

A long standing debate

But many will at least say put the indirect on it's own circ. For 3 zones with only 60K of heat loss, I'd say 1 circ with 3 zone valves: save energy. I would also recommend outdoor reset and priority controls for the indirect. No sense in getting more boiler then you need.

Ron Schroeder

Neither plumber seems to have a good grasp of hydronics. A circ won't push th water too fast and "miss" the toe kick heaters. That just can't happen but too much velocity can cause many other problems like velocity noise, zone valves slaming close, excess electrical usage etc.

Also a circulator doesn't maintain a constant velocity no matter what the demand. The velocity will depend on the pump curve and head that the circ. sees. The circ. or circs. need to be sized for the specific system.

My personal preferance is to have one properly sized circ. for the indirect with proper sized piping and flow-checks to get the rated recovery from the tank and a seperate circ. for the heating zones. Each heating zone would have it's own zone valve and flow-check. Depending on the particular system, the heating zones might need a differential pressure bypass.

Zoning with valves will usually save electricity. A typical circ draws about 80 watts while most zone valves draw less than 20 watts each. Some like the Taco ESP, Caleffi, Danfoss etc. draw less than 3 watts each.

When you get your new system piped, make sure the expansion tank is on the supply side and the circs(also on the supply) pump away from the expansion tank. The circs should not be in the return.

Some people think that multiple circs. will increase reliability since if one fails, not all of the zones fail at the same time. This could happen but it is very rare. I sometimes use 2 circs. for heating on larger systems and put half of the zones on one circ. and half on the other. By using isolation flanges on the circulators, a failed circ. can be changed out quite quickly without having to drain the system.

Ron Schroeder

Joe Mattiello_2

nicely done

One more potential problem because of velocity is erosion. Residential systems should not exceed 4 ft per second.
Joe Mattiello
Technical Support Technician
Tel. 401-942-8000 X 484
Fax. 401-942-2360
1160 Cranston St
Cranston, RI 02920
joemat@taco-hvac.com

Ron Schroeder

Hi Joe,

How about a Taco ESP in 1 1/4" with a FULL PORT ball valve? I have had several installations that could have used a zone valve with the same Cv as the pipe that it was in.

I'll try to be good until Christmass since I put it on my wish list. ;-)

Ron

Joe Mattiello_2

ESP valves are not full port.

Are you inquiring about an ESP full port version, because they are not full port? Joe Mattiello
Technical Support Technician
Tel. 401-942-8000 X 484
Fax. 401-942-2360
1160 Cranston St
Cranston, RI 02920
joemat@taco-hvac.com

Ron Schroeder

Yes, I know, but if you ever come out with a 1 1/4" model, make it a full port....please, please, please...

Jed_2

Joe

That's what I thought, but... the reps are trying to tell me they are full port, or nearly so. They are larger than most ZV ports, though. Nice valve. How's the return(failure) rate been on them since the re-design?

Jed

John White

Returns

Jed,
The return rate is essentially nil since the redesign.
Like all Taco Products!!!
Interested in any other ESP feedback
Thanks, John White

Paul Pollets

ZV's with PBD

I'd be using one circulator with 3 zone valves and a pressure bypass differential to protect the pump from dead-heading as the ZV's close. I like a separate circ for the indirect, but if it's on priority zoning, it wouldn't matter. I use very reliable actuator heads like Oventrop on a TRV body. which comes in straight or angle. Why use so many pumps when the flow rate for each zone is under 2gpm, except for the indirect?

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Weezbo

Pump Happy *~/:)

pumping away and pump happy is a bit like choosing the correct amount of Xd nails for an application vs nailing as many as the board will contain without requiring welding:)

Ron Schroeder

Hi Paul,

I always use a seperate circ for the indirect, even with priority zoning. Otherwise the indirect's ZV would be a bottleneck. If Taco ever makes a 1 1/4" full port ESP (another blatent hint)I might change that.

What size TRV bodies do you use? What is their Cv?

Ron

Joe Mattiello_2

ESP 3/4\" has a 8.4 CV


Hi Jed
The ESP as I mentioned is not a full port valve, but why are you getting hung up on a full port valve? The ESP has a generous 8.4 cv, assuming maximum flow through ¾” piping is 6 gpm if we do the math (6/8.4) squared = .5 psi pressure drop, or 1 foot of head through the valve. The ESP valve has been very successful in the field and look forward to an esp suitable for an open system.

Joe Mattiello
Technical Support Technician
Tel. 401-942-8000 X 484
Fax. 401-942-2360
1160 Cranston St
Cranston, RI 02920
joemat@taco-hvac.com

Jed_2

Thanks, Joe, and John

I'm not really getting hung up on the "full port" thing. But some of my cusomers have( why, I don't know--they've been using the old standards for years). They just look through the port and say, hey, that's not full port. It's a nice valve, with great features. I insisted on it for a multi-zoned chilled water system with five SpacePak air handlers, and Multiaqua chillers. Works great. Wanted to use circs, but, alas, couldn't get the Load Match circs in time. As it turned out, those circs on the Multiaqua's are beasts, so no problem with the ESP's. I will save your response and have some good rebutle( I know, it's in the spec sheet).

I will definitely spec the ESP's on all ZV systems. I will be surveying a very large HVAC system this month for recommendations to switch to an HV heat/cool changeout for the same client as the chiller system. This will be a complete revamp of a way over-engineered beast that is grossly inefficient.

Thanks, Joe, for your support. You have helped me. I went to Bruce Marshall's class last Tuesday, and think he is great. He also advised me and a customer on an unusual control application. Ask him about it. I sent him a Visio drawing based on his vision of the solution. This is the kind of technical feedback a dumby like me needs.

Thank You,

Jed

Ron Schroeder

Hi Ron Jr.,

In most cases a full port ZV is not needed, in fact a more restrictive valve is sometimes an advantage as it will tend to balance zones.

In a few cases a full port valve can allow a smaller circ. For example, a Buderus LT-160 indirect and a full port 1 1/4" ZV with all 1 1/14" piping and minimal elbows will reach it's rated 15.4 gpm thru the coil with a 007 circ. With any more restriction than that, it would take a larger circ.

You can put an indirect on a zonevalve but it takes a larger circ or the recovery will be compromized. .....but in some cases even the compromized recovery is far more than the customer needs.

By the way, under flowing an indirect coil will not take as many BTUs from the boiler and can promote short cycling of the boiler durring DHW recovery. Changing from 1" to 1 1/4" piping to my indirect changed the number of burner fires from 3 burns to only one long one on each recovery of the DHW tank.

Another example for a full port ZV would be if you had a full port zone valve between closely spaced 'T's in a primary loop, you could divert to the seconday loops (if they were low restriction like boilers)without additional circs. I have done similar with full port ball valves to manually select main and backup boilers with just a single valve per boiler.

Ron