Admittedly a newbie, I've seen a number of schematics for multi-zone radiant systems in which the zone flow is controlled by individual circulators rather than having a single circulator and individual zone valves. 

I can understand this in large systems where a single circulator is not big enough, but, is this approach preferred even for small (2-4 zone, small sq ft) configurations?  I ask this because I've seen small off-the-shelf MZ systems in which the zone flow is via individual pump.

Circulators seem to be somewhat more expensive than zone valves, require higher voltage control, and, I would expect, don't turn 'off' completely as a zone valve would (ie, any back or forward pressure might leak through the circulator)  This last one might not be a real problem, just imagined by me as I think about the construction of a pump vs valve...

Tom

There really is no such thing as an "off-the-shelf" condensing boiler. MZ is one of the few condensing boilers which does not modulate (a severe handicap in my opinion). Their are several factors involved in choosing cirulators over zone valves including boiler/system flow, number and size of zones, distribution system efficiency and others. It all starts with a heat load analysis. I use zone actuators for most of my residential work.

Sorry, I wasn't clear.  I wasn't aware there was a boiler called 'MZ',  I didn't mean this.  I meant to say multizone system.  I was referring to prepackaged systems with manifold, controller, and individual circulators.

Tom

Your question is one that seasoned professionals disagree about regularly. I doubt you will gain helpful knowledge here or elsewhere, as these are specifications properly determined by many design variables based on the system to which they will be applied.

Actually, your response was just what I was looking for - there isn't a hard and fast rule for one over the other and the one that seems right for the application is probably as good as the other.  I was just trying to avoid making some 'catastrophic' mistake in taking a zone valve approach for my application.

Thanks!

Tom

I disagree with Morgan.

We used to be a zone by pump house, because zone valves we were aware of were unreliable.

That is no longer the case. Most thermal actuators or zone valves out there today have very nice, long, reliable service lives.

Prepackaged panels use pumps because they don't know what you are hooking up to, and whatever it is probably is not "designed", so they are taking a "CYA" approach.

Beyond not believing what you can do with flow (as I've said elsewhere, most homes up to 5000 square feet can be pushed with just one UP15-58... the same pump often used as a "zone pump" in pump zone systems), and some argument about "the whole system not going down if a pump dies"... which doesn't apply to most mod/cons since they all have boiler pumps that, if failed, take out the whole system... I don't see any reasonable argument for pumps these days. Other than the obvious "no one is doing the math" which would favor pump systems.

But, five years ago you would have seen me argue just as passionately that attempting to use zone valves would doom you to a lifetime of head replacements and reoccurring failures. Things change ;)

How many people do you suppose, on this blog (or the RPA for that matter), fully understand what you just said? I agree the pre-packaged panel is over-pumped by design.

I am a minimalist like you, but find situations where a 1558F will drive a whole house, and others situations where multiple pumps satisfy minimum flow requirements for freeze protection, indirects, heat exchangers etc.

As for reliability; I never saw the argument to start with. We have both changed pumps AND zone valves decades old. I like the new zone actuators most (for their low energy draw) and use them on radiant floor and Euro-panel designs, but still employ a lot of pumps using multi-speed settings for very exact balancing.

As for pump failure. I often use a single pump with bypass for many of my ModCons, but if I use two or more, the ModCon pump must go down to kill my domestic hot water and my space heating both.

As I mentioned, I doubt this friendly exchange will help the DIY guy and still wonder why I a novice will spend thousands of dollars on system he knows virtually nothing about, but not a dime on a RPA certified designer like say... you!

heeheehee

to be clear, when I say "one pump" I mean one system pump for zoning, I'm not talking about domestic, heat exchangers, or primary/secondary piping arrangements. Those are all separate issues.

Having working for a company that sold the old wirsbo actuators and sparco zone valves, I can tell you: it made me stay away from the ZV technology, for years. Perhaps other brands were better, I don't know.

I also disagree that this is "unhelpful" to a DIY guy. I don't have anything against DIY; if you've got the time, more power to you. however, it often means making decisions like doing a harder-to-screw up zone pump system instead of zone valves, but you need to know what the tradeoff is. It is, quite simply, multiple times as much electrical usage, forever.. it won't break the bank, of course (unless you are doing a sick number of zones) but calling each pump $5/month on an outdoor reset heating system is not wildly out of line either.

We manufacture a 1 1/4 T stick for zone valves and one for pumps , 1 1/4 w/ 3/4 T on a 4 inch pattern for zone valves, 1 1/4 w/ 3/4 T on a 8 inch pattern for zone with pumps, Combined with 1 3/8 cushion clamps and some unistrut and you will have a good start to a clean mechanical Room, less cost than the pump in a box approach.
Depending on the size of house, usually will determine the type of application. For instance a larger home may have 7 manifolds, it is not uncommon to sub zone a manifold or 2 with actuators and have the primary zone work done with pumps. I like pumps, easy to wire, easy to do diagnostic, easy to swap, easy to balance, positive distribution....
Dan

and only wasting electricity forever, what a deal ;)

If you include wirsbo/sparco actuators as "zone valves" I understand your trepidation...poor guy.

heheehohoho

Actually, this DIY guy knew exactly what Rob was saying and I appreciate the info.

I don't mind spending a 'dime' on an RPA certified designer for my new house (assuming I can find a good one locally) and I might even pester Rob to help me convert my house in Belfast, ME (when I get around to it).

The beauty of this forum is that we DIY guys can learn what's important and what isn't and then make knowlegeable decisions on who and what we should do for each of our projects.

In this case, I was mostly thinking about my small workshop system for which y'all been so helpful in another thread.  Keeping everything but the pump at 24 VAC greatly simplifies my thermostat setup and, if I use valves with built in end switches, then these can control my pump directly without any additional controller (might need one relay depending on the voltage rating of the end switches).  The hot water heater has it's own temp control.  

Tom

Rob, I am guessing you have done the math so When you heat that 5,500 square foot house and only a 1,200 foot area is calling for heat is running that big pump cost effective, because on the build out actuators cost about as much or more as TACO 3 speed or what ever your pleasure pumps. Keep in mind I am talking about manifolds with say 4-6 circuits as one zone/one pump.
One big pump has got to be sucking some amps when it is only hitting a portion of a home?
I know as Badger says it is the o'l argument of preference, We supply one particular designer like this all the time, a 00-11, 12 loop manifold, 500 foot loops and a pile of actuators. Not my recommended system, I am confident you keep your circuits short but its the same basic design, right, why not a couple of pumps, Is the performance cost that different?
And yes I have not actually done the math on this one.
Dan

Dan,

I push 5,000+ square foot homes with the same lonely little pump (UPS15-58, similar to your "taco 3 speed") that is most commonly used on zones of any size in residential building, though I might have to run speed 3 instead of speed 1, you'll note that's not a huge differential in power usage. I am not using large pumps with higher amperage or voltage draws: they are not necessary. When I do run 500 foot loops, you can rest assured it's because the flow rate requirement is extremely low, not because I up-sized a pump. I never run a larger pump than necessary to push the flow I need, and I size my loops to make the minimum size pump work. We also, of course, use a pressure bypass if small zones are present to keep the pump stress and noise factor down.

Pumps might be cheaper in some cases, but on larger loop count zones, I just use a single zone valve for a whole manifold instead of actuators. The cost is very similar to a pump.. except for operational cost, which is much lower of course. In the end, a zone valve system will be slightly more expensive because of a few additional loops to keep head down, a bypass, and overall material costing. But it won't be much more expensive, and it will be much more energy efficient, and much more "tweakable" as far as balancing is concerned. Unless of course you really cram some resistance in on your zone pumps which doesn't help their power usage or lifespan any ;)

Two pumps is fine too. If you only have two or three zones, the difference is small. But on larger zone count systems, zone pumps are simply a waste of electricity and bad design.

It's a "matter of preference" in the same way lots of things are "matter of preference". That doesn't mean that zone by pump is as good as zone valve systems for anything more than a small number of zones (2, maybe 3). It just means some people don't prefer to design their systems for energy efficiency. I can't really sugar coat that for anyone: there is good design and bad, and zone pump systems are, these days, largely just bad design. I'll fault my own ignorance for sticking with them myself as long as I did but I will defend the choices I made at the time as the best I could make with the info I had in those days. Now I have better info and I make better choices. Such is life. The difference isn't worth shooting anyone over, but if you know how to make better choices, why wouldn't you?

This all holds true, unless the zone valve designer is like that other guy you're talking about. Then you'd be better off with several smaller pumps instead of one big hog. That's truly poor design.

And to think my hero used to be Super Man!

Go get'em Rob:).

Ok Rob,
I like both systems, I like zone valves, I like pumps, We design both ways, and we developed as I said earlier a nifty manifold stick just for zone valves for zoning manifolds, however we would place all zone valves in the mec. room, home run supply/returns.
Soooo I went and did the math (searched the math net)
Here is how it breaks out, I had to cob together a couple formulas,
Example;
20 volts * 355 amps = 7100 watts
7100 watts / 1000 = 7.1 kilowatts
7.1 kilowatts * 20 hours = 142 kilowatt hours


Amps x Volts = Watts. Amps x 120. 1 amp would dissapate/use 120 watts of power.

.75 amps X 120 volts= 90 watts x 24 hrs day=576 watts day x 30= 17280 watts month /1,000= 17.28 x .11cents KW =$1.90 per month running pump 24/7

.75 amp = TACO 3 speed 1.1amp on high speed
.11KW is NW rates

when you look at the cost of bypass valve ($85.00 or so and labor/additional parts) that adds up as well. I agree it is less to operate, but is there a huge difference ???

I checked a TACO zone valve power consumption, you are right there is a large difference here.
12.84 watts charging moving?
1.44 watts stand by

Dan

I'm not sure of the math you are doing. why are you calculating volts and amps when pumps are already rated in wattage?

at any rate. 90 watts x 24 hours a day is 2160 watts/day, not 576, check your math. Multiple your cost to run by about four and you're more accurate. about $5/month, as I said, which is not unreasonable (and assumes a pretty low electric rate these days.. many people pay close to double that rate).

Again though, it's not about cost justification. it's about efficiency: it doesn't cost much more to design around one pump instead of X pumps. It saves energy to do so. It will pay back: and after that, it's just reduced energy usage.

If you save $10/month on two pumps for six months a year, $60/year savings, the bypass has a 1.5 year payback. not bad. add a couple more loops, and payback is still in a reasonable timeframe. But the real payoff is, If the cost of electricity doubles, you don't have a big power hog hung around your neck. and in the meantime, you can balance a system much more aggressively because it's not wildly overpumped.

again: this isn't so critical I would shoot anyone for it. But a bank of pumps simply says "don't care, and didn't do the math". It's not good design. I guess that might sound like I'm shooting someone for it, but you can compare this to my comments about "proper" systems in low load environments and see the difference in tone pretty easily I hope ;)

ouch, my bad on the math, thanks for pointing that out, so much for thinking during my first cup of Joe.
So this presents a compelling argument in favor of Motor Zone valves......
Very good, You still might double or triple that additional cost for the by pass and labor, especially if you are using multiple manifold locations.
Dan

Yes, and now have some fun. With the new ECM pumps... the pump might go to triple the cost, but it drops the bypass... AND will vary its power draw down to very nearly zero.

Now you can have a multizone pumped system for a very small power consumption, not even the basic 90 watt circulator. only question... how long until pump replacement is needed with one of those things? not sure...

Or, what happens if you have 4 zones and you drop 3 pumps. 5 zones, dropping 4? Payback gets pretty darn quick with higher zone count systems.

OK I'll bite, We sell a lot of TACO and B&G but I have yet to hear of the ECM option, perhaps I am not seeing what you reference clearly. I understand how this would be a great asset,what manufacture has this option, or is ist a control function like TEKMAR injection?
Dan

Wilo EcoStratos is the only one available right now in residential sizes. I think Grundfos is the next up to bat with the "alpha". I've only used one so far... going to see how it goes... but the technology is the future, for sure. it's been big in (of course) europe for quite some time, and in commercial sized systems.

Wilo. I just attended one of Ziggy's courses and think you will find they will last for decades. Motors like to run and if you have ODR, they should run for the entire season.

I have several specified, check back with me in a decade or two:).

Actually, with multiiple, muti-speed pumps, it is possible to use less energy as each is designed for a specific task and energy is used by pounds of water moved. I my zones are unusually different e.g. heat exchange or snow meltiing, radiant floor in basement and one for the garage I might opt for many pumps. These pumps rarely run at the same time and properly balanced, use only the energy they must. This is a very common commercial practice.

Lets face it, if it was easy we wouldn't have much to do.

I like it,
Dan

right sizing pumps are very important it's true. but until they make properly sized circulators for residential zoning... which they don't, unless you're aware of an optimized 1 GPM pump out there I haven't seen... that pump does not exist for zoning these days. when you have multiple temperature loads, obviously you have no choice but to pump. at least until someone invents a mixing zone valve ;)