Zoning with pumps vs. ZV

You have to watch when zoning with pumps. Very easy to install 500W to 1kW of pumps which might cost you $100-$200 in electricity per month just to pump water.

To me the simplest and most flexible is a single delta P pump with manifold. You can put actuators on the manifold if you want thermostat or TRVs right on the rads or leave some of the zones always on. If you want a larger zone with many rads, you can add a 2nd manifold on its own zone valve.

The a nice bonus about this type of setup with a modcon or heat pump is you don't need to control the pump at all.

In europe we use one Circ and TRV's/Zonevalve for energy savings and ease …kinda like Kaos mentioned. This topic has been discussed many times before and everyone has a different opinion. 😑

I have a house with some honeywell zone valves that are 40+ years old and work just fine. In another house replaced (the motors) 3 on of 4 honeywell zone valves that were installed 10 years ago. Think the quality has gone down hill badly.

In uk zone valves are about £100 and a small grundfos pump £150, so it is pumps for me every time. The newer ones with electronic controls the power consumption can be quite low - not quite as low as zone valves but close. With older fixed speed pumps the power consumption does add up quickly.

Each job has it's own "Best Way" to zone a system. I am not adverse to zoning with pumps as long as there are only a few zones. 40 years ago, when the most common circulator pump was the B&G 100, zone valves made sense because the pump performance curve on that circulator was excellent for the small GPM of only one zone valve calling, and was equally well suited to the larger GPM of all the zones calling at the same time.

When you design a system with more that 5 zones, the valves are the way to go. Perhaps a 10 zone system may have 2 pumps (5 zone valves each) or you might use a priority zone pump for an indirect DHW tank and a system pump for the CH zones with several zone valves. You just need to do the math to be sure that you are not moving too much water thru the boiler too fast when you have say 8 zone pumps operating all at the same time moving 32 GPM on a 125 BTUh net boiler. That much extra water flow may not have the most efficient heat transferring ability.

As I said in the beginning of this post: "Each system design has it's own 'Best Way' to zone the system". I use both Valves and Pumps depending on the circumstances.

It's almost impossible to have too many per circulator unless you're restricting the pump to the favorite 007. Choose a proper pump and you can run ten zones. If I were going to run 10 zones, I'd select one ECM DP pump.

………….easily solved with a few butterfly valves on the closest zones with the least resistance.

I agree, without some sort of flow control, some zones will be left waiting…………….I have that situation in the house with 9 zones. The flow upstairs is compromised when the three rads below it are calling. Thankfully, upstairs needs a fraction of the output as compared to the first floor.

There is two different setups we need to look at. Something existing say a two storie house with baseboard loop for each floor, two pumps. If those are monoflow it gets more challenging as high head pumps are spendy, at that point you are probably better to look at single pump with zone valves.

Anything new build, if the setup is not home run, you are wasting your time and not doing the home owners any favor. Even baseboard heat, each room should be run back to the boiler. You don't have to deal with multiple pipe sized, many fittings, trying to wrestle 1" pex, or leaks along all those fittings. At that point single pump and manifold is the way to go.

If you also plumb a good chunk of the house as an always on zone (ie main area, kitchen/bath/mud floor heat) you can save on zoning.

The main thermostat now only needs to control the main circ or the boiler. The 2nd floor bedrooms can be on a slave zone (heat only when main zone runs) as you generally want those to run colder than the rest of the house anyways. This has the bonus of putting a large minimum load onto the heat source which avoids short cycling.

With a good outdoor reset curve, you can even skip the main floor thermostat but that is hard to sell. This means you can run a typical 4 bed house place with a single delta P pump, two thermostats and 4 zone actuators (3+TRV on gest bedroom is better) even if there are 10 zones on the manifold.

@Big Ed_4 Any zone valve setup, manifold or discrete valves, you want a delta P circulator. Since these run in constant pressure mode, the flow rate through the zones does not change when other zones open. This makes it really easy to commission, turn on all zones, set the the flow for each once and done. Works great.

Which is better…..well that debate has been raging for years. We did a webinar a little while ago that put that debate to bed!

Watch it here!