Constant Circulation with Zone Valves Idea

billyboy

New house build.
Multiple zones with thermostats & zone valves, Taco ZVC

1 Alpha pump for system, line cord plugged in heating season, Constant pressure mode.

If 1 or more thermostats are calling for heat, only those zone valves are open, and
heat is added to system via ODR controller injection. (this how many systems operate)

Idea:
If NO thermostats are calling for heat, ALL zone valves are open, and
heat is NOT added to system.

This can be done with a N/C (normally closed) relay point powering each zone valve, The relay would be controlled by the Taco ZVC isolated End Switch.

Paul S_3

maybe I'm missing something, I really don't understand what your asking? the alpha is delta p pump on constant circ, tstats are usually set a little above room temps just as a hi limit....if the reset curve is set properly in the injection controller everything should operate ok....was a heat load calc done? are you worried about the pump running with all valves closed? what about a DBV I don't know if they work properly with a delta P pump, but wouldn't the pump slow down to basically nothing if all valves do shut? why not use the autoadapt mode? I don't use much alphas....I guess the the wiring can work when the iso end switch opens it will also de energize a GPR .....all zone valves will be powered through its NC contact and open...do these zones valves have end switches or no what type are they? if they do what would prevent them from making and turning boiler on? am I understanding this correctly? long day....

billyboy

I'm not asking a question, I'm presenting an idea & looking for comments.

The idea is how to achieve constant circulation with 1 pump & zone valves

Gordy

Delta p

Robert O'Brien

What are you trying to avoid? Boiler maintaining temp when tstats are satisfied and OD temp is below WWSD?

billyboy

Gordy yes, as I posted:
"1 Alpha pump for system, line cord plugged in heating season, Constant pressure mode."

Robert, what I'm avoiding is: a separate pump for each zone to get constant circulation.

Gordy

If thermostats are satisfied, and you want all zones still open for constant circulation then expect overshoot.

Whith out knowing the emitter types proportional valves should be used such as a trv at the emitters.

billyboy

I would expect overshoot if heat was still being added to system, say from a boiler, but I use buffer tanks.

All zones will be high mass slabs, I might use TRV's, if they incorporated a slab sensor as my Tekmar 519 thermostats do.

billyboy

If implemented as I proposed, any extra heat in a zone that just was satisfied would be moved into the other cooler zones.

Moving heat around in house when no zone is calling for heat is important to me as solar gain could be an issue.

billyboy

The thermostat has a delta between the temperature where it turns on & turns off, this delta in a slab would be many BTU's

Constant circulation will move heat around between zones.

Gordy

If your ODR is set optimally then it should be just adding enough btus to off set the heat losses of each zone. The thermostat would be nothing more than a high limit switch specifically for the case of solar gains in your case. Hence that zone would stay closed.

However if solar gain is a real issue, and you want to utilize it for other zones then I see your objective more clearly. How much benefit is another matter. It depends if the solar gain is designed in, or just a monkey on your back. If the latter then maybe a means of controlling the solar gain may be more productive.

hot_rod

I think it could be done with three way zone valves, draw it out. It would take some control work to drive it under the various conditions.

hot_rod

hot rod said:

I think it could be done with three way zone valves, draw it out. It would take some control work to drive it under the various conditions.

http://www.pmmag.com/articles/88410-zoning-with-constant-circulation-br-john-siegenthaler

Firecontrol933

Solar gain is a short term gain and trying to mitigate it with a long term mass emitter is going to be problematic at best.

If your goal is to stop the flow of heat into a zone that is experiencing short term solar gain by stopping the charging of the slab and then reversing the process and removing the energy already in it to try and maintain space temperature I don't see it working. Why? Because of the time involved unless your slab isn't high mass..... say a lightweight overpour.

Even if all of the solar gain issue was limited to gain to the slab itself, your tubing would have to be at the very surface to effectively remove that energy in the short term.

Solar gain is best resolved by designing to mitigate it during the design phase of the home or adding mass to the areas affected that will absorb it and give it off very slowly so as to not have much effect on the space temperature. Shading either natural or artificial also works.

One last very effective way is to incorporate a zoned forced air system that will move this excess energy to where it's needed. We installed a forced air zoning system into one home that had massive solar gains from the east and west. Once the zoning system was brought on line the homeowner reported less than 1°F difference throughout the home 24/7. You do need a system that is designed to recognize and take advantage of excess temperatures in one space and be capable of moving it to a space that needs it.

billyboy

John Siegenthaler & many others have written about the benefits of constant circulation, efficiency gains of 10-15% over bang-bang are reported.


Thanks for link Hot Rod.
U have described fig1 before & I like it except:

1. It requires a pump for each zone.
2. it does not mix water (redistribute heat) between the zones when not calling for heat.
I think this mixing can be accomplished by adding a 3-way globe valve + an in-port into the A leg of each 3-way zone valve. The 3-way globe valve would send some portion of the A leg flow to the next zones A leg in-port, etc. etc. etc.

billyboy

differential pressure bypass valves seem like a waste of $$$

DP pumps like the Alpha are the ticket

billyboy

https://books.google.com/books?id=-EgzoB9D4kQC&pg=PA346&lpg=PA346&dq=heated+floor+continuous+circulation+benefits&source=bl&ots=3knAuE3F7i&sig=RkkSA0ysn1YD90HF6Rvp0KM8BOg&hl=en&sa=X&ved=0ahUKEwj1w8ajzaXNAhUkyoMKHcl_BCYQ6AEIMjAE#v=onepage&q=heated floor continuous circulation benefits&f=false

hot_rod

billyboy said:

differential pressure bypass valves seem like a waste of $$$

DP pumps like the Alpha are the ticket

DP bypass valves were invented mainly for single speed circulator to prevent grossly over-pumping multi zoned systems, especially with micro-zones or manifold zoning loop by loop. There is still a time and place for DP bypass valves, especially if you have "banging" zone valves

No doubt ∆P circulators are a more elegant means to get a handle on over-pumping, and they save electrical energy to boot.

billyboy

Paul S

"I guess the the wiring can work when the iso end switch opens it will also de energize a GPR .....all zone valves will be powered through its NC contact and open"

Each zone valve needs a separate N/C relay contact point so-as to not feed each other. They power each zone valve independently but concurrently. They are connected onto the ZVC output to ZV terminal screw.

It requires an additional 24vac transformer with enough VA to power all zone valves concurrently through the N/C contacts.


" ...do these zones valves have end switches or no what type are they? if they do what would prevent them from making and turning boiler on? "

I questioned this also, it looks like the ZVC ignores the end switches if it is not powering the zone valves. How else could it work with 2 wire zone valves with the end switch terminals jumpered?

Just one set of zone valves with end switches.

SWEI

Firecontrol933 said:

Solar gain is a short term gain and trying to mitigate it with a long term mass emitter is going to be problematic at best.
...
Even if all of the solar gain issue was limited to gain to the slab itself, your tubing would have to be at the very surface to effectively remove that energy in the short term.

In my experience this strategy can work, even in houses with proper passive solar design. We typically use two zones even for very basic systems: one for rooms with solar gain and one for the rooms without. Opening the zone valves and running the pump (a 10-15W ECM circ) can help spread warmth to the rear rooms during shoulder seasons.

SWEI

There are no calls. The pump runs in constant circulation as long as the OAT is below WWSD. We power down the boiler and leave the pump running 24x7. It basically spreads out the thermal gain in the slab as the gain comes in. You collect more BTUs by lowering the average temperature of the irradiated portion of the slab.

We'll eventually start looking at slab temps and making smarter decisions. It's a work in progress.

SWEI

Radiant cooling can approach heating flux rates when a slab is in direct sunlight. Haven't logged the ΔT on the water yet, but an IR camera or even a temp gun will shock you when comparing the floor temps on a clear, sunny day.

bob_46

I wana know how he's gona get all the zone valves to open when none of the stats are calling without burning out all the heat anticipators ?

bob_46

Wait I just figerd out how to do it with a spdt relay on each zone triggered by the end switches. Now they won't close ! I think you would need a latching circuit that would un latch when a stat calls.

JUGHNE

I make a feeble attempt to redistribute solar gain from my sun room using the AC air handlers. The hot room RA ducting (high wall grills) is connected to the AH that supplies the cool rooms. The cool rooms RA is connected to the AH that supplies the hot room.

The sun room has infloor heat seldom needed.

This crazy scheme lets me cool my 2300 Sq Ft house (plus basement) with just one of the (2) 2 ton AC that are in the AH's. 4 tons are turned on when AC is started, after cool down one AC (my office T-stat) is switched off and the other zone T-stat is the control for the remaining AC. (Happens to be in the bedroom that is referred to as "her" room, but I'm easy ). Once cool temp is reached for the entire house, the one 2 Ton unit cools and dehumidifies pretty well. Company comes and 4 Tons on line as needed. We just went thru 2 high 90 degree days and now it is 60 overnight with 80 daytime, windows open now, etc.
(Actually should have went with 2 X 1.5 ton units.)

billyboy

OK Does my idea have merit?

billyboy

Say I have ODR injection controller reset slope (curve) set aggressive to allow for sudden cold weather.

I would have a bit of overshoot in each zone (the Tekmar 519 thermostats will try to minimize this), this will increase the probability that all zones will not be calling at one time.

billyboy

I said this wrong " this will increase the probability that all zones will not be calling at one time."

S/B this will increase the probability that all zones will be off at the same time.

billyboy

The cost of another 24vac transformer + enough N/C relay contacts (1 contact for each zone valve) would be small.

I already have a bunch of transformers & 4 pole, double throw 24vac coil relays.

hot_rod

I think the challenge with unique projects like this is determining if it really saves or reduces energy costs. sometimes the energy required to run the pumps and controls is more than the thermal energy saved or offset.

Now if the goal is to increase comfort and piece of mind moving the solar gain around, I say go for it.

If you have the time, knowledge and budget to cover it, we would be glad to hear how it works.

I doubt it would be a sellable system, but it sounds like a fun tinkering project.

It reminds me of those deep sand bed radiant slabs that are used in the Wisconsin area. Thermal panels dump energy into the bed all summer and fall, and the building "flywheels" its way through the winter. Control and comfort are in the eye of the beholder.

Gordy

What you are trying to do is btu redistribution. As Hat says the narrow delta results in little heat transfer to other zones especially high mass ones. Also remember there will not always be those days of thermal gain. If the thermal gain is considerable I would store it rather than redistribute it. Redistributing may lead to unintended consequences.