Zone Load Synchronizing - Is it worth it?

Andruid_2

I'm not sold on zone load synchronization.  If it costs a thousand dollars to install a control that synchronizes the loads in a house, how long until it pays for itself.



I'm considering this for a house with slab on grade radiant floors.  It's approximately 3000 square feet and 8 zones (I'm sorry I don't have the heat loss).  The outdoor design temperature is 10 degrees F.  And the heat source is an air to water heat pump.  The heat pump has a relatively low amp draw on startup.



The heat pump will control the temperature with outdoor reset, as there is no 0-10vdc input for third party controls.  So, zone load synchronization really is the only benefit I'm getting from the third party control.



Is zone load synchronization worth it?

NRT_Rob

first

it doesn't cost thousands of dollars to install load sync. Load sync is just one feature on a control that usually has many other features that are also worthwhile for various reasons.



If you are really only installing zone managers to do load sync, then the cost is more like a few hundred, presuming you would have used the thermostats anyway for other excellent features like predictive logic or floor sensing, networkability, etc.



so anyway, back to your question. Is load sync worth it? in your case, I don't know. You probably need a buffer tank of some kind with your heat source, and you have high mass radiant. load sync probably won't be much benefit in that case.



other features inherent in your control system are probably more worthwhile.

scott markle_2

I vote yes

I think you are overstating the price difference a bit, between conventional stats and zone relay VS. a synchronizing control such as the tekmar TN2. If you want this much zoning your already committing a lot of resources to thermostat wiring, zone valves, isolation, etc. Were not supposed to discuss pricing but i think if you subtract the cost of all the conventional stats and relays this upgrade is less than you state. Considering the significant cost and relitivly long payback periods of a Ground source geo/radient system I think it's silly not to include this.



Alternately I'd consider pairing down the number of zones even consider omitting indoor feedback altogether if the house is tight and doesn't have any crazy glass features this can work fine for a set it and forget it type. Balancing manifolds can help match areas of the house with different loads. Do you really need this much control, slabs are so sluggish anyway , they are not well suited to setback and will disappoint the user who wants to make frequent changes to a thermostat setting.



If you feel you must have so much zoning and don't want to use a synchronizing control consider leaving a perimeter loop of each individual zone"wild". IE don't kill all the loops in a zone when the stat is satisfied. Leaving a perimeter zone wild will help moderate the inertia issues and micro load cycling.



Also I believe that honywell makes a paired down AQ zone control that does synchronization without all the other stuff.

scott markle_2

zone sync without boiler control

Rob,



Can you wire a Tekmar zone manager without a boiler control (420 or whatever)? How does the zone manager get it's power?



While the backside wiring on the newer tn2 house controls and need for an external transformer is a bit less tidy, I appreciate the lower cost of this this line and the two wire thing is huge for retrofit.

NRT_Rob

not sure about tn2

we haven't been using tn2 because we don't like the floor sensor interface (which might be fixed now) and they have not had a 2 stage thermostat. we might soon though... it sure is nice to have a 2 wire option.



in tn4 the zone manager has its own transformer, so you just line in, and the reset controls get their power from the zone manager, not vice versa. You lose indoor feedback and other boiler control features of course, but you keep zone sync, program master, etc.

Terry O

Check out an AQ Honeywell

Honeywell AQ controls offer zone sync and many other features for far less than $1000..... and we have had pretty good luck with them!

burky1957

Tekmar tN2

For 8 zones, use two 313 or 314 tN2 wiring centers with four tN2 thermostats per wiring center. This will give you zone synchronization. You can add an 033 timer for setback schedules for all the zones. By adding an 070 outdoor sensor, the outdoor temperature will be displayed on all the thermostats. This can all be done without a house control.

Andruid_2

What I'm feeling so far . . .

I don't believe I need the synchronization.  I have an air to water heat pump with a variable speed compressor (modulating heat source) that has outdoor reset and DHW control already built into it.  I'm heating a high mass radiant slab and pumping with a Grundfos Alpha.



Am I right in believing that even my smallest zone will get a sufficient run time even on a mild day (thank you high mass and outdoor reset).  If that's the case, what's the point in using synchronization?

NRT_Rob

well

I assume you have an Altherma since it's the only modulating ASHP I am aware of.



if so, you need several gallons of water outside the unit to satisfy its buffer requirements.



so if you use a buffer tank, you don't need zone sync. OTHER features that may come with a sync system might be nice, like master programmable thermostat type stuff or floor sensors, but not zone sync itself.

Mark Eatherton

The worst thing you can do to any piece of mechanical equipment....

is turn it ON. Especially if it is a bang/bang heat source (either BANG, its on, or BANG, its off). Modulation is the key to efficient operation. Sounds to me like the only missing component you are short would be modulating flow (non electric TRV's at the point of load). But even with a modulating heat source, you will eventually have some short cycle issues, and that is where the buffer tank comes in.



If it were me, I'd use a large reverse indirect as your buffer tank, thereby preheating your DHW with the ultra efficient heat source, and giving yourself a convenient place to park BTU's, wiating for enough demand to run the compressor continuously.



When is SOMEONE going to come out with a variable speed GSHP? If and when they do, I will jump back into the arena. Until then, I am not interested... I know that Florida Heat Pump Co (now Bosch) threatened to but not sure if they ever did, and  can't tell by looking at their web site wether they did or not.



ME