Wilo Stratus with TRVs

Harvey Ramer

Will the Wilo Stratus or the Grundfas Alpha work in a radiant system with every zone controlled by a Thermostatic Radiator Valve? What happens whe every zone closes and the pump is deadheaded?

If this does not work would it be a good idea to run your piping as though you were putting a differential bypass in, but instead of the differential bypass, install a normally closed TRV with a remote sensor set at 65 degrees, somewhere in the center of the house?

I am not very good at writing. My paragraphs typicaly consist of 1 sentence. Hope you all can make cents of it.

icesailor

WILO Stratus & TRV's:

The Stratus if it is the variable speed pump, will slow down to almost nothing when confronted with your situation. I saw this in a demonstration at a WILO Eat and Peek at the supply house. I replaced my Taco 007 with one that runs 6 Taco 571 zone valves. It works well, No problems. But the pump will stop as the zone valves close so it should never be dead headed.

You should have some sort of zone control with a thermostat along with your TRV's I would think. Or, at least the room with the thermostat should be set lower than all the other rooms with the TRV's.

IMO.

Simply Rad

the perfect system

Harvey......Some how you stumbled into the" in my opinion" perfect system.  First, the Wilo or Grundfos (EMC) pumps are the number 1 energy saving devise in our industry right now. Next, you are going to have the ultimate in comfort with the concept of continuous circulation.  The pump is hopefully always pumping, that's the perfect world, to TRVs that modulate flow....with a full range of flow.  The TRVs are non electric so no control wiring or transformers.  Simply and elegant!  The final piece of the puzzle is fine tuning your heating curve on your heat source.  Make sure the heat source(boiler?) is set up deliver the supply temperatures that closely represent your heating loads.  Outdoor reset is the concept...basically the colder it is outside the warmer the heat source and vise verse of the warmer it is outside the cooler the heat source.  This is a very important concept to help maximize the comfort level with the TRVs. 



By the way how did you figure out the idea of the Wilo and TRV system



Happy Holidays



Jeffrey 

Unknown

ECM Pumps With TRV Systems

Interesting question.  In reality, an ECM circ wouldn't "see" a TRV any differently than a typical zone valve.



Deadheading is no problem due the Delta PV control strategy (lower differential head at dead head vs max speed).  This control actually tries to track a system curve, reducing differential head as flow and friction loss decreases.



The ECO has a max wattage of 59 Watts at full speed and 5.8 at zero flow.  Deadheading a constant speed circ is a heat issue (especially a wet rotor).  I can assure you there is no heat generated at 5.8 watts.



One other "interesting" thing to consider...  On "non-radiant" systems with TRV's and system setback what happens to the TRV's when the system fluid temp is lowered by system setback (if there is one)?  They will likely open - causing an overall system flow increase and more power to be used by a standard circ.  ECM circs have an user selectable "pump setback" feature -  when the pump "sees" a system setback it will run at min speed, automatically returning to normal operation when the system returns to normal operation or there is a call for heat during system setback.



Difficult to explain but way cool non the less...

furnacefigher15

TRV

Nothing changes with a TRV (thermostatic radiator valve) with setback or reset. They respond to space temperature, not water temperature. If a TRV sees a drop in space temp, the valve throttles open, regardless of system water reset temperature. However if the reset temperatures are too low to provide any heat, then the valve will be wide open.



As far as a trv out in a random location, that seems unnecessary. If using a typical pump, I would opt for the differential bypass.



As far as wilo goes, I'll defer to them.



Side note:

If the radiators are fed from a monflo system, no bypass is needed, and a ecm motor may not save much energy

Harvey Ramer

I was thinking

I was thinking of using the I-Series (w/outdoor reset) mixing valve from taco to adjust water temps.

For the heat source i'm still not sure. mod/con boilers have minimum flow rates so I would have to add a primary circ. AO Smith has the Vortex water heater now which might be better suited to this application. It is 96% efficient, very speedy recovery rate, 6 year warranty and 60 gallons of hot water to slowly trickle into the system.

I have been researching for quite a while trying to design a system that takes minimal amounts of electricity and costs way less to install without sacrificing comfort and efficiency. I live in an area with lots of Amish folk and they don't have electric. This system would have to run off of a small solar panel charging a couple 12 volt batteries then running through an inverter and so powering the system. Every watt counts!

Harvey Ramer

Is it not true

that a circ, when deadheaded loses any resistance. ( It would see zero head pressure? Will this pump not try to maintain a certain differential pressure? It would seem to me that in this situation the pump would rev up trying to create a pressure differential.

Don't get me wrong, if you say it can be deadheaded I believe you. I'm just trying to wrap my mind around it.

ChasMan

Magic Alpha's

The Alpha doesn't seem to mind being deadheaded. Doesn't complain no matter how fast I close the valve. They do not like air however, even when you set them to fixed speed three, they will not help much if you have air in your lines so make sure your system is easy to purge.

Also, the flow dynamics of an Alpha are not the same as other fixed speed circulators I have had like the Taco 007 and the Grundfoss 15-155. It is difficult to describe but if the pump is close to an elbow it tends to surge ever so slightly which causes the IFC to clatter more than on other pumps so try and accomidate a longer length of straight pipe in and out of the Alpha.

Also, regarding Convectors and TRV's and ODR. The concept works perfectly well however, when the temperature drops rapidly 50 degrees outside in two hours, mass and insulation is your friend. It doesn;t work all that well in a drafty house. You will apopreciate a control that allows you to boost the temperature of the boiler when you have company and bring in a load of firewood or something and want to take the chill off fast. Some controls make it easy. Others, push menu up arrow button five times... go to installr menu, select x then y... Crazy stuff. Not mentioning any names DeDietrich

Unknown

ECM vs Standard Circs

Furnacefighter - I have to tell you your Wallie name is excellent.  I had Dan over to WILO years ago and he quickly pointed out our biggest competitor in the USA are the forced air guys.  Never a more accurate statement said!  But on to the explanation of ECM...



A standard circ will increase it's differential head as the flow decreases (trade off, less flow more head and visa versa).  That's why it tough to keep zone valves lasting and controlling heat in shoulder heating seasons.  And it causes noise when the last zones are trying to close (unless there is an energy using by-pass).



ECM pumps have a permanent magnet rotor.  The software in the brain (VFD) sees the relationship between the spinning magnetic field of the rotor and the motor stator.  When a valve in the system opens or closes the circ sees the pressure "push back" or change on the discharge of the pump, sees a change in the rotor/stator magnetic field relationship and adjusts it's speed and differential head based on the setting of the circ's control logic.



Differential Pressure Variant (Delta PV) is simply the relationship between max speed and dead heading.  When an ECM circ is set at say 12 feet, that means it's 12' at max speed and exactly half of that at zero flow (6').  This is referred to as an inclining performance curve - less flow, less differential head - the opposite of a constant speed circ.  Remember, a friction loss curve is inclining as well - and overcoming friction loss is all a circ is there for (while providing flow).



And, you are correct, variable flow circs are not recommended for mono-flo systems.  They are constant flow and require the right water velocity across the tees for them to work.

SWEI

mixing valve?

Should not need a mixing valve at all if you have only one type of emitter and everything is sized right.  Mod/con boiler will manage the temp and handle outdoor reset itself.



A smart circ is going to cut your electrical load significantly (in addition to just working better overall) and you can make it all work with just one circ if you pick the right boiler and pipe everything properly. If you use a diverting valve instead of a separate pump for DHW, you can shave a few more Watts (and maybe even a few dollars as well.)