Zone Valve durability

Techman

Can a HW or Erie(Pop Top) Zone valves,24v, be energized for months on end ,24hrs/7days a week? This is on a radiant system.Both Zone Valve and System Circ ran & ran & ran.

hot_rod

Sure. We estimate around 5000 cycles per year on a typical zone valve in a heating climate like N Wisconsin. We datalogged a system there for a winter. We cycle test Caleffi ZVs to 100,000 cycles, so a 20 life expectancy.

System conditions effect the life expectancy, operating temperature, fluid quality, number of cycles, load on end switches, input voltage, etc. Just like any electro-mechanical device.

I'm not fond or N.O. Zvs. Some engineers design dorm and apts with these to assure a no power condition allows all zones to open and hopefully prevent freeze up. But this keeps power on the valve for long periods, like the entire no heat season, up to 9 months in some climates.

Curious auto why the circa and valves are 24/7? Not a typical load profile?

If for some crazy reason that is required I'd look at a low current draw thermo-electric style ZV. Less power consumption and no current draw in full open, on most but not all brands.

Techman

Tks. These Zvs are NC. This one particular zone is rated at 0.2gpm/0.4 head/(1) 175' loop.And with all of my radiant wisdom( I'm a newbie w/ this) I think the zone by itself is so small and does not bring on the Injector Circ.The enable sw. is set for 10% on & 5% off. By raising other zone temps ,then the cold M. Bath floor starts to get warmish. The HO says, no warm toes for 2 years, system new, 2 1/2- 3 years . Only a few hints of not cold floors in this zone.

Harvey Ramer

Hey Terry,
How is the tubing installed in this bathroom? Stapleup, extruded plates, above floor, ect...
Also what kind of insulation is underneath? How many exterior walls and are the rim joists sealed well? Big windows or rugs? Is it central to the house without any exterior exposure? If so that thermostat may hardly ever call for heat leaving you with a not warm floor. Bathrooms typically don't have a lot of floor space left over to act as radiant heat source. I have done some bathrooms with extruded plates and the tubing spaced every 4" to provide sufficient heat. If the entire system is running on one water temp/ODR curve, this is necessary sometimes for certain areas.

What kind of control strategy? Radiant manifold with actuators for zoning and an injection mixing system controlled by a tekmar control; boiler pump, mix pump, system pump? Is the system running on an outdoor reset curve? If so, what are the parameters, min temp and max temp at design condition?

Does the manifold have flow indicators so you can confirm adequate flow to said loop? What is the temp difference between the supply and the return of this loop after 15 minutes of operation?

If it is an actuator, make sure it is compatible with the manifold and is properly seated and secured. Otherwise it may not open the valve the whole way. I have seen that before.

Techman

Hay Harvey. This problem zone is in thin slab, one outside wall ,108 sf, . Is this possible? The tekmar control is set for Terminal#1 -slab- hi mass- which are all lower level zones and the 1st fl are all Terminal#2- thin slab-lo mass- Term #2 setting is 20* warmer.Then another "is this possible?" Two system circs ("6 & "7)are both fed by one VS circ. Circ #6 -3 zones- M. Bed, M Sitting & M.Bath (the cold fl zone). Now on Circ #7 its 5 zones, two zones (slab)are set at 70* , a 3rd zone (slab) is not used. And the last two zones off of Circ #7 are both thin slab, and these two zones are for a Guest Room & G.Bath. Both of these stats are set down to 60*. So, the big "is it possible?" Is it possible that the small M.Bath zone requirers any/all of the other zones to be running so the M.Bath can steal what it can??????

Harvey Ramer

Ok, thin slabs do require a higher water temp than a high mass slab. You will have to change the setting in the tekmar to Terminal#2 so the cold zone receives an appropriate water temp for the application.

Doing so may or may not have a side effect. Injecting a higher water temp into the high mass concrete zone, may cause some temperature swings. I would try it though and see how it does. If it is undesirable, you will have to split the system to 2 different water temps, meaning an individual controller and injection pump for each Water Channel (temp). Where the thin slab would be receiving a higher water temp and the high mass concrete would be receiving the lower water temp.
It may, however, not come to that. The thermostat will shut off flow going to a certain zone once the floor surface temp reaches equilibrium with the heat loss from the space. It will depend somewhat on the floor covering and how well insulated the space is.

There are also some Tekmar controls that can operate 2 Water Channels, ODR curves. For example, if there is a call from the low temp zone, it will operate along that ODR curve. If there is a call from the high temp zone, it will mix the water to a higher temp and follow a higher ODR curve. If there is a simultaneous call from both the low and high temp zones, it will revert to the high temp ODR curve.

Some trouble shooting tips;
The ability of a space to reach setpoint depends entirely upon the floor surface temp and area. Lets assume a surface temp that can range from 70° to 82°.

If the surface temp is 78° to 82°, and the space does not reach set point, chances are you don't have enough floor surface area to properly heat the room.


If the surface temp is in the 70° to 74° range and the room does not meet set point, check the following;

Ensure appropriate flow to the zone.
Check the entering water temp and the returning water temp. If the DeltaT on the zone is small, say 7° or lower, it means you probably aren't leaving enough heat in the zone due to one of the following;

The entering water temp is not high enough to produce appropriate heat flow in regards to the tubing application method applied.

The entering water temp is to low to overcome the floor covering R-values properly.

The tubing is applied incorrectly, such as staple up or any other method that restricts heat flow from the tube to the floor.


If the DeltaT is higher, say in the 12° to 16° range, you are leaving heat in the floor but it is escaping to fast in directions other that the room. If this is the case, check for appropriate insulation underneath and all around the perimeter of the floor in question.



These are just generalized tips that work in the majority, but not all applications. They are no substitute for a proper heatloss calc, but in most cases it will give you a feel for what's going on.


Harvey

j a_2

Harvey, I like your thinking….

j a_2

Slightly off subject, here in Mass. driveway snow melt is very uncommon…How about your area..?

Harvey Ramer

They are definitely not the norm. There's a few here and there.

Techman

Boy, I like this thinking stuff. I'm learning a lot. On this job I brought on the Guest Bath ( smaller than the M.Bath) and it brought on the VS circ. So ,now I'm thinking a water flow problem in the M.Bath zone. On paper, it says all of the zones are based on a 20*TD.

icesailor

I look at it this way. You can have all the designed Delta T's you want. You can have a room that needs 20' of baseboard with a 20 degree Delta T. You can put in 10' of baseboard with a 20 degree Delta T. It will work about half of the time because it only has 1/2 the radiation needed. Bathrooms and Kitchens are a witch to heat with radiant. Tube under vanity's, water closets, bath tubs and showers don't do not unless you want hot toilets etc. If you have a 10' X 20' kitchen with base cabinets on both sides of the long wall, you have a space 6" X 20' to put effective tube to heat the room.

Harvey Ramer

20° Delta-T is high for radiant. Normally you will design around 10° Delta-T. After all, you want the floor to be the same temperature across the room.

I'm sure you already checked this, but make sure the tekmar is actually receiving a heat call when the M. Bath thermostat calls for heat. You could have a bad, or improperly wired end switch on a zone valve or relay panel.

Harvey

Techman

Morning Harvey, The Delta T is on the the spec sheet, Tks. The tekmar shows a mix demand, and the system circ is running. And the other 7 zones on the VS circ all bring on the Vs circ.

Harvey Ramer

Which model is the Tekmar? What are all the input sensors that are connected? Specifically, does it have an indoor feedback sensor? If it does, you may want to remove it. The indoor sensor is best suited to single zone systems. If, for example, you have an indoor sensor in a particular zone and that zone is satisfied, it will lower the mix target setpoint to any subsequent zones that are calling for heat.

What kind of boiler is it? Condensing or conventional? Is there a boiler protection sensor wired in?