With the pump in this position, the proper flow rates can be generated through the distribution system. Unfortunately, the old habit of installing circulators so they pump into the return side of the boiler has resulted in systems such as the one shown in Figure 2. In such installations, almost all the hot water from the boiler outlet is routed through the internal porting of the mixing valve and back to the boiler inlet.
This happens because flow leaving the discharge port of a circulator only "cares about" getting back to the inlet of the circulator. The path of least resistance is through the porting of the mixing valve rather than through the floor circuits. Only a trickle of hot water flows through the latter. The high supply temperature and extremely low flow rate lead to very large temperature drops along the circuit and severely hinders heat output.
Any heat that makes it out to the floor circuits is more of a coincidence rather than planned occurrence. Although this piping can regulate the supply water temperature, it offers no protection against flue gas condensation within the boiler.
Any cool water returning from the distribution system that doesn't flow into the cool port of the mixing valve goes directly back to the boiler. In low-temperature floor heating systems, the return water temperature is often 85 to degrees F. This is well below the dewpoint of the water vapor in the exhaust gases and causes sustained flue gas condensation whenever the system is operating -- even under design load conditions. This can quickly lead to severe fireside scaling and corrosion. It can also quickly destroy a galvanized vent connector pipe.
One way to solve this problem is to install a second mixing device as shown in Figure 4. This device may be another three-way mixing valve or one of several available "preset" thermostatic mixing devices specifically designed for boiler protection.
Air is always an enemy in any hydronic heating system, but even more so in an open system. The location of the air eliminators in the heating system is critical in how effective, or hindering, they may be. A properly placed air vent should allow for quick and simple removal of the air upon initial commissioning of the system and for easy inspection or service at a later date.
Typically an air vent is located wherever the fluid in the system flows horizontally and then turns to go down. At that point use a tee in place of an elbow and install the air vent on the top of the tee. Should an air vent ever be installed on the intake side of a pump? If the pump is located at the outdoor furnace then there should be no need for an air vent on the intake of the pump.
The piping should be simply routed from the connection at the furnace down or horizontally into the pump. If the pump is in the building it should be positioned so that, if at all possible, there are no air entrapment points in the piping before the pump. If this cannot be avoided, then an air vent may be installed at the air entrapment point on the intake side of the pump if the location of the vent is at least two feet lower than the water level in the outdoor furnace.
If this vent is opened when the pump is on, it may draw air in through the vent and add to the air problems in your system.
When servicing more than one heating load in a system, the order you supply each demand is quite important. When a heating system is designed it is important that this temperature drop be taken into account in order for each component in the system to meet its demand.
The typical order is as follows:. Typical design temperature required is F. Finned copper tube design. A radiator installed in the plenum of a forced air furnace or a fan unit with a radiator built in. A floor heat system that is hung with clips or transfer plates to the underside of a floor, in a wall, or even a ceiling.
In this method the piping radiates its heat through the air surrounding the piping and then into the room through the floor, wall, or ceiling. Aluminum heat transfer plates may also be used in this method to boost the performance in high heat loss areas. A special stainless steel or titanium heat exchanger may be used to heat the pool or hot tub water. A piping system embedded in a concrete floor such as a basement, garage, or workshop.
A floor covered with a topping pour of gyp-crete or concrete would also fall into this category. Typical design temperature required is 80 F. A piping system designed to melt and evaporate snow and ice from outdoor areas such a sidewalks, driveways, or decks.
This piping may be embedded in concrete or hung in staple up fashion depending on the application. Typical design temperature required is 40 F. When designed properly, this enables the maximum amount of heat to be extracted from a minimal amount of flow from the outdoor furnace.
Less piping, smaller piping, smaller pumps and lower heat loss. That translates into money saved in both initial set-up and long term operating costs. If we look at the last two items in the Order of Operations list above we see that the water temperature required for slab heating a basement, workshop, or snow melt area is significantly lower than what we generate from our outdoor furnace.
We need to cool that water down before we send it into the slab. One way to do this is to take heat off the water in other areas before we supply the floor as laid out in the Order of Operations.
But what if those heat loads are satisfied and are not taking any, or enough, heat off the water? We need to be sure the water temperature going to these slabs is carefully controlled or several problems can result. If we have floor heat in our workshop and our thermostat calls for heat and our pump starts feeding F. Very little, for awhile. Concrete is heavy and it takes a long time to warm that mass up even a few degrees.
The conventional thermostat may call for heat for an hour or so before the floor has warmed up and heated the room to the point where the thermostat is satisfied.
Now what? The thermostat turns off and the cycle repeats itself, right? If we have been feeding F. This can cause the temperature to overshoot our thermostat set point by several degrees making the room uncomfortably hot. Floor heat does not only warm up the air in the room but everything in the room as well. These objects, and the building structure itself, act as another heat storage mass. These objects slowly release their heat to the room as the building cools down and this can keep the temperature above the thermostat set point for another period of time.
Now our thermostat calls for heat again but the floor has been off for so long that it has lost a significant amount of temperature and it will have to run for a lengthy period of time to start contributing heat to the room. In the mean time the building continues to loose heat and may actually drop slightly below the the thermostat set point causing things to get a little cool in the room.
Now the cycle repeats itself. This is only one of the adverse effects of supplying water that is too hot to a floor. Floor coverings may also be damaged as a result of this excessive temperature. Hardwood floors can dry out, shrink, and crack. Carpets can loosen and concrete can crack. Needless to say it is very important to control the water temperature going into a floor.
Can you control the temperature by just slowing the flow by closing a valve a little? The water will come out of the floor cool but it causes uneven heating across the floor. The first part of the loop will be excessively hot and the last part of the loop may not be hot enough. Controlling the fluid flow is not nearly as effective as controlling the temperature.
We need to keep the flow up to the proper rate to provide even distribution of the heat across the floor and proper conduction from the water through the pipe. There are several ways to accomplish this, two methods we will look at are using Thermostatic 3 Way Mixing Valves or Injection Mixing.
Thermostatic 3 Way Mixing Valves are basically what they sound like. A valve with three ports, Hot, Cold, and Mix. Most valves are adjustable from 80 to F. The Hot port is teed into your primary loop coming from your outdoor furnace. The Mix port goes to your floor heat pump and then to your supply manifold feeding the floor.
The return manifold from the floor gets teed back into the primary loop down stream of the first tee. The Cold port on the valve gets teed in-between the return manifold and the tee going back into the primary loop. These valves work excellent for basements, garages, and smaller workshops as they are designed for fairly low flow.
Once you need more than 4 or 5 gpm you should look at injection mixing. Injection Mixing is a technique that works beautifully for any system from a house to an industrial building. The basic costs tend to be higher for this type of system but there are many added benefits.
If freeze protection is an issue, than a closed system with anti-freeze is a good idea. The down side is two heat sources. All water heaters waste heat energy, even when the burner is off and the unit is sitting idle between heating cycles. Granted, the unit dedicated to heating the floor only wastes heat during the winter months. But standby losses for six months out of every year can add up. The other consideration is efficiency. Two low or moderately efficient water heaters are much more costly to run than one high-efficiency unit.
As air leaves a system, the pressure will drop. When the Radiant heating system heats up, the pressure will increase, but when it cools, it will drop in pressure….. We recommend that you maintain at least 15 psi when the system is cold. The Closed system expansion tank is pre-charged and should not need any pressure.
If pressure is dropping below the 15 psi, it is an indication of air still trapped in your system,….
We recommend Propylene Glycol not automotive, Ethylene Glycol antifreeze. The cap on the air eliminator is closed when it is tightened clockwise and opened when the cap is backed off counterclockwise a few turns, so that daylight is visible through the slit in the cap,…The air eliminator cap may be removed if you wish, but is not necessary.
Determine how much antifreeze your system requires by adding the total amount of fluid in the tubing 2. Radiant Floor Company includes this information on your worksheet.
Determine what percentage of anti-freeze to water mixture is recommended by the manufacture of the heat source. Ratios can vary. The proper mix is also influenced by the degree of low temperature you wish to protect against. However, if you are using a conventional boiler degree water for a heat source, a mixing valve is required.
See below. This pre-assembled, panel system comes right out of the box just as you see it here, including pump, pre-wired controller, expansion tank, air eliminator, in-line thermometers, and various gauges and valves. The entire package is pressure tested against leaks and as few as four solder connections can tie it into your system. A zone. Tips for properly installing these mixing valves in radiant heating systems.
Three-way Mixing Valve Installation Guide 1 Introduction The Uponor Three-way Mixing Valve A, A is a microprocessor-controlled valve designed to regulate the supply water temperature to a radiant heating system by modulating the position of the valve. Radiant heat mixing valve diagram furthermore diy open storage part 1 wood not oil together with opensystem further radiant floor heating furthermore under floor heating further boiler heating system furthermore using wood gasification boiler for space heating and repurposed thermal storage tank together with water heater installation voucher along with furthermore central.
Thermostatic power Taco Mixing Valves are for controlling water temperatures in pex radiant floor heat and other hydronic applications. Taco Power Mixing Valves are also for solar hot water tanks when needed to reduce water temperature to safe levels for home use.
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