For Residential jobs, the design build process ideally works
as follows. First, an estimator from D&D sits down with the
homeowner or contractor and goes over the boiler location,
zone layout, manifold locations, and system design. Then the
estimator measures the total square footage for each zone. These
square footages are then used to determine the boiler size, determine
the amount of radiant tubing or baseboard, and size the copper
distribution piping. The estimator then puts together the
optimum components for the job and writes up a proposal.
After D&D is awarded the job, the company’s Mechanical Engineer does a room by room heat loss analysis on the home to determine the exact heat load for each room and also to obtain a tubing layout guide for the plumbers. Then the engineer finalizes the design by sizing all system pumps, pipes, and boilers. The final selections are then transferred to shop drawings and control drawings that are used by the plumbers to construct the system.
Then D&D’s plumbers install and start up the system. Once the job is complete an Operating and Maintenance Manual is provided to the homeowner. In addition, the homeowner can opt to have a D&D service technician come out to the home and perform annual maintenance checks.
SYSTEM DESIGN & CONSTRUCTION METHODS
The following sections describe the design and construction methods used by D&D for hydronic heating and snow melt systems.
Radiant Heating: D&D designs and constructs radiant heating systems with homeowner comfort as their number one priority. The majority of all radiant installations use ½” PEX tubing with an oxygen diffusion barrier. The oxygen diffusion barrier prevents oxygen from getting in the system and oxidizing ferrous components. For ultimate comfort, D&D installs indoor tubing on 6” centers (sometimes 9” centers are used in garages or basements). Installing the tubing on 6” centers provides an even heat and eliminates hot and cold stripes that can be felt with tubing installed on 12” centers.
During the installation of radiant tubing, D&D installs the tubing 6” away from all walls. In addition, D&D does not run tubing under interior walls or under cabinets. For additional comfort, tubing is often installed under shower pans and tubs.
Homes are broken down into different heating zones with brass manifolds for each zone. The manifolds are located in the walls of closets or in the crawl space. Copper piping and cast iron circulating pumps distribute the hot water from boiler system to each manifold. The manifold then distributes the hot water to the tubing in the floor. The manifolds have individual valves for each loop of tubing. The length of each loop is uesed to determine the position that each valve should be placed in to balance the flow to all of the loops. On the copper distribution pipe from each manifold, a zone valve is installed. This zone valve opens when the thermostat for that zone calls for heat.
Baseboard Heating: D&D installs baseboard systems in such a manner that they provide a comfortable heating system. The home is split into zones and the baseboard for each zone is distributed throughout the rooms for that zone. Where possible, baseboards are installed on exterior walls near windows and doors.
Copper piping runs to and from each baseboard zone system. On the supply piping in the mechanical room, a zone valve and purge/balance valve is installed. Where it is possible the return piping is branched together to save money.
Snow Melt Systems: D&D installs 3/4” PEX tubing on snow melt systems. The tubing is placed on 9” centers. D&D typically designs snow melt systems based on 125 btu/ft2. Snow melt systems are charged with glycol in order to achieve a 40% antifreeze / 60% water mixture. On large systems, snow melt systems are often installed with a separate stand alone boiler.
Boiler and Control Systems: D&D uses and installs a number of different types of boilers including: copper fin tube, cast iron, stainless steel, non-condensing, near-condensing, and condensing type boilers. D&D strives to match the appropriate boiler with each job. Some of the design considerations that are taken into account include: application, venting and combustion air options, heat load requirements, and efficiency requirements.
D&D uses primary/secondary piping systems and does everything possible to protect non-condensing and near-condensing boilers from being shocked with cold water (shocking the boiler with cold water can cause condensation, boiler sooting, poor performance, and eventually lead to boiler failure). In addition, D&D uses injection pumping or mixing to protect the boiler in radiant and snow/melt applications and also to temper the water for the flooring or concrete slab.
For condensing boilers, D&D uses primary/secondary piping.
Tempering devices are typically not needed with condensing boilers
due to their ability to operate at low temperatures.
D&D uses a variety of controls systems, which range from prepackaged systems to field constructed systems. On almost all jobs, D&D uses some form of outdoor reset on the boiler and/or on the hydronic heating system. In snow melt systems, D&D typically installs automatic snowmelt controls with a snow/ice sensor and a manual override. On smaller snow melt systems, automatic controls are not cost effective, so manual controls are installed instead.
Domestic Hot Water Production: When it is feasible, D&D heats the domestic hot water for the home off of the boiler. This is done through a stand alone heat exchanger and a storage tank or through a built in heat exchanger located in the storage tank. Using the boiler to provide hot water for the home provides a cost savings to the homeowner because boilers are 82% to 92% efficient whereas standard water heaters are 76% efficient.
Spa/Pool Heating: D&D can also incorporate spa and pool heating
into the boiler system. The spa and pool heating is done through
a heat exchanger and pump piped off of the primary loop. For
spa and pool heating, the boiler capacity is increased to enable
the spa or pool to be heated at the same time as the house. For
control of the system, a setpoint controller can be used or a
heat demand signal can be provided from the spa/pool filter controls.
Small Systems: For very small residential hydronic heating systems (homes under 1500 square feet), it is often feasible to install a gas or oil fired water heater with a special built in heat exchanger that is used to provide hot water for the heating system. These systems save the homeowner money because they do not have to pay for the expense of a boiler system.
Hydronic Heating Products
D&D has experience using hydronic heating equipment made
by a variety of manufacturers. D&D strives to provide owners
with quality equipment that is pocketbook friendly. In addition,
D&D is also a local representative for Weil McLain. D&D
stocks Weil McLain boilers and parts. This plays to an advantage
for the homeowner because in the event that something does break
or wear out we have a replacement boiler or part to quickly get
the heat back on.
The following items are some of the residential hydronic heating products that we have installed and/or recommend.
Weil McLain, Triangle Tube, and Lochinvar
Circulating Pumps: Grundfos, Bell & Gossett, and Taco
Controls: Tekmar, Erie, Goldline, Honeywell, and Caleffi
Storage Tanks and Indirects: Bradford White, Advance Metalpres, and Weil McLain
Radiant Tubing and Manifolds: Wirsbo and Rehau
Baseboard: Embassy, Sterling, and Runtal
Heat Exchangers: Flat Plate, Triangle Tube, and Weil McLain
Hardwood Floors Tested Over Radiant Heat: Launstein