Joined on November 22, 2003
Last Post on October 6, 2009
@ October 6, 2009 4:13 PM in slab in basement how long to heatupIt depends. If the slab has insulation underneath, as well as at the edges, a 4" slab can warm up to setpoint in as little as 8-10 hours. If the slab is missing the edge insulation and has no insulation under it, it can take days, or even forever as the ground will suck a lot of heat out of the slab until the local ground temperature and slab temperature come into equilibrium.
A normal room thermostat is a device that senses "air" temperature. The slab will be radiating heat, and not necessarily heating up the air at the same rate, hence many people with improper slab control get overshooting/undershooting because the slab's response time to a change in heating water temperature is a heck of a lot longer than what the room temperature change time can be with a poor building envelope.
A temperature sensor imbedded in the slab to monitor the slab temperature can help reduce the overshooting (Check Tekmar's line of Controls), but a slab heating system coupled to a poorly insulated building envelope that allows quick changes in the room loads is a bad combination, and all the band-aids, baling wire, and chewing gum in the world won't help.
@ July 28, 2009 10:36 AM in Seattle, 100+ wed. ?? what's up with thisYeah, tell me about it - the weather folks up here are saying this is a once in a lifetime heat wave we've been having. Unfortunately the HVAC Engineers (me) get the calls from the Clients whose brand new buildings aren't cooling enough. Facts don't sway opinion - the outdoor summer dsign in our area is 28C (83F) and if the outdoor temp is above that, well your indoor temp climbs as well. Funny how all the LEED and Energy Conservation design goes out the window when these people feel entitled to their 72F (22C) indoor temp, on demand, no matter what.... Me? I'm in an older heritage building with the AC system consisting of opening windows and a couple desk fans we have running. For a few days a year, the heat can be dealt with. Many people have lost their tolerance and require instant gratification...
@ July 23, 2009 4:26 PM in Chilled water coil won't condensateThat air velocity at the coil seems way too high - I never design coolng coils for more than 500 fpm air velocity. On the other hand, there is a contradiction in your data - if the supply air temp is being supplied at 55F, saturated 55F air can only hold so mch moisture, and if that air in the space warms up to 72F, AND no other source of moisture is present, the ambient relative humidity should only be 55% +/-. If your ambient RH is higher, you may have building envelope infiltration problems - warm, humid air leaking into the building.
@ July 23, 2009 2:19 PM in Chilled water coil won't condensateIf the chilled water temperature is "scheduled", or reset based on OAT, and it runs at a higher CHW supply temp than originally designed, then the coil may not get cold enough to create condensation. With an entering air condition (assumed from your post) of 73%RH at 72F, according to the psych chart, you need an average minimum CHW temperature in the coil, and corresponding leaving air temperature of at least 60F to start condensing moisture from that airstream. If in fact, your CHW entering temps are the usual 44F, to a leaving temp of 56F, you should be condensing like mad. If you are not, then yes, you could have too high an air velocity through the coil and you aren't cooling the air off enough to condense much. Information is required as to what is the entering and leaving air conditions at the coil as well as the average face velocity - should be less than 500 feet per minute depending on coil configuration (4-row, 6 row, how many fins per inch, etc.) The other part of the issue is if the CHW control valve is modulating only based on space temperature, you may need to run the cooling coil and control valve open more often based on space humidity to accomplish the dehumidifcation function, and then reheat the supply air to maintain space temperature. This is a common Museum/Archives/Art Gallery design- the cooling coil has to be designed and controlled for both space temperature as well as dehumidification, and many time you need reheat after the cooling coil, as the air gets cooled off too much by the dehumidification function.
@ July 14, 2009 4:27 PM in IT WORKS IT WORKS!!I'm not surprised you get the "deer in the headlights" looks when you've asked about radiant cooling systems. It's not been applied very well in the past, nor has it been supported by many people in North America. Check Dr. Stan Mumma's website at Penn State - lots of good info there, mainly on suspended radiant cooling panels and Dedicated Outdoor Air Systems (DOAS). A couple years ago the Clinton Library got some press on it's radiant floor cooling system, as another large scale commercial radiant cooling system. Google guys like Peter Rumsey, Peter Simmonds, and myself to see what we've been doing. Lots of info out there. Flack and Kurtz have been doing some radiant floor cooling systems, as well as Interface Engineering out in Portland. The new Vancouver Convention Centre out here has over 400,000 SF of radiant floor system in it.
@ July 14, 2009 10:39 AM in IT WORKS IT WORKS!!Check out what Davis Energy Group has been doing in California- there have been operating commercial radiant cooling projects out there since the mid-late 1990's. The first "large" scale commercial radiant cooling system was installed at Pier One in San Francisco in 1999, and it's been working well since. That building is right beside the Ferry Market building there, where the passenger ferries come in just west of the Oakland Bay Bridge. The first large institutional radiant cooling slab system in Canada was installed in 2001 at the ITC Building at the University of Calgary - a bit of a hybrid system, but still a large scale radiant cooling system in a multi-storey building. I've been designing radiant cooling systems for the last 10 years out here on the Wet Coast (Pacific NW) and there are many large scale commercial and institutional radiant cooling systems now operating out here. I am just going out tomorrow afternoon to do the One Year warrantee review at the City of North Vancouver Library project - horizontal slinky coils under the slab on grade and side-cuts of the underground parkade, feeding a W-W heat pump plant and two dedicated outdoor air units (DOAS) on the roof. Made it through the first winter and a couple recent hot spells with no problems.
@ June 1, 2009 10:39 AM in Your personal heating system?East and west double glazed windows, insulated shell, manual window shade control, and a 15,000 btuh Valor gas fireplace in the living room that occasionally gets fired up on cold days. We have a mid-efficiency scorched air furnace that only comes on a couple days during the winter. Low Tech, reliable and low life cycle cost. Easy to control and works the same year after year.
@ April 6, 2009 10:26 AM in Any fly fishers?I just lick the monofilament as I pull the ends to tighten the knot. I usually hold the tag ends in my teeth as I release the mono from the little clamps and pull the knot almost tight, then let go of the tag ends, give the knot a lick and pull tight. The only break-offs I've ever had were generally at the clinch knot at the fly. I haven't bought a tapered leader since my first fly rod some 15 years ago, and always tie my own leaders, so a tool like that is indispensible. Practice, practice, practice....
@ March 31, 2009 3:25 PM in Any fly fishers?Ask five different fisher people and you'll get a split between triple surgeons knot and a blood knot for tying tippet to leader, or for making your own leaders from monofilament sections. This is the best $7.00 bucks I ever spent: http://www.kaufmannsstreamborn.com/Catalog/Accessories/Knot-Tyers/DENBLOODTYR/ A blood knot tying tool. The hatch is on, the trout are rising and you gotta tie on a new piece of tippet or leader, and your hands are shaking, and you are fumbling 6x tippet material riding in your float tube in a hurry....this tool has been a staple in my fishing vest for years (buy a few, you'll want to have spares).
@ March 30, 2009 4:00 PM in Any fly fishers?I'm also in the Pacific North (north) West, (Vancouver, BC), and the nice thing is that I have an opportunity to practice my casting all year round (note "casting" not "catching"). I have about 6 fly rods for various purposes - a 4 wt for dry fly trout fishing on rivers and small lakes, a variety of 5 and 6 weights - 2 in a 4-piece configuration for packing in, and a couple regular 2 piece 6 wts. for large river/lake fishing, and my "pool-cue" - a 9 wt., 10 foot Sage that I use during salmon season. Yah gotta have the right rod for the job around here, dontcha know... I also tie my own flies and I find the whole aspect of fly fishing to be a totally relaxing experience- you HAVE to pick up the knowledge of the natural cycles, bugs, critters, fish etc, and I find for me it's evolved into going for a hike on the river with a fly rod to do a little fishing while I'm communing with nature. Right now it's cutthroat season and steelhead season, so I ought to be getting out soon again....
@ March 16, 2009 6:58 PM in Legionnaires' bug at hospitalI just did a quick check of the Building Codes on a Google search, and as far as I can make out, there is no maximum "wait time" for hot water to appear at the faucet/shower/outlet other than for some Hospital specialties. So, couple that with all the low flow fixture installations in the last decade, and the fact that domestic hot water recirc/heat maintenance systems are designed based on "nominal good practice", it means that there are a heck of a lot of 120F DHW systems with low flow fixtures that are allowing even more semi-stagnant cool DHW to sit in the pipe branches to low flow faucets and shower supplies, that people will run until they get warmish water at the outlet. Solution is easy-Code must stipulate a maximum wait time for getting hot water to the fixture, and to minimize the amount of non-recirculated/ non-heat traced branch pipe to the outlets. I'm still battling Code Officials up here in the great white north that insist on full flow "fixture unit" sizing (based on 1947 Hunter curves for full flow fixtures) to be used for pipe and drain sizing, even though the same Building Codes mandate low flow fixtures everywhere in the Province....please explain the logic....Oh, yeah, the Building Code wasn't meant to be logically applied.....
@ February 16, 2009 10:52 AM in What is Building Envelope?The building envelope is described in the other post, but it is also the primary heating and cooling "system" that affects indoor environmental quality. The houses we build in North America are not much better than "wooden tents", and in order for both high indoor environmental quality and low energy use, we need to tighten up the building envelope FIRST before designing "active" HVAC systems. The HVAC designer MUST know how the thermal loads act through the building envelope before applying indoor comfort systems. I've yet to meet many people that understand what "overall" thermal performance is, as opposed to just taking the insulation R-value and centre of glass thermal performance and using those numbers in canned programs.
@ February 13, 2009 10:59 AM in Faucet Aerators and hot water supplyIt's not so much the aerators, it's a "system" issue. The plumbing codes and design standards haven't caught up to the low flow faucets yet. Unless the DHW recirc line is connected closer to the faucet, you will have a "dead leg" of hot water pipe. Say it's a 20 foot length of 1/2" pipe from where the recirc pipe connection is made, and it will contain about 0.8 gallons. The first time someone turns on the tap it will take about 0.8/0.5 = 1.6 minutes, or more to get hot water to the tap. The longer the pipe, and the bigger the pipe feeding the faucet, the longer it will take hot water to get there. The green buildings world is learning about this- there are many brand new green/LEED buildings with poor hot water delivery due to the extensive use of low flow fixtures and using "standard" recirc and DHW heat maintenance design. My own standard is to design the piping to have no more than a 10 second wait time for hot water, and that can be accomplished by either taking off the DHW recirc connection within 3 feet (1M) of the faucet, or use some HWAT electrical heat maintenance cable wrapped on the DHW pipe to within 3 feet (1M) of the faucet. The problem that retro-fitting older systems with new low fixtures at sinks is that more water ends up being used and wasted while people wait longer for hot water at the tap. So tell me again how much water we are saving with retro-fitting low flow faucets again?
@ February 10, 2009 11:48 AM in Ground Loop Heat Pump problemsAny problems with corrosion on the ferrous pumps? Usually I spec all bronze, as the HDPE piping is not an oxygen barrier material and can introduce oxygen into the system...
@ January 7, 2009 1:17 PM in Radiant Cooling - againI always hear this fear of condensation with radiant cooling - what temperature do you think you "need" to run the radiant cooling system and surface at? Typically 64F will provide about 19-22 btuh/SF from a ceiling surface at 64F surface temperature. A properly designed ventilation system (one of the three legs of the stool) has to be designed to dehumidify the outside air you must provide into the house/room/building, if you are in a humid climate. Yes, the dehumidification of the air can result in cooled ventilation air being provided, so then you can run the radiant cooling system a bit warmer (66-67F) to "blend" the sensible cooling from the de-humidified ventilation air with the radiant cooling to achieve the cooling load balance in the room. If this is new construction, build it tight (Buildingscience.com) and infiltration of humid air should not be an issue. Penn State (Stan Mumma) has done some studies on how much effort you need to get visible drops of condensation on a radiant cooling panel, and it does take quite an effort! See this link: http://doas-radiant.psu.edu/papers.html and find the paper entitled: "Chilled Ceiling Condensation Control", plus there are others there along the same vein.
@ January 6, 2009 10:37 AM in Radiant Cooling - againIf you haven't already checked out Robert Bean's Healthy Heating website (lots of radiant cooling "total comfort system" design material there), and done some Google searches for "radiant cooling" then I'm not sure what more you can gain here- there is a ton of material out there on the web-library on how to do it, how to design it, and doing the load calculations. The most important part of the system is building envelope quality (must be high) and solar gain control design. Regardless of whether a slab is doing radiant heating only, or combined radiant cooling and heating, the thermal mass reaction time must be understood - and this means that the building envelope has to be designed and built in a way that MINIMIZES fast-acting heating/cooling load changes inside the rooms. Then apply the heating/cooling system, then apply the controls. There are three legs of the human comfort stool- mean radiant temperature control, ventilation air control, and humidity control. Anything less and the stool falls down. The suggestion by Bob Gagnon about using the ceiling is also a good idea- faster system reaction time compared to a slab system, and more exposed surface area, so the hydronics can operate at slightly lower heating temperatures and slightly higher cooling temperatures with all that surface area working for you (better system efficiency/lower energy use). Floors are always problematical- floor coverings/finishes, furniture masking, etc.
@ December 17, 2008 6:27 PM in Radiant heating as \"Green?\"Low exergy system, creates great indoor comfort = great indoor environmental quality. Can use renewable heat sources for low grade heating water, highly efficient energy transport system using water to carry energy around a building rather than large amounts of air. Properly installed and controlled it can use much less energy to maintain comfort compared to all-air systems.
@ July 21, 2008 3:48 PM in European AC and VentilationThe clay tile buried pipe system is just a variation on earth tubes. The warmed bouyant air in the vertical tube(s) in the house will "pull" the outdoor air in through the buried earth tubes, where the air will be cooled by the ambient lower ground temperature and provide low grade (low exergy) cooling to the space. Can work well in many climate zones.
@ June 5, 2008 8:34 PM in radiant floor heating and leedThe radiant floor alone cannot be calculated. It's the whole building energy use that has to be modeled using a proper energy modeling software package. The catch is that nearly all of the conventional building energy modeling tools are based on core calculations that are all using instantaneous "air" temperature so you have to "adjust" (fudge, manipulate, play with) the program to to properly simumate a mean radiant temperature and "resultant" temperature model to get anywhere near close to realistic results for a combined mean radiant system in a building.
@ May 9, 2008 5:45 PM in Best Live Concert You Ever Saw1. Kiss Destroyer tour 1976, Cheap Trick opened and were fantastic, but the Kiss show was second to none. 2. Triple bill of Ted Nugent, Scorpions, and the Pat Travers band 1980? 3. Blue Oyster Cult 1979 4. Yes, in the round 1978 5. Hoyt Axton, Commodore Ballroom Vancouver, 1984ish - up and dancing with the new wife, what a great time. 6. Roxy Music, with opener Images in Vogue, 1981ish 7. ABBA in Edmonton, 1978ish (I'm mostly a Metalhead, but the girlfriend of the day....) It was actually a pretty good show. 8. The Highwaymen (Waylon, Willie, Johnny, and Kris) in 1983? - future wife was into country music, but good show) There have been others, but those are the top of the list.
@ March 16, 2008 11:35 PM in geothermal hydronicI have to agree with your basic issue of electrically powered "stuff" in terms of the source energy issue. We haven't seen the failures of the water to water heat pumps around my area. We've generally been getting the WaterFurnace brand, and getting good local support, and the system operating parameters haven't been "extreme". We're very careful to balance the energy loads, and being up in a heating dominated climate, we always have some supplemental heat to insure that the geo-exchange field loads are balanced.
@ March 16, 2008 11:32 PM in geothermal hydronicThe photos are of a project that will be in the commissioning stages in a couple months. It's a bit of a hybrid system since the heating energy for the building is coming from a local district energy system, which is supplemented by a large array of solar water heating panels. The geo heat pump system for this particular project is going to be a primarily cooling only system, and the climate it's located in has maybe 30-40 days during the summer where free cooling from the DOAS air supply will need the radiant cooling to be operating from the heat pump plant. We also have bypass valving around the heat pump unit to use direct ground temperature heat exchange for the mid-range cooling for the radiant slab when we only need 18C to 20C water in the slab. The heat pump plant will provide the 16C water when we need it during the July/August period. The predicted EER in cooling will be over 24. Not bad. The slinkies are buried onto native wet clay soil, and there is a constant flow of ground water through the sub-soil zone there, so we have very good soil conductivity. It's only a 45 ton cooling capacity plant for a 32,000SF building. The energy efficiency is in the building envelope design, keeping much of the solar gains out of the building and using supplemental natural ventilation and the displacement ventilation air supply with 18C (65F) air supply. There is another building locally (Gleneagles Community Centre) with virtually the same type of systems, except that one has the geo-exchange loops placed 2.5 meters (8 feet) deep under an outdoor gravel parking lot. It's been operating for over 6 years now, with no problems other than a few circ pumps that had to be replaced under warrantee, early on in the project's life. Another local project - the City of Vancouver National Street Works Yard offices uses a water to water heat pump plant, but with vertical boreholes for the geo field. That building uses DOAS displacement ventilation as well as suspended radiant heating/cooling panels, all served from the heat pump plant. It's been running for 3 years now, no problems.