Joined on November 26, 2011
Last Post on March 6, 2014
@ March 3, 2014 9:10 AM in Hydronic off new DHW for BasementGiven the topic, your post would probably get more eyeballs in the Main Wall.
Do you have a heat loss calculation for the house, especially the basement? Is the basement occupied regularly or intermittently? Is there insulation under the slab?
@ March 2, 2014 9:38 PM in Unequal circulators in seriesis for drainback solar in a multi-story building.
@ March 2, 2014 7:38 PM in Pictures of existing system that needs replacementFirefox 27 on Mac OS X.
@ March 2, 2014 7:20 PM in htp boiler 0-10 signalI'm not familiar enough with the Pioneer to know offhand what it uses for OAT. SWT is a 10k Type 3 (common as dirt.) Whatever it is, I'll bet JCI can get you a replacement for under $10.
@ March 2, 2014 7:10 PM in noisy slab sytemis on the inlet side of the pump? And the outlet feeds all five loops in parallel?
300' of SDR9 PEX flowing 1 GPM with 80ºF water presents 10.8 feet of friction head. At 120ºF the number drops to about 10 feet. If your loop lengths are accurate and the embedded PEX did not get crushed or kinked during installation (or during the slab pour) it's probably the tankless HX. What make and model is the tankless?
@ March 2, 2014 7:04 PM in Installation of Hot Water Heating Pex Pipes and Runtal Radiatorsrarely carry more than 1 GPM. In a home run system, that is all they have to carry.
In a series baseboard system, the pipes have to carry several rooms' worth of flow.
@ March 2, 2014 5:59 PM in noisy slab sytemcould most likely be run at a 15º ∆T, which would require 6.7 GPM. Running a concrete floor at a 20ºF ∆T is a recipe for uneven heat, especially with long loops.
Heat loss calculations already include several safety factors. If I had to guess, most of them come out 20-30% higher than the actual demand (assuming the correct outdoor design temp was used.) Combine this with the fact that ODR with constant circ removes the need for a pickup factor and you can often get by with a fair amount less than they predict.
ODR with a non-modulating heat source (even though yours modulates its input, it puts out a fixed water temp) involves mixing of cool return water from the emitters with hot water from the heat source. The mixing valve or injection pump is adjusted based on the outdoor air temp to deliver the right amount of BTUs to the slab. Because it adjusts before the indoor air temp changes, it offsets the flywheel effect of thermal mass in the slab. And yes, you may still need more GPM in order to move those BTUs into the slab.
If you can't afford to implement ODR, at least get a thermostat with PWM and a slab sensor. Uponor and Tekmar come to mind here, there may be others.
@ March 2, 2014 5:32 PM in noisy slab sytemCan you post a picture of the tankless, pumps, and pressure tank?
@ March 2, 2014 4:36 PM in noisy slab sytemThe overheating will be reduced significantly, if not completely eliminated. If you have a lot of solar gain, you can sometimes prevent that from overheating by careful location of the outdoor air sensor. Running a high-mass emitter system without ODR is like trying to drive a car with the accelerator pedal bolted to the floor, using only the clutch to control your speed. Now replace that car engine with one with one having 3-4 times the power and see how things go. Adding ODR and hydraulic separation gives you a throttle and a transmission to work with.
If you don't know what your actual BTU requirements are, how can you know how much flow you need? Sorry to sound like a broken record here, but you really do need to begin at the beginning before you start changing parts.
@ March 2, 2014 4:17 PM in noisy slab sytemAn ODR-controlled mixing valve, some hydraulic separation, and perhaps a buffer tank will do the trick.
What is the design day heat loss requirement? How big is the tankless?
@ March 2, 2014 3:32 PM in noisy slab sytemso before you start changing parts, be sure you fully understand what is needed. A heat loss calculation together with the tubing layout (spacing, mostly) will tell you how many GPM at what temperature is required to heat the space. That, combined with the head loss will tell you what pump(s) to use. Your huge ∆T is the result of hot water hitting a cold slab. If the water circulation is constant but the temperature is controlled by ODR, the space will be more comfortable and demand less of the boiler. It can also reduce pumping requirements in many cases.
@ March 2, 2014 2:13 PM in marble tops on radsbut you might want to start a new thread as you clearly have some issues with your system.
@ March 2, 2014 2:05 PM in noisy slab sytemreally, really, really, really prefers constant circulation using ODR.
@ March 2, 2014 2:04 PM in Solar Thermal is Deadmakes sense with a year-round load that requires higher temperatures. Frito-Lay uses it to fry Sun Chips http://tonyseba.com/industrial-scale-solar/sunchips-are-now-made-with-the-sun/
@ March 2, 2014 1:59 PM in Rattling coming from baseboard heating systemin the right places, so we used it! I think we saw a photo here of one like it about a year ago -- could they be the work of the same genius?
@ March 2, 2014 1:42 PM in Trol A Temp Replacement wiringdo you have between the stat and the unit?
@ March 2, 2014 1:40 PM in htp boiler 0-10 signalbecause we run our own PI loops on the controllers, which allows us to dynamically modify them for indoor feedback. I know the DX-9100 supports PI and PID loops, but I've never had a chance to dive in on one.
@ March 2, 2014 10:34 AM in htp boiler 0-10 signalthe 0-10V input does not set a temperature, just a firing rate. The onboard limits for boiler max temp will throttle back at this point if your ODR control has not.
@ March 1, 2014 11:47 AM in Heating-Cooling Loss and Gainis currently working on this, in the form of a radiant heating and solar code.
@ March 1, 2014 11:42 AM in Beating a dead horse.that Jstar and MarkS are tinkering with http://www.midcointernational.com/products/low_nox/
@ February 28, 2014 10:44 PM in Pickup factor. Help me understandClearly written, evidence-based, and entirely useful.
@ February 28, 2014 9:00 PM in I figured out how to calibrate a Pressuretrol!it appears that Honeywell has a serious QC problem (as opposed to an actual design defect.) This could be a good thing.