Mike T., Swampeast MO
Joined on June 25, 2002
Last Post on November 6, 2008
@ August 12, 2008 7:51 PM in replacing cast iron with veha panel radYou definitely have a converted gravity system. Unfortunately, few people actually understand how gravity systems function either originally or when converted to forced flow. I won't quibble with Veha's statement that their panels need far less flow than cast iron (even if my gut tells me that it's dead wrong), but I will tell you that original gravity systems maintain a reasonable balance after converson ONLY because the system flow is MANY, MANY times greater than under gravity. Let me give you a VERY important term with regards to hydronics (hot water heating): Delta-T Delta-T is a combination of the Greek (I hope) word for change--delta--and an abbreviation for temperature. In other words, it is "change in temperature". Delta-t and elevation are the engines that drive gravity circulation. Under gravity circulation you could VERY easily feel the delta-t across a radiator by putting one hand on the supply pipe and the other on the return. Under forced circulation not only will you not feel the difference, but you'd have a hard time measuring the difference. Flow through the radiator is so many times greater than required that delta-t (like resistance to flow) becomes effectively immaterial. Change the piping such that your new panels receive the "proper" flow for the "proper" delta-t and despite being similar in output to the original, their output will drop relative to the iron rads because their average temperature is significantly lower. If you pipe such that far higher than required flow is allowed through the panels in an attempt to duplicate the delta-t in the rest of the radiators, you'll be bitten in the ass because the panels have less mass and hold less water and consequently have less heat to deliver after the thermostat is satisfied and circulation stops. I know of one and only one way to "zone" an original gravity system in a typical residence serving multiple floors without a COMPLETE re-pipe: Thermostatic Radiator Valves (TRVs). Those things someone told you can be wasteful... Again, I won't quibble but only say that they are ignorant of gravity systems both before and after conversion. This is ESPECIALLY true if you're trying to mix fairly compatible (say standing iron and panel rads) in the same system. TRVs are the highest value control device I have ever seen, but to get the greatest value in a converted gravity system you should also use a condensing/modulating boiler--preferrably using only a SINGLE circulator, just as you have now. Combined, fuel savings in the order of 50% can be expected in a typical gravity conversion system while comfort level increases! If you cannot handle the added expense NOW, my best advice remains, "Keep those iron radiators!"
@ August 12, 2008 7:02 PM in replacing cast iron with veha panel radI presumed that it had already been converted to forced flow.
@ August 12, 2008 12:25 PM in replacing cast iron with veha panel radFrom your description of the system it's almost certainly a gravity conversion system. The real clincher is smaller piping to higher, farther radiators. These systems have extraordinarily low head loss (resistance to flow). As a consequence, you have to be very careful about making piping changes. If you significantly increase head loss to any radiator (as could easily happen if 1/2" piping were used) flow to the radiator will drop. Be forewarned that heating disasters often begin by removing a kitchen radiator that's in the way... Gravity systems are almost always two-pipe systems. You should see at least one pair of large pipes running parallel to one another that get gradually smaller the further they get from the boiler. The two connections on each radiator will lead to separate main pipes. Is this what you see?
@ August 11, 2008 6:37 PM in Economizer payback softwareHere's the closest I could find. Yes, they can save when functioning properly but they are well known for never working properly to begin with as well as becoming a maintenance headache. Notice that components and controls of the finest quality are suggested for effective operation over a reasonable lifetime with reasonable maintenance. Since they draw outside air which is often much dirtier (and I'm not even mentioning insects), I have heard suggested that they must have a pre-filter and that the only "proper" pre-filter is a motorized, automatically advancing roll filter which only adds more cost and complexity. Methinks that economizers are best used in applications where proper maintenance is a near guarantee--say a full-time, qualified superintendant or a long-term service contract that guarantees routine maintenance. VERY easy for economizers to waste more energy than they can save when improperly installed, controlled or maintained. Unfortunately most wind up with all three problems and are abandoned when bills (maintenance and fuel) go sky high.
@ August 11, 2008 12:51 PM in HW HeaterPotentially a BIG problem--deadly disease (Legionella)--if the very same water is used for domestic consumption.
@ August 8, 2008 6:13 PM in Brand names you can't do withoutCrest, Oral B, Yuban, Dell, Hewlett-Packard, Milwaukee, Rigid, Craftsman, Johnny Walker, Viessmann
@ August 7, 2008 6:37 PM in how do TMVs function?I agree Vinnie. None of this is in any way esoteric and any contractor with reasonable hydronic knowledge--not just residential plumbing--will have no problem offering you a number of options of both boiler and appropriate control systems.
@ August 7, 2008 6:34 PM in how do TMVs function?Yes, the purpose of using a motorized mixing valve is so you can reset only the supply temperature to the floor without lowering the temperature in the boiler to the point that condensation damage could occur. In general, non-condensing boilers need to see about 140F return to ensure that no condensation damage can occur. By resetting only the mixing valve a conventional boiler will come up to temp rapidly so it can operate near the conditions intended by the designers which--ideally--will also be the most efficient. Only one conventional oil boiler that I know of has no low temperature limit. There is at least one "near condensing" oil boiler that can operate safely at lower than normal temps, but it cannot recover energy from the condensate--instead it is routed to a highly corrosion resistant area where it is safely evaporated. Condensing oil boilers are becoming a bit more common, but low sulfur oil is required. While low sulfur diesel fuel is now mandated, I'm not sure if low sulfur fuel oil (identical other than color and taxes) is widely available. The only fuel oil that seems to be used in my area is waste oil.
@ August 7, 2008 3:00 PM in how do TMVs function?What was I thinking? Three-way, NOT four-way, valves are preferred for use with mod-cons as four-way valves can result in higher return temps to the boiler. As to why, I must confess that I'm relying on what manufacturers say and have never made drawings and compared flow path to see just why. My assumption is that when a mixing valve is used with a mod-con it's in conjunction with primary/secondary and a dual-temperature system. Will try to add some sketches later, but have a big job looming that will take nearly all my time for the next few days.
@ August 7, 2008 1:37 PM in how do TMVs function?If yours is a conventional (non-condensing) boiler, the generally preferred (and safest to the boiler) way of adding reset to your system would be by using a motorized thermostatic mixing valve connected to the reset controller. This allows the boiler to operating in the proper temperature range while ensuring that the temp of the water circulating through the floors is best suited to the weather. If yours is a condensing boiler, there is usually no need for a mixing valve unless you also emitters other than floors which in general require not only a higher temperature, but a steeper reset curve. Four-way mixing valves are highly preferred with condensing boilers as three-way mixers will raise the return temperature to the boiler and thus reduce efficiency needlessly.
@ August 6, 2008 9:51 AM in Circulator efficiency in Solar/Wood radiant system1) 330 gallons may sound like a lot, but as far as storage for solar space heating goes, it's tiny. Each gallon weighs about 8.33#, so you about 2,750# of water. One BTU will heat one pound of water 1 degree Fahrenheit. Say your system needs at least 120F water to operatate in moderate weather and that you can heat the tank to 160F, a difference of 40F. 40 * 2,750 = 110,000 BTUs available for use. That's not going to last very long in a house of your size in your climate. 2) Evacuated tube panels have to maintain vacuum in the tubes--that's why they are considered less long-lived than flat panels. BUT, this vacuum is what allows them to maintain their efficiency in cold weather. Evacuated tubes aren't really more efficient than flat panels, they just maintain their efficiency in a far broader range of conditions. 3) I believe it utterly impractical to use active solar space heating in your location--unless the house is extraordinarily well-insulated with high consideration for passive solar collection and you have an extremely high budget with little concern for "payback" in any reasonable length of time.
@ August 6, 2008 7:48 AM in mod-con heat ex. cleaningYep! Plastic or nylon brushes only. Metal brushes will scratch the HX which will only lead to more rapid accumulation of gunk and more difficult cleaning.
@ August 4, 2008 4:48 PM in condensing boilersPrimary/secondary with condensing boilers is ALL about ensuring a proper range of flow through the heat exchanger at all times. It has nothing to do with allowing them to condense. In fact, in systems where secondary (emitter) flow significantly exceeds primary (boiler) flow--quite common--it can be easily demonstrated that condensation (and thus efficiency) are reduced. If flow through a mod-con goes too low, it's VERY easy for these rapidly heating boilers to exceed their safeties before the control system can react. If on the other hand flow is too high, velocity through the HX as well as its head loss will increase dramatically causing excessive wear, excessive electric consumption (to circulate water) and even [potentially] a reduction in heat transfer efficiency. Primary/secondary is not an absolute requirement with mod-cons, but you can't just plunk one into any old system without it. The general requirements for use without primary secondary are: generously sized radiation that can fully absorb the full boiler output at around 160F supply; non-electric (proportional, like TRV) flow control on all or nearly all emitters and; extremely low head loss in the emitters and associated piping.
@ August 4, 2008 1:58 PM in Converting Boiler back to coal from oilI believe that components critical to using solid fuel are typically removed when converted to oil or gas; among them the burning grates and mechanism that allowed clinkers to be broken up with reasonable ease. While anything can be done, I suspect that custom forging such components would be extraordinarily expensive.
@ August 1, 2008 5:49 PM in thermostatic heads vs. central thermostatYour GB does not necessarily have outdoor reset capability, instead using the main control unit (thermostat) for indoor reset. Outdoor reset is an option to the GB that may prove necessary in your situation. Proper placement of the main control unit (when outdoor reset is not used) is essential and could be very difficult in a duplex; especially if there is no common space like a good sized entry hall.
@ July 29, 2008 7:48 PM in Circ pumps vs z valvesYes, that's exactly what I'm saying and I am from MO. Dan Holohan explains the LAW that GUARANTEES such behavior simply perfectly in Pumping Away. Unless this is a gravity conversion system (HUGE PIPES), you should DEFINITELY switch to "pumping away" with a conventional boiler "down for some modifications". Such is simply and ideally shown in SUPPLY.JPG
@ July 29, 2008 7:20 PM in Circ pumps vs z valvesOnce you have the ability to control heat authority via your proportional flow control, you can manipulate systems and sub-systems for the most efficient (lowest) heat authority allowing expected response in a space of differing construction methods and occupant desire.
@ July 29, 2008 6:27 PM in Circ pumps vs z valvesSorry--forgot to mention manufacturer's manuals... For most conventional residential boilers there's no reason not to pump away regardless of where any included circulator is attached or the "typical system" illustrations in the manual. When a circulator is not included, you'll find that most will illustrate "pumping away" in their manuals. You stand to gain high benefit at almost no additional cost. (Even with copper sky high a few feet of BX is cheap.) For mod-cons, the situation is VERY different with many manufacturers specifically and only showing pumping towards the PONPC. With mod-cons, the heat exchanger itself is the prime restriction in the system--the "only" restriction if primary-secondary. The heat exchangers are also able to deliver heat very rapidly. If the circulator pumps away from the PONPC it will add to the fill pressure seen by the boiler's safeties. Should load suddenly drop with the burner at high output, system pressure could momentarily rise above limit before burner output is reduced. By pumping towards the PONPC into an HX of known, and predominate resistance, the boiler sees nothing higher than static pressure and as long as mfgr. piping and circulator selection instructions are followed there will be no chance of approaching sub-atmospheric pressure. As a group, the heat exchangers used in mod-cons have very high resistance to flow. The Triange Prestige is the standout with a uniquely flowing HX design that maintains transfer efficiency at relatively low velocity by guiding laminar boundaries towards the path of their own destruction.
@ July 29, 2008 5:31 PM in Edge insulation ??Here's a site-built way that should prove effective and extremely durable. Polyurethane caulk is expensive but extremely durable and capable of covering large gaps. Keep the gap is kept consistent (say with double 2x wood forms), you can pre-assemble the insulation for bottom and core of the "gap" using nails and latex caulk.
@ July 29, 2008 4:40 PM in Circ pumps vs z valvesWhen the pump circulates towards the expansion tank connection (PONPC), it can only do so by reducing pressure at its' inlet. In high head (or all-too-common overpump) situations, the inlet pressure can drop to sub-atmospheric thus having the ability to literally suck air. PONPC = Point of No Pressure Change
@ July 29, 2008 4:01 PM in Driving LessNot a graph, but here are the residential distillate annual consumption statistics Notice the general decline in use as [presumably] fewer homes are heated with oil. Gigantic drop in 2006 would [seem] to come from a number of factors: calendar year 2006 was quite warm in the NE US with fuel oil prices climbing and continued--perhaps accelerating--fuel changeover (mainly to natural gas). Fuel oil for residential use is about 15% of total distillate consumption with most being used for transportation.