Mike T., Swampeast MO
Joined on June 25, 2002
Last Post on November 6, 2008
@ November 6, 2008 9:23 PM in Gravity system questionsEarly 20th century gravity conversions are the only systems I've worked on and I've yet to see any leaks caused by the conversion to forced flow either recently or many decades ago. Sounds like you want to use forced flow for the primary and gravity flow for the secondary. Many have questioned and pondered but nobody to my knowledge has accomplished such a hybrid beast. The problem you would face is that the forced flow would fight with the gravity flow and forced being forced, it will win. Result would be a boiler (be it mod-con or conventional) hitting high (or reset) limit with extremely little energy making its way to the radiators. Copper fin baseboard and standing iron radiators are the worst possible mix in a system and a nearly guaranteed disaster in the same zone. Iron radiators have lots of mass and lots of water content and will give off heat LONG after the boiler stops firing and/or the circulator stops running. Fin baseboard on the other hand has comparatively no mass and no water content and will stop giving off heat very shortly after the boiler stops firing and/or the circulators stops running. Dan Holohan's book "How Come" gives GREAT information for converting gravity systems to forced flow. You are correct that you will bring the supply and return pairs together using a very simple and very safe rule of thumb. Take the largest pipe size, cut in half then drop one size. For example, if the largest supply mains are 2 1/2" you would use 1" for the new piping. IMHO it is best to strip the mains back to horizontal and use only bushings (not couplings) to reduce the pipe size. This is one place where it doesn't seem to matter in the least how you split the flow between the two branches--bullheads don't seem to cause any problem. Do though be VERY careful about making changes to the piping. If you follow "monkey see, monkey do" you will have NO problem--if you start reducing pipe sizes to "modern" standards, watch out! Some say they prefer to rip out the piping and re-do with home runs or other modern piping. Utterly unnecessary unless the homeowner insists that the big pipes MUST be removed. Your finest conversion will find TRVs on ALL radiators and a mod-con well suited for a single circulator system (and the TT Prestige is one). FAR cheaper than replacing the piping. Homeowners will be astounded by the comfort, energy savings and versatility. Just never, ever, ever, oversize a mod-con and keep pestering for smaller...
@ October 27, 2008 4:22 PM in They don't make em like this anymore!Watch ebay. I've seen (and posted here) a number of that style. Not positive, but believe they're only for steam as they don't appear to be connected across the top.
@ October 24, 2008 6:48 PM in baseboard tempsI won't say that there's anything "magically efficient" about 180F average supply temp, but do remember that conventional boiler manufacturers used this "rule of thumb temperature" for many decades, just as they used plus/minus 10F operation and 20F delta-t in the emitters. Particularly with low mass, highly convective emitters such as fin baseboard, such is darned easy as long as you pipe appropriately considering the available circulators. I do like to think that manufacturers consider the systems in which their boilers will be installed and will design them to operate most efficiently given the long-standing "rule of thumb" design ideals.
@ October 24, 2008 5:46 PM in installing used boilerJames, Obviously you've determined that the boiler is suitably sized so my best advice is to include cost of any transportation; use your normal replacement cost and offer no guarantee other than that any new piping is suitable to the boiler installed.
@ October 24, 2008 5:42 PM in baseboard tempsYour system would seem to be following the "rule of thumb" which finds a 180F "base" temperature with a control with a plus/minus 10F differential. In other words it starts firing at 170F or below and stops firing at 190F or above. For a conventional (non-condensing and non-modulating) boiler, such is likely the most appropriate setting as it [should] allow the boiler to operate in its most efficient range as much of the time as possible. This does of course assume that the boiler is well-sized compared to the baseboard emitters. Lowering the temperature (as jp suggested) either by manual or automatic means, does not necessarily mean that there will be much--if any--energy savings with a conventional boiler and if you go too low (either manual or automatic) you risk condensation damage to the flue and boiler. Condensing/modulating boilers are completely different beast and your fuel bill WILL benefit (often greatly) by using the lowest possible temperature across the greatest length of time.
@ October 24, 2008 5:24 PM in Lifespan of newer bladder based expansion tanks?Most certainly! Search for a recent post by Brad White on just this topic. Nitrogen is effectively inert and will have not affect the bladder. "Air" on the other hand contains oxygen with that nasty little habit of oxidizing other things... Such keeps us alive, but it kills many of the things we make. With a well sealed, well-designed fluid-side system (where oxygen stays dissolved), proper tank sizing and nitrogen on the "air" side, something tells me that modern tanks might last nearly as long as the c. 1922 plain steel tank still serving perfectly in my basement. (Of course it has a B&G Air-Trol fitting to ensure that the air inside of it STAYS inside of it...)
@ October 20, 2008 9:33 PM in Tomorrow - a 98% eff modcon furnace - GrandPAHI sure hope that it will be installed in a very well sealed, well balanced, fully returned duct system designed for heating only.
@ October 20, 2008 9:30 PM in Gravity system with Circulator, New boiler, Higher billsSupply mounted so that it diverts the supply through the boiler (directly into the boiler return) until it hits about 140F and then proportionally directs the "extra" into the supply to the radiators. The supply to the emitters may well never approach 140F, but your conventional boiler will be operating in the "sweet" range where it is supposedly most efficient. Only one pair of 2" mains? Again, that sounds rather small for a gravity system.
@ October 20, 2008 7:04 PM in Gravity system with Circulator, New boiler, Higher bills2" sounds rather small for the mains of a gravity system unless the horizontal runs are quite short--I've even seen 2" branches to large radiators on the ground floor near the boiler. Is the 50' of horizontal main in two separate and distinct supply/return pairs? If not, such sizing sounds similar to what I've seen in early standing iron systems designed for forced circulation. If a multi-floor home are the branches to the lowest (and particularly closest to the boiler) floor larger than the upper? If not, it is certainly not a gravity system. Regardless I would suggest that you look into a thermostatic bypass valve type ESBE. It will allow your conventional boiler to come up to it's most efficent operating temperature and "bleed" the proper amount of energy into the system. Upon observation, one of the men I most respect here once called the operation of the ESBE "almost magical". In a way it gives you the benefits of primary/secondary piping without the additional expense of another circulator.
@ October 20, 2008 6:43 PM in Blown-in insulationGREAT reply Brad. I must add that in my renovation experience, earlier cellulose insulation (not the new "dense pack") tends to settle significantly while fiberglass tends to stay pretty well where it was installed. Unfortunately though, blown in fiberglass seems to be awful with regards to infiltration--if the wind can blow through the outer wall skin it will blow right through the fiberglass as well... I've also found that there's no such thing as a "waterproof" house. They may start almost perfectly so, but over time and under "unusual" weather conditions they all seem to leak. Blown in cellulose will absorb water just like a sponge and since air does not move through it easily, it can set up some ideal conditions for rot. Fiberglass on the other hand does not [appear] to be affected by small amounts of water and since air can move through it rather freely, it tends to dry relatively quickly before nasty problems set in. I've been watching a number of high end (for my area at least) homes built in the last 18 years or so and most of the style I call "multi-gable monstrosity". They are NOT faring well and I suspect they'll rot into the ground well before my old frame house built in 1903. I can only hope that my small, recent addition using modern framing (but old solid sheathing with plain old tar paper on the outside) will fare well and that my meticulously installed batt fiberglass wall insulation won't cause a problem despite some water intrusion that is historic, ongoing and seemingly unstoppable in "unusual" conditions.
@ October 20, 2008 3:32 PM in old boiler and new radiant floor heatingSince the conditions where they will be installed vary so greatly, most manufacturers of electric floor heating systems call them "floor warming" the implication being that they would not guarantee that they alone could heat the space. Despite having hydronic heat available for floors, I used electric for the majority of my master bath (the shower is hydronic). It has a cast iron radiator as well (with a TRV). It is on a Northeast corner, with significant exposure and a very large glass block window. In typical weather, the electric floor heat cycles and the radiator is stone cold. If yours is a rather typical old house downstairs half bath with short, single exterior exposure and a smallish window, I would suspect that an electric floor system would be sufficient--especially if you can nicely insulate any exterior wall. One of my baths (fully internal) is located between two bedrooms that are normally kept at about 55F. The bath floor has hydronic heat (constantly circulating) and the doors are kept closed. Despite an air temp that rarely exceeds 62F or so in the heating months and a floor temp that is generally "neutral"--only warm in quite cold weather, I find it the most comfortable "reading room" in the house during the early morning.
@ October 20, 2008 3:13 PM in Boiler CorrosionI have zero working experience with firetube boilers, but "lots of moisture from combustion coming back down the stack" sounds like VERY bad news for any boiler that's not designed to recover heat from and handle the corrosive power of condensed flue gas.
@ October 20, 2008 2:59 PM in old boiler and new radiant floor heatingAlmost anything can be done with hydronics--for a price... Unfortunately, a number of things will likely be working against you and what might seem a simple proposition could become extraordinarily expensive for proper comfort, control and system efficiency. My gut reaction is to suggest electric floor heating under tile for use in the half bath. Before you remove the radiator however someone should verify that the floor alone will provide sufficient heat. Small baths often have a deficit of heatable floor area. The electric heat could easily be extended into wall(s) if necessary. While it's sometimes possible to just "tap in" to the existing system for a floor, temperature and time are likely to be your enemies. Many heating systems with standing cast iron radiators operate at a quite low temperature--too low to be used for "underfloor" heating methods yet too high to be used for "above floor" heating methods. Even if the existing supply temperature is suitable, the problem of time can occur. Most old systems with cast iron rads find the circulator and boiler running in unison. With their large water content, iron rads give off their heat slowly for a long time after the burner stops firing and the circulator stops moving water. Your floors will have little water content by comparison and while the temp may be suitable, it likely won't be "on" for long enough and the floor may well never get sufficiently warm. A separate zone for the bath could be added of course, but be aware that this cannot only be quite expensive, but that it can be extraordinarily inefficient as running a boiler suitable for heating the entire house just to heat a half bath will introduce a HUGE amount of cyclic waste (especially with a conventional, cast iron boiler). If you really want hydronic heat for the bath floor, I would suggest finding a very good hydronic heating contractor--not your average plumber. Again though, I really suspect that electric will be your most comfortable and cost-effective method for such a small area.
@ October 20, 2008 12:44 PM in Boiler CorrosionCould the fuel be the real problem? Was the boiler designed for wood burning instead of coal, oil or gas? I believe that the combustion gasses from wood are very corrosive, especially if the wood is not very well seasoned. From your description, it sure sounds as if you're getting significant condensation of the flue gasses. Are you using any sort of "recovery unit" in the flue? If so, I'd get rid of it. Is the boiler perhaps massively oversized and you're essentially underfiring it with a much smaller fire than it was designed to utilize?
@ October 20, 2008 12:30 PM in DIY ModCon CleaningLooks good Brian. The accumulation in mod-cons (variously described here as "coffee ground" and "mouse turds") seems quite variable and of unknown origin. Nobody seems to know if it's coming from the combustion air, the fuel, a combination or something else.
@ October 20, 2008 12:26 PM in Attic heatYou might want to consider a mini-split inverter unit, especially if you have any need for air conditioning. These are extremely efficient and not terribly expensive. Electric baseboard is inexpensive and quite comfortable but will be rather expensive to run at $0.12/kWH. I hope you have good insulation!
@ October 20, 2008 12:16 PM in Is there a PVC cover for this fitting?The fitting is called a "bell reducer" (at least around here) but I have no idea if commercial, formed insulation is available.
@ October 20, 2008 8:46 AM in How to determine set back recovery timeSteve: Nearly every modern electronic setback thermostat uses some form of "smart" recovery. While it will take a number of heating/setback cycles to learn, eventually it will turn on the heat at the proper time to get the space heated by the time you set. Do though be aware that at the end of recovery, about the only thing that will be up to temp is the air itself. Walls, furnishings, etc. will likely be much cooler and you can easily set up very uncomfortable conditions for a large crowd. (This is especially true for a poorly insulated masonry structure.) To keep occupant complaints to a minimum, you'll likely have to experiement a bit to determine how long before you expect a crowd to set the recovery time to end and allow the air and structure to achieve a better balance.
@ October 19, 2008 1:54 PM in in floor heatingThe foil radiant barrier has no effect when covered by a solid on both sides. By very definition, there is little or no radiant energy to block.
@ October 19, 2008 1:46 PM in What is this \"trap\" and original flow direction?On a relative scale at least, overhead gravity systems had abundant motive force and did not suffer from the same difficulties found in many multi-floor gravity systems. They were of course, VERY expensive--all that big pipe going to the attic never came cheap... When your system was converted to forced flow, I suspect that the "trap" you see was intended to arrest gravity flow, but I highly doubt its effectiveness; especially on the return where the forces above would easily overwhelm such a shallow "trap" at the very bottom. Even if it were installed on the supply, I have a sneaking suspicion that flow in the system could reverse itself when the circulator is not running. The original supply line(s) will be VERY large and will follow as short and direct a route as possible up to the attic with NO branches until the where the main(s) turn horizontal. From the attic down, piping can get quite complicated in a multi-floor system. Remember that BOTH supply and return are moving DOWN towards the boiler. Usually the supply would be carefully "split" to supply rads that may or may not be on the same floor. Sometimes the return from an upper radiator can become the supply to a lower radiator. Were I truly a "dead man" I would have used the return from an upper floor bathroom to supply a lower radiator. With the exception of what should be VERY short horizontals in the supply, everything horizontal you see in the basement should be the original return. In a larger home (where these systems were usually installed) I would expect to see a fairly complex system of returns in the basement, likely with two or more branches gradually increasing in size as they near the boiler location where they may have merged.
@ October 17, 2008 5:50 PM in \"But you were more money\".........heatboyThe "primary" loop runs clean through the last circuit shown on the right side of the pic with bullhead tees attempting to divide the rest. Talk about battle of the circulators...