Joined on December 28, 2006
Last Post on May 19, 2011
@ December 29, 2006 10:59 AM in Monitor MZ25C ProblemsBarbara, The first thing I would check is your calculated building heat loss and the amount of radiation connected to it. No better place to start for the long term. But while you are at it, make sure the internal circulator is on high speed (speed 3). Without sufficient radiation to dissipate the heat created by the boiler, the return water will come back much closer to the leaving water, the heat does not go to the space (the objective!) and the unit cycles. I suspect this may be at the root of it. Was the entire system installed at once or was this a retrofit to existing radiation? Does it have a pre-MZ track record? I own an MZ, the same as you have, with separate DHW. (EDIT: At first I thought the "C" was for "Combi" but we do have the same unit.) One thing I always found annoying was the lack of modulation and propensity to short-cycle. The other thing is that if my DWH tank is set too high (much above 60 degrees C or 140F) the unit shuts down on high limit and has to be re-set manually. It seems you do not have THIS issue... Your issue may be one of the system match-up and not technical, so let's start there. Did the contractor or vendor perform a calculated heat loss and what did it say? How much radiation is there and is it apportioned to each room's heat loss? How is the boiler piped? In series direct to the house? Or Primary-Secondary? Your issue could also be one of not having a secondary circulator and relying on the internal circulator. The MZ has a relatively high internal pressure drop hence may not have sufficient "head" or pressure available to serve your radiation. Hence, flow will go down and the temperatures shoot up. The internal circulator is 3-speed and should be set to the highest speed. Check that while you dig for other paperwork (if any). If I had to do it over again, I would have gone with a modulating condensing boiler, not a condensing on-off boiler. With some work (buffer tank and Outdoor Reset) this has been overcome to some extent. The MZ is a rugged unit with some design flaws -beyond not modulating- and has to be properly applied. I might use it as a first stage in a building with a much higher heat loss but connected to a building with a heat loss much below 60,000 BTUH it will cycle a good deal of the time. Brad
@ December 29, 2006 10:34 AM in Heating degree days, Wrong?"A lot of commercial office building's HVAC systems are designed using degree days instead of BIN or an actual heat loss / gain load calculation." Mike- I have never used such a method to calculate H/C loads in any system. I might use the DD method to corroborate/triangulate a calculated heat loss and as a reference value only (beyond the energy consumption figures of course). Can you elaborate on how such a DD method would be used alone to determine the actual heat loss when the building is only on paper? Or is it a method much as I would use to cross-check an existing structure? Not a challenge, just seeking to learn what might be another way to do something I have never contemplated. As for Degree-Days and commercial work, I will offer that we commonly use a Base-50, not the Base-65 so often used in residential work. Not suprisingly, with tighter houses, that Base-65 should be coming down eventually. I can see easily Base-60 in retrofitted houses with higher internal gains. With good insolation, much lower. Maybe even Base-50! And how cool is that?
@ December 28, 2006 11:48 PM in Progress....You are not that old to remember the volcano. Get off it. :)
@ December 28, 2006 11:39 PM in 230,000 sq ft paper mill conversionAs Steamhead and others suggest, a heat loss and radiation survey is a must-do. Do you have an architect you are working with? Are you planning on insulating and improving the envelope? Write me off line and let's see what can be done. I am in Massachusetts, Boston area. There are also excellent steam practitioners in the central MA area. It is at once a blank slate. The condition of the piping is critical and it could go either steam or hot water. Steam has the ring of history to it. Sounds like an interesting project. Brad
@ December 28, 2006 9:56 PM in Contender & T80/T50 MunchkinThat would defeat the purpose. The Contender, as I understand it, is not a boiler but a water heater (not the domestic kind and there is a more specific term which escapes me at the moment)for residential applications which may not require an ASME stamp. If they use the term "boiler" it has to have an ASME rating and stamp. There are other features designed/simplified to bring the price point down somewhat also.
@ December 28, 2006 7:29 PM in exspansion tankpost this as a new question so that you get your own responses specific to your needs. Brad
@ December 28, 2006 5:47 PM in Help we are freezingWhen you say vents do you mean fins on the radiators? The vents are small chrome cylinders located about half-way up the radiator opposite the entry valve. Assuming one-pipe steam of course. If the air vents are clogged or not passing air, steam cannot enter it is as simple as that. Replacement vents may run you about $20 each and adjustable ones about $30. Check on line if a local plumbing and heating supply house or Big Box Store is not near you. Also I have to ask if the valves are open (never assume, must ask).
@ December 28, 2006 5:38 PM in Couple of steamersMake sure your vents are working well, free and clear. Vent your mains well. If your radiators are half hot I suspect the vent may be clogged. Crank the pressure down. Ounces if you can but as low as you can set it. Less pressure, less force for banging too, plus the steam will move faster. Many aspects but I would start with the "air out, steam in, water back" mantra. The system should heat evenly and quickly year round if it is vented properly. That you may not get all heated before the system shuts down could be as simple as that the radiator in the room with the thermostat is working very well for you. It may be that partial firing is all it takes to satsify that while the outlying radiators do not see the steam much. In milder weather the time between firings is longer so the perception and reality that the average radiator temperature seems less is true. It will be as hot as it gets at first then cool closer to room temperature on a mild day. On colder days, the firing rate (cycles per hour) are greater so the radiators are on average hotter at a given time.
@ December 28, 2006 5:29 PM in YO!! ME! Here it comes again!!You cannot make that up, can you? We have Thomas "Mumbles" Menino... wanna trade? :) After Scott Milne installed his snow melting path system it was inevitable that we would have no white stuff in sight.... you on the other hand, yes, go sharpen that shovel, watch the ticker and your health in general. Take care, Brad
@ December 28, 2006 4:30 PM in thermal trapsOnce filled, the system should hold at least it's cold-fill pressure and may increase by 5-8 PSI when fully hot, depending on the size of the expansion tank. Any drop below your cold fill pressure is usually a leak. Check your fittings, valve stems for signs of weeping and corrosion. Leaks may not be obvious. A drop or two an hour add up. Hard to see that small a leak on a given day. DO get a Backflow Preventer. Watts 9D is a common brand/model. About $40 last time I checked. Just do it. You could be drinking that stuff. 15-20 PSIG in a 2-story house does not concern me. Just have enough cushion below your 30 PSI relief valve setting, that's all.
@ December 28, 2006 4:25 PM in Hard Water or Softened Water for Hydronic SystemWith softened water, you have a higher sodium (salt) content which is not helpful. Minerals in hard water tend to precipitate out when heated and can be kept in suspension with proper chemical treatment/dispersants. Check out Rhomarwater.com for some back-up and good general information. The deal is, a properly constructed closed heating system should only need to be filled once, vented and topped off. If a system has repeated make-up water using hard water, that is an entirely different issue. Hard or not it will shorten the life of a system. The amount of minerals in a single fill should not be so bad as to plug up a system or cause a noticeable problem, unlike your water heater. If my water were that bad, I would move :) Personally, I filter my make-up water via a GE SmartWater filter to remove sediment, chlorine and some organics, that is about it. The water I have is Quabbin Reservoir water and is not very hard.
@ December 28, 2006 4:18 PM in thermal trapsthere should be a backflow preventer and I hope that there is. This will eliminate a tell-tale backflow condition you may have, lower pressure in the domestic water line which entices thermal flow not to mention direct flow. The fact that the flow is happening at all is cause for concern. The heating system and domestic water system must be disconnected from one-another. For typical thermal migration conditions, a drop or dip of 28 inches would be enough. This represents 1 PSI of pressure to be overcome. If the thermal gradient is quite high and the building is tall, doubling this is recommended.
@ December 28, 2006 4:11 PM in Central MA referralDavid Sutton and Mike Grinham come to mind, being near Middle Earth :). Not to the exclusion of others of course! Do check around and use Find A Professional too as Dan suggested.
@ December 28, 2006 2:29 PM in 230,000 sq ft paper mill conversionoperating machinery and if so, at what pressure? Coupling the post-process steam to heating systems has been done for well over a century and a half. The higher pressure that turned a mill beam engine or turbine would be reduced to heating-level pressures at the end of the process and run through piping to complete the condensing at least partially. The application is routine. One thing to keep in mind is that the process load (machinery) can far exceed the heating and ventilating load. So if the boilers are no longer driving machinery, expect to do some careful analysis of radiation versus boiler capacity. Expect some over-sizing. If you own the whole building you have more options than if you own just a condo unit within it. Where is it located?
@ December 28, 2006 2:25 PM in Progress....The Medieval Warming Period (MWP) when crops grew in Greenland. Some scientists into GW theory wanted to get rid of that part for it discredited the "hockey-stick graph" promoted by Professor Mann at UVA and made the upward tick look like the other side of the bathtub. Hard to look at a narrow band of time, geologically speaking and call it a trend. Ebbs and flows are the norm. We flatter ourselves that we have that much to do with it. As posted above, we cannot predict the weather more than a week out yet deign to say what happens 30 years hence.