Best Of
Re: Oil to propane, Kingston NY area - EDITED.
But, how many people actually get proper maintenance done?
It's the same basic principle that makes me favor probe-type low-water cutoffs on steam boilers as opposed to float-type. Folks tend to forget to blow the float-type ones down. Yes, probe units do need to be checked annually, but annually is not weekly.
ISTR @Mark Eatherton once ran a mod-con without maintaining it, just to see what would happen. Its efficiency dropped noticeably. I've forgotten how much, it's been quite a while.
Re: Oil to propane, Kingston NY area - EDITED.
I certainly have not forgotten. In fact, I support the decision to use CI due to the complexity of the mod-cons and the inability to find proper parts and service personnel.
I simply wish to prevent anyone from comparing a 92% mod-con to a 84% CI. This is not a fair comparison.
There are degreed engineers on this site that are doing exactly that and they do a disservice to all people who come here seeking advise.
I also wish for you to note that the mod-con will consume 869 Therms for the season vs. 1140 Therms for the CI boiler for the season on a house that uses 80M BTU for the season.
Figure $2.50 per therm and the annual savings is $677.00. An argument can be easily made that the mod-con can be maintained PROPERLY for less than this value, and, if maintained, it can last more than 10 years.
LRCCBJ
Re: New Propane Boiler Options
Thank you for the article you posted, @Kaos , these are all good things to explore. The example in that article presents a scenario requiring room air dehumidification when it was 90°F outside; this is much different scenario than operating a heat pump water heater in cold climates when outside air is cold and dry.
The ASHRAE article I referenced indicates that heating discharge air from a heat pump water heater is a possible solution as the air impacting a surface can cool it down below the dew point. This is not easy without an external source of heat. Although the discharge is localized, it is informative to see the following analysis on the impact of a heat pump water heater on a room the size of an entire home:
"The best-case scenario for installation in an enclosed space would be a closet the size of an entire house. …The HPWH would be able to extract about 6.2 kBTU of heat from the air (5.3 kBTU sensible + 0.9 kBTU latent). This is not enough heat for a single heating cycle in a typical 3 to 4-person household of this size. Furthermore, cooling indoor surfaces down near 45ºF for more than an hour, multiple times a day, carries a high risk of moisture damage and mold in most climate zones. If the air mass in a 1,625 ft² room does not contain enough energy to heat the water, neither will the air in a smaller room."
Roger
Roger
Re: New Propane Boiler Options
@Kaos , the controls have to be designed to allow stratification of the tank so that continuous cold water make up feeds the plate heat exchanger. The entire system has to be designed properly or you end up with lower performance and the boiler finishes hot which wastes energy (as it does with a conventional indirect tank and combo/instantaneous systems).
Regarding heat pump water heaters, the article indicates this is a common problem that has to be solved before widespread use of heat pump water heaters. This makes sense because the rooms (and outside walls) are chilled as part of normal operation. This introduces a new mold and condensation problem in the outside walls that did not exist before the heat pump water heater was installed. The authors identified the following issues:
- Inadequate heating capacity compared to advertised specifications.
- Real-world efficiency significantly lower than rated efficiency.
- Moisture-related damage and mold growth.
And believe the issues generally track back to two primary causes:
- Insufficient access to the thermal resources inside the building.
- Improper handling of cold exhaust air.
Roger
Roger
Re: New Propane Boiler Options
@Kaos , you’re spot on about micro zoning - it will keep the boiler idling and waste energy.
But the most efficient state for a boiler is when it’s off, so the best design is thermal purge so no energy is wasted at the end of each cycle. Properly designed indirect tanks with plate heat exchangers and thermal purge will exceed the efficiency of combi boiler water heating. Last month's ASHRAE journal also had an article that highlighted why heat pump water heaters have major issues (water damage and mold in enclosed spaces of outside walls due to cold discharge air), they operate at outputs and efficiencies far below their ratings (the rooms cool off and drop performance as there is no external heat source to feed it). Further, Vermont has relatively “cheap” residential electricity ($0.225/kWh recently) compared to the rest of New England, but that’s still $6/gal propane and $9/gal fuel oil equivalent so the cost to operate the heat pump water heater is more even without including the effective impact of running a small air conditioner in your home in the winter. Most of the boiler country in the US does not have comparatively inexpensive Canadian electricity prices found in some provinces you reference.
Roger
Roger
Re: Need help choosing between Comforto (Granby) and ThermoPride oil furnace
I sell quite a few Thermo Pride furnaces. They are hard to beat, and were recently acquired by Beckett, another industry leader in the oil market. I would personally inquire about the heat exchanger warranty, then have a startup analysis performed to make sure the new heat exchanger was not subject to excessive temperatures. Most of the oil highboys can be set up to be anywhere from 70,000 to 125,000 Btu input based on nozzle selection. If you are short on return air, the tech should just configure the furnace with a smaller nozzle, and adjust the fuel/air accordingly. Just my .02
Re: Torque Wrench
That's the only thing I used a torque wrench for was putting a CI boiler together. Lots of variables with a torque wrench. How you pull or push, lube etc those little thing can throw things off by a mile.
Re: Vent placement in home 2-pipe steam heat system
Not bad. I still think you are still overlooking the importance of the different function of the vents allowing steam to get to the radiators and the vents controlling the radiator output, however.
If the runouts to the various radiators are relatively short, then there will probably be very little to be gained in terms of speed of delivery to the radiators, and indeed only large systems need vents on these runouts (or in a tall building, on the tops of the risers). In that situation, the radiator/outlet vents perform the dual function of venting the runout (minor) and controlling the heat output and hence system balance (primary function).
Now you theorize that if you tripled the venting on the radiators they would heat faster and be as balanced or unbalanced as before.
If by "heat faster" you mean that steam would arrive at them faster that may — or may not — be the case. Beyond a certain point, however, increased venting — main or radiator — may not make any significant difference at all. There are two factors involved here.
The first is that when the boiler first starts to make steam at the beginning of a cycle the pressure at the boiler is extremely low and the flow velocity off the air is, thus, also low — and largely controlled by the pressure drop in the piping unless the venting is extremely restricted.
The second is actually more important: as I mentioned earlier, the steam is condensing in the main (or runout) as it tries to heat the main up. This is influenced most by the weight (physical weight) of the mains and the insulation around them. I honestly have never run through the math on this, but it is my experience that a maximum apparent velocity of around 20 feet per minute is to be expected for an insulated main or runout, and half that — or less — for an uninsulated one (I have observed an extreme case of a two inch, uninsulated main in an uninsulated crawl space which had an apparent velocity of around one foot per minute…).
It is interesting to note that during the warmup, the steam is moving in the warm portion of the pipe at a considerable velocity — but the air in the cooler portion of the pipe is still very very close to atmospheric pressure and hardly moving at all.
On the balance of the system. Increasing the venting proportionally on all radiators — tripling, for instance, as you suggest — may or may not affect the balance of the system, but as a generalization it will. This is because there are three major factors in determining system balance: the maximum power output of the various radiators, which is controlled entirely by their size (the "EDR") and does not vary; the rate at which the radiator reaches that capacity, the length of the boiler run cycles, and the interval between boiler run cycles. It is quite rare — it does happen — for most of the heating needs for all the radiators, or even the majority of them, to reach their full capacity in any one run cycle. This is true even for systems which have been carefully designed to match the available radiator output to the required space heating needs, and even then only under more extreme conditions. Further, it is also the case that for most normal heating needs the various radiators will need to provide varying amounts of their possible output; for example, a radiator which is three times as large as is needed for a space on a certain day will need to be limited to a third of its capacity, which a radiator which is only half again as large as the requirement would need to reach about two thirds of its capacity.
Now. What governs the capacity of any given radiator? Two factors: the vent size, which controls the rate at which air leaves the radiator and thus how fast steam can reach all parts of the radiator, and the boiler cycle length which, in combination with the venting rate, will determine whether a given radiator reaches full capacity — if indeed it ever does.
Now if you increase the venting rate on all the radiators on a previously balanced system, it is quite likely that some of the radiators which did not previously reach full capacity will now do so — and the system will be out of balance.
Sorry for the dissertation, but I have the impression that you are really interested in the actual physics and dynamics of your steam system — and it's not quite as simple as it might look at first glance.
