Oil vs Gas as 2nd stage
We currently have a single pipe steam system that heats 3 adjacent 16 apt buildings. (for a total of about 48apts) The source of the heat and hot water is a single large oil burning boiler. In an effort to make the system more efficient, we are considering adding 3 individual water heaters to allow…
We currently have a single pipe steam system that heats 3 adjacent 16 apt buildings. (for a total of about 48apts)
The source of the heat and hot water is a single large oil burning boiler.
In an effort to make the system more efficient, we are considering adding 3 individual water heaters
to allow us not to run the Steam boiler in the summer.
We would however like to utilize the heat from the boiler when it is available in the winter.
This can be accomplished by connecting the water heaters after the boiler.
Our plumber has advised us that we use modern Gas Water heaters as they will be easier to maintain.
This however will require us to redo the piping as the Gas boilers are supposedly not allowed to be
in the same room as the big Boiler.
Luckily the individual buildings have old flues from coal days, which can probably be relined and used again.
Is there any benefit to getting gas heaters other then them being more common?
First of all the tank is never “drained”, only cooled.
Second, the Heat Timer has nothing to do with the domestic hot water production. Only recently have they incorporated that technology into their panels.
The hot water control is a parallel circuit with its own high limit setpoint.
This is a fairly common arrangement.
I don’t think the boiler controller (Even though it is the latest Heat Timer Platinum) is smart enough to do a “gentler” burn cycle to just heat water. I still don’t understand how you intend to control the burn cycles vs water in the holding tank.
We just had a Holby mixing valve installed so that the superheated boiler water would get mixed in with cold water in order to keep it at a nice stable temperature at the faucets.
Now, I do agree with you that the longer cycles that are a lot farther apart may be more efficient but that probably depends on how much water is being used at a particular time. Meaning it’s probably about the same or worse at peak times, and better during long idle times.
Ideally the pump would circulate the water through the boiler’s coil while the boiler water is hotter then the water in the holding tank. Once that is reversed the pump would stop until the water in the holding tank would be drained to a set level OR the boiler is fired again because the water in the tank got bellow some set temperature.
Does that sound like something that can be done?
Yes, some percentage of the start of a heating cycle is always the least efficient, so it is good practice to limit the amount of start cycles. Boilers run most efficiently when they are deep into a run.
You don’t have to heat the boiler as if you were trying to make heat for the building to do this. It is a much gentler cycle.
Fewer, longer cycles produce the most efficient results.
If the tank cools below a set point, it will trigger the pump, then circulate water between the two as the burner fires (in most cases).
There are several ways to do this, but it’s usually a very good way to go.
Master Plvmber, so what you are saying is that longer burns that are farther apart are more efficient then shorter burns closer together? How so?
The boiler is a very large heavy gauge steel boiler, so I’m guessing that if it is allowed to cool, heating it all up again at each burn cycle will waste heat. If I am mistaken in my logic, please explain.
Second thing, you recommended to add a holding tank near the boiler with a circulating pump. That will extract as much heat out of the boiler as possible while it is hot and then shut down? What happens when the water in the boiler is cooler then in the holding tank? Can the holding tank trigger the boiler controller to turn on the boiler when the water level goes bellow a certain point?
The type of storage tanks do matter.First someone has to do a calculation of the amount of daily gallonage,next the storage has to be set-up to maintain close to even water temperature at peak times.You can tie in a storage tank to an oil-fired water heater,which can give you fast recovery with storage or tie in the storage to the boiler.The turbo-max storage-tanks work well with a regular storage to enhance the even temperature of the water,better than most storage tanks.
I have always been a proponent of oil fired hot water heaters. You already have oil and flues in the boiler room. flue capacity is a necesary calculation by sq in/BTU, so they may be OK to vent with existing oil fired boiler.
The advantage of oil fired hot water heaters is there unbelievable recovery rate. Storage based systems (gas or boiler based) are adequate most of the time, but can get slaughtered during peak usage (before work, at night).
The ability in a pinch to make new hot water quickly if needed, is a deal maker. I have found that oil companies do not charge as much for service contracts at the same site, and it is a pleasure to shut down cold the big boiler.
What size storage tanks would they need for a building that size?
We’ve been thinking about adding a storage tank to our oil-fired tankless setup. 25 unit building, abt 4200 gallons per day of water consumption (all water, not just hot). We burn roughly 17 gallons of oil a day during non-heating season to supply hot water.
If you’re using tankless coils set in your boiler, you would get good results adding a storage tank and having the boiler run fewer, longer, more-efficient cycles than it does now. You wouldn’t have to tax your flue with the extra fuel usage or incur the costs of moving any piping.
The boiler probably burns at a higher efficiency than a free-standing gas or oil water heater would anyway.
Me:
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