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Old 10-25-12, 03:40 PM   #21
Piwoslaw
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A month ago I cleaned out the boiler's heat exchanger, and I did it better than last year: I used an old bicycle spoke to remove the debris and deposits between the HX's fins. Lots of work, took lots of time, but I estimate that the clogged spaces between fins reduced the HX's surface area by 5-8%, so it was like new again

Unfortunately, a week ago the boiler stopped working. The serviceman said that one of the electronic modules is bad and the whole motherboard must be replaced. The boiler is 12 years old, the model has been out of production for a decade, so replacement boards are non-existent. Now I have a boiler hanging on my wall which probably only needs to have a resistor or relay replaced to be perfectly good, but nobody can tell what needs to be done. In fact, the serviceman said that (besides the bad board) the boiler is in very good shape, much better than most younger models.

So we spent a week struggling with a small electric heater to keep the temperature in the house above 15°C (59°F), we usually keep it 1.5-2°C warmer. But today we finally got a new boiler installed, which is ...
[drumroll]
a condensing model

It's been running for only an hour now, so we are all soaking in the heat, but I did get a chance to go through the manual. If I understand everything correctly, then the boiler's efficiency is over 97% with 80°/60°C supply/return temperatures, but 107% with 40°/30°C. My system's temperatures are close to 45°/38°C, so I should be taking advantage of the condensing effect. Every drop of condensate means more heat got extracted from the fuel

As I get used to this new boiler I'll post updates.

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Old 10-25-12, 04:24 PM   #22
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Sounds great! That should be good for a solid ~15% reduction in fuel usage.
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Old 10-25-12, 11:52 PM   #23
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I sure hope so!
So far the first burn was much longer than usual, but this may be because the house needs to warm up, plus the new boiler is rated at 18kW. The old boiler was 23kW, but was installed before the house was insulated and the windows upgraded.
Since yesterday evening it has filled an 8 liter bucket with condensate. I've noticed that the condensate that drips down is not warm, as I expected.

I have yet to clean up the basement and hook up the temperature sensors and radiator fans.
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Old 10-26-12, 07:15 AM   #24
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Is it also a modulating model?
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Old 10-27-12, 12:29 AM   #25
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Yes, it has a cylindrical burner which can be modulated between 6.5 and 18kW.

Reading through the manual I found something new which my old boiler didn't have: The circulation pump has two speeds, but they are not controlled with a switch like on other pumps I've seen, but instead the computer controls it via 4 wires. One of the options in the computer's menu is pump speed: High, Low, or Modulated. In the latter case you set a deltaT parameter (default is 20°C) which tells the comp to keep that temperature difference between supply and return. If the difference is greater than the deltaT parameter, then the pump's speed is High, otherwise it's Low. It takes 5 minutes for the computer to decide to change the pump speed.

Yesterday evening I got my temperature sensors hooked up and noticed that the supply temperature peaks at 40°C even though the boiler is set to 48°C. My temperature sensor is pretty accurate (DS18B20), tucked under the insulation right at the exit from the boiler. I'll check with the IR today. The return temp maxed at 31°C.
I also wanted to add a sensor between the primary and secondary heat exchanger to see how much I'm gaining from the condensing function, but after looking inside it appears that everything is all bundled up in one neat package

BTW The boiler model is Ariston Clas Premium Evo System.
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Old 11-05-12, 12:06 AM   #26
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Small update: The boiler is working just fine I'm getting about 1-1.5 liters of condensate for each on cycle (2-3 cycles per day with this weather). I found out that each liter of condensate is worth more than 0.6 kWh of extracted heat It too early to see how much more efficient this boiler is, though.

I'd like to have the condensate collect in a barrel to use for flushing during the winter, when we have no rain water, but I'll have to ask the family if they are willing to cooperate.

I moved the temperature sensors inside the boiler, in fact inside the closed space around the combustion chamber, but they are still showing funny data. They are under insulation wrapped around the copper tubes, less than a centimeter from the boiler's temp sensors. Yet my sensors still show lower numbers, for example when the boiler claims supply/return to be 50/38°C then I'm seeing 42/32°C, but when the boiler is off and everything cools down to 14-25°C, then both sets of the sensors show the same temperature.
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Old 02-07-13, 02:21 PM   #27
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Our new condensing boiler rocks!!
During the three previous 7 month heating seasons (Oct 01 - May 01) my ratio of cubic meters of gas to HDD was 0.63, 0.57, 0.51, resp. The average for the first 4 months (Oct - Jan) of this seasonis only 0.37!!
This is mostly due to the following
  • Condensing. Lots of free energy was going out through the chimney.
  • Closed combustion chamber. The open chamber in the previous boiler was sucking up lots of house air, which had to be replaced by cold outside air. Last year our basement's temperature was down to 3-4°C, with -3 to -5°C on the floor next to the fresh air vent (= hole in the wall). This year it is 10°C, with the floor being only 2°C less. The vent is stuffed with foam
  • The new boiler is not as oversized as the previous model. Plus I have more control over many parameters, allowing me to tweak efficiency. Ask Mrs. P, she'll tell you how much time I spend in the basement, or at least reading the manual over and over again.
  • She'll also tell you how much she has to complain about the room thermostat being set too low. But it's not worse than last year. I'm being good this, really
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Old 02-07-13, 02:49 PM   #28
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Default Feed temp? Return temp?

Quote:
Originally Posted by Piwoslaw View Post
Our new condensing boiler rocks!!
So you're using radiators right?

Are they the cast iron type or are they the aluminum fin type?

Do you know what the temperature is of your feed water in the pipe that is coming from your boiler?

And the return temp in the pipe that is going to your boiler?

I'm just trying to get some idea of what is typical...

-AC
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Old 02-07-13, 11:30 PM   #29
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Yes, old cast iron radiators with large diameter plumbing, holds 250-300 liters of water total. As opposed to most other systems of this type, our radiators are quite large, I'd guess at least 20% larger than what I've seen in other houses. Lucky for us we can keep the supply temperature down.

Normal temperature for this type of system is 60/40°C supply/return, I've been able to keep supply below 50°C (40° when it's above freezing outside). Return temps can be only 5°C below supply if the boiler has been work in lowest setting for 1.5-2 hours, but I'm still getting condensate.
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Old 02-08-13, 06:27 PM   #30
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Quote:
Originally Posted by Piwoslaw View Post
Normal temperature for this type of system is 60/40°C supply/return, I've been able to keep supply below 50°C (40° when it's above freezing outside).
Hummmmm.....

To put into units that are more familiar to me,

60C = 140F

50C = 122F

40C = 104F

I was just thinking how this would go if you were to implement a heat pump to heat your water.

There are some heat pumps that use CO2 as their refrigerant, that could hit 140F (60C), but they are pretty new technology and would be expensive to buy.

But at temperatures of 122F (60C) and below, You could use a pretty standard heat pump. You could even hack one that would work for you... but as I recall, the Polish landscape is not littered with old air conditioners.

You could use the Build It Solar Fuel Comparison Calculator to see if there would be any advantage to using a heat pump. The calculator comes up with typical US defaults, but I'm pretty sure you can manually enter your local values and do a valid comparison.

Also, I seem to recall that you were experimenting with using small fans to increase the efficiency of your existing radiators... do I remember correctly?

If yes, did it improve things significantly?

Best,

-AC

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