That I don't know. I suspect it will modulate on any mode. However, it seems to be cycling on a regular basis anyway. Even modulated right down, my average heating requirement is very low. It is an Edwardian terrace. I calculated 8.4kW when it is -3C. At 10C outside, my requirement will be a fraction of this (probably around 3-4kW) which is below the modulating range. It definitely is modulating down, though, as the gas rate at the meter varies.
At some point, I might bother to redo the heating circuit with a TMV and pump to make the radiators cooler and reduce the return temp.
The pluming I get from it is very slight whatever the return temperature, especially compared with the Icos I had in the last place, which created sufficient fog bank to have saved the Tirpitz.
Do you have a feeling as to whether this is because the bottom modulating point is less or because it's condensing more internally and delivering to the condensate drain?
I'm not quite sure. We were going to pull the condensate drain apart and take a peek, but never got round to it, as I needed the cooker point moved the same day.
One major difference is that the flue is much longer. Not very long, mind. However, it does have a couple of bends, an extension piece and a vertical flue terminal. This would give a much greater chance of flue condensing.
I still don't know if it isn't pluming because the flue gas is too hot, or too cold for major condensing at the terminal. If anything, there are more wisps at higher return temperatures than lower ones.
It seems a shame really, having gone to all the trouble of having the terminal in a place where pluming wouldn't be a problem! (It goes out through the roof).
I put a tundish under mine to be able to see the flow.
Could have an influence, I suppose. I have a flue kit which is a bend and straight out through the wall, with a downward slope back to the boiler.
Given the current conditions, it's probably because it is modulated down. Don't forget that the volume of condensate produced depends on the burn rate as well as the low temperature - i.e. less gas, less water. Also, it looks like this boiler modulates by varying fan speed. This influences the velocity of the flue gases, and I would assume that the longer time spent inside, the greater the amount of condensation inside.
It would appear that different designs have different characteristics.
The Greenstar seems to have a minimum power level of 7.5kW vs. the Ideal's 9kW, although that doesn't suggest a huge difference. Perhaps the heat exchanger arrangement - although both seem to be downfiring types, the Greenstar looks like it has a tall heat exchanger at the side, whereas the Ideal has a shallower one at the top.
My boiler drops down to about 3kW on CH output, and under those conditions, there is very little visible from the flue and a steady drip of condensate - perhaps 2-3/second. The only time when there is a more substantial plume is when the boiler starts a hot water cycle with a totally cold cylinder. Then it is wound up to about 28kW with full fan speed and a temperature difference across it of 25 degrees plus. Under those circumstances there is a fairly hefty stream of condensate into the drain. That only lasts for a few minutes, though. There is a temperature sensor on the cylinder, and as the water temperature approaches the set point, the boiler modulates down
I had a bucket under the Isar I did a few weeks back, and got a steady dribble of condensate (it was a cold night, in a cold house, and we'd fired up the system for the first time). But we couldn't see the flue.
When I measured the gas rate it was approx .01 m^3 in 15s immediately the boiler fired up (not measured over the usual 2 minutes for a digital meter as the boiler modulates down too soon) indicating a heat input of 25.73kW. After about 30s(?) the boiler modulated down to half that, staying at that sort of rate for several minutes until it turned off. (It was too cold, late and dark to take more gas rate samples, but when Christian gets a webcam set up on the meter and we can OCR the readings I'm sure we'll get some really interesting data :-)
Well, Worcester-Bosch got back to me. From the horse's mouth:
I tried it (with a chisel instead of a screwdriver and a piece of offcut T&E rather than a plastic rule). It worked easily with hardly any force. I think that the lever idea works not because of the extra force that could have been applied, but because it applies the force at the specific angle if seems to require.
It's too early to say what the recovery performance is now. I haven't even had time to ensure that the flow temp gets above 75C, as I only had 2 minutes to spare and it was during a 3 minute anti cycling cut out.
"Andy Hall" wrote | John Stumbles wrote: | >But the gas regs require a 25mm separation from electrical cables :-) | Well I've heard of some excuses..... | Is that power as in mains cables or any cables though (as a matter | of interest)?
I must confess I thought the BT man was taking a bit of a short-cut when he cable-tied a neighbour's line down the outside gas pipe.
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