Thirteenth lunar month of central heatingTwelfth lunar month of central heatingEleventh lunar month of central heatingEvaluation: a year from installationTenth lunar month of central heatingIndex
Fifth lunar month of central heating
by Unknown - 15:12 on 27 January 2014
Fifth Month
If you are a newcomer to this blog, it might be best to begin by reading earlier instalments of the blog, perhaps starting from "Why we installed a Smart".
| Total kg pellets used | 1121kg |
| Average daily kg (days in residence) | 40.04kg |
| Metered kilowatt hours to central heating/hot water | 2928kwh |
| Gross kilowatt hour value of pellets | 5380.8kwh |
| Space heating (calculated) | 1595.73wh |
| Efficiency (based on measured input, metered output to central heating and calculated space heating) | 84% |
| Cost of pellets | £232.99 |
| Potential RHI subsidy | £392.94 |
During this month, we were not away at all, so the average consumption per day has been calculated for the full twenty eight days for the lunar month. Except when there was a high wind with cold weather, we had two sessions of 6.30 to 10.30 then 12.30 to 22.30. During this month we did normally use our wood stove in our first floor study during periods when the upper floor central heating zone was off (this had not been necessary in September, nor for almost all of October). We were happy with the Smart's performance throughout, although there was an issue that arose when we had a series of power cuts. I'll report on that elsewhere together with some other minor glitches in its operation.
The following notes are for anyone who wants a technical explanation of the table.
- The calculated efficiency given above is calculated by a new method which is a refinement of my previous methods for calculating efficiency. There does need to be a special method for calculating efficiency because of:
- the effect of the load valve in our system when heating up from cold:
- There is an ESBE "load valve" in our system which prevents water from circulating through the central heating system until the Smart 120's boiler has has heated up sufficiently. This load valve gradually opens up. I have measured the effect of this and it is quite marked. In its normal operation at output level 5, the Smart 120 is designed to output at a rate of 17.5 kilowatts to the central heating/hot water and 5.2 kilowatts to space heating. However when it is heating up, the effect of the load valve restricts its output to the central heating to a rate of about 6 kilowatts and so about 16.7 kilowatts is directed to heating up the Smart 120 itself and the surrounding space. During its heating up phase, the Smart works at output level 5 for about 20 minutes and during this period about 2 kilowatt hours go to the central heating/hot water and 5.9 kilowatt hours heat up the Smart and its surrounding space. After this heating up phase, so long as the water temperature stays high enough, the Smart works in its normal way.
- the effect of the load valve when the water temperature drops because the programmer switches between heating zones
- In our house there are two main heating zones, the upper floors and the ground floor. The ground floor is divided into two zones, the sitting room and the rest of the ground floor. There is also the hot water tank with one associated radiotor in the utility room. The programmer switches the flow of hot water to heat the zones we have scheduled to be on at particular times of day. When a new zone is switched on, the water temperature in the Smart's boiler drops and the load valve restricts the flow of water until the boiler has heated up again. The effect of this is not as great as when the Smart first heats up, but is still considerable. I have measured this effect and, when the water temperature is low the Smart outputs at a rate of about 12 kilowatts to central heating/hot water and so 10.5 kilowatts to heating itself and the surrounding space. If it is 15 minutes before the water temperature recovers, then this means that 3 kilowatt hours go to central heating/hot water and 2.675 to heating the Smart and surrounding space. In our house, there is quite a lot of switching between zones and this factor is important.
- the effect of the Smart reducing its output level (and hence the ratio of water heating to space heating) as its water temperature climbs towards its target
- At output level 5, the Smart is designed to output at a rate of 5.2 kilowatts to the room and 17.5 kilowatts to central heating/hot water, thus the ratio of space heating to central heating/hot water is about 0.297, but at output level 1 it is designed to output at a rate of 2.4 kilowatts to space and 4.5 kilowatts to the central heating/hot water giving a ratio of 0.5333. At other output levels, the ratio is in between these two extremes. Consequently, the overall ratio of space heating to central heating/hot water depends on the extent to which the Smart turns itself down as it moves towards its target temperature.
- We have recently changed the thermostat in our load valve and the result is that it begins to open at 55 degrees but only fully opens at 65 degrees. We have reset the target water temperature to 70. As a result it operates at output level 5 with a full flow to the central heating/hot water at 65 and 66 degrees, then reduces its output level down to 4 at 67 ... and down to 1 at 70. Previously our load valve thermostat began to open at 60, but was only open at 70 and our target temperature was 74. I had thought this change might make a difference to efficiency, but it does not seem to make much difference.
- My new method of calculating efficiency is the result of working out a typical schedule for the Smart's changes in water temperature and output. On the basis of this (together my measurements of the effect of the load valve, and Klover's indformation about normal ratios of space heating to central heating/hot water at different output levels) I have calculated an overall ratio of space heating to central heating.
- For information, in previous months I had three estimates of efficiency which I used for previous months. These estimates for the fifth month would be a "lower bound" bound estimate of 71% (simply based on Klover's ratio for the Smart's maximum output level), an estimate of 79% allowing for the effect of the load valve during heating up, and an estimate of 81% allowing in addition for the effect of the load valve during zone change. The new estimate of 84% is different (a) because it is based on actual measurements of the effect of the load valve as opposed to calculations of its effect (b) because it allows for variations in the ratio of space heating to central heating/hot water as the Smart's output level changes.
- In an earlier posting, I commented on studies of in situ efficiency of condensing boilers which indicated an efficiency in the low 80s. My measurements and calculations suggest that the Smart does match their efficiency. Of course, my estimates of efficiency can only be regarded as approximations if only because the ratio of space heating to central heating will vary from day to day as the external temperature and the wind chill on our house varies and affects the heating up time and the output levels of the Smart.
Comment from suzie at 14:40 on 01 February 2014.
we are very nerviously looking at the Klover (the nerves being caused by a very bad experince of a log burning cooker with a back boiler but a desire to still stay away from oil.)You blog is great and i think we will be going the same route.
Comment from Justin at 22:08 on 08 February 2014.
I'm seriously considering a Smart 120 to run a new heating system for my 1991-built timber-frame house in the Scottish Borders, currently heated by electric storage heaters. One minor concern is that we'll need a twin-wall flue due to the timber frame construction, and I'm curious to know whether that will work with the rumoured soon-to-appear insulated hotplate cover(s), which I'd like to use to minimise heat output to the kitchen. Any notion whether there's enough space from flue to hotplate to make that not a concern?
Also, I note your comment "there was an issue that arose when we had a series of power cuts. I'll report on that elsewhere together with some other minor glitches in its operation." - could you give us a link to that please?
Many thanks for your very informative blog about the Klover, it's been incredibly informative and very interesting to those of us looking to install similar systems.
Also, I note your comment "there was an issue that arose when we had a series of power cuts. I'll report on that elsewhere together with some other minor glitches in its operation." - could you give us a link to that please?
Many thanks for your very informative blog about the Klover, it's been incredibly informative and very interesting to those of us looking to install similar systems.
Comment from Roy at 18:12 on 09 February 2014.
Would like to hear about your experiences of power cuts. We are considering a clover and live in a rural area. We have a pumped system and would like to understand how the clover deals with a power cut. We cannot use a conventional back boiler without a re-plumbing exercise on the hot water.
Comment from suzie at 18:06 on 20 April 2014.
ok we jumped, not sure firing up the Klover last thing thursday eveing before easter not ideal. So the good thing is unlike our log burning cooker boiler that ate £1000 o logs this winter and left us still shivering we came home from a pub meal to the kitchen at 26' and the Klover still going even though we thought we set it to go off 30mins before we got home.So far our feeling is its great but we just need to learn how to control it. We have however cooked 2 loaves and currently trying a roast......
Comment from John Caley at 22:54 on 02 November 2014.
Hi am considering having a clover 120 in
my new build instead of a ground source
heat pump.I was told that in an entire
year full blast it would only use one tonne of wood pellets but reading your article here it seems to suggest that it
40.04kg surely that's a lot more than two tun per year?
JohnCaley tel 07624 439957
Comment by Roger:
At full blast it will use far more than 1 tonne, but I doubt if it would be necessary to run it at full blast in a newbuild. Our house is big and old and we find it easy to consume about 8 tonnes a year even with our house divided into zones and not all heated at once. Heating the whole hose might take us up to 12 tonnes. With a well-insulated draft-proof new build, you could get by on much less than this, but we can get through half a tonne in 3 summer months for water heating and cooking, so you should think in terms of several tonnes in a year. A thermal store would help you to be selective about when you run it for cooking.
my new build instead of a ground source
heat pump.I was told that in an entire
year full blast it would only use one tonne of wood pellets but reading your article here it seems to suggest that it
40.04kg surely that's a lot more than two tun per year?
JohnCaley tel 07624 439957
Comment by Roger:
At full blast it will use far more than 1 tonne, but I doubt if it would be necessary to run it at full blast in a newbuild. Our house is big and old and we find it easy to consume about 8 tonnes a year even with our house divided into zones and not all heated at once. Heating the whole hose might take us up to 12 tonnes. With a well-insulated draft-proof new build, you could get by on much less than this, but we can get through half a tonne in 3 summer months for water heating and cooking, so you should think in terms of several tonnes in a year. A thermal store would help you to be selective about when you run it for cooking.
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Many thanks, will continue to follow with great interest! Sheryll