More leakage

The leaking is fairly complex. With some difficulty we have established exactly which valves on the manifold are paired on circuits. Obviously the same order on out and return manifolds would have been much too easy! - so the photographs taken before burying were useful, but one can check by putting the ground loop circulating pump to 'continuous on' (menu 5.11). Then when the second valv of a pair is closed nothing happens, whereas when any other return valve is closed the pipework makes a perceptible sound as it relaxes.

But the actual behaviour is confusing - basically the system does not leak if the (5.11) pump is running all the time, presumably because there is some negative pressure on the return half of the loop. So one needs to go round shutting the loops one at a time in succession, for a week or so each to be sure (the fluid level varies a bit due to thermal expansion). This does look to work and we are moderately confident of which loop, and if the conjecture above is right whcih borehole, is involved.

Leakage

The ground loop continues to leak steadily at about 3 litres/month as it has been doing from January, whether or not the GSHP is operating. It is difficult to locate the leak in the manifold manhole because the ground is wet anyway - but the suppliers now agree that it is feasible to use flourescein dye and a uv 'torch' and we will try this.

Details

The inability of the electricity company to read the meter persists - every reading so far has been accompanied by a phone call asking me to re-read it! The 'smartness' is not enough to enable automatic reading but enough to confuse the people.

The leak on the ground circuit persists - at about 0.25l per week. No-one seems to have any suggestions here and the leak is probably too small to be traced, even if it is visible.

The house monitoring system (at http://www.welserver.com/WEL0412/ ) continues to be extended, now with a rainfall monitor. This is an adapted version of the Oregon unit, with an extra magnetic reed relay (from Maplin) added so that a signal is generated from the WEL's pulse inputs as well as the Oregon readout (which is not compatible). The WEL detects the switch closure and only connection is required. The sensor is a tipping unit with alternate emptying reservoirs, rather like a Japanese fountain, and only detects whole mm.

Still learning!

Well it seems that when the system was installed our electrician mis-connected the external (to the GSHP) house heating circuit pump (P1 in IVT speak, this is the usual circulating pump that all systems have) across the terminals for the ground loop circulation pump (P3), with the effect that it operated (& hence the radiator circuit water circuated) only when the GSHP was running instead of continuously. This explains all the oddities of the temperature movements before and after the accumulator tank, which have now gone away as I have re-wired it! (so much for more complex theories). Also the lounge (fan convector) now works much better. The transition is clear towards the left of the lower image above, after which temperatures hardly vary through the accumulator tank and the lounge temperature (yellow) rises to normal. One does wonder whether this might have been affecting the system last winter when we had high return temperature alarms, though of course the effect will be larger now when the GSHP is only on occasionally.

FTR this was an accidental observation after I deliberately switched P3 to continuous to see more clearly what the ground loop temperatures are doing (the average outgoing had come above the average return - but this is an averaging artifact). They do in fact behave normally top above - purple outgoing, blue return - note the ~10 minute delay for the fluid to circulate round the loop and the return temperature to drop).

Renewable Heat Support

Well the government did announce support last week - but not until 2012 for domestic systems and details are extremely vague. But GSHPs are in and ASHPs are not - as with the non-residential scheme which starts in July.

See:-

http://www.rhincentive.co.uk/

More re-heat and more meters!

On comparing the performance of radiators with the heat throughput expected of the steel/plastic/copper structure it appears that, even though steel is 200 times better than plastic the heat loss by convection is still, by 10*, the major restriction. Consequently it should be fine to use the plastic grid as an external radiator for summer re-heating, subject to its uv resistance.

Of course we had a new meter installed as part of a change to 3-phase, and the installer described it as 'smart', though the suppliers (also eon) subsequently denied this. It appears, however, that the installer was correct and this meter is now described on the website (if one checks this specific installation) as 'able to be read using sms'. Photos clearly show that this is right. On the other hand the system of (e-mail) requested meter reads and occasional calling readers is still in place, and no remote reading is actually happening. The offered website 'energy tracker' just uses this monthly data. In fact the meter reading person has not even (on the second attempt) absorbed the idea that the meter is now in a box outside the house and he just leaves the usual card instead!

Note added 1/3/11
The meter was read by the meter man yesterday when we were out, but it appears that he inverted the day/night readings. So we have given two more (sets of) readings today which apparently allows this to be corrected. The meter does give 8 readings altogether, possibly associated with the potential ability to feed-in power.

Summer ground re-heating

Since the circulating fluid temperature for equal in and out (from the ground) now looks to be about 5-6 degrees, compared to 8-9 last autumn, there is significant ground cooling as expected. We could hope for this to even out over the summer by conduction or ground water movements, but for the borehole depths this might take centuries!

IVT do normally (in Scandinavia) do re-heating by circulating the fluid through an air heat exchanger (without power except for the pump and air fans), giving free air conditioning and, if most of the outgoing air from the house ventilation passes through (which looks hard) some efficiency gain. But this is a pretty expensive (>>£1k) option. It is also not well-suited to our system in which the GSHP is far from the bulk of the house. On the other hand it should be sufficient just to pump the ground fluid round and through an external (cool) 'radiator' in summer and let it heat up naturally. Any condensation would then just drip outside. Options for this (conventional steel being unsuitable for corrosion reasons) could be commercially-available Aluminium or stainless radiators, adapted compact ground loop grids from Ice Energy (?plastic) or a sufficient length of a grid made up specially of copper pipe (estimated some 15-30m of 38mm pipe might be needed). These could all be bolted to [the outside of] an outside wall near the GSHP and the flow re-directed with valves. The WEL should tell how well this works and we are trying to get power estimates from IVT, but a 'radiator' power of a few kW as normally reckoned (albeit for a larger temperature differential to ambient) looks about right to me.

Fluctuating temperatures

An interesting result for the lounge (fan convector) temperature. The top pairs of curves here are for the out and return heating circuit (5 degreeC per division vertical (zero on the base), and a 2 hour window horizontally). The yellow is the lounge temperature and the red just an on/off trace showing whether the GSHP is working. The outside temperature is very close to zero Centigrade, and has been for a day or two.

Note:-
- The GSHP runs on a fairly long cycle of some 35 minutes (this varies with conditions)
- The fluctuation in lounge temperature is in sync with, and has amplitude about proportional to, the heat circuit temperature (that is about 2 degrees p-p for the room at 20, and 5 p-p for the water at ~50).
- other rooms also fluctuate like this but a good deal less; but the radiators in these rooms have a large heat [hot water] capacity whereas the fan convector (even this big one!) holds very little water.
- the radiators are all balanced to give a substantial temperature drop (~10 degrees) in normal conditions
- the heating circuit is continuously pumped

So one might deduce that the room heating was in dynamic equilibrium with its heat losses with a time constant of less than 30 minutes. But in fact the house temperature varies rather slowly compared with outside conditions with time constants of days. One might wonder about placement of the sensors but mobile thermometers do much the same. So perhaps there are several time constants involved. Hard to know without shutting off the system and watching the temperature fall!

Certainly the rather long cycle time of the GSHP may be fine for ordinary radiators, and even more for underfloor, but it would be good if it were much shorter for fan convectors. I do not see how to achieve this! As a possible fudge one might re-arrange the circuit to put a conventional radiator or some kind of insulated tank in series with the fan convector as a reservoir - but this looks rather complex. As already noted the 'accumulator tank' does not mix significantly and does not provide any significant reservoir function.

More surreal electrics

Two phone calls from the supplier in the past week. One asking for feedback on the installation process (though I have already done this online), and one trying to confirm AGAIN that we only have one meter. The latter difficulty seems to arise because back in October someone created a new account for the new 3-phase meter instead of switching it on the existing account. But this has come back many times now and the systems seem unable to get it finally straight! Even though the addresses are the same and the meter install and removal were done by eon-branded staff getting this permanently nailed seems to stretch the system.

There must be a great opportunity to sell them decent tracking software...

Filtered Rock

Well I checked the filter on the ground loop cicuit as recommended and was astonished by this substantial lump of stone & cement (I think). Still it clearly was filtered and there seemed little else. There is no significant fluid loss.

There is also an air-bubble-type sound from the ground loop near the GSHP when operating; not loud but interesting. I have tried the vent on this (when the p[ump is not operating), though the tank is barely above this. We shall see.

More balancing

Well more efforts to rebalance the radiators (to balance the temperature drops across them*) seems to have brought the lounge (fan convector) up a little, though it still is a little low (and fluctuates more). One radiator in particular was seeing too much flow, and thus presumably hogging the hot water. There is no discernable effect on the overall return temperatures but the fan convector seems to run more often and produce more heating.

* by adjusting the 'lockshield' valves at the opposite ends from the thermostatic valves. This is fairly standard and I used thermometers to get 10-11C drops, though pros apparently do it by feel (if at all!).