6 x 30 tube 58mm Panel Project Report

[desperate]

Hi Kristen

how about PIR,s or time delay switches for the secondary pump


Desperate

[kristen]

Sorry Desperate, I've got so many pumps! which one are you referring to?

[dhaslam]

Are you considering more insulation for the tanks?    I have to increase the insulation on mine because the heat pump will be  stretched to reach high enough temperature  and I don't  want to loose more than a degree or two at most.   Also even is summer there are days when solar has to be boosted a bit just because it has lost several degrees overnight.

[kristen]

I think I should be doing that. I'm losing 10C per day from my system as standing losses.  I don't know if that is from the tank, or the pipework - I suppose I should isolate the tanks on a day when I am out and record the change, and then compare against the 10C I see on days when the pipework is connected.

One thing extra tank insulation would help with (regardless of the pipework situation, I think??) is if the tank is raised to a very hot temperature.

Ideal for us, in Winter time, is to burn the boiler late afternoon, and if it goes out at, say, 10pm with the store at 85C, just as the thermostat falls-back to the night-time setting, then I don't really want any heat leaking into the garage overnight until the CH starts demanding at 5am or 6am.

Additionally, the fact that the tanks are in teh Garage makes a case for more insulation because the Delta-T to garage, during the winter, is pretty much the same as if they were outside! I have plans for a partition wall across the garage, and I can then heavily insulate the "Boiler & Thermal Store Room"

[KLD]

Kristen
One of the fancy thermal store manufactures in Germany put it quite bluntly in their requirements: store only the surplus, use the heat as close as possible in time to producing it. This is one of the reasons why I thought a separate DHW tank might help. You could then run the main store at lower temp, especially over night when there is actually no need for any heat. The smaller DHW store could then more easily be heavily insulated and thus provide for the morning HW need. The main tank would still hold enough heat for running the CH to take the morning chill out, before firing the log boiler.

The DHW circulation still seems to rob quite a lot of heat. Maybe you could try manual switches located by the taps. So, instead of turning the tap on briefly, off again, count to 20, and have "instant" hot water, you'd press a button, count ...
There should be wireless switches available to make installation easy.

Your installer will probably  at you when you ask him to put yet another cylinder in 


Klaus

[kristen]

I've changed my mind a bit ...

Changing the switch over from top-coil to bottom-coil down to 60°C (initially  set to 80°C then 70°C) seems a good compromise.

The Solar will, it seems, readily get the top up to 60°C, and thereafter it makes sense to raise the whole tank to lower temperatures, instead of just raising the top to higher temperatures i.e. heating via the bottom coil, once all is above 60°C. Whole tank got up to 60°C yesterday, starting from 46°C.

Actually, going back to earlier conversation, perhaps my "coils in series" would do the best job once bottom of store reaches 60°C.  That will favour the top of tank, and create some additional temperature gain at the top, which will help if we then have some poor days. At the risk of adding yet more complexity , coils-in-series should only continue if the Delta-T between Top and Bottom coils is "small".

We did consider remote [by each tap] switches.  The trouble is how do you know if the circuit is hot, or not?  You run some water, and then decide that it isn't.  So you press the button. Counting to 20 doesn't work I'm afraid (unless you are lousy at Maths!) it takes at least 2 minutes to get the water hot at the far taps [possibly could have installed a larger / faster pump].

I think what we have works well, in practice.  There is almost always hot water available during the day and, hopefully, not at night or when the house is unoccupied.

On first use the pump comes on a timer (set to about 5 minutes I think).  That is cancelled once the return temperature gets to 40°C. It also sets a 1.5 hour delay, so the pump won't run again for quite a while.

Having said that, every little tap use on the water circuit (hot or cold) trips the pressure switch, which annoys me [even thought the 1.5 hour timer prevents excessive pumping], and you have to run the hot tap hard, first thing in the morning, top cause the pressure switch to trip.  A really sensitive flow switch, on hot circuit only, would be better.

I could finesse it by having the cutoff sensor at the furthest tap, so that the pump only runs until 40°C arrives there.

Hmmm ... I should do an experiment when the circuit is stone cold to see how long it takes for hot water to arrive at each tap. A good project for summer holidays and small children!

I basically come back to the fact that my house needs twice as much energy as the average to heat the DHW; and whilst I would like to improve that, I have now got a lifestyle comfort that the family like.  Its all mute in the winter, the DHW energy contributes to whole house heating.

The system is far better than what we had before where a gravity circuit heated the DHW and there was always hot water at any tap ... and the boiler fired regularly during the day.

[desperate]

Kristen
sorry for the vague post, I was referring to the domestic hot water circulation pump(bronze), use a PIR with timer built in, in each bathroom to trigger the pump just when you need it, you could do the same in the kitchen/s or a time delay switch, so not every visit to the kitchen activates the pimp.

Desperate

[kristen]

Thanks Desperate, I think I've covered it my previous post. Not sure this would be a significant improvement on what we have got - and would lead to "Run tap, not hot enough, press button ..." plus the hassle / cost of wiring it in (switches in bathrooms or batteries wireless - hard to get through the significant number of walls to the remove sensor ).  But I'm still listening if folk think it would still be a better solution.

I need to get a sensor on the circulation pump so that I know exactly how often it actually runs.  It may just be that the excess energy usage is people running the hot tap for short periods, and "re-heating" the long-legs on the circuit.

[wookey]

I go away for a trip and Kristen has planned, started and finished the whole thing before I get back!

I think we discussed the Navitron website figures for input heat being, well, 'wrong', sometime last year, and I muttered quite hard about the figure remaining on the website for months.

Yes, here: http://www.navitron.org.uk/forum/index.php/topic,3741.msg36587.html#msg36587
and here: http://www.navitron.org.uk/forum/index.php/topic,3921.0.html
and http://www.navitron.org.uk/forum/index.php/topic,620.0.html

And the FAQ _still_ says you can get 14kWh/day from a 20x47 panel, which after a whole year really does deserve some reporting to trading standards. Come on, guys, its not funny anymore. Navitron presents itself as an honest outfit that will provide realistic engineering numbers. Publishing massively inflated numbers for the output of your panels is in direct contradiction of this image. Anyone can make a mistake, but not fixing it, after repeated pointing-outs, for over a year, looks very bad, and could reasonably be considered deliberate.

Kristen, using the more realistic numbers in the above threads I reckon you are likely to be looking at an average of around 54kWh/day in June/July - i.e about half the numbers you've been working from.

[kristen]

"using the more realistic numbers in the above threads I reckon you are likely to be looking at an average of around 54kWh/day in June/July - i.e about half the numbers you've been working from."

Thanks Wookey, but that is seriously worrying as I have based on my sums on the published figures.  Some people have suggested those figures are optimistic in this thread, but I hadn't clocked that feedback before installation.

I installed 6 panels instead of the 5 I intended to, so have over-spec'd by 20%, in expectation of some loss from less-than-ideal. If I have to install a further 6 panels to get what I need that will increase my panel cost by 240% and make the economics completely non-viable for me, not to mention that I don't have enough roof space.

I don't think I will come close to 50% of target, with the figures I have so far this month. (see below)

I wasn't here to monitor the system on the best day we have had, but it looks like my best days will be just over 50% of the published figures.  I don't think that is going to make an "average" for the month of 50% of the figures.

I have the benefit, I presume, of economies of scale - 6 panels should have less losses, relatively, than a single panel system.

We've had good weather since the installation, bar a couple of days. Thus I don't see that as being sustainable for the whole month - the average is likely to be less.

I'll see if I can find insolation levels for an airbase or somesuch near here, and compare with long term average.

I am calculating based on the heat gain, plus the standing loses that I expect [will have occurred in that interval], plus the metered DHW used. Its coming out pretty close to the kWh recorded by the TDC3

Edit: Table modified to add data for subsequent days

Date	|	K's kWh	|	TDC kWh	|	Pump	|
08-Aug	|	31.88	|	-	|	-	|
09-Aug	|	28.74	|	-	|	-	|
10-Aug	|	12.78	|	-	|	-	|
11-Aug	|	54.58	|	-	|	-	|
12-Aug	|	5.83	|	-	|	-	|
13-Aug	|	11.67	|	-	|	-	|
14-Aug	|	-	|	-	|	-	|
15-Aug	|	-	|	-	|	-	|
16-Aug	|	-	|	-	|	-	|
17-Aug	|	-	|	-	|	-	|
18-Aug	|	32.78	|	38	|	-	|
19-Aug	|	40.71	|	47	|	5	|
20-Aug	|	43.75	|	42	|	6	|
21-Aug	|	46.14	|	47	|	5	|
22-Aug	|	-	|	42	|	6	| (Failed to record data manually )
23-Aug	|	66.28	|	61	|	6	|
24-Aug	|	23.76	|	21	|	3	|
25-Aug	|	37.59	|	35	|	5	|
26-Aug	|	17.49	|	22	|	3	|
27-Aug	|	46.65	|	49	|	6	|
28-Aug	|	26.47	|	28	|	4	|
29-Aug	|	-	|	25	|	3	| (Failed to record data manually )
30-Aug	|	10.03	|	12	|	1	|
31-Aug	|	41.99	|	45	|	5	|

(Edit: average 33.38 kWh for 17 actual daily readings 08Aug - 31Aug, TDC average 36.71kWh for 14 daily readings)

Early figures had the sensor in the wrong place, so no sensible kWh from the TDC3, plus I was not recording pump-run-time. 14-17 Aug I was away.

Early figures may be a bit dubious (insulation not complete, some tuning done since) but the average is 28.7kWh per day [up to 20-Aug inclusive]

Navitron published figures suggest that I should be getting average of 96.4 kWh per day in August

Edit: September 2009 figures are later in this thread here

[dhaslam]

And the FAQ _still_ says you can get 14kWh/day from a 20x47 panel, which after a whole year really does deserve some reporting to trading standards. Come on, guys, its not funny anymore. Navitron presents itself as an honest outfit that will provide realistic engineering numbers. Publishing massively inflated numbers for the output of your panels is in direct contradiction of this image. Anyone can make a mistake, but not fixing it, after repeated pointing-outs, for over a year, looks very bad, and could reasonably be considered deliberate.

The worst part is that systems could be installed with smaller panels than needed which  reduces sales as well.    I would probably have added a third panel if I had more accurate output figures.

[rob26440]

Panel kWh – published v achievable.  My view….

Published figures.  Are they based on reality (i.e. a real system in “normal” weather conditions with verifiable measurements over a period – say at least 1 yr. in a specified location (latitude/longitude/direction/elevation)?

Or are they “laboratory” results using controlled, ideal and unnatural conditions – such as: short term, in-house environment, artificial lighting, no wind/rain etc, controlled ambient temperature, carefully optimised system settings and conditions (such as v. low starting temperature of the water to be heated with consistent, high insolation), advantageous plumbing arrangement, additional insulation, sophisticated measuring devices…? The list goes on.

Real installations have unique conditions that will reduce heat gain and make measurements inaccurate or difficult to assess.  Allowing for variations in siting and the changes in the weather conditions, other areas where gain will be lost or inaccurately measured are: inability to establish the starting conditions throughout the system, inefficient/faulty installation, less than optimum elevation, incorrect pipe sizing, sensors poorly/wrongly located, poor insulation (on pipes, controls, and cylinders), controller incorrectly set up, and inability to monitor water usage & temperatures accurately.  Again, the list goes on.

So, in summary, I expect it is very difficult to provide a figure based on all the variables reality provides but the published figures should describe the circumstances in which they were achieved and include a “caveat emptor” style health warning.

And finally, whatever my TDC3 registers in kWh – I reckon I get about ½ that using my relatively crude measurements made on occasions during the past 2 years.  Am I satisfied?  Yes.  It works much as I expected.

[Kombi]

I basically come back to the fact that my house needs twice as much energy as the average to heat the DHW

Well your house needs only half as much energy as the average to heat it up; you don't expect as well the same for the hot water, do you???  

Nicolas

[Eccentric Dyslexic]

It must be difficult for manufactures like Navitron to publish figures from actual instalations and compete with other manufacturers that hype thier figures.  Navitron panels may be perfectly capable of producing thier quoted figures otherwise theyd surly not be selling them and openly talking and helping others to get the best from thier systems.   In an ideal world, we would have a gov funded org that compares like with like and publishes results in a reasonable time scale of new items coming on the market, or laws requiring manufacturers to fund thier own independant analasis.  Navitron sell to buyers in the south of Europe who may well be able to achive the figures quoted as being achivable.  But to be absolutly honest, and quote real world figures Navitron would be out of bussness surley, is this what we want?

Steve

[Justme]

  But to be absolutly honest, and quote real world figures Navitron would be out of bussness surley, is this what we want?

Steve

This is starting to taste bad to me.

Why would telling the truth make them go out of business?

In business mode one, we miss lead people about the product so they buy less of it & are unhappy with performance.

In mode two we tell the truth, sell more product to less people (cos some wont spend the extra cash) that are happy with how the system works.


Mode one has lots of unhappy customers that tell EVERYONE they meet, see, forum with.

Mode two they tell lots (but not all cos that human nature) of people they meet, see, forum with


I know which I would want (from both sides of the fence).

How do the navitron quoted PV specs compare to real world results?