Solar Tubes/Flat plate/back boiler rads or hot water

maximus31

hey all,Im thinking of installing the <snip>(30 tubes/2 flat panels) and maybe a 300 litre triple coil cylinder.has anyone installed this system and how do they find it?,tubes vs flatplate im undecided ,was told theres little difference in terms of efficiency.i was told the tubes lose their vacuum after time?these tubes do not have the fluid running dwn through the middle as opposed to the other type.my other question is,would a backboiler be a good idea from an insert stove(thats what im fitting) in the livingroom or a range/stove in the kitchen.my plumber reckoned there was too many rads(12 dwn stairs and 9 upstairs) for a backboiler to heat and that heatng the water would be a better option as opposed to the rads,the house is 2500sqr ft in total.it will have two thermostatic showers and one electric shower along with a bath.would appreciate all advice here coz alot of ye here know the score.thanks

quentingargan

In relation to tubes -vs- flatplates, while they may both produce roughly the same total heat over a year, the flatplates are better on hot sunny days, but tubes are better in cloudy weather because of their superior insulation.

For that reason, the tubes tend to extend the season. If your house is well insulated (and it should be...) then the heating is off for long periods. When the heating is off, your hot water tends to come from electricity and is more expensive. For that reason, you might prefer tubes as their season will fill more of the "non-heating" season.

Yes, all tubes will lose their vacuum after about 20 years and will have to be replaced. I prefer the Chinese vacuum flask type because replacing them is a lot cheaper and easier. Replacement flasks are about €5 each. Tubes with a single layer of glass have the copper permanently attached so you have to replace the whole tube, which is a lot more expensive.

I wouldn't see much point in trying to heat a heap of radiators off a back boiler unless it is a pretty substantial stove. We do manage to heat our own house using wood from an old-fashioned range in the kitchen. We fitted a stove in the sitting room, but haven't lit it since we got the range fixed up:)

ccsolar

Hi Maximus31

I would consider a 30 tube collector a bit on the small side for a 300ltr tank, especially in the winter months, you would be better to go for 40 tubes and still get good performance in winter.
Tubes and flat plate performe well in the summer months but as Quintin said the tubes work better in cloudy conditions and are if you have any problems with the tube, they can be replaced very easy and at a low cost.

Cc

Evergreen

ccsolar wrote: »

I would consider a 30 tube collector a bit on the small side for a 300ltr tank, especially in the winter months, you would be better to go for 40 tubes and still get good performance in winter

You can't judge evacuated collectors based on the number of tubes, some manufacturers require more tubes than others. For example a Ritter Solar recomend storage of 80L per square meter on their panels which has just 6 tubes 24 tubes per 320L), Thermomaxx recommend something similar which only has 10 tubes per meter (30 tubes per 320L), on the other side I have seen tubes from Solar direct where they recommend 60 tubes per 300L.

At the end of the day you need to match the output from the panel with the storage and not the number of tubes.

saibhne

Evergreen wrote: »

At the end of the day you need to match the output from the panel with the storage and not the number of tubes.

Very true, and make sure the output calculation for the panel is relevant to your locality and your installation. Different types of evacuated tube panels behave differently at different times of day and when installed at different orientations and pitches.

Also the output from the panel will be higher than the output of the total system which will be influenced by heat losses from the pipework and cylinder. So be careful about making a decision based purely on the energy output of a panel alone.. Look for how much energy the system as a whole will produce as this is the energy that will actually be able to be used by the homeowner..