Would 70 tubes be too many???

[stevie_f_2004]

I have 50 tubes on a 300l store - installed it in March and has provided a huge amount of hot water this year so far.  Gas usage has plummeted to almost nothing over the summer months.

I have the store limit set to 95C and it would go into stagnation often during June/July so I think it is sized about right.  It has hit high 80s this month on good days.

Just about to fit a wood burner with back boiler to top it up over the winter months.

Greentangerine

Where abouts are you located? The geography sounds similar to myself.

[wookey]

I've got 40 x 47mm on a 114l tank - that's ~3l/tube. So your 66*58 on a 300l tank is pretty-much equivalent. I'm using a side-arm PHE rather than a bottom coil though.
I get plenty of days in the sumer when it gets to 90C and dumps. And it keeps the landing pretty toasty for much of the summer (the tank insulation could be much better - it's a very old tank predating fancy things like PU insulation, and our retro-fit insulation isn't great because one day this is all going to get modernised).

Your hot water usage is probably much more than ours, so it'll probably be OK in general but if you you go away anytime in the sumer half of the year the whole thing is going to get very toasty. Make sure your heat dump is adequate for the full 5kW load. Something like a hot-tub would be an excellent place to put all the spare heat.

We just use the CH system for dumping - just using 2 small radiators and it they barely get warm. I was surprised how little dumping is needed to keep the tank temp down. It just goes to show that 2kW isn't very much house-heating in a typical British house (and probably that my tank insulation is rubbish and uninsulated pipes under the floor lose a lot of heat, etc).

[greentangerine]

My 50 * 58mm tubes are on a south facing roof in Dorset, just outside Weymouth. 

They are on a single storey attached double garage with a PV installation on the main house roof (and that's generated 2438kWh in the 8 months since it was installed).

[desperate]

Hi Stevie

We have 60 *47mm tubes into a 216 litre tank, as Wookey says we are on a similar ratio to your proposed set up, personally I think the advantage realised in the usefull amount of heat in the winter is well worth the extra complications of setting up a heat dump. After all getting rid of heat is easy compared to generating it, also I feel that as the tubes and the fixing of them is a relatively small part of the whole system, it is cost effective to over spec the collecter within reason.

Desperate

[Brandon]

I agree with desp and wookey, in the long run the extra work and cost in having a greater collector area and a heat dump are more than outweighed by the winter gains.

I run 30*58 on a 114l tank

[stevie_f_2004]

Thanks for the replies....The additional tubes have been delivered and I have week off work next week so Monday morning I'll be cracking on with the installation. I'll post some pictures when it's finished.