Armaflex HT and 90 degree compression joints

[catfordbags]

I installed my system a couple of years ago. I was talking to an expert a couple of weeks ago who told me most solar thermal systems run at quite a low efficiency and i reckon my weakest spots are me 90 degree bends on me pipe run. So after reading a couple of threads on here and not really thinking about it i've popped out and bought a roll of Armaflex HT tape.

Is there some special technique for taping a 90 degree bend ? It seems almost impossible to do a good jo of it.

[guydewdney]

nope - it looks like the cats regurgitated dinner. Thats life.

[wookey]

I've used the next size up of armaflex (i.e big enough to go over the compression nuts). Then a tub of armaflex glue lets you make really neat mitred joints. Like this: http://wookware.org/pics/solar/070-img_2796.jpg.html (compare with previous pic).

[dimengineer]

I installed my system a couple of years ago. I was talking to an expert a couple of weeks ago who told me most solar thermal systems run at quite a low efficiency and i reckon my weakest spots are me 90 degree bends on me pipe run. So after reading a couple of threads on here and not really thinking about it i've popped out and bought a roll of Armaflex HT tape.

Is there some special technique for taping a 90 degree bend ? It seems almost impossible to do a good jo of it.

I'm curious - what did he mean by "Quite a low efficiency". From your comment I take it that he means that  a lot of the energy collected does not get into the DHW system & gets lost on the way?

[catfordbags]

I assumed he was talking about energy loss from pipes, pump  and cylinder etc - hence I am trying to make a better job of my insulation....

I have two more questions

1. - is it worth insulating the expansion vessel or is that over the top ?

2. - i am going to re-armaflex pipework between the roof slates to the manifold because it was always a bit of a botch job. I will pop it into armaflex then tape it with armaflex tape. Just wondering what is the best way to then weatherproof the armaflex ?

[wookey]

You shouldn't insulate the EV. If that's got hot then you want to be dissipating heat as much as you can.

I used aluminium tape round my armaflex to protect it from the sun and the birds. Seems to work fine. People have also used fibreglass, plastic boxes and other sorts of tape.

[tim_h]

Just wondering what is the best way to then weatherproof the armaflex ?

I used sections of rubber from car tyre inner tubes. It is similar to what is sometimes used on industrial process pipework.
Have a look at this thread: http://www.navitron.org.uk/forum/index.php/topic,10516.msg115217.html#msg115217
I don't know if it's the best way, but I was pleased with the results!

[Mike N.]

2. - i am going to re-armaflex pipework between the roof slates to the manifold because it was always a bit of a botch job. I will pop it into armaflex then tape it with armaflex tape. Just wondering what is the best way to then weatherproof the armaflex ?

I'm about to bring my rooftop bleeding arrangement down to a manageable level and will be running the armaflex inside Wickes mini guttering down pipe (50mm), which also gives the facility for pipe clips and bends. For the manifold to roof bit, the biggest potential heat loss area, I'm going to make something rather larger with more space for insulation (currently an off cut of down pipe, but could be as large as you like (Soil pipe?)

Mike