Hi, in case Borderman is gazing at the new boiler. I think you'll find the box is just a header with the air release, RV, gauge mounted on them as a set. The box bit is the thick insulation that quite properly surrounds everything purchased from anywhere but the UK.

Cheers, Mike up North

ahh of course. Thats the problem with laddomat, the thermovar has a polystyrene surround too.

Hi mjn... I've knocked up a schematic to help explain... It shows the setup in the picture on my previous post from behind. I hope this helps. If you want a pic of the actual setup, just ask.

Ed.

hi borderman,
I hope you dont mind me intruding into this discussion,but i'm intrigued as to the inlet to your pressure vessel. I guess theoretically it can go anywhere in the system, but I was told to put mine on the return pipe ,- cooler water in contact with the rubber membrane etc.. Is this just individual plumbers preference?
for mjn,
Introducing large quantities of additives into large systems can be a problem. I've designed a filling point into mine, a simple funnel with a shut off valve, although I was told that inhibitors would be unnecessary, if the system was clean to start with, as once the water was de-oxygenated, and wasn't constantly being added to, - (well tested and sealed to start with I guess),- it would remain clean. Although I've introduced a couple of strainers,with isolating valves, into the system, just in case.
mike,

Yes I have acutally plumbed min in at the bottom (return) for that reason. My main concern was conflicting information about if I needed one each side of the laddomat - which borderman confirms my commonsense that says no.

Interesting re inhibitor - my chemistry is a little rusty (excuse the pun) but i rememver putting nails in jars of different liquids etc and to get rid of teh oxygen you had to properly boil the water. Would heating to 95 degrees 'drive'off all the oxygen?

I would hate for my rather expensive boiler and tank to rot prematurely for the sake of £50 inhibitor - anyone else have any views?

I always assumed that the oxygen was taken up by the steel, i.e. becomes iron oxide and so unavailable for further corrosion.

Hi,
If you leave it open vented you wont need the expansion vessel (which you have paid for), but you would need a similar sized expansion tank in the loft to cater for the water expansion. The increase in volume with temp remains the same, except than in open vented systems it goes up to the tank, whilst in sealed systems it cant, so the exp vessel excepts the volume balancing that against the rise in pressure. With such a large volume a small temp rise gives a large expansion volume and hence the potential for a very large rise in pressure, hence the large vessel.
You only need to run at about 0.5 bar (5m) pressure above the static pressure (height from top rad to lowest point (when cold). So you may only need to run at say 1.5bar. This should be factored in to sizing the exp vessel along with an accurate assessment of the water volume and expected temp ranges. I suspect your vessel is sized to cater for worst cases, so will be bigger than you need anyway.
Although your buffer acc probably is rated to 3bar you won’t be running your heating at that pressure.
The open vented systems tend to connect the feed/exp tank at the lower end of the buffer on the boiler return as when the system cools this would be feeding cold water into system. You can also use more than one exp vessel. 2 vessels at different points is acceptable providing the volume is the same as for the big one.
Don’t forget to insulate the exp vessel as well and all the pipes.

Yes – the pressure can put strain on old joints and unions.

Cheers, Mike up North

hi Ed,
I think you are right to be concerned about old rad valves etc. The valve unions where they enter the rad itself can often be a problem. I've decided that whilst the system is drained I'm replacing all the old, (25years) TRVs and lockshields. Fitting with good quality PTFE cords and sealers and then dry pressure testing for 24 hours or so. I recon that the time and expense will be worth it in the long run. and may save me adding inhibitors. There is no reason why a well installed pressurised system should not hold up between annual services without constantly adding more water. I'm not without a bit of trepidation though, about the CH circuit holding up, but I guess there's only one way to find out.
mike.

hi Adwindrum,
I don't know if I've misunderstood you, if so ,apologies, but the rise in pressure is due to the rise in temperature, and the extra volume of water occupied by the heated water within the sealed space of the whole system.

mike

hi Adwindrum,
Assuming a pressurised system with associated pressure vessel. The pressure vessel is first charged (they are more often than not pre-charged) and adjusted to about .5 bar although some say .8 bar, this pressure acts as the cushion to accomodate the increased water volume. The system is then filled with water to the brim, bleeding off excess air in the process. The water when heated then causes the pressure increase both in the water side of the system, accumulator,rads,boiler pipework etc.. and in the air side of the system, the other side of the rubber diaphram in the pressure vessel. Any excess pressure, over and above your design parameters,is dealt with by the pressure relief valves which are often calibrated a few decimal places above your working pressure, which in your case appears to be 1.5 bar.
Thats my undestanding of it, although someone is sure to correct me. if so be my guest I'm still twisting pipes together at the moment.

mike.

hi,

About 2150mm high and about 1200mm wide,on average, including a 100mm insulated jacket. Thats for a cylindrical one, or you could look at the oval ones from Akvaterm if access is a problem. You will also need to allow space at the top of the tank when installed for plumbing and air vents etc. It would be wise to allow a 2400mm ceiling ht.

mike.

Thanks Mikes both

So up it is.. Sigh. Planning.

Cheers
Helen

Hi All
Great info here on this thread, I've been following with great interest since August. Having now taken delivery of an Atmos 25GS boiler, does anyone out there know where one might obtain an Akvaterm 1400l oval tank off the shelf in the UK?

Cheers,

Steve

Thanks Mike,
I'm actually awaiting a response from Peter de la Haye to a mail I sent them earlier, so I suppose I'm on the right track. I might find out about the 1500l Akva type while I'm at it, as the space issue is not totally crucial - its going to be sited in a 6M x 4M outbuilding, and whilst I would certainly prefer the minimum-of-width footprint, I'd in fact be able to accommodate either. After reading someone else's comments re the better stratification qualities of the taller, cylinder-type tanks, I might be better to go and measure again and reconsider what best to try to order. I wasnt' sure whether Akvaterm had any stockists with tanks actually physically available here in the UK or not. I had been offered a 1250l tank from abroad, but the delivery of this has not materialised, nor have I been offered a delivery date, so I'm starting to cast the net a bit wider. I also see from the Atmos website that 1500l should be about the minimum size of charging tank compatible with the DC 25 GS.

Cheers, Steve

Dunster Wood fuels sell Akva tanks and seemed to have some stock in the spring. I've ordered an Akva tank (non-standard) from Peter de la Haye, the order was placed with Akva on the 3rd of September and was completed by the 24th of September. I don't know when it's actually going to be delivered though! He quotes 4-5 weeks delivery.