Ariston Primo 210 Litre Unvented Indirect Cylinder

newcomers · 11 Apr 2007

Thinking about having one of these installed, but im concerned about the pressure in the property.

I have a 15mm water main coming into the property, but the pressure on the taps didnt seem that great, Got a gauge on it and its reading between 2-3 bar.

Would this be enough for the cylinder, and would it make any difference increasing the water main to 22mm after the valve inside the property?

Thanks as always

Rob · 11 Apr 2007

Its flow rate that counts. 20l + is ideal.

newcomers · 11 Apr 2007

So I guess stepping the main upto 22mm is ideal then?

Rob · 11 Apr 2007

probably, but whats the flow rate as it is?

Agile · 11 Apr 2007

Surely flow and pressure is part of physics or science at GCSE level?

One wonders why 90% of the population cannot understand what they mean.

gas4you · 11 Apr 2007

You ideally need 3bar + to get the most from this. 22mm cold feed will be a must at your pressure. Increasing pipe size will increase available flow but pressure is needed to give good balanced hot & cold. pressure balancing valve will keep pressure to 3 bar so ideally you need more to allow for pressure drop when more than one outlet is used

newcomers · 11 Apr 2007

Having tested it yet, but im thinking that there will be 5 taps, a shower and a toilet all coming off of the main, so while im redoing the heating system and cylinder, I may as well increase the main as well, or do you think that as long as im getting 20L + then leave it?

gas4you · 11 Apr 2007

you will need the pressure as well. Unless you have about 5 bar then you will have to increase supply to 22mm. Most un-vented M I's recommend 22mm cold inlet

newcomers · 11 Apr 2007

Agile said:
Surely flow and pressure is part of physics or science at GCSE level?

One wonders why 90% of the population cannot understand what they mean.

This is still one thing that bothers me actually........pressure affects flow, more pressure will mean more flow right?

So, what happens if I have 2.5 bar pressure on a 15mm supply, but then up the main to 22mm, will I then have less pressure but more flow? Would this affect the cylinders performance?

Basically, I dont want the cylinder to run out of water, which is what happened to a friend of mine!!, but at the same time, I'd like a decent amount of pressure.

gas4you · 11 Apr 2007

pressure remains same with pipe size, larger pipe gives greater amount of water

newcomers · 11 Apr 2007

gas4you said:
pressure remains same with pipe size, larger pipe gives greater amount of water

See, this is still one thing I really cant get my head roud

gas4you · 11 Apr 2007

Think of it like a gravity hot water system. Hot pipe off cylinder is 22mm to give quantity of water. Pressure is related to 'head' of water from cold tank in loft. if you increased to 28mm you would get more water (volume) delivered but at the same pressure as the 22mm. Thats why gravity systems have bath hot in 22mm and new mains/combi systems need it in 15mm

newcomers · 11 Apr 2007

gas4you said:
Think of it like a gravity hot water system. Hot pipe off cylinder is 22mm to give quantity of water. Pressure is related to 'head' of water from cold tank in loft. if you increased to 28mm you would get more water (volume) delivered but at the same pressure as the 22mm. Thats why gravity systems have bath hot in 22mm and new mains/combi systems need it in 15mm

That makes sense, but surely if part of the main coming into the property is 15mm, and then from the inside of the house onwards is 22mm, then it will still only be as good as the 15mm, almost as like only as good as the weakest link, if you get what I mean?!

gas4you · 11 Apr 2007

Yes you've got it. Un-vented manufacturers assume that we have all got up to date incoming mains pipe sizes, that is why a good survey is important before fitting/advising the fitting of an un-vented cylinder

Rob · 11 Apr 2007

Thats why you have to renew from the street.

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Ariston Primo 210 Litre Unvented Indirect Cylinder

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