Intergas xtreme 36 ok?

[bobbidill]

Mains pressure systems (combi, thermal stores & unvented cylinders) have to be fitted properly, not having one 15mm cold mains pipe snaking around the house with the combi, or unvented cylinder, teed off it like it was just another sanitary appliance. Shower is king, all pressure and flow must be prioritized for the shower. Water takes the line of least resistance, make the shower hot and cold the least resistance in the system. It needs:

• Have its own 22mm cold feed from the stopcock to the combi even if the mains pipe is 15mm
• A full-bore stopcock
• Split the combi feed and cold outlets at the stopcock. Fit a tee for all cold outlets, except the shower. This can be 15mm in most cases.
• tee off the combi's cold feed, for the shower cold supply, just before the combi. Any flow pressure fluctuation around the combi will act of the hot and cold of the shower.
• have a dedicated hot pipe from the combi for only the shower.
• have the hot & cold outlets and taps on flow regulators (they are combined flow regulators and isolation valves) - you do not need firehose flow and pressure on bathroom basin taps, kitchen taps, toilet, dishwasher, etc.
• one flow regulator can do the dishwasher & washing machine which can get away with 6 litres per/min. In fact one regulator can do all the cold outlets, except the shower and bath, which should not be regulated.
• the shower hot and cold pipes should have no tees off these pipes. The shower hot & cold needs dedicated pipes.
• no flow regulators on the shower hot and cold.
• Use the equiv to Raindance shower heads, that consume less water.

Doing it this way it auto balances the hot & cold system to a large degree, the flow regulators on the the outlets fine tune the balancing, so no huge cold slugs while in the shower when the kitchen taps are turned on. This applies to all mains pressure systems.

Combined Flow regulator/isolator tap. A flow cartridge is inserted into the side - 6 litres/min, 2.5 litres, etc. A kitchen only needs 6 or 8 litres/min on hot and cold (I find it fine with 6), dishwasher/washing machine only 4 litres/min (a minute or so longer in the wash cycle is neither here or there), toilets can be 4 litres/min. 2.5 litres/min in a small downstairs toilet hand basin. Fit none on the showers.
Part number 17527 plus flow cartridges from 2.5 litres/min to 15.
https://www.bes.co.uk/flow-regulator-ball-valve-cp961-15mm-17527

Thanks again hard-work, very interesting. As I've said, I'm learning as I go, having had no previous plumbing experience or indeed knowledge, hence the questions. Is the full bore stopcock you mention just for the shower or the main stopcock for the entire house? Where you say fit a tee for all the cold feeds aside from the combi at the stopcock, would this mean that the combi would have it's own separate cold feed and all the others would be tee'd off, having been split first from the shower feed? I'm not clear how the location of the shower cold feed tee effects its function, would you be able to enlighten me further please?

 

[hard-work]

Full bore stopcock for entire house. If none is there, replace.

From the stopcock have a 22mm pipe to the combi, a dedicated pipe just for the combi. Just after the stopcock a tee. This tee supplies all the cold water to all the taps, dish washer, wash machine and toilet. Taking the shower cold feed from combi cold feed near the combi mean any fluctuations in flow and pressure around the combi are pretty equally applied to the hot & cold to the shower - well they will not be wildly out.

 

[bobbidill]

Full bore stopcock for entire house. If none is there, replace.

From the stopcock have a 22mm pipe to the combi, a dedicated pipe just for the combi. Just after the stopcock a tee. This tee supplies all the cold water to all the taps, dish washer, wash machine and toilet. Taking the shower cold feed from combi cold feed near the combi mean any fluctuations in flow and pressure around the combi are pretty equally applied to the hot & cold to the shower - well they will not be wildly out.

Thanks!

 

[hard-work]

When people push unvented cylinders remember there is an annual service charge. Megaflo says so on the side of the cylinder, to have it serviced annually. Otherwise this may happen. Read this page on this thread:
https://www.diynot.com/diy/threads/indirect-thermal-store-pre-heating-to-combi.460222/page-2

 

[bobbidill]

I’ve measured the static flow and pressure today which were 30l/min and 3.6bar respectively. The adaptor I had to measure them dynamically didn’t work and so I’ll try and get hold of another tomorrow to remeasure.

 

[Dan Robinson]

static flow

Wasat then?

 

[bobbidill]

The pressure and flow measured from 1 outlet, without another flowing. I’m a novice so may we’ll have used the wrong terminology Dan.

 

[bobbidill]

It does sound like an oxymoron!

 

[bobbidill]

No he hasn't, all that's established is that there is no space for an unvented

Nothing can be decided nor suggested correctly until flow and pressure is established ..... simples!

Madrab, apologies for the delay in obtaining this information. The mains water pressure and flow rate are 4.6bar and 24l/min. The dynamic water pressure and flow rate, as measured today with 2 outlets running were 2.5bar and 10.9l/min. Hopefully that helps in establishing what we should do, given that we have no room for an unvented cylinder. Thanks.

 

[Madrab]

OK, with that dynamic flow then unfortunately you could only really feed one shower (outlet) at a time. You need to look at a mains or the household distribution pipework to allow the supply flow to be maintained if you want to up the Hot water delivery to the outlets.

Space Heating requirement aren't over 10Kw therefore your boiler input size will be more to satisfy the HW heating demand. At the current cold water dynamic figures, your original Extreme 36Kw choice should happily deliver those levels.

 

[bobbidill]

OK, with that dynamic flow then unfortunately you could only really feed one shower (outlet) at a time. You need to look at a mains or the household distribution pipework to allow the supply flow to be maintained if you want to up the Hot water delivery to the outlets.

Space Heating requirement aren't over 10Kw therefore your boiler input size will be more to satisfy the HW heating demand. At the current cold water dynamic figures, your original Extreme 36Kw choice should happily deliver those levels.

Thanks Madrab. Would there be any benefit in using a 38kw Combi instead, if we increased the inlet pipework? The dynamic flow was measured through a narrow bore hose pipe.

 

[Madrab]

With a static pressure of 4+bar dropping to 2.5 bar and a mains flow of 24L/Min then increasing the supply pipe diameter into and distribution pipework around the house should improve the dynamic flow. Once you've increased it then you're back to the limit of how much hot water any given combi can give you.

The higher input the better in that case but even then most, if not all, combi's HW output will be noticeably affected when more than one hot outlet is open at the same time.

 

[bobbidill]

With a static pressure of 4+bar dropping to 2.5 bar and a mains flow of 24L/Min then increasing the supply pipe diameter into and distribution pipework around the house should improve the dynamic flow. Once you've increased it then you're back to the limit of how much hot water any given combi can give you.

The higher input the better in that case but even then most, if not all, combi's HW output will be noticeably affected when more than one hot outlet is open at the same time.

Thanks Madrab, the supply pipe diameter is 28mm and whilst we could go up to 32mm, the cost of doing so directly from the mains would be prohibitive. We could do so from the boundary meter though. Do you think this would be worth while given that there will still be the 28mm pipe from the mains? What's the largest diameter distribution pipework we could use in your view please? I've been told 22mm. Thanks again.

 

[Madrab]

@ 28mm then that should be large enough for a suitable mains supply as long as the pressure and flow from the mains is maintained. 22mm is really as large as you need to go for domestic distribution pipework.

I would expect you to see more than 10.9L/min @2.5 bar with that size of mains though TBH. Definitive test would be a 22mm full bore lever stop tap on your supply and then a 22mm feed from that branching to 2 outlets then check dynamic readings again.

 

[bobbidill]

A new development has arisen in that we may have eked out enough space to fit an indirect unvented cylinder. This is dependent on us being able to install the system boiler above it in the same cupboard. This leads me then to seek more of your advice please. 1. Is it possible to fit the boiler directly above the cylinder in the same cupboard? 2. The mains water inlet is 25mm, not the 28mm I had originally thought. With the flow and pressure previously mentioned, will this be adequate for a loft and 1st floor shower? 3. What size cylinder and boiler would you suggest and which brands? I've been looking at a Joules Cyclone 250l cylinder. As ever, thanks for sharing your wisdom!