Best spec for high pressure hot water to multiple outlets?

[PeterW]

45 minutes ago, Adsibob said:

What’s a buffer tank? Is that the same as an expansion vessel? I’minstalli g a low loss header as well, as I thought that would make the boiler more efficient. 

Buffer is a big LLH. Who has sized it ..?

 

46 minutes ago, Adsibob said:

so each zone will need its own thermostat. So I will need 9 tados.

Can the boiler talk to more than one Tado, and how does that interface into the manifold ..?

[Adsibob]

10 minutes ago, PeterW said:

Can the boiler talk to more than one Tado, and how does that interface into the manifold ..?

You can have a maximum of 25 Tado devices in your home, which unless you live in Buckingham Palace should be plenty. There is also a limit of the number of devices per room, but again that is generous, something like 7. More details here: https://support.tado.com/en/articles/3752302-how-many-devices-can-i-add-to-a-room-in-the-tado-app

 

All devices talk to the app on your phone (also accessible on a web browser should you lose your phone). The way it works is you get a bridge which you plug into your wifi router and then all the devices talk to that, therefore only one of the devices needs to 'connected' to the boiler. If the heating is on more than one zone, then unless you have a boiler, such as most of the current Veissman range which can connect to the bridge wirelessly without needing anything plugged in to the boiler, you need to buy a separate dongle called an extension kit and that is plugged into the boiler. If everything is just on one zone, you can hardwire a tado thermostat (very easy to do as the connections are just like a traditional thermostat) to the boiler, and then create pseudo zones on the radiators by using smart tado TRVs on each radiator.

 

As for your question on the interface with the manifold, I think this article answers your question: https://support.tado.com/en/articles/3482224-how-does-tado-control-underfloor-heating-systems but if it doesn't, definitely worth contacting Tado support who are always very proficient and responsive. If you have a UFH system where each zone has a thermostat, you simply replace each thermostat with a tado thermostat and buy the wifi dongle to speak to them and an extension kit so the app can also chat with the boiler.

 

[Dan F]

5 minutes ago, PeterW said:

Cost of a plate flow with buffer - and finding the space for another 200 litre tank - you may as well put a bigger tank in in the first place. 

 

There is no additional tank. A larger tank and PHE solve two slightly different, but overlapping, concerns:

- Large tank gives more stored hot water.

- PHE helps improve the ability to supply hot water (e.g. for a third shower) when the tank is at low temp and still reheating, which is the scenario @AliG mentioned.

 

I agree that a larger tank is easiest/cheapest approach to get more water but there is the dilution/reheat nuance that needs be be considered.  If you are using a boiler and tank re-heat time is only 20min this is clearly a non-issue, it's when using an smallish ASHP with longer reheat times then hot water availability, and not just capacity, needs some thought too.

 

[PeterW]

8 hours ago, Dan F said:

There is no additional tank. A larger tank and PHE solve two slightly different, but overlapping, concerns:

- Large tank gives more stored hot water.

- PHE helps improve the ability to supply hot water (e.g. for a third shower) when the tank is at low temp and still reheating, which is the scenario @AliG mentioned.

So you mean replace the UVC with a thermal store ..??? Stored heat is stored heat, you can’t create more of it and a PHE system brings in more complexity and moving parts such as pumps and flow switches. A PHE tails off quicker than a UVC too - it’s why TS systems go colder quicker as you’re losing the body of heat. 
 

Given the choice of 400 litre TS and associated systems and 400 litre UVC I would go with UVC every day for a gas or ASHP set up. If you really need fast response then a 40kW system boiler with a high gain coil in the tank is the correct spec. 

[Adsibob]

On 16/01/2021 at 08:00, PeterW said:

consider a secondary loop run in 10mm that only serves the basins and kitchen / utility tap as that will be more than adequate. We changed a permanent running install to one that ran 5 minutes every hour in a commercial building and reduced the water heating costs by £100/yr using a £20 timer.

Thanks @PeterW, but was just wondering about this... if I just run the secondary loop for the kitchen tap and the three other basins in the house, that’s going to be about 35m to 40m in secondary loop. Using a 10mm pipe for that would hold about 0.1l per m (I’m assuming!), so say 4l in total. How does that compare to the volume of water in the secondary loop in the commercial building you mention?

[PeterW]

Probably around 25-30m of 15mm and 22mm pipe, but the pump was already installed and the timer was added to reduce run times and the costs were significantly reduced. 
 

 

[Nickfromwales]

2 hours ago, Adsibob said:

Thanks @PeterW, but was just wondering about this... if I just run the secondary loop for the kitchen tap and the three other basins in the house, that’s going to be about 35m to 40m in secondary loop. Using a 10mm pipe for that would hold about 0.1l per m (I’m assuming!), so say 4l in total. How does that compare to the volume of water in the secondary loop in the commercial building you mention?

The point is moot, as a 10mm pipe will clear a 40m dead leg in less than a minute. If you use the Grundfos Comfort pump then maybe a bit longer, as it's a super low energy / flow pump which crawls the water around ( based on strategic use / utilisation ). 

I've several projects where there are basins and sinks run in 10mm supply pipework ( no hot return circuit ) and the flow rate is adequate for filling a sink etc. 10mm is more than 'man enough' for this application, plus lower CSA and lower losses too.

[Adsibob]

9 hours ago, Nickfromwales said:

The point is moot, as a 10mm pipe will clear a 40m dead leg in less than a minute. If you use the Grundfos Comfort pump then maybe a bit longer, as it's a super low energy / flow pump which crawls the water around ( based on strategic use / utilisation ). 

I've several projects where there are basins and sinks run in 10mm supply pipework ( no hot return circuit ) and the flow rate is adequate for filling a sink etc. 10mm is more than 'man enough' for this application, plus lower CSA and lower losses too.

@Nickfromwales thanks for that. Are you suggesting that if I use a  Grundfos Comfort pump on the secondary loop and 10mm pipes for the secondary loop (and just use this secondary loop for basins), I won't need to install a timer?

 

Will 10mm be enough for the supply to a kitchen sink given that will need more water than a hand basin (it's a large sink)? 

[Dave Jones]

On 16/01/2021 at 08:00, PeterW said:

How are you storing heated DHW from a combi..? Or are you suggesting that you use the heating circuit to keep a local tank hot and then replenish it from the combo flow when it kicks in ..??

 

 

 

 

yes some sort of thermal store arrangement. Problem is each plumber has a different solution, may go direct to Worcester boche and see what they recommend .

 

 

[Dan F]

6 hours ago, Adsibob said:

@Nickfromwales thanks for that. Are you suggesting that if I use a  Grundfos Comfort pump on the secondary loop and 10mm pipes for the secondary loop (and just use this secondary loop for basins), I won't need to install a timer?

 

Will 10mm be enough for the supply to a kitchen sink given that will need more water than a hand basin (it's a large sink)? 

 

If you use the auto-adapt pump you wouldn't need a timer (assuming they work well). With the others it depends how much heat loss you want to avoid. As they are low-flow and temperature controlled then will minimize energy usage, but you are still keeping return loop hot all day without a timer. Also depends on you usage patterns.

 

I've gone with 15mm (11.5mm internal) for the kitchen sink as velocity is bit too high with decent flow rate otherwise.  For bathrooms sinks, I think @Nickfromwales is referring to 10mm radial to basins, rather than a loop in 10mm.  (10mm is plenty for a single basin, but not for 2/3+ basins that may be used at the same for IMO)

[Nickfromwales]

13 hours ago, Dan F said:

 

If you use the auto-adapt pump you wouldn't need a timer (assuming they work well). With the others it depends how much heat loss you want to avoid. As they are low-flow and temperature controlled then will minimize energy usage, but you are still keeping return loop hot all day without a timer. Also depends on you usage patterns.

 

I've gone with 15mm (11.5mm internal) for the kitchen sink as velocity is bit too high with decent flow rate otherwise.  For bathrooms sinks, I think @Nickfromwales is referring to 10mm radial to basins, rather than a loop in 10mm.  (10mm is plenty for a single basin, but not for 2/3+ basins that may be used at the same for IMO)

You can use a timer + AA pump   Each instance is individual to occupancy / usage. No right or wrong here. 
A loop in 10mm for the HRC ( hot return circuit ) is what I was referring to above, and deffo not suitable for feeding 2 or 3 basins, unless you do away with an NRV and allow DHW to flow down each direction to the outlets ( a bit like an electrical ring main ) but that’s quite unorthodox and wouldn’t be something I did by design, more of a “work-with-what-you-got” solution.

The advice and disciplines change for folk who are doing / have radial plumbing vs those who have series plumbing. With the latter, you may as well just do a series loop in 10mm and T off for each HRC serviced outlet accordingly. Advice also changes again for new installs by design vs retro fitting something to cure problematic dead legs. 
No one ‘standard’ solution.

[Onoff]

I'm not as think as you drunk I am btw...

 

Repeated the test this morning in the bathroom and it's nominally 1m before the basin tap gets even warm then 1m15s until hot.

 

Up in the loft I have these pipes dropping down. Hot comes a fair distance from the cylinder in 22mm then drops to 15mm. To get quicker hot is it "just" a case of putting a T in then a pump back (to where?). Triggered by an occupancy switch? There'll still of course be a short dead leg from here the couple of metres down inside the wall to the basin / bath:

 

 

Can anyone recommend a cheap pump?

 

Edit: I do feel as I'm being somewhat cajoled into this...

Edited February 28, 2021 by Onoff

[PeterW]

@Onoff a hot return on a standard cylinder can be a bit of a faff as you need a non return valve and the only place you normally can tee back into is the cold feed unless you put an Essex flange on the tank near the top. 
 

Easier than an occupancy switch is a timer that comes on 1min in 60mins from 6am - 11pm as that just circulates enough to allow it not to cool too much between pump cycles. 
 

Cheap pump ...? eBay is your friend.  

[Onoff]

4 minutes ago, PeterW said:

@Onoff a hot return on a standard cylinder can be a bit of a faff as you need a non return valve and the only place you normally can tee back into is the cold feed unless you put an Essex flange on the tank near the top. 
 

Easier than an occupancy switch is a timer that comes on 1min in 60mins from 6am - 11pm as that just circulates enough to allow it not to cool too much between pump cycles. 
 

Cheap pump ...? eBay is your friend.  

 

I've a Surrey flange in the top of my tank...any good?

[PeterW]

Don’t you use it for a shower..??

 

Needs to be about 6-8” down the tank ideally. 

[Onoff]

1 minute ago, PeterW said:

Don’t you use it for a shower..??

 

Needs to be about 6-8” down the tank ideally. 

 

Yes, it's the take off to the shower pump. 

[PeterW]

Yeh so no point pushing back into it. How big is the tank ..?

[Onoff]

Just now, PeterW said:

Yeh so no point pushing back into it. How big is the tank ..?

 

I'll have to measure it and get back to you.

[Nickfromwales]

https://www.bes.co.uk/1in-bsp-female-outlet-brass-essex-cylinder-flange-12266/

[Onoff]

51 minutes ago, PeterW said:

Yeh so no point pushing back into it. How big is the tank ..?

 

Right, circumfrence measured around the insulation is nom 1500mm. Height from the floor to top of insulation nom 1055mm. Thinking then it's a 180L cylinder.

[PeterW]

More likely a 130 litre cylinder as the insulation will be 35mm thick or so. 
 

Assume this is in the plan to replace ..?

 

Is the heating set to W-Plan as I assume as it’s oil you keep the hot water on constant ..?

[Onoff]

17 minutes ago, PeterW said:

More likely a 130 litre cylinder as the insulation will be 35mm thick or so. 
 

Assume this is in the plan to replace ..?

 

Is the heating set to W-Plan as I assume as it’s oil you keep the hot water on constant ..?

 

The hot water is on timed. Basically this:

 

 

I however added 2 2-port valves to zone upstairs and downstairs CH.

 

 

[PeterW]

Ok. What programme is the hot water on though ..?

 

And is the 3 port over to water when it’s off ..??

[Onoff]

13 minutes ago, PeterW said:

Ok. What programme is the hot water on though ..?

 

And is the 3 port over to water when it’s off ..??

 

Sorry, what do you mean what programme? Times?

 

 

No idea on the second question.

[PeterW]

So when the hot water comes on, does the 3 way valve spin over to open or does it just heat the water ..??

 

With a HRC and small cylinder you may want to add a midday time slot to the programme. Would also say that if it can heat a tank in 30 mins then most likely it’s sub 150 litres.