Dead Leg, Electric Showers and Eddi

[mike2016]

Hi - hoping for some thoughts / advice?

 

I just had a solar pv system commissioned on my 22 year old house. Two storey semi detached. I've had a small amount of excess so far and my mind started wondering how best to use it....I was too late with the blue pills..!!!  

So, the PV system has an Eddi diverter keeping the upstairs hot tank at 60oC when there is excess. It makes me really want to use the hot tank more than I do currently. I'm also thinking about how to solve a problem I have in the kitchen.

 

Current Hot water cylinder usage:

• Upstairs hot taps
• Ensuite Shower (1 adult user, hot flow is ok but not great)
• The odd bath
• Kitchen Sink

There is an electric shower in the main bathroom that myself and one other adult uses, 3-5 minute short showers each. Flow is good enough from cold tank in attic. 

 

PV System: 4.2kw PV array, 6kwh battery, Eddie diverter to immersion

Gas Heating - standard condensing boiler (not a combi) and radiators with Thermostatic valves

 

Issue #1: The kitchen hot tap has a 30 second dead leg - 1/2 inch copper pipe feed

Issue #2: Options for Triton electric shower in main bathroom - can I use the hot water tank instead?

Issue #3: Best use of any additional Excess PV

 

#1: Currently the electric shower and screen are mounted at the foot of the bath. The hot water tank is on the other side of the wall at the foot of the bath. The ensuite is 6 feet away. The existing bath shower hot head pressure isn't the best, it might just be the old hose though. I'd like to use the hot tank for showers but have a fallback like an in line Siebert Eltron system that only kicks in if the water isn't hot enough to give the 38oC shower needed.  Maybe add a Digital shower but am concerned about the hot water pressure as I'm on the same level as the tank.  

 

#2: For the kitchen I've been looking at instant hot water taps, the Grohe model mixes with the dead leg water and provides hot water until the hot tank water arrives downstairs. I have capacity for some additional background load given I have a battery. Some type of insulated storage tank that buffers the dead leg and keeps itself at 60oC or so would be ideal. I'm trying to avoid paying for more filters though as I've a 6 stage filtration system at the kitchen sink with its own tap already, unless I can integrate that. Instant boiling water would be nice though! I can't see how I'd be able to add a re circulation circuit into an existing house but is that an easy or difficult option? I've no return pipe for it.... 

 

#3: One more option I'm considering is adding a second output to the Eddi and connecting it to an LHZ electric heater in the living room - it's the coldest room in the house, 3 outside walls. Undersized Radiator. I'll be doing triple glazed windows and external wall insulation at some point but thought having a second use for excess useful - we have no FiT currently. Might not be enough excess in winter when it's most needed though.....

 

It's great to see the house doing something it's never done before. 

 

Edited October 13, 2019 by mike2016
screenshot missing kwh values

[PeterW]

So... you can’t feed an electric shower with a hot feed from a tank - overheat stat will shut it down. 
 

You can however fit a digital shower, and with some clever pipework you could use one of the pumped ones to give you a decent flow, just re-use the existing cold feed from the tank to the electric shower as the feed to the riser. 
 

Cold leg could potentially be resolved with a return in 10mm Hep2O carefully threaded through the house but costs for that and a bronze pump will far exceed the wasted water it will save. 
 

Also consider increasing that tank temp - 75c from the solar and a TMV on the output to blend it down to 52c will give you a lot more useable hot water. 

[joth]

1 hour ago, mike2016 said:

For the kitchen I've been looking at instant hot water taps, the Grohe model mixes with the dead leg water and provides hot water until the hot tank water arrives downstairs

 

That's an interesting option. I've been looking at the Quooker Combi for exactly this purpose -- I don't want a secondary return in the kitchen as it's fairly random when we want hot water there, and open plan so can't easily use motion sensor, so would mean running the circulation pretty much constantly to be any benefit. (Bathrooms are much more predictable and reactable, in comparison).

The Quooker combi install manual only supports a cold-water only supply mode, i.e. using it means 100% of kitchen hot water is coming from the cold supply quooker element heater tank which is suboptimal as we'll have ASHP, and it adds a risk of running out too is using a lot.  I was thinking to try feeding the combi tank from the DHW water supply and just "see what happens", but going with the  GROHE Red that explicitly supports it might be a better idea. (It does mean 99ºC water rather than 100ºC though... LOL)

I can't find a standby heat-loss claim for the GROHE Red, it just says it's 10¢ per day at German electricity prices, which I think works out about  (0.33kWh/24 hours=) 13W so similar but just a bit more than the Quooker claimed 10W

 

 

 

 

 

[Jeremy Harris]

11 minutes ago, joth said:

 

That's an interesting option. I've been looking at the Quooker Combi for exactly this purpose -- I don't want a secondary return in the kitchen as it's fairly random when we want hot water there, and open plan so can't easily use motion sensor, so would mean running the circulation pretty much constantly to be any benefit. (Bathrooms are much more predictable and reactable, in comparison).

The Quooker combi install manual only supports a cold-water only supply mode, i.e. using it means 100% of kitchen hot water is coming from the cold supply quooker element heater tank which is suboptimal as we'll have ASHP, and it adds a risk of running out too is using a lot.  I was thinking to try feeding the combi tank from the DHW water supply and just "see what happens", but going with the  GROHE Red that explicitly supports it might be a better idea. (It does mean 99ºC water rather than 100ºC though... LOL)

I can't find a standby heat-loss claim for the GROHE Red, it just says it's 10¢ per day at German electricity prices, which I think works out about  (0.33kWh/24 hours=) 13W so similar but just a bit more than the Quooker claimed 10W

 

 

 

One of the things I wish I'd done when I bought our boiling water tap was get the model with the larger reservoir and thermostatic mixer option for feeding hot water to the tap.  I only discovered that this was an option when the thing arrived and the instructions included details for installing the model that would supply hot water as well as boiling water.  Ours is made by the people that make the Red for  Grohe, I believe, as it seems nearly identical.  I did notice that as soon as Grohe started to market the Red in the UK, Itho Daalderop seemed to stop selling their stuff here. 

[mike2016]

The Grohe Red has the following feature which is what I'm hoping to take advantage of or find a cheaper way to get the same result. I think this is what JSHarris is referring to.....

Customers may want to also purchase the Coldfill Mixing Valve (40841001) to replace your low-pressure kitchen tap, which mixes mains water with kettle-hot water to give you immediately warm water too, meaning no waiting for water to heat up, and less water wasted.

 

[Jeremy Harris]

44 minutes ago, mike2016 said:

The Grohe Red has the following feature which is what I'm hoping to take advantage of or find a cheaper way to get the same result. I think this is what JSHarris is referring to.....

Customers may want to also purchase the Coldfill Mixing Valve (40841001) to replace your low-pressure kitchen tap, which mixes mains water with kettle-hot water to give you immediately warm water too, meaning no waiting for water to heat up, and less water wasted.

 

 

 

Yes, it is.  Just needs the larger boiler, plus a thermostatic mixer valve.  I did look at converting our Itho Daalderop tap so that the hot water supply came from a mixer fed from the boiler and cold supply, but by the time I decided to do it, Itho Daalderop had stopped selling in the UK.  I have looked at buying the bigger boiler from the Netherlands, and then just adding an ordinary thermostatic mixer, but just haven't got around to it.

[joth]

18 hours ago, JSHarris said:

 

 

One of the things I wish I'd done when I bought our boiling water tap was get the model with the larger reservoir and thermostatic mixer option for feeding hot water to the tap.  I only discovered that this was an option when the thing arrived and the instructions included details for installing the model that would supply hot water as well as boiling water.  Ours is made by the people that make the Red for  Grohe, I believe, as it seems nearly identical.  I did notice that as soon as Grohe started to market the Red in the UK, Itho Daalderop seemed to stop selling their stuff here. 

 

This is interesting to know.

Looks like Grohe claim 15W standby so 50% higher than the Quooker combi. They also show the tank being filled from the cold supply, any idea if there's any technical reason it couldn't be filled from the DHW supply? This would reduce the time it takes for hot water to come through the pipe when running the kitchen hot tap, and also reduce the amount of work the boiler has to do to get the contents back up to boiling.

Some reviews say the filters are one of the more expensive to replace, haven't researched that side much yet.

 

 

 

[Jeremy Harris]

10 minutes ago, joth said:

 

This is interesting to know.

Looks like Grohe claim 15W standby so 50% higher than the Quooker combi. They also show the tank being filled from the cold supply, any idea if there's any technical reason it couldn't be filled from the DHW supply? This would reduce the time it takes for hot water to come through the pipe when running the kitchen hot tap, and also reduce the amount of work the boiler has to do to get the contents back up to boiling.

Some reviews say the filters are one of the more expensive to replace, haven't researched that side much yet.

 

 

The DHW supply may not be potable water, hence the reason for insisting on filling from the cold supply.  The filters are needed if you have hard water and don't have any other water treatment on the incoming supply.  They are just a mix of an activated carbon filter and often a phosphate dosing filter.  The activated carbon is there to reduce any adverse taste (like chlorine), the phosphate dosing is there to reduce the chance of any solid limescale build up inside the boiler.  It may well be cheaper to just use a whole house filter and phosphate dosing unit than use the very expensive filters that come with these taps.  If you don't have hard water, then the phosphate dosing treatment is pointless, anyway.

 

We reduce the power consumption of ours by having it run from a time switch, so the boiler is off overnight.  I also fitted an easy to access isolator switch, to turn it off when we go away.

[joth]

17 minutes ago, JSHarris said:

The DHW supply may not be potable water, hence the reason for insisting on filling from the cold supply. 

 

Ha yes I meant to add, I assumed they only want cold input as they can't assume hot supply is safe to drink. But then, outside of the kitchen the cold supply traditionally isn't safe to drink either so if that's the reason it'd be helpful to state explicitly rather than rely on a hot vs cold assumption.

If we have pressurised UVC then as I understand it the WRAS regulations require it to be just as good quality as the mains cold supply so this issue wouldn't be a worry. (Plus the boiler is literally boiling it so double protection)

 

We're in a very hard water area so planning whole house softener, so yes I should just ignore the built in filters. Thanks.