Idiot's guide to all things tech & mech, please!

[DreamHouseDreamer]

In the outline spec for the new house yet to be built, there will be an ASHP, a MVHR unit, large mains pressure water cylinder and wet UFH throughout.

 

That will be what keeps the house warm and will also provide hot water, or so I understand, at all times.  Living rooms and bedrooms (and a few other locations) will have fresh air vents.  Kitchen and bathrooms (and maybe elsewhere) will have air extract vents.

 

The energy for all of this will be generated, as much as possible, by a solar array on the entirely south facing roof (10 kW capacity has been suggested to us) when possible, and bog standard domestic single phase supply from the grid otherwise.  The entire house will run off only electricity, wherever it comes from.  There is no gas immediately nearby, neighbouring houses are heated by oil. 

 

To store the energy from the roof panels, we are aiming for a Tesla Powerwall 2 (if we can get delivery in time - we are told at least 10 months delay currently).  One solar supplier we have spoken to, the only one to so far produce facts, figures, vaguely comprehensible numbers is where the 10 kW roof array size comes from.  This individual also warned that to run the house as much as possible from what we generate, we'd actually need 2 x Powerwalls.  Our aim, cost and practicalities willing, is to achieve an energy positive house.  Yes, we know we missed the boat with FITs, but we also understand there will likely be a replacement in the pipeline, and nothing has been announced yet only because the UK government has been sidetracked by some minor kerfuffle beginning with B. 

 

The house will - like most self builds - be as well insulated, air tight and thermally efficient as possible.  Thus, we understand that actually, heating demand will not be great and that the house should warm up quickly, even with UFH which can have a 'delayed' reaction. If heating was to be turned off, would loose heat very slowly. 

 

So far, so good.

 

I know I don't understand almost anything about how any of the kit mentioned above actually does any of what it is supposed to do, but my role is to influence product selection based on my requirements rather than choose the products themselves or do the technical calculations to size any item correctly.  So, what I'm wishing to learn is more what the differences are between what different models/capabilities in terms of upgrades from a basic model that does no more than it says on the tin.  

 

For example:

 

Which item of kit would you need to adjust or have a different model, if you wished to be able to adjust humidity in a room as well as temperature?

 

Which item of kit would you need to adjust to enhance fresh air coming into a room?

 

Which item of kit would you need to adjust to enhance/boost stale or smelly or damp air from a room (such as kitchen or bathroom)?

 

What kit (or more than one individual unit) would you need to upspec if you wanted to add room cooling?  Is this achieved by cooling the air coming into rooms or by having the UFH pipes circulating cold water?  Or both?

 

And the million dollar question:

 

We would really love an uninterrupted power supply set up - and this, as far as we know, is not yet available at all in the UK, and only rudimentary versions are available elsewhere (elsewhere being USA and Australia), and only from Tesla apparently.

 

We get power cuts, in winter when it's windy thanks to all the overhead power cables in our area, we get quite a few.  They can last from 30 seconds to 8 hours.  We are in a relatively low population rural area with no industry or hospital nearby so we know the area is not listed as priority for reconnection when there are storms (blurted out by a man from UKPN when fixing a break one day!  ? ).

 

What's the point of all this high tech kit if you cannot use any of it when there's a power cut?  I won't even be able to boil a kettle for a cuppa?

 

I think I've wittered on more than enough.  Please ask questions if you need more details to offer any comments.

 

Thank you one and all.

 

DH Dreamer

[scottishjohn]

its called a diesel generator -with auotstart up 

[Jeremy Harris]

Most of the concerns you have about ventilation will be handled by any well-specced and installed MVHR.  If you want comfort cooling, then an MVHR with built in air-to-air heat pump will provide a modest amount of cooling, but nowhere near enough to overcome a house with a fair bit of solar gain.  If you think overheating may be an issue, then it's almost certainly likely to be cheaper and more effective to just fit an air-to-air heat pump.  These are almost always reversible, so will also provide supplementary heating if needed.

 

Tesla isn't the only player in the home storage market, and there are other products available that will provide uninterruptible power to a designated set of circuits.  Personally I'm not at all convinced that the Powerwall 2 is good value, and neither am I convinced that it's user interface is that great, having looked at how it tries to automate stuff with hidden control functions that I think would be better made accessible to the user.

 

Getting a house to run in winter without grid power is damned difficult.  We have a 6.25 kWp PV array and there are plenty of days in winter where we don't generate enough to cover the house background load, let alone have any excess to store.  It wouldn't matter what sized battery system we had we still wouldn't be able to charge it from PV for much of the time in winter.  In winter we intend to just charge the battery from E7 off peak electricity (something that's a bit flaky with the "intelligence" built in to the Powerwall, it seems).  The idea is that we hope to be able to power the whole house, 24h/day, from off-peak electricity.  Being able to charge the battery from PV in summer will be a bonus.  Our house is all-electric, and has a pretty low energy demand (the EPC is A107, with an energy "consumption" of -35kWh/m² per year)

[Dreadnaught]

16 minutes ago, DreamHouseDreamer said:

We would really love an uninterrupted power supply set up

 

The prohibition on using a house battery to continue supplying electricity during a power cut is, I believe, to protect any line workers working on the power lines.

 

I think that there are ways to maintain power in a power cut by using a separate isolated circuit for crucial items powered by a house battery.

[Ed Davies]

Tesla might be the only solution to power cuts at the moment in the form of a packaged solution aimed at the domestic market. Dunno. But more generally there are lots of systems that can do this sort of thing easily. For example, un-interruptable power supplies used in data centres and it's very common on yachts to have an inverter/charger which allows shore power (from a socket on the dock) to run the house loads and charge the batteries with the capability, of course, to continue to run the house loads from the battery when shore power is not available. E.g., https://www.victronenergy.com/inverters-chargers/multiplus-12v-24v-48v-800va-3kva Obviously, there's a limit to how much energy and power you have available from such systems but it'd keep you comfortably doing most things for a longish power cut.

[Ed Davies]

27 minutes ago, JSHarris said:

If you think overheating may be an issue, then it's almost certainly likely to be cheaper and more effective to just fit an air-to-air heat pump. 

 

I'm surprised you suggest that rather than cooling the UFH with the ASHP. Is that just because of this thing about the RHI not allowing cooling to be enabled by default or is there something else?

[Jeremy Harris]

Off the top of my head I can think of systems from Sofar, Lux and Growatt that all offer a UPS capability on a separate circuit.  The Lux system offers 3.6 kW per inverter/charger, and also offers a parallel connection function, so output power on both the primary and always-on circuits can be increased by just parallel connecting inverter/charger units.  Their system is "plug and play" with the Pylontech LiFePO₄ rack mount battery packs, which makes for an installation that's pretty much as easy as the Tesla Powerwall 2, and which is modular, so allowing more flexible configuration. 

 

It's also cheaper than the Powerwall 2 and doesn't suffer from some of the automatic stuff that tends to cause the Powerwall 2 to under-charge from E7.  Essentially the Powerwall 2 tries to limit battery cycling by estimating consumption for the following day and only charging the battery up to what it thinks that's going to be.  If the usage pattern is fairly constant this works OK, but if there is a fair degree of day-to-day variability then it tends to fall over a bit.

[Jeremy Harris]

2 minutes ago, Ed Davies said:

 

I'm surprised you suggest that rather than cooling the UFH with the ASHP. Is that just because of this thing about the RHI not allowing cooling to be enabled by default or is there something else?

 

It's really just that cooling the UFH means having a custom designed UFH system, with valves to isolate the UFH from any hot buffer and an additional thermostat to control cooling.  I've done it and it works well, but our system isn't exactly off-the-shelf.  An air-to-air heat pump is a neat, fairly cheap, off-the-shelf system, that any competent person should be able to easily install and maintain.

[DreamHouseDreamer]

Thank you all for your replies.  I typed this, went and made a cuppa and responses are already coming in.  Wow, you guys are on the ball.

 

To respond to each point made that I can comment on:

 

@scottishjohn  Is there really such a thing as a generator with auto start up?  While we have dismissed a generator for being noisy, awkward, smelly, where the heck do you put it?, how much diesel would we need to have lying around?, is it safe? and other reasons, it was actually my first thought before 'im-indoors told me I was bonkers.  Seriously, I don't see how we could site one in the plant room, with building regs consent, etc.   However, I'd be interested to learn more if you are serious.

 

@JSHarris  Inevitably, without a crystal ball, I cannot answer how much solar gain we will get - both useful in winter or detrimental in summer.  The house is designed to face south - for privacy, to maximise views and for that south facing roof for the solar array.   Most of the patio doors will face south.  However, the house is designed to not have an endless amount of wall to wall glass like many contemporary houses have, and all south facing windows or patio doors will have powered roller blinds set to lower to reduce excessive solar gain (don't ask how, I cannot get my head round any of that - it's one of 'im-indoor's tasks to resolve).  Notwithstanding any of that, when we visited a few new build houses last summer during that heatwave for ideas, as part of choosing architects, while doing general due diligence, etc and despite being told that they're so well insulated, the houses won't be that hot - they were not in every case a comfortable temp, and the owners of some we sweltering and putting on a brave face.  Our biggest concern and the real reason for wanting/needing so sort of cooling capability is for sleeping in the south facing master bedroom. 

 

Anyway, what you are saying is that some cooling can be easily addressed, I just need to specify the right type of unit.  So what features should I be looking out for?

 

Tesla may not be the only player in the power storage market, but they have the most compact power storage units we have seen.  We have been recommended to use a different, extra device between the solar collector system and the storage unit to control, monitor, report energy - which presumably would have better user interface/control.  Anyway, what other brands should I research?

 

Yes, we know about actually managing to run the house in winter just from self generated power.  We are looking into this - and I didn't want to go into too much detail above.  We understand there are power suppliers out there who have variable pricing bands and times and in winter we should recharge the batteries overnight from the grid at the cheapest rate to use during the day at peak pricing periods.  Have not yet started to research energy suppliers.  This needs to be tied to our need for an elec car charging point (a planning consent condition) despite no plans to ever own a EV.

 

@Dreadnaught  Your comment on why there are no approved UPS units in the UK makes sense.  We got a long winded explanation from one of those darned solar panel salesmen, but I think you expressed it more succinctly.  UK networks don't have downstream power safety breaker, only upstream.

 

@Ed Davies  I will look at your link for boat/shore power in due course and see if I can understand it.  Assuming our storage batteries have enough power to run the house for the duration of any power cut, the UPS would only need enough power to switch the house from grid to battery when there is a power cut.  The system clearly would still need to know there's been a power cut so that the house runs under some sort of low power mode with perhaps some sort of a warning if any high consumption items was turned on like oven, etc.   Yet another Q for 'im-indoors, then!

 

@JSHarris  I'll go google those brands you mention and read them up.  Maybe the electricians and solar guys we have been dealing with so just prefer Tesla.  It's certainly the brand everybody mentions.  Including unprompted when we spoke to those manning stands at the various home building shows we have visited over the last 2 or so years.

 

Thanks again, everybody.  Most useful.  Watch this space for more questions for those with lots of patience ........

 

DH Dreamer

 

 

[Dreadnaught]

10 minutes ago, DreamHouseDreamer said:

without a crystal ball, I cannot answer how much solar gain we will get

 

You can model it with some precision in PHPP.

[Jeremy Harris]

17 minutes ago, DreamHouseDreamer said:

@JSHarris  Inevitably, without a crystal ball, I cannot answer how much solar gain we will get - both useful in winter or detrimental in summer.  The house is designed to face south - for privacy, to maximise views and for that south facing roof for the solar array.   Most of the patio doors will face south.  However, the house is designed to not have an endless amount of wall to wall glass like many contemporary houses have, and all south facing windows or patio doors will have powered roller blinds set to lower to reduce excessive solar gain (don't ask how, I cannot get my head round any of that - it's one of 'im-indoor's tasks to resolve).  Notwithstanding any of that, when we visited a few new build houses last summer during that heatwave for ideas, as part of choosing architects, while doing general due diligence, etc and despite being told that they're so well insulated, the houses won't be that hot - they were not in every case a comfortable temp, and the owners of some we sweltering and putting on a brave face.  Our biggest concern and the real reason for wanting/needing so sort of cooling capability is for sleeping in the south facing master bedroom. 

 

Anyway, what you are saying is that some cooling can be easily addressed, I just need to specify the right type of unit.  So what features should I be looking out for?

 

Tesla may not be the only player in the power storage market, but they have the most compact power storage units we have seen.  We have been recommended to use a different, extra device between the solar collector system and the storage unit to control, monitor, report energy - which presumably would have better user interface/control.  Anyway, what other brands should I research?

 

Yes, we know about actually managing to run the house in winter just from self generated power.  We are looking into this - and I didn't want to go into too much detail above.  We understand there are power suppliers out there who have variable pricing bands and times and in winter we should recharge the batteries overnight from the grid at the cheapest rate to use during the day at peak pricing periods.  Have not yet started to research energy suppliers.  This needs to be tied to our need for an elec car charging point (a planning consent condition) despite no plans to ever own a EV.

 

 

As above, modelling with PHPP would be a very wise move, as that will give you a reasonable indication of overheating risk, and from your description of South facing glazing, and, in particular, the South facing bedroom, I think modelling would be extremely useful. 

 

When thinking of blinds, then it's worth remembering that external blinds are massively more effective than internal blinds at reducing solar gain.  I'd go so far as to say that internal blinds are pretty ineffective with decent 3G glazing, based on our experience.  Overheating was the single biggest problem we had initially, and I dearly wished that I'd been able to fit external blinds or shutters and that I'd made provision to fit an air-to-air heat pump (I'm still looking at ways to try and do this - not easy after the house has been built and decorated).

 

MVHR with cooling is available from Genvex, Paul and probably one or two other companies, but it won't be powerful enough to overcome the effect of a lot of solar gain.  Our Genvex can deliver around 1.5 kW of cooling, which is no where near enough to remove the heat we get from solar gain on a hot day; we need more like 3 or 4 kW to deal with it, and MVHR just doesn't shift enough air to be able to get close to that.  I have modified our UFH to include cooling from our ASHP, and it works very well at keeping the house comfortable, but it's not a particularly standard set up, so if you're using an installer then the chances are you may find a bit of resistance to the idea, really just from a lack of familiarity more than anything else.

 

The Tesla Powerwall 2 has a pretty comprehensive user interface, with loads of data available, and I doubt you'd need anything in addition, TBH.  Be very wary of people trying to sell you stuff you may not need, or that may not do what you wish to do!  There are other systems available from Sofar, Growatt, Lux and a few others.  The Tesla Powerwall 2 is neat, but knowing what I do about lithium chemistry batteries (I've built several electric bikes, a boat and a motorcycle) there's no way on this earth that I'd have that size battery pack inside a house.  My battery pack is going in a detached metal shed behind our house, so that if the worst happens the risk of the whole house going up is much reduced (I've had fire training on how to extinguish a lithium fire with graphite extinguishers and it's far from easy to extinguish).

 

Fitting an EVSE from the start is a wise move, as sooner or later all homes with off street parking are going to need one (we have two, one at either end of the drive).  If looking to fit more than one EVSE, then it's worth looking at total demand and how this can be managed.  I use an Irish unit, that has a current-sensing relay and contactor and that switches power to just the priority load when demand rises above a certain threshold.  The unit was designed to be used with electric showers on houses with a relatively low incoming supply capacity (a relatively common problem in parts of Ireland) but it happens to be ideal for managing the maximum load when two EVSEs are fitted (I don't know why Garo don't market it for this purpose:http://www.meteorelectrical.com/distribution-control/consumer-units-accessories-1/garo-priority-shower-board-choose-priority.html).

 

When it comes to electricity suppliers the market changes almost by the day, but I've opted to refuse a smart meter (for a lot of good reasons) and stick with E7.  So far that's working well, with around 2/3rds of our consumption being at the off-peak rate.  I'm hoping that I can shift to close to 100% off-peak usage with the battery system, which I think should be achievable (although not with the Tesla Powerwall 2 as it is currently configured - it doesn't really seem to work that well at optimising off-peak consumption).

[ragg987]

1 hour ago, JSHarris said:

It's really just that cooling the UFH means having a custom designed UFH system, with valves to isolate the UFH from any hot buffer and an additional thermostat to control cooling

Not necessarily. We used the built-in controller in our ASHP to provide UFH cooling, plus the ASHP manufacturers room thermostat to provide heating and cooling control in one unit. All we needed use to set a link in the unit to enable cooling. No need to add any other components or controls, just switch the word "heat" for "cool" - e.g. the heated buffer becomes a cool buffer.

 

My view on battery storage is that it is not (yet) cost effective. I divert extra solar to my DHW, and having a hybrid electric vehicle helps to consume some of the excess electricity.

 

3 hours ago, DreamHouseDreamer said:

Which item of kit would you need to adjust or have a different model, if you wished to be able to adjust humidity in a room as well as temperature

I don't think this one was addressed - our MVHR keeps humidity steady at around 40 to 50%. Why would you want to adjust this? It is possible to add a humidity sensor to the MVHR which would boost it when (e.g.) showering.

[Ed Davies]

1 hour ago, DreamHouseDreamer said:

Assuming our storage batteries have enough power to run the house for the duration of any power cut, the UPS would only need enough power to switch the house from grid to battery when there is a power cut.  The system clearly would still need to know there's been a power cut so that the house runs under some sort of low power mode with perhaps some sort of a warning if any high consumption items was turned on like oven, etc.

 

Simplest would probably to have two consumer units: a high power one directly off the mains for stuff you'd accept the loss of in a power cut like the oven, immersion, washing machine, etc, and a low power one off the UPS of whatever form you have running everything else.

 

It'd be well worth doing some measurement of your current power consumption both instantaneously and averaged over a day to get some numbers to work from.

[ProDave]

One point that has not been mentioned.  To have more than 3.68KW of solar PV (or any other microgeneration) requires prior approval from your DNO who may or may not charge you for network upgrades or may just refuse it.  Before you commit to buying a 10KW system, seek permission from the DNO so you know you will be allowed to connect it.

 

In an area prone to power cuts, I would not rely 100% on electricity and trying to provide your own in a power cut.  For instance we have a gas hob powered by a pair of 47Kg propane cylinders that will boil a kettle with no power to the house.  And (dare I mention it) a small wood burning stove that will heat the whole house without power.  Those and a couple of camping lights and we can survive, keep warm, and cook for however long the power cut lasts.

 

Take that load of requirements away and your battery storage becomes more about self using stored power than removing reliance on the grid.

[Jeremy Harris]

1 hour ago, ragg987 said:

Not necessarily. We used the built-in controller in our ASHP to provide UFH cooling, plus the ASHP manufacturers room thermostat to provide heating and cooling control in one unit. All we needed use to set a link in the unit to enable cooling. No need to add any other components or controls, just switch the word "heat" for "cool" - e.g. the heated buffer becomes a cool buffer.

 

 

Our buffer is always warm, has to be, as it preheats our hot water, via a PHE, hence the need for a means of isolating it. 

 

[Jeremy Harris]

56 minutes ago, Ed Davies said:

 

Simplest would probably to have two consumer units: a high power one directly off the mains for stuff you'd accept the loss of in a power cut like the oven, immersion, washing machine, etc, and a low power one off the UPS of whatever form you have running everything else.

 

It'd be well worth doing some measurement of your current power consumption both instantaneously and averaged over a day to get some numbers to work from.

 

The main issue is really demand management and staying within the rating of the incomer.  This is usually managed by diversity, but diversity cannot be applied to some loads, including EVSEs and electric showers, so some other way of protecting the main fuse is needed when there are multiple, long-duration heavy loads.  Using a current-sensing relay to switch off non-priority loads is a reasonably good way to do it, as it doesn't rely on human control.  At least one EVSE  (the Zappi) has a built-in load sharing capability, but the simplicity of a current-sensing relay and priority-switching contactor appeals to me, as it's reasonably fail-safe.

[DreamHouseDreamer]

Wow, thank you all for this huge quantity of input and responses.  All so very much appreciated - even if, for the mo, my brain is spinning with so much tech stuff. 

 

I am going to have to digest it carefully, follow up links, research some bits that are complete gobbledegook to my non tech mind and make some sense of this before I can figure out what will work for us, and anything else.

 

My bad for not describing one feature correctly.  We will in fact have external roller shutters, integrated into the window fittings - that when fully lowered are total blackout.  These should be helpful against solar gain as well as security, and we will have tripled glazed windows and patio doors. 

 

There's no way we can have propane in the new house for even a domino hob unit - I've already investigated that.  It's what we have in the existing house.   In the event of a power cut, if we cannot resolve the power issue, we may be BBQing outside, come rain or shine.  Woodburner is a possibility if we can get a 3kW one that I like and is affordable.

 

DHDreamer 

[PeterW]

10 hours ago, DreamHouseDreamer said:

There's no way we can have propane in the new house for even a domino hob unit - I've already investigated that. 

 

Why not ..?? It needs a 12mm copper pipe, this can be run in the floor or even to a domino unit in a utility room ..?

 

Unless you have some sort of external garage then a diesel backup generator is a non-starter as they are big and bulky. There are a couple of big brands - Panda is one that springs to mind - and they use voltage sensing and grid disconnects to manage the loads etc. The problem with all of that is that when you micro breaks in your supply you can end up triggering the genset for 5-10 second starts that are really bad for the units.  

 

You'd need to spend £7-8k on a decent setup, and then add in £500 for a diesel tank (500 litres) and you’d also need to run at least half of that off every few months as red diesel doesn’t like sitting. Add in £2-300 a year for servicing and genset replacement every 15 years for TCO.  

[Triassic]

39 minutes ago, PeterW said:

Add in £2-300 a year for servicing and genset replacement every 15 years for TCO.  

Might be worth reading about Paul’s backup generator, it’s decades old and works just fine. No need to replace it every 15 years?

https://lifeattheendoftheroad.wordpress.com/category/listers/

 

[PeterW]

11 minutes ago, Triassic said:

Might be worth reading about Paul’s backup generator, it’s decades old and works just fine. No need to replace it every 15 years?

https://lifeattheendoftheroad.wordpress.com/category/listers/

 

 

Agree however there is a difference between Paul and how he lives, and a modern house with all the MVHR / ASHP and other day to day stuff that I think we are discussing here. I may be wrong but I think what the OP is looking for is full turnkey with automation etc. 

[Triassic]

I agree, my response was to the idea that a genset would require replacement every 15 years. Paul only runs his every so often and it’s decades old. The only thing a normal user would need is a service every so often, and with a deisel what is there to service?

[Ed Davies]

Paul's house is a new build with MVHR / ASHP, etc. You're probably thinking of his old croft house.

 

https://lifeattheendoftheroad.wordpress.com/tag/akvaterm-store/

[Sue B]

We have a touring caravan for our holidays (I knownit’s Boring but great for holidays with the dogs).  When we had a power cut that looked to last into the evening, we decamped into the caravan where everything is set up to work perfectly without electric.  I cooked dinner, had a shower and had the heating running.  Quite disappointed when the power came back on.  We will not have anything other than electric in the new house and not going to worry about it.