Energy Efficient System?

Elz182

Hi all, we live rurually and moved into our home 2.5 years ago. The heating system consists of:

- Two air source heat pumps (supposedly installed incorrectly as they are different sizes but plumbed together so the smaller one is permanently off).
- Screed underfloor heating with two manifolds, which has recently been serviced/flushed/cleaned
- The upstairs bedrooms have traditional wall mounted radiators 
- Very large hot water tank 
- Solar panels 

We have a relatively good feed in tarrif (FIT) for the moment but our fix for electricity we use ends next month and British Gas have advised they expect bills to triple. Since we moved in, the income from the solar panels has more or less covered the cost of the electricity bills each year - this wont work in the future!

If I'm honest I don't really understand how all these systems work together or in fact how we should use them (originally we were advised to leave the heating set at the same temperature throughout the property all year round).

Does anyone have any resources or advice for me to get to grips with it all and understand how to maximise efficiency? Or are Air source heat pumps just not that good (they seem to cost a fair amount to run)? We were recommended to switch to HVO last year but I don't think it's really commercially available at the moment?

I'd appreciate any thoughts or insights you might have! 

FreeBear

Pop over to https://forums.moneysavingexpert.com/categories/lpg-heating-oil-solid-other-fuels and post the same question there. Some of the regulars have ASHP and can advise on how to best set up the system.

Persoanlly, I'd turn the heating off during the summer, and if you don't need the hot water, shut the whole system down. I'm on gas here for both CH and HW - It gets turned off for the summer, and I rely on a kettle & electric shower when I need HW. Heating costs are minimal at the moment, so switching to heat pumps doesn't make sense at the moment for me (at least financially).

Bendy_House

In theory, an ASHP coupled with UFH is pretty much ideal. I understand ASHPs 'should' give you 2or3 times the heat output for electricity consumed, or possibly more, but they can vary.

Since you have a 'very large hot water tank', I'm guessing it's a Heat Store, which is designed to be 'charged up' with hot water, which can be from a number of sources, and then this 'store' of 'heat' is used to supply the house, CH and, possibly, DHW (tho' the temp would have to be higher for that).

In theory, you have a good setup there. Things to look at are, is it working as well as it should be?! Do the PV panels send surplus leccy to an immersion in that HS? (If not, that surely is a biggie).

And, how best to run the system? That, I don't know. I wonder if the smaller ASHP is for summer use, mainly for DHW? I dunno.

What is the insulation level like in the house?

How big is your PV system?

Any potential for adding a couple of solar-heat panels? (These might be able to take over completely in the summer, giving you all the DHW you'll need. Certainly if coupled with a PV- supplied immersion, surely?)

And is there the potential to add a battery or two?

It 'sounds' as tho' you have the potential for one of the best systems away from natural gas.

Elz182

@Bendy_House thanks so much for taking the time to reply. I couldn't quite figure out DHW as an acronym (direct hot water)?

We think the two ASHP were installed based on the size of the property to heat but because they are different sizes they should be plumbed separately due to the requirements of the PSI for each but this was incorrectly done by the previous owners...(according to the engineer we could actually get to help us!) So the smaller one was turned off to avoid it constantly switching on and off - the large alone seems to do about enough, but in a very cold year it probably won't cut it.

The insulation is good, relative to a large building 150+ years old...I'm not sure there's much we could do without significant outlay (double to triple glazing for example).

I will have a look into the solar heat panels, the current PV array is 3375 annual kw according to the installation paperwork and the panels are cleaned every 6 months or so...

I will definitely see if I can figure out if excess electricity goes to an immersion.

It's been really interesting and a steep learning curve (still on it  clearly!) and few tradespeople in our area are comfortable with the system! 

I've been thinking about installing a smart system so it can be controlled across the property electronically but as there's no boiler it'll work out about £2.5k so haven't bothered so far! Not sure we'll see a significant enough return to worry about it but it's another possibility.

Bendy_House

DHW = domestic hot water, the stuff that comes out your tap

I would research to the point that YOU fully understand your system before considering changing anything. Relying on one guy's visit and assessment is risky.

If you post a photo of your large hot cylinder, folk should be able to ID what it is. Telling us the make and model will help too!

I presume it does have an immersion heater fitted? Trace the supply cable and see it it goes to a box of gubbins that might mean it runs off your PVs. Any names like 'Immersun', for example?

To NOT have this would seem a real waste to me. Free stored heat.

I'd also be interested in how your DHW is heated. Often, with Heat Stores, this is done 'instantly', on demand, by having a coiled pipe inside the HS, and it's warmed by the stored hot water.

If you have, or wish to have, a stove, then choosing one with a back boiler will, again, be able to add to this HS.

Elz182

You are an absolute star, thank you so much. I was a bit nervous about posting but it's been great. 

I'm trying to learn which is part of why I've posted here (before hubby decides everything needs to change!) I'll be taking some notes on the brands/makes/models etc and will be back 🙂

We do have a log burning stove (again that was already installed) but no back burner or anything clever (we do cook on it in winter though!)

markin

 What is your kwh usage of the house and how much is for the heat pump? I'll take a guess at 9000 kwh total?

The cheapest option could be to simply install a separate 2kwh solar panel system and make sure you have a solar diverter to use spare without importing from the grid, With an  iBoost or the IMMERSUN, Do you have roof space or a barn?


You can still sell your power to the grid, Octopus offer around 7p kwh, look into the different tariffs on the Energy or Green forums.

Bendy_House

From what I understand, Elz already has a decent PV system AND FIT, so any surplus generation from this is theirs to use with no penalty. Chances are, for much of the time, they'll already have ~2kW going unused, so an Immersun (or similar) should be a cheap addition and pay for itself very quickly.

I'm not sure what sort of 'Smart' control system you were thinking of, but - at £2.5k - that doesn't seem to be cost-effective, at all. Hive, for example, reckon annual potential savings of just over £100, so that's fine when it only costs around that much to install...

150 year old house? Not usually suitable for effective ASHP use, as very high insulation levels are usually a prerequisite. What are the insides of the external walls like? What is on them? If it isn't obvious, is it possible to contact the previous owner to ask? I'd suggest that this is pretty significant info.

If you use your log burner regularly in winter, then it's a shame it doesn't have a back boiler, as this could be a significant source of CH & DHW, but whether it's worth changing (or having a bb constructed for the exiting) is hard to know. You need specialist info from 'renewable' forums, as this 'might' come under 'biomass'!

Your single biggest energy savings will be had by - if you can - just shutting off heating to any part of the house that you can, and reducing the living areas to a min. Eg, over winter, move your bed to a small downstairs room, and simple shut off all heating to any unused rooms such as bedrooms. For any unheated room, crack open their windows to 'vent' position, close their doors, and leave them - they should be perfectly fine.

Of course, if you have a family, that could be a bit cruel

Another thought, if your house is a fair size, the it might be worth weighing up the future running costs of ASHP vs a Biomass boiler. I 'think' Biomass comes with grants, but it IS initially costly. Someone would need to do the sums.

I know this will be a medium-to-long term project, but if you could update the thread with any of your findings, developments and decisions, I think many would find it useful and interesting

And, as Markin suggests, it'll be useful to start noting down actual energy consumption figures, and go back as far as you can. You can then monitor these to note any changes.

Elz182

I'm in the info gathering stage, so got a huge pile of paperwork I'm going through to record everything- then will come back with a summary to see what we think! I hope it will provide useful for others too. 

The building was changed to a residential property in 2010 so a relatively recent renovation!

Bendy_House

Elz182 said:

I'm in the info gathering stage, so got a huge pile of paperwork I'm going through to record everything- then will come back with a summary to see what we think! I hope it will provide useful for others too. 

The building was changed to a residential property in 2010 so a relatively recent renovation!

In that case it should be to very decent insulation standards - which makes sense since they fitted an ASHP. What are the walls made of? And I wonder what they added to them to insulate it?

Have a look at the Planning Portal on your LA's website, see if it's there. I think it should be, in which case it'll almost certainly detail the work required to pass the Building Regs at the time. That should be a great read :-)