mvhr and minimal other heating

[Ed Davies]

5 hours ago, scottishjohn said:

so maybe my nutty professor idea of a 5000 or10000litre concrete tank insulated to death  on outside could be a winner

 

My nutty professor idea is a 10'000 litre tank reasonably well insulated on the inside. My primary heating will be leakage from the tank - I can even see myself removing insulation in, say, February to get a bit more heat out of it. More likely, run a few small radiators off it. To be determined in the light of practical experience.

 

Primarily heated from solar thermal with maybe some spare energy from the PV going in there, particularly in bright weather in the autumn.

[ProDave]

I wired a house that had a system a bit like that.  It had a massive thermal store, I don't know the capacity, but it was huge.  It was "odd" in that it was not fed from any top up feed, but you were supposed to check the water level from time to time and top it up.

 

It was heated with a WBS that put only 2KW into the room, and 10KW to water. The theory being you light the stove perhaps once a week and burned it until the tank was hot enough, then that provided HW and heating for the next few days.

[Jeremy Harris]

I think I've mentioned before that a friend of mine converted an old chapel (which by coincidence was one where my great grandfather had been the minister around 1890) and he built a well-insulated concrete block room right in the centre, that he filled with granite rocks.  He picked the rocks up, one by one, from the nearest beach and transported them in the back of his 2CV.  He acquired a few old storage heaters and added the "bricks" from them, rewiring all the old storage heater elements so they would run on the lower DC voltage output from his home-made wind turbine (which was made from a modified lorry dynamo, I think).  Each room had an insulated door over a vent that lead into the stone thermal store, and opening any of these doors turned on a fan that drew air in from the entrance hall and slightly pressurised the thermal store room.  Air flowed around the lumps of hot granite and out via the opened vents to the rooms that needed heat.  It seemed to work pretty well, given that the chapel wasn't particularly well insulated (but was down in West Cornwall, where the climate is very like Dumfries and Galloway).

[Thedreamer]

I'm installing a joules aero, it's a hot water tank with a heat pump on top.

 

It draws heat from around the house. I'm hoping our south/west facing glazing will provide sufficient solar gains to allow this extracted heat to be replaced. These ducts also extract moist air in bathrooms and I've planned to put one in a small airing cupboard where our stove pipe will run through. 

'

Backup heating will come from electric heating if need first thing in the morning. For the winter evenings we plan to have a small 4-5kw stove centred in the middle of the house. I have pretty much an endless supply of wood/peat.

 

Never been convinced by underflooring heating, you always hear people on grand  designs/building the dream say they hardly turn it on. It would have been harder to install because of our    suspended timber floor. 

 

Hopefully this will result in the electricity bill being minimal, but if doesn't then who knows what I will do. 

[PeterW]

16 hours ago, scottishjohn said:

your solar pv is 250-350 for 325watts

 

Not quite sure where you’re getting the numbers but solar PV panels are about £90-100 at most now, and a full 3.6kw system can be had for less than £2.5k. 

 

To get the same from ST you would need say 40 tubes which with a pump station, glycol and the rest would be around £1.7k. The issue is on a sunny warm day, you don’t need hot water so it becomes a stagnation issue. You could go to a 4,000 litre store but notwithstanding the sheer size, it would set you back £3k for the tank. And you can only use a certain amount of hot water a day ..!

[Guest Alphonsox]

27 minutes ago, Thedreamer said:

Never been convinced by underflooring heating, you always hear people on grand  designs/building the dream say they hardly turn it on.

 

That's either because they ran out of money during the build and so can't afford to turn it on,  or because the the build is heated by internally generated smugness from knowing they've appeared on telly with Kevin - The rest of us have to resort to more conventional means. ?

[scottishjohn]

lets face it a sensible scheme done by folk who have half a brain +not falling into the obvious traps wouldn,t make good TV - so no chance of being of any interest to  to kevin 

now the cob castle was a good case in point .

I like the idea but surely some sort of temporary  porous  formers on outside and the use the digger to compact it would have a more sensible idea 

[scottishjohn]

3 hours ago, Ed Davies said:

 

My nutty professor idea is a 10'000 litre tank reasonably well insulated on the inside. My primary heating will be leakage from the tank - I can even see myself removing insulation in, say, February to get a bit more heat out of it. More likely, run a few small radiators off it. To be determined in the light of practical experience.

 

Primarily heated from solar thermal with maybe some spare energy from the PV going in there, particularly in bright weather in the autumn.

my idea of the insulation on outside of tank is to use the concrete as a large heat store which should stop the panels from stagnating  --concrete will hold 5 times as much heat as water ,but heats up and cools down slowly. and get to 90c by end of summer and when tank drops below min set temp divert solarinput to smaller buffer tank or direct to floor +switch back when it makes more than is needed for immediate use.

I had a calculation done 20 years ago by thermomax when i fitted first tubes --with my house it worked out I needed 20000litres storage +6x20tube panels to get  80c by end of summer for full years supply with a small possibility of needing to use electric inline boiler as back up -heat loss they claculated at 1.7c per week using 140mm of phonelic foam on outside. anymore and the difference is really academic -just cost outweigh the extra thermal gain

now we are talking about a totally different house so numbers must be just a small fraction of that.as that same house uses £800 in electric for the ASHP --

my feelings are it still won,t be practical . 26mx2.6mx2,6m water storage tank +another 140mm of insulation all round the concrete +--but I,ll wait till heat calcs are done for final decision 

[scottishjohn]

3 hours ago, ProDave said:

I wired a house that had a system a bit like that.  It had a massive thermal store, I don't know the capacity, but it was huge.  It was "odd" in that it was not fed from any top up feed, but you were supposed to check the water level from time to time and top it up.

 

It was heated with a WBS that put only 2KW into the room, and 10KW to water. The theory being you light the stove perhaps once a week and burned it until the tank was hot enough, then that provided HW and heating for the next few days.

you will get big heat losses from the evaporation of the water if not a sealed and slighty pressurised..

you would have probably been just as good to use the old  roman method --duct chimney around house wrapped in fire bricks  and use all the heat from the logs and the flue gases. LOL

[Ed Davies]

Ah, OK, you meant insulation outside the tank. I thought you meant the tank being outside the house. I meant the tank being inside the house (so all the heat leakage will contribute to the household heating).

 

19 minutes ago, scottishjohn said:

concrete will hold 5 times as much heat as water

 

What? The specific (per unit mass) heat capacity of water is more than four times that of concrete. The volumetric heat capacity of water (per unit volume) is double that of concrete. OK, you can heat the concrete to many hundreds of °C whereas water goes elsewhere if you heat it above 100 °C at normal pressures but I don't think that's what you mean.

Edited November 12, 2018 by Ed Davies

[Jeremy Harris]

4 minutes ago, scottishjohn said:

my idea of the insulation on outside of tank is to use the concrete as a large heat store which should stop the panels from stagnating  --concrete will hold 5 times as much heat as water ,but heats up and cools down slowly. and get to 90c by end of summer and when tank drops below min set temp divert solarinput to smaller buffer tank or direct to floor +switch back when it makes more than is needed for immediate use.

 

 

 

 

Wrong way around, I'm afraid.  The heat capacity of concrete is only 880 J/kg.K, water is 4,182 J/kg.K

 

[scottishjohn]

LOL

well thats that idea  trashed--but it will slow down heat leakage and should  help to stop stagnation by keeping temp down until the concrete heats up , ok then less concrete more  water storage--but still think it will be a non starter due to cost of tank with all complications of expansion of concrete etc -

I do have 5000litre grp  10bar pressure vessel I converted years ago +insulated etc --but wife would not let me bury it in the garage

a work of art making the copper  solar coils  22mm input split into 12 X10mm pipes wound up looking like a hill billy still  and out put coil was 1" single copper coil at top of tank 

tank is 8ft long x 5ft diameter all cradled in astrengthened  plywood box--weighe 5tons when full  and 130mm phonelic foam around it then air gap and double bubble foil then air gap and plywood outer casing

my workers were quite worried when i pressurised it to 4 bar to test it  all .

all good fun --myabe i,ll weigh in the copper and make it into a simple garden water storage tank at new house--or maybe just try it first for a season in the new garden -and so what temp i can get it too--loads of space to play about 

If i still have the energy after building new house!!!

 

 

 

 

[ProDave]

2 hours ago, Thedreamer said:

I'm installing a joules aero, it's a hot water tank with a heat pump on top.

 

It draws heat from around the house. I'm hoping our south/west facing glazing will provide sufficient solar gains to allow this extracted heat to be replaced. These ducts also extract moist air in bathrooms and I've planned to put one in a small airing cupboard where our stove pipe will run through. 

 

I have never quite understood these types of water heater.  They seem a good idea to cool the house in summer and make use of that spare heat, but at any time you are heating the house they don't make that much sense to me as you need to replace the heat they suck out of the house,.

 

I guess if that replacement heat comes from a heat pump, then in effect the water is heated by a 2 stage heat pump?

[Hecateh]

8 hours ago, Declan52 said:

Not sure how your plumbing skills are with regards connecting all the pipework up to a manifold but even if it's only a few hrs work  for a plumber it might be money well spent. 

I'm not sure if this is the same for other areas but for me 'a plumber' has been an expensive mistake as they have little to no experience of ufh.

[Thedreamer]

8 minutes ago, ProDave said:

I have never quite understood these types of water heater.  They seem a good idea to cool the house in summer and make use of that spare heat, but at any time you are heating the house they don't make that much sense to me as you need to replace the heat they suck out of the house,.

 

I guess if that replacement heat comes from a heat pump, then in effect the water is heated by a 2 stage heat pump?

 

In the summer this system will help to stop over heating.

 

In the winter, we will probably be out of the house most of the day, so should just tick away extracting any solar gains and heat the water steadily. Winter temperatures are pretty mild here as we are really close to the coast.

 

If it's cold in the winter the stove will go on and should just take a few sticks. I probably have enough wood felled here for about ten years so the 'missing' energy will come from wood.

 

 

[Jeremy Harris]

1 minute ago, ProDave said:

I guess if that replacement heat comes from a heat pump, then in effect the water is heated by a 2 stage heat pump?

 

That's about the only use case where they make sense, really, especially for the majority of these units, that are based on units that are very commonly used in the Far East, and aren't optimised for use in a UK climate.  The exception to this are the carefully designed combined exhaust air heat pump and MVHR units, that utilise the heat coming from the MVHR exhaust without increasing the air flow rate.

 

Always worth having a look on Chinese manufacturers sites, like Alibaba, and playing spot the Chinese import being sold with a different name here in the UK, as there are literally hundreds of these units on sale there. 

 

[scottishjohn]

8 minutes ago, Hecateh said:

I'm not sure if this is the same for other areas but for me 'a plumber' has been an expensive mistake as they have little to no experience of ufh.

I doing relativley low heat plumbing --not a real boiler then have a look at unponor q+e system --no soldering using pex pipe--pretty idiot proof

Edited November 12, 2018 by scottishjohn

[Declan52]

6 minutes ago, Hecateh said:

I'm not sure if this is the same for other areas but for me 'a plumber' has been an expensive mistake as they have little to no experience of ufh.

Very true I should have included "a few hrs work for a plumber who has plenty of experience with UFH systems". 

[Hecateh]

2 minutes ago, scottishjohn said:

I doing relativley low heat plumbing --not a real boiler then have a look at unponor system --no soldering using pex pipe--pretty idiot proof

 

1 minute ago, Declan52 said:

Very true I should have included "a few hrs work for a plumber who has plenty of experience with UFH systems". 

 

I am now on my 3rd plumber and this one does seem a decent plumber and gas engineer (and genuine person/tradesperson) in general BUT even they have only installed one ufh previously and have happily heated my previously unused system to way above the 27 degrees that is the max for the installed flooring.  

 

One also said he couldn't understand why I had opted for UFH as radiators were very efficient now. 

[Thedreamer]

2 minutes ago, JSHarris said:

 

That's about the only use case where they make sense, really, especially for the majority of these units, that are based on units that are very commonly used in the Far East, and aren't optimised for use in a UK climate.  The exception to this are the carefully designed combined exhaust air heat pump and MVHR units, that utilise the heat coming from the MVHR exhaust without increasing the air flow rate.

 

Always worth having a look on Chinese manufacturers sites, like Alibaba, and playing spot the Chinese import being sold with a different name here in the UK, as there are literally hundreds of these units on sale there. 

 

 

I've not fully researched this area yet. But I believe the Joules Aero is an upgrade on ESP Ecocent which from speaking to my plumber, designer and others, although seems to function well, seems to require the anode to be changed more regularly. 

 

From reviewing the Joules website these appear to be manufactured in the UK or Ireland. I hope this is the case as I would hate to think it has been put together somewhere in China.

[Jeremy Harris]

Here's a selection of Far Eastern all in one heat pump water heaters: https://www.alibaba.com/showroom/all+in+one+heat+pump+water+heater.html?fsb=y&IndexArea=product_en&CatId=&SearchText=all+in+one+heat+pump+water+heater&isGalleryList=G

 

The Ecocent was certainly a Chinese import, even though they tried at first to pretend it wasn't.  When I spoke with ESP about it a few years ago at the Swindon centre they said that they were importing the units and modifying them for the UK market, which seemed to be true, based on what I saw.