Sustainable heating??

In the next couple of years we intend to remodel the back of the house, put in a downstairs shower and toilet, and do various other things.

This will include replacing the current boiler and doing something with the hopeless hot water system - at the moment you have to run the water for a couple of minutes before anything approaching hot water comes through.

Obvious choice is a combi boiler situated close to the kitchen and bathroom to give short pipe runs and on demand hot water.

However this is also an opportunity to 'go green' with for example a heat store, solar water heating on the roof, a wood pellet boiler. This also gives the option of adding other heat sources such as a solid fuel stove with back boiler to heat water in the winter. In this case the pipe runs are likely to be longer but good lagging and a pump may help the 'instant hot water' requirement.

Is this a feasible option? It looks expensive compared to a combi boiler - at least three major components at least compared with one - and the financial (as opposed to moral) payback may be unrealisitically long.

Has anyone gone down this route?

Is anyone contemplating it?

For us it will be a 'now or never' thing as once the house is done we have no intention of mucking about with it for some considerable time.

Cheers

Dave R

Reply to
David WE Roberts
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We have solar heating (for hot water) and it's wonderful. We haven't had the hot water heater on since about May. Our last four or five gas bills have been refunds (compared to our neighbours, who are paying upwards of =A31000 pa.)

We have friends who installed a ground source heat pump and they report very good results, but you need a big garden.

Reply to
Rotwatcher

I've just done the solar panel thing (Navitron evacuated tubes) - still need to burn gas as the weather recently hasn't been that good, but only for 10 minutes each morning now rather than the hour or so before.

Biggest difference is probably the triple insulated tank - it's directly heated from a conventional boiler (standard Y-Plan - not had a chance to change that yet), and additionally heated by a back-boiler in the cooker (Stanley range cooker - bit like a Rayburn), as well as indirectly heated via a coil from the solar panel (which is the only pressurised bit in the system) Internal coil/heat exchanger in the store to provide hot water via a mixing valve to keep the exit temp to 50C

The cooker runs most of the winter, but only weekends in the summer, (it's the only source of heat for that part of the house in winter) so the store ought to be much more efficient at keeping the hot water the cooker generates in a more usable state.

A future plan is to replace the conventional boiler with a log-burner, but the issue then is how to heat the house when we're out for a day in the winter ... I have half-baked plans to dump the store into the radiators, but who knows yet.

If you've got a south facing roof, then go for it. Cost of all the bits for me was just under £2K. (Panel/tubes, tank, pressure vessel, valves and lots of copper pipe & fittings) I only wish now I'd gotten a larger panel and tank!

Gordon

Reply to
Gordon Henderson

On Wed, 9 Sep 2009 11:04:40 +0100 someone who may be "David WE Roberts" wrote this:-

All feasible.

Make sure the thermal store has enough tappings/coils for the sources of heat you might use. Solar needs a coil, assuming you want it to be on a separate circuit filled with antifreeze and pressurised to better resist flashing to steam under stagnation. Other sources of heat and radiators can just be on tappings.

If you are considering underfloor heating this is in many ways best fed by a coil fairly low down the store, to get a better temperature for it, though it is possible to mix down hotter water.

You may want a separate shower coil for mains pressure showers, while having the rest of the hot water system as the better gravity fed system via a separate hot water coil.

If in a hard water area plate heat exchangers are the thing to do for, though they are more expensive.

Is there a problem locating the store near the kitchen and bathroom? The pipes from solar and other heat sources can be well insulated to minimise losses.

Reply to
David Hansen

Solar HW usually fails to ever pay its costs off, but its not impossible to make it work financially. Have fun designing a system that will do so. Needles to say professional systems are the least likely to pay their way.

NT

Reply to
NT

I agree that if a system is "professionally" installed then the payback time can be very long indeed - mostly due to the so-called professional installers ripping the customers off... (IMO - e.g. a relative paid 4 times what I paid for my system, but she got a 15% grant so that was OK. Err...)

However a DIY install, which is what I've just done ...

The capital outlay for me was just under £2K and it's already saving me money - a mere 10 minutes of gas burn a day rather than the 1-1.5 hours it would normally take to heat the old tank up in the morning. Today the suns been shining all day and the bottom of the tank has gone from

27C to currently 58C and there's another 3-4 hours of usable sunlight to go. At this rate I won't burn any gas tomorow at all.

Now, it can probably be argued that part of my savings has come from having a much more efficient water storage system, but even so - I'm getting free hot water today, and enough for tomorow too!

I have to say, one of the reasons I wanted it wasn't to just save money, but to get-back at the greedy energy company shareholders.. Even so, I appear to be doing both. It will take some time (and a winter) to fully work out the payback time, but I don't care - I can see savings already, so I'm happy.

Gordon (OK, still cavorting about like an evangelical maniac, but I think it's quite exciting!)

Reply to
Gordon Henderson

Hard experience is always interesting. I assume this is your =A32k total self-installed system?

Can you give any more information on your store (as it's easy to spend =A32k on one of those alone!) What is it? Did it have internal coils already, did you add them yourself and were they designed specifically for solar use? Are you monitoring tank temps in this system? Do you see good stratification of hot & cold water, did you attempt to encourage this, and do you think it's important in an efficient system?

Reply to
Andy Dingley

Yes.

I got the kit from Navitron and they made (or arranged to be made) the tank for me. I had an idea what I wanted, and arranged the details on the phone with them.

I started with this kit:

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made adjustments on the phone.

The tank is essentially one of these:

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has 2 internal coils - one for the solar loop to dump heat into the tank, and one for the hot water extraction - this is a coil that enters at the bottom, spirals up the full height of the tank and exits at the top. I wish I'd taken some photos through the hole for the immersion heater now (which I fitted with a blanking plug - might put in an electrical immersion heater in the future)

It has 2 other pairs of connectors for direct heating - 22mm and 28mm for the conventional boiler and cooker boiler respectively. These are approx. 1/3 down for the entry and 2/3 down for the exit, just above the inlet for the solar coil.

And finally, it's got a cold feed and expansion bottom and top, respectively which is connected to a small conventional F&E tank in the loft.

So it's a thermal store as opposed to a heat bank. There is no external heat exchanger and associated pump - it's all done via the internal coil which is finned for maximum heat transfer. We live in a soft water area, so I'm not concerned about anything scaling up. (8 years and the kettle is still clean)

The cost from Navitron for the kit just was just over £1,700 - tank, panel/tubes, pump, controller, expansion vessel and some pipe insulation In addition, I bought 15mm and 22mm copper pipes, a few bags of elbows, sleeves, etc. and other misc. items - everything's soldered where possible. I upgraded some existing valves to full-bore levers, changed some leaky pump isolators and so on. (Screwfix to the rescue!) I was able to recycle a lot of old copper tubing from the old setup as I went though.

I have 2 temp sensors in the tank - it came with 10mm tubes fitted to put the sensor into the middle of the tank (they're sealed at the far-end!) The bottom one is in-between the entry & exit of the solar coil, (which in in the bottom quarter of the tank) the top one just under the hot-water exit. There is a 3rd sensor at the solar panel, and that plus the tank bottom sensor is used by the controller to turn the solar loop pump on. (Simple difference which is all programmable in the controler) The 3rd sensor goes into the controller too, but isn't used for anything right now, other than to display it.

I plan to use the top sensor to turn on a heat-dump pump during the summer when the tank temp exceeds 90C to stop it boiling. (The controller can do this)

The tank does seem to naturally stratify and I think this is good. When it's low on heat, reducing the hot water flow makes the most of what's left in it - the cold entering the bottom through the coil does take what little heat is left in the bottom of the tank while leaving the top as hot as possible. I've seen the bottom at 25C and the top at 50C when looking. (I got the cheap controller TDC3, so I can't put it on the house LAN to remotely check it)

Other than convection from the solar coil, water in the tank only gets agitated by the boiler pump - so 10 minutes in the morning, and even then, the bottom of the tank doesn't see much of an increase. (I have the pump set to slowest speed) I've yet to see how the cooker boiler is going to affect it though - I've only done one trial run of it so-far, but we'll be cooking this weekend, so will find out more.

It's still very early days for this yet, so still getting "used" to it and working out how to make maximum savings. E.g. the run to the bathroom takes 20 seconds and it's in 22mm pipe which I can't practically change, so we've decided that we'll wash hands in cold water rather than waste a long 22mm pipe of hot, but we're not afraid to take hot when we need it - the kitchen is much closer and piped in 15mm from the tank, so minimal lag to get hot water.

Not tried filling the bath up yet - I suspect it may require a gas burn if it's not been sunny...

Gordon

Reply to
Gordon Henderson

Just out of interest, Gordon - whereabouts are you ? It would be useful to know if it is sunny Spain, not-so sunny Cornwall of definitely un-sunny Scotland.

Rob

Reply to
Rob G

I am not sure that isn't self contradictory.

If our boiler fires once every two days in summer to heat the water, its unusual..

Hot water is NOTHING. you spend more on kettle heating to make tea, or cooking the sunday roast.

Its the 24x7 burn to keep the house warm when there is a 35 mph -5C wind blowing that costs the REAL money.

About a grand over the winter..in my case.

Have fun designing a system

Indeed.

Reply to
The Natural Philosopher

Devon.

Gordon

Reply to
Gordon Henderson

I've had solar HW installed for 2 years now. It's based on a 30 tube Navitron panel, and a custom-made conventional (vented system) cylinder with two coils from a different supplier. (Can't remember who, a company recommended on here at the time)

Like other posters my boiler rarely runs over the summer, and the solar system acts as a pre-heat on the HW cylinder over the winter, reducing the gas used then a little.

According to it's controller, it's stored just over 5500kWh in that time, which, assuming a 100% efficient boiler would cost £177 in gas costs with my current supplier. I don't know what the efficiency of the boiler is, but if I assumed around 60% (cast iron heat exchanger, non-condensing) would equate to about £250 in saved gas costs - which agrees with the vastly reduced gas bills. Like another poster I had bills in credit for ages until their system & direct debit caught up with my reduced consumption.

My total solar cost was about £2k however I was replacing the cylinder with a custom-made short'n'wide one anyway as part of a CH re-plumb, zone split-up and airing cupboard move around so the extra cost for a solar coil was minimal.

So... the payback time financially is long. Very long. If gas prices rise the time will reduce, but as a money-saving method it's not really worth it. I'm no tree-hugger and not convinced on the 'saving the planet' aspect either - obviously there is a 'carbon footprint' in making the solar equipment in the first place! Going for a condensing boiler may have a quicker pay-pack time, I've not done this as the existing one is only 8 years old, has been 100% reliable and the location is not suitable for a condensing one (flue problems) so would mean a major re-plumb.

Alan.

Reply to
AlanD

Like other posters, my boiler rarely runs over the summer.

And I have no solar panels at all!

Reply to
The Natural Philosopher

WE save hot water costs simply by not having many baths.

The only slar that makes sense domestically is a heat pump.

Reply to
The Natural Philosopher

So instead of paying for gas and leccy, you paid other companies for parts that were made using said gas & leccy?

NT

Reply to
NT

Yes.

Gordon

Reply to
Gordon Henderson

,

Boom!.... Boom!

Reply to
Heliotrope Smith

I get the impression that you live on your own or use another means of heating water. When I lived on my own I put the boiler on for HW when I needed it which was about every two days. The water stayed hot enough in the well lagged tank for washing. I started this when the time switch broke and the (much reduced) gas bill arrived before I got around to fixing it, so I didn't bother...

I'd be happy to still work on that system now but the with a SWMBO'd and two kids it wouldn't work. They are far to used to hot water as and when they want not in 30 to 60 mins time.

Reply to
Dave Liquorice

Same here. My boiler has been on 4 times since late April and then only to spin the pump. Gas cost=0.

Reply to
PeterC

Thanks for all the replies so far.

For those who don't run the boiler in the summer - neither do we as the effeciency of the hot water system is so dire that we don't like to use it. When we need hot water (not often) we boil a kettle.

We do like to shower every day, though, which is O.K. at the moment because we have an electric shower but we would prefer a shower with a higher flow rate which means a combi boiler or a tank and shower pump. We have experience of both - previous Suffolk house had a big tanks and pump which ran two showers. Berkshire house we fitted with a new combi boiler.

Siting the hot tank near the kitchen and bathroom is tricky - the airing cupboard is over the stairs and towards the front of the house and there is no obvious place at the back of the house where the kitchen and bathroom are to put the tank. The situation could be improved by replacing the old tank with a modern fully insulated one and lagging all the pipes under the floor. If we went that way we would put in a much larger tank and a shower pump.

However if we install a combi boiler we get all the storage space in the airing cupboard plus the tank space in the loft and shorter pipe runs as well because the boiler will be in the kitchen and close to the bathroom.

So the choice initially is stored water or combi, with a lean towards the combi. However the stored water option does allow solar heating and part time solid fuel devices to be added to the equation.

Nobody so far has responded about wood pellet boilers. Has anyone any experience of these? Soilid fuel is generally a pain in the ass compared to gas, but burning wood could be a greener option. Wood burning as a main source of heat tends to cost in more if you have enough land to grow your own wood, though. Loads of wood for a wood burner tend to cost at least as much as a gas bill to provide the same level of heating. We used a log burner (open fire) then wood burning stove because we like a 'real' fire but it doesn't seem to provide cost effective heating if you have to buy your wood from third parties.

Cheers

Dave R

Reply to
David WE Roberts

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