spec for new oil CH & HW system - erm......

[jim]

Hi, been looking at replacing boiler and HW arrangements for some time now and would appreciate some more "non-vested interest" comments and ideas please!

House/Fuel:- ancient solid wall det. house, no gas, on the end of an overhead power cable:- is oil still my only real option?

Water supply:- private spring-fed gravity system with only sufficient pressure to reach current HW &CH header tanks at "head height" on top floor.

as part of house refurb we envisage:-

1) a showerroom on top floor - 2) relocating 1990s "inefficient" oil fired CH boiler (i.e. installing a new "efficient" one) 3) changing/relcoating HW arrangements to recover space taken by HW header tank and HW cylinder

advice so far is to install whole house pump, new pressurised system oil boiler, pressurised HW cylinder for =A36k. This would apparently also entail new bigger water supply pipe from current external tank - alot of digging and f..ing about from me + few hundred more =A3 for a "suitable" pump

I would also like to consider (with your help) a) whether it's worth; and b) how best to; allow for future heat sources e.g.1. we already have 2X wood burners that could have boilers fitted or changed to ones that do; e.g.2. ground source/water source (a few small streams about within 30-40m of the house); others I have not thought of properly yet- solar???

Currently lurking at the back of my mind are:- if whole house is pumped - what abt when there's a power cut/ or worse

- future energy crisis power cuts ? - will I then be reliant on a genny, if only to run the F..ing pump?

would a "simple" shower pump be a better solution for the top floor showerrroom?

do i want a pressurised HW cylinder or will that limit what I can do with it re: new heat sources?

should I stick with header tanks or go pressurised?

Help!

Your comments most welcome

thanks in advance for any pointers/ thoughts

Jim

[robgraham]

Jim Two things I can comment on - I suspect that you won't get a total answer from one person!

A pressurised hot water tank may well not apply in your situation as you are on a low pressure private supply. The point about those tanks is that they run at mains pressure and consequently you get mains pressure hot water. There is also the downside of such tanks that I understand that they have to be professionally installed, you have to inform your insurance company and have them inspected on an annual basis.

In conjunction with your interest in alternative heat sources, the heat store configuration would I think be a better option as effectively any source of heat can be 'plugged' into it. OK it means a heat exchanger for the DH water but they are not expensive and are very efficient - someone else wold have to reply on their performance in a low pressure situation.

One solution if using a conventional system for blending various heat sources is the Dunsley Neutraliser - it'll come up on Google.

I'll watch this thread with interest. Rob

[Andy Hall]

Seems like it unless you've priced LPG.

Given that you want to have pressure at the taps and the shower, there are only really two ways to do it.

- Storage in the roof with gravity feeds and pressurised output using shower pumps etc. This uses space in the roof which you've said you don't want to do

- Pumping and pressurising on the supply side. You still need space for the water accumulator but it doesn't have to be on the top floor. I have a friend in Norway with a system of this nature. He has a large cabin by a lake and can extract water from it. The pump and accumulator are in the basement. It all works very well but you can hear the pump coming on when water is used, although only for a short distance around the door to the basement. The pump is pretty quiet. Overall it seems to work well. For practical purposes it's like a mains fed system. The whole thing was bought as a packaged system built into a steel frame complete wih filtration and all controls.

Possibly. You need to have a water cylinder with several coils at different levels to do this, or you could just pre-warm the water in a separate cylinder.

Not economic

Unless you have some fairly substantial battery storage. This kind of pump for pressurising the whole system is somewhat more electricity hungry than a shower pump.

It doesn't make a difference. You are transferring heat via heat exchangers and coils. Keep in mind that a large pressurised vessel has to be professionally installed whereas an open vented one does not.

It seems to be a trade off.

- Pressurised system will take less space, give pressure results all over the house, cost a fair bit to implement and be somewhat vulnerable to power failure

- Open system could probably be improved. For example you could fit several smaller header tanks or use long thin ones and gain some space. You would be more immune to power failure. Showers will still work without pump, just not quite so well.

If I were doing it, I would probably look to go the pressurised route but make sure that there is adequate backup. Overall, the space saving may not be that significant other than you are moving the issue from one place to another.

[Dave Liquorice]

Oil is about 60p/l, burn a litre in an hour and you get about 10kWhr of =

energy as input to say a 75% efficient boiler so about 8kWhr of useful energy. That works out at 7.5p/kwhr that is pretty much what I pay for electricity on an online, direct debit, domestic tariff...

Oil prices are very volatile and rise much more rapidly as crude prices =

change compared to electricity. They also fall but not with quite the sa= me fast response.

I don't know what it is with wanting high (mains) pressure hot and cold.= I feel it's more of a "fashion" thing like combi boilers. Bear in mind tha= t pressurised HW cylinders should have a regular inspection by a qualified= person.

The only time you really *need* a decent head (say >1 bar) is for a shower, that can be done with a shower pump, no need to pressurise the whole system.

Personally I'm looking to add both a wood burner with boiler and thermal= solar to our current oil based heating/hw system at the same time add a =

heat bank/thermal store. With the possibility of also heating that store= by electricity, either mains if oil gets really expensive, or from a decent sized wind turbine (5kW or so rated).

How much flow and fall do you have available from those streams? 20l/sec= and 30m head will give you a few kW of hydro power.

Heat pump energy is "low grade". The temperature of the water coming out= of one is only about 40 or 50C not hot enough for domestic hot water or =

normal radiator based heating. Fine for under floor heating though.

Yep... Make sure that all the wood burner boiler loops are open gravity =

ones so you don't need power to open valves or circulate the water. You =

may need manual valves across electric ones to dump heat and/or get some= circulation in the heating during a power cut.

IMHO yes.

Look at a heat bank/thermal store this should be able to take multiple heat sources much easier than a pressurised system.

[cynic]

Yes and no. It is probably the simplest and easiest solution but don't discount the alternative energy sources. Do make sure you fully explore the costings and don't accept the claims of the marketeers without justification. In other threads the claimed output of wind generators does not match the average real life situation.

You could either use a comercial pressurisation unit with an air bladder chamber, non return valve and a pressure switch or you could raise your storage tank and use a high/low level stop/start float switch arrangement. This is probably the simplest in terms of technical requirement and maintenance.

You may achieve sufficient head from your raised storage tank or you might need a shower pump. alternatively the pressurisation unit would sort this out in conjunction with an unvented cylinder. Using an oil fired combi would be another solution but you would not have the option of using solar contribution to your hot water if you wanted to.

You may not gain as much as you think from a new boiler over a 1990s unit. By that time there were some pretty efficient units around. Again do the sums!

See above

As you say a lot of f ing about but done once. The place for the pressurisation unit would be best at source but then weatherproofing and electrics required both for motor power and controls cabling. You need to do some digging either way.

How much are you gong to do yourself? Solar hot water systems kits available for around a grand - a lot less than the big bucks the commercial installers want from you. The streams you mention - are they sluggish or would there be sifficient height of head available for a turbine generator with grid- tie system? They should provide a decent heat source for a heat pump however. Are they yours or is someone likely to want to charge you silly fees for using them? Beware EA and River or authorities and jobsworths wanting to obstruct your plans.

What is the power supply integrity like in your neck of the woods? If you only get a power cut exceeding a few minutes duration every two or three years so what - a small geny is pretty cheap.

Depends how much you want to pay and if you are willing to install additional coils now. Solid fuel systems can be inherently difficult to control the output as fire takes time to die down even after the thermostat says no more heat thank you. Not insurmountable but is the house unattended for extended periods?

I would retain a (raised) potable water header tank for the Domestic water supplies with high/low supply pump control. The radiator system could be pressurised if you so desire. The above is my personal outlook hope it helps

[jim]

yes I've been reading about the negatives... pressure wise that's why the plumbers want to talk =A3100s for a whole house pressure pump....

Looks like I may end up pumping the supply (with fiddly new pipe from tanks grrrr) I fancy a heat store for the flexibility alone.

thanks I'll check it out.

cheers Jim

[jim]

Well I could do but only with a pump of some sort to lift the incoming supply up to tanks in the roofspace, but would I get enough head for a decent shower on the floor below?

that sounds interesting - as part of the refurb we have inlcuded a boiler/plant room - how big are accumulators? the ones I've seen so far are pressure vessels strapped to pumps??

presumably with a heat store I wouldn't have coils per se? direct in to the heat store?

yeah I'm beginning to see!

space is available just not where it is now and in any case there ain;t enough head at the mo for a top floor shower..

Cheers Jim

[jim]

I can't raise the external tank height, tho possibly could add a larger internal tank in roofspace - that would need a pump though... and would I get enough head for a reasonable shower on the floor immed. below it?

where is a good place to gather this sort of efficency detail for older boilers please?

mmm wouldn;t fancy that if avoidable - the external tank is somewhat exposed abt 60m up a muddy stream gully/valley.

They aren't very big streams and when I looked at the head etc for power generation I was getting figures of 100w in winter....only way I could see was huge battery banks (=A3=A3=A3) and a lot of pratting abt..

That's what I had in mind - anyone have experiences please?

Well they cross our land en route to the small local river - does that confer "ownership"? No-one else makes use of them for any purpose I am aware of; after us they pass through or under 2 neighbours' property/ land and into the river...

Any ideas on what bases they may object/obstruct? is extracting heat classed as "abstraction" for e.g.?

true enough

I was thinking of wood burning stoves with secondary boilers in - not a "wood powered boiler". I was imagining that when thermostat(s) say "enough" the output into the room (with the stove in) would then receive the full output of the stove - does that sound OK? current stoves (without boilers tho can be retro'd) are rated at 8kw and 12kw

- presume these are theoretical maximums? tho we have been known to "get a sweat on" (25+degC) in the depths of winter :>)

If I had a heat store - would I need extra "coils"? couldn't I plumb in "straight" to the store?

Can you point me to any costings/info/sources for potable water header tanks please? also same for the sort of pump you describe?

Many thanks to all for the interesting info and ideas! Cheers Jim

[cynic]

Ok so a standard shower pump would be a solution.

Old boiler figures are dificult to find as manufacturers only push their new products. Maybe OFTEC could help. When you have your boiler serviced do you get combustion figures quoted on the service sheet? (you should)

A weatherproof hut would sort out that problem. A couple of armoured cables would be simpler to install than a frost risk pipe. (As long as the existing pipe will stand the elevated pressure)

When you said 60m up a valley did you mean 60m higher or simply that far away?

There should be the option of asking for a quote from one or more of the alternative energy installers

Its amazing what "rules" and charges "they" have hiding away until they find out you have installed something. If it was my place I have no neighbours with a view of what I get up to. Your situation may vary

Good point but beware of local water hardness. If you use a simple unit with an internal tapwater coil it can become scaled up inteernally and very expensive to rectify. Use a separate plate heat exchanger although this will require a primary pump

Plumb Centre or one of the competitors

Ditto or BSS

[jim]

Er... If i will still need a shower pump - why bother with relocatingtanks and other pumps to fill them - how about a "negative head" shower pump keeping same tanks heights (altho different locations) as i have now?

sheet?? :>) from memory last guy said 85% but went on about newer ones being measured on a different scale and so figures not comparable?? boiler is Boulter Camray with a Riello GX burner

mmm the pipe's going to be the weak link I expect, assuming I have to replace the pipe, what are the advantages of all the extra hassles of huts, cables etc? sounds expensive

sorry yes I mean far away

water is very soft here. sorry lost me there - tapwater coil? heat exchanger? for the secondary heat sources?? or have I missed something?

many thanks Jim

[cynic]

No problem - they do have a small maintenance requirement and rely on a non return valve shutting off tightly which sometimes is affected by particulate impurities in the water but nothing insurmountable. If the version you choose employs a shaft seal make sure it is protected against leakage (such as mounting over a drained tray) This is basically the same as a commercial pressurisation unit but on a smaller scale

Camrays covered a range of stages of evolution from a fibreboard shell with a crude heat exchanger to more modern high efficiency models. The Riello GX burner can be set up to be highly efficient. I would be suspicious of over optimism with 85% and if the results came from one of the cheaper analysers it may have been based on too quick a reading where the dt had not attained its final value (a common failing). In excess of 82/83% may still be a reasonable expectation

SNIP

What is the existing pipe? MDPE (Alkathene) should be fine, Galvanised steel laid properly may also be pretty good. Its a how long is a piece of string situation really.

SNIP

No but I am watching progress of a neighbour who has commissioned

to put in a ground source heat pump and they offer other source options such as water extraction. This might be a useful place to start.

SNIP

For very soft water its matterless. Basically there are heat stores on the market with the body of the vessel holding the heat and the hot tap supply being heated by passing through a coil within the body of the store. Works fine but if the inside of the coil scales up due to hard water its an expensive thing to sort out!

SNIP

HTH John