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Author Topic: Keeping central heating pump going in power cuts  (Read 8174 times)
bernieyorks
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« on: December 04, 2013, 12:54:17 PM »

I have a fairly powerful multifuel stove ( Stratford SEB 20 ) that heats water and 6 radiators largely with scrap building timber.  When we had a power cut that lasted about 10 hours last winter I managed to keep the stove just ticking over but it was almost boiling the C/H water and the hot water because the pump wasn't running and thus the heat dispersed round the house. Two of the upstairs radiators will work by gravity if the pump is off. 

As seems likely in 2015  power cuts may become a regular thing. I would like to build a cheap system that will keep the pump going if the power goes off and thus keep the house warm. I can remember power cuts under the Heath government where cuts were imposed on a rotation basis. I wouldn't imagine each one being longer than say 6 hours.

I would imagine a car battery and an inverter will do the trick. Anyone done this? Any ideas? I must emphasise I want a cheap system not a Rolls Royce version costing hundreds of ponds.   
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martin
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« Reply #1 on: December 04, 2013, 12:58:50 PM »

UPS and extra battery (ies) Wink
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biff
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« Reply #2 on: December 04, 2013, 02:44:07 PM »

Hello bernieyorks,
               If you scroll back through the threads you will find the solution to a similar problem.A small UPS,perhaps a apc600va 400watt x 12volt(I think)
    Just plug it into the mains and plug your circulation pump into the UPS.Get a qualified spark to do this for you. The battery on that particular little UPS,Toggle switch + green light toggle switch,is only 5ah which is usless really so your spark could rewire it to an external pair of 100ah sealed lead acid batts (preferably Yousa).This would autmomatically come to life and drive the pump in case of a powercut and give you plenty of time to go down to the shop and buy a decent generator, hysteria
                                                Biff
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Other-Power
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« Reply #3 on: December 04, 2013, 10:57:43 PM »

The quasine? current on UPS's are around 2amps, so a 24 volt version, most small APC, will pull 50 watts regardless of what they are running, so a 50watt pump load will mean the UPS is only running at best 50% efficency.  A power inverter and battery maybe a better option, or a DC pump, not sure how the variable speed permenant magnet pumps work, if they can run on AC and or DC?

Cheers

Jon
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derekmt
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« Reply #4 on: December 05, 2013, 12:51:37 PM »

try one of these pumps , i have one on the DHW circiut

http://www.ebay.co.uk/itm/Brushless-Dc12V-Magnetic-Drive-Pump-528Gph-Motor-Speed-Variable-0-100-50C-1240-/190978153363?pt=UK_HomeGarden_Garden_PondsWaterFeatures_UK&hash=item2c772f5b93
Max Flow    2000L/H
Max Head(lift height)    4.0M
Power Supply    12V/3.8A
Max Water Pressure    8 Bar
Waterproof Level    IP68
Max Operating Temp    100C/212F
Working Life    More than 30,000 hours
Power Cord    1.0M(bared)
Weight    approx. 650g
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bernieyorks
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« Reply #5 on: December 06, 2013, 07:59:46 AM »

Thanks for your ideas everyone. I'm doing some research into various types of UPS. There is a ready made piece of kit I have discovered, either made or just sold by a firm called Greymetal, that costs 150 minus battery. That claims 4 to 5 hours of use, but it seems to me that how long you get depends entirely on the battery or batteries you use in any system.
Regarding the pump ; the present one is a good quality Grundfoss one that has lasted 20 years and I've learnt to leave things alone that work well. If it broke down I might consider making the system 12volt but all the pipework, pump etc. is packed into a tight space between the chimney breast and a cupboard and doesn't leave room for a transformer, which would have to sited somewhere else.  Could I get a transformer that provided 12 volts to the pump and kept a battery charged? Would I lose efficiency by having a pump working permanently working through a transformer at 12volts?
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martin
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« Reply #6 on: December 06, 2013, 09:04:18 AM »

There really is little point - just keep your existing pump, and use a simple UPS with extra batteries - it'll charge the batteries, and automatically switch in when there's a power cut (the only 12v part being the batteries and charging circuitry)
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biff
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« Reply #7 on: December 06, 2013, 10:00:22 AM »

If you have got 20 years out of any pump then you are doing extremely well,
                     Then you cannot compare the old pumps with the new ones for energy saving,some of the new ones run on 5 watt.,The last one I fitted uses 25watt on its higest speed.I would not wait untill the pump lie down on a Chrismas eve or just when you come back from 2 weeks holiday because thats exactly when they will break down. "2 turkeys with one stone"
                                                                   Biff
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mjallum
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« Reply #8 on: December 06, 2013, 11:58:21 AM »

I have a ups as a standby for our back boiler, it works great for about 30 mins which is plenty of time to crank the generator up. I always thought that if the geny failed I would simply  couple up a tractor battery  with jump leads which should give quite a few hours of back up
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Other-Power
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« Reply #9 on: December 06, 2013, 04:26:24 PM »

I know I am repeating myself but UPS for light loads have very poor efficiencies, better to keep at DC to use power direct of use a power inverter suitably sized to meet the specific load to minimise conversion losses. 

Seeing as we are talking about power cuts, converting the small reserve of power at the highest efficiency is logical move.

Cheers

Jon
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martin
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« Reply #10 on: December 06, 2013, 04:33:07 PM »

Agreed,  but I'm looking at being pragmatic - with a small ups and a couple of extra batteries, you wire it up, walk away, and leave it to do it's stuff  like switching on when required (sod's law the powercut will be when you're not about to switch things on and off) - it's cheap, cheerful, and does the job with the least hassle - by all means add refinements like standalone inverters, but for a simple "down and dirty" answer the ups and batteries works well. Navitron used to sell suitable ups' as they were much used in solar hot water systems..........
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bernieyorks
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« Reply #11 on: December 07, 2013, 09:46:24 AM »

Thanks for your interesting ideas etc. I'm still looking at what's available in the UPS field.
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bernieyorks
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« Reply #12 on: December 08, 2013, 05:28:15 PM »

I've looked at various UPS and batteries and am coming round to the idea that a may be better off with a small generator as I could possibly keep some lighting on as well when the power is off. My CH pump is on the same circuit as the immersion heater , which is rarely used ; maybe once in the last year. There are 2 ring mains 1) kitchen and small extension 2) the rest of the house  and an upstairs and downstairs lighting circuits.
I've never dealt with generators. What's the best way to connect it in the event of a power cut? When the power comes back on does that cause a problem?
If its easiest I could connect the  CH pump to the ring main via a fused spur and then connect the generator to the ring main unplugging anything that overloads the generator.
I rewired the house and understand that but nothing about using generators as a standby.
If the power goes off during the night it's  never caused a problem with the stove as I shut most of the air off when it is running during the night; so its not generating enough heat to boil the water and if it did I'd soon wake up. Also 2 of the upstairs rads work with gravity and dissipate some of the heat.
I don't need a system that works automatically I'll expect to connect things up manually.
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w0067814
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« Reply #13 on: December 08, 2013, 06:35:58 PM »

http://www.navitron.org.uk/forum/index.php/topic,21552.msg249071.html#msg249071

Apt timing re small generators if not already seen.
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bernieyorks
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« Reply #14 on: December 08, 2013, 07:07:27 PM »

That was useful thanks. I'm still not sure how to connect up the generator temporarily to the house wiring.
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