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Author Topic: Recommended inverter to run C/Heating pump  (Read 2431 times)
Arthway
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« on: August 03, 2015, 05:55:57 PM »

New to the forum, so hope this post is in the correct section.

I'm hoping some kind souls could help here.  We have a Grundfos pump that runs our central heating system (Type UPS 15-50 130 - P/N: 96281422), and a Horstmann Cenaurplus C17 Timeswitch Programmer installed.

I'm intending to install one or two leisure batteries (approx 100-115aH each) so that we can run a 12v inverter to keep the system operational should the mains fail.

I gather the Timeswitch contact rating is 3 (1) Amp at 230v (whatever that means?) and am unsure what the pump requires to successfully come on.

Would appreciate advice on what would be a suitable size inverter to use for the above.

Thanks
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jonesy
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« Reply #1 on: August 03, 2015, 09:55:22 PM »

The pump looks like it will take a max of 100W, plus a little for the timer and boiler, say 120W. Assuming the motor is a little inductive, say total 160W. So a 200W inverter would do.  You might get 8 hours out of one of those batteries at that load.
Do not buy unbranded junk off eBay no matter what the advert says it is good for, or how good the spec is. You'll need something with low distortion output, often called pure sinewave.
If you already have the batteries for a caravan, then that's fine.  But buying batteries that will just sit there until you might need them will not last many years and they ain't cheap, just for a possible problem for a few months per year.  Cheap batteries will always let you down.
If its just emergency use, thing about using the car as a quietish generator.  A cheap genny will just annoy the neighbours in a few hours.
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Arthway
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« Reply #2 on: August 07, 2015, 10:26:17 PM »

Thanks for the helpful reply.  Smiley

The pump appears to have three speed settings, and is set to the slowest one.  I'm not sure what you meant by "the boiler" - what we have here is an Esse Oil Fired Stove, which is the sort that does not require electricity to actually run (vapour type - V40), so there is only the pump and the timeswitch that uses electric power to allow circulation for the radiators.

We were looking at getting a pure sine wave inverter as you suggest, and probably something like a Enduroline Calcium Leisure Battery from Tayna that can be connected to a CTEK Charger/Conditioner (most of the time). I need a decent charger to sort out several of our vehicle batteries. The charger we have is out the ark so it'll get a fair amount of use.

I read somewhere that it is not very efficient to have too powerful an inverter if the load is on the small side, so it looks like a 200W would fit the bill.....
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TheFairway
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« Reply #3 on: August 08, 2015, 03:27:58 PM »

Out of curiosity, I looked up the pump details and found that it had been superceeded by an Alpha 2 model which offers much reduced power consumption and option for variable speed control for a number of scenarios.

Apart from it may be a way to reduce the power needs of the OP, I wonder how much of a direct replacement this may be for our c/h pump, a BG badged version of a Grundfos.

I am quite concious of the power draw of our pump and whether in our scenarios with automatically timed radiator valves meaning that often only a small number of radiators are actually on, this variable output pump woukd work well.

Im not sure what type of radiator configuration we have, but we do have a bypass valve.

Not sure if its a DIY fit.
« Last Edit: August 08, 2015, 03:34:46 PM by TheFairway » Logged
nominous
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« Reply #4 on: August 10, 2015, 11:23:58 AM »

What is the cost of a good inverter verses the cost of a DC pump and a suitable PSU to drive it?
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biff
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« Reply #5 on: August 10, 2015, 12:25:48 PM »

If you have a mains supply,
                      You could go the UPS route and invest in a smart apc 650va, the older type with the cream metal casing. If there are no storms forecast and the weather is good, you can switch off your little UPS and leave it till the weather gets doubtful, Then plug your circulation pump or fridge into it and plug the UPS into the mains. So your little UPS stays silent while the mains is flowing but when the mains shuts down,the UPS does what it,s name says, it continues to supply the power without interuption and will continue to do so until the Battery runs low.
  You can decide what length of time you wish it to run for by the size of the battery. The factory fitted batt is only 7ah 12v so its not going to last very long (but long enough for you to shut down your PC), So a couple of SLA,s like Yousa 100ahs would give you many hours on a pump set at 25watt or a low energy chest freezer converted to a fridge by either an externally controlled sensor or just a plain old fashioned timer,set to come on 1 hour out of every 5. (works perfect)
  There is no fan on the apc650va smart. It is simple to operate and not too hard on the juice. + they sell for buttons on eblag. If you have a job for one of these, You will get to admire them and like them because they are ultra reliable. They would never charge a couple of 100ah yousa but a small solar PV panels would.
                                                                                     Biff
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Scruff
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« Reply #6 on: August 10, 2015, 04:46:12 PM »

I dunno about Ctek because they're over-marketed and over-priced imho and only go to 14.4V for sealed batteries. Properer batteries like the option of 14.7V or 14.8V.
If you have a look at 6V golf cart batteries you'll find much better batteries for about the same price. Comparing the 2 x Enduroline 12v 115Ah to 2 x mystery brand 6v 235Ah at Tanya; the 12volts are 0.115 per watt capacity
6 volts are 0.12 per watt capacity

6 volts are a combined 12kg heavier.

Leisure batteries are junk.  wackoold

Regards battery chargers float charging a battery, chargers are highly inefficient at low duty cycles. Not to be confused with float charging on a float charger (like a 1.2A trinket, haven't got one so haven't tested it).

I've recently tested a few of mine performing at float stage.
My PSU powered solar controller is 10% efficient.
My 20A Sterling is 10% efficient and my 15A Victron is 1% efficient.
...switching losses.
Which works out about 35 a year to run the Sterling and 14 a year to run the Victron.
« Last Edit: August 10, 2015, 05:52:33 PM by Scruff » Logged
jonesy
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« Reply #7 on: August 10, 2015, 05:24:17 PM »

The APC ups are pretty good as Biff says.  But don't load them continuously at 650VA for more than about 20 mins otherwise the mosfets overheat and all go fut, then that's a new ups required.
They are not plug and play, in the same way as a branded inverter would be ie follow the instructions, but it's pretty obvious how to wire them. I reckon about 75% efficient with a quiescent load of 1A/12W. So that means a 75W load would required 100W from the battery + 12W, so 112W in total.
The cheaper the inverter, the worse the efficiency.
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Scruff
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« Reply #8 on: August 10, 2015, 05:43:00 PM »

... otherwise the mosfets overheat and all go fut,

If they are rated to that load all you need is to upgrade the thermal design. eg. mount them on bigger heat sinks with fresh thermal paste and duct some forced air across them.
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biff
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« Reply #9 on: August 10, 2015, 07:29:18 PM »

The reason that I specify the 650va x 12 volt ups, (cream metal casing),
                                                                       Is because I have used them myself. Our old system (still there as a standby system) consisted of a 1200ah yousa battery bank, 2 x 80watt solar panels,(4 years of a 450watt x 12 v w/t, a c40 and the little 650va x 12 volt ups. This is what we used during the long winter evenings, for watching telly, running the circulation pump and lights + charging the laptops. In all the time we used it, I doubt if it conked out more than twice because of overload.
.
 It has a 12v car docking plug for mobiles. It was well used when we got it. I hung on the wall in the corner with cut down wallplate straps and piped an 8double socket ring main from it. It is on that wall for 8 years at least and any sign of overheating would reveal scorch marks. I gave a few to friends who got good results as well. None overheated that I know
  Last year I removed 4 of the 100ah Yousas and reduced the bank to 800ah. The batts are still full but now I am thinking of removing them and plumbing in a 850ah 24v forklift. She says it will never be needed but we did use it lately when I crashed the turbine in January. I am reluctant to make it redundant because it served us so well. Prior to this we had a series of stupid modified sine wave efforts, all blew up apart from a maplin 300watt pure sign wave inverter but it was very sore on the juice so we tried the 650va and never looked back.
  Of you really want to know,how well these work. stick a load on one for 6 months and you will have your answer.
                                                                            Biff
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jonesy
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« Reply #10 on: August 12, 2015, 10:01:31 PM »

 I've melted 3 in total. 1 was a fully 2kva rated external battery and the fan failed, one was a 650 that I put on to charge some batteries and forgot about and then put some real loads on, and I forget why the third went pop, but you could smell the varnish cooking in the transformer way off.
You won't get scorch marks Biff. They don't get that hot. Only around 100 150C.  The silicon inside the mosfets just cant liberate enough heat. Apc don't even put a temperature sensor on them, or in the transformer, which is the other problem area. Again, they reduce the copper right down for intermittent use, which is why most 3kva 230/110 site transformers are typically 20 mins on, 10 mins off.
An old ups is without a doubt a cheap way to get an inverter.  Ive run them all day at 1/3 marked rating, or full rating on ones with an external battery connector.  Mine are all less than 10 years old, and I suspect they keep cheapening the design.  The heatsinks on the newer transformerless ones are tiny
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