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Author Topic: Replacing a pump and tank with a Thermal Store  (Read 10125 times)
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Posts: 2

« on: January 30, 2017, 09:52:06 AM »


I'm looking at adding a Thermal Store to the current heating setup in my house and would appreciate some advice!

The house is 4 bedroom and was built in 2003. We moved in just under 4 years ago and the range was already installed. It's a 4 oven oil fired SORN which I understand was manufactured in Ireland. (Don't think the company is still trading). It heats the central heating and hot water. Simple to use via a thermostat in the Range which we shut on and off manually or via a timer and never had any issues.

The system is gravely fed by 2 water tanks in attic and there's a small copper tank in a cupboard upstairs. Both hot and cold go through a Salamander 1.5 bar pump but the pump only kicks in when using the hot.

The 3 main issues I have is that the pump is noisy and is definitely on its way out. When not running it sometimes purges itself and makes a racket now and again and we have to switch it off on the mains plug. Secondly the water tank is small so can run out quickly once a bath is filled. Finally the water pressure to cold is at least 3 bar but for showers etc we can only get 1.5 due to the pump.

What I'd like to do is remove the pump all together, as well as the tanks in attic and run the pressure from the mains so it's more powerful and also double (at least) the size of the hot water storage tank. Would a thermal store be able to do this? I'm not a Plummer but aware that if we keep the Range on for heating it's also continually heating the water so a conventional water tank won't do.

Due to the house being relatively modern it's very warm anyway. We switch the Range of from approx April to Oct. Water is then heated via an emersion heater in the tank which is on a timer in the day. We also have a 4kw solar panel system on roof.  For cooking in summer we have an induction hob which fits into the SORN and a halogen oven on the work surface.

This set up means we use about 1200 litres of oil every 20 months and annual electric is 1000 which is about the same I get back from the solar panels FIT.

I don't want to get rid of the Range as it's a feature an very low cost to run. I just need to sort out how I can improve it based on the issues above.

Thanks in advance.

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« Reply #1 on: January 30, 2017, 12:13:46 PM »

There are some drawbacks to using a thermal store.   One problem is that  the water needs to be about six degrees warmer than the  you would normally need for DHW  because of the temperature loss in transfer. Also the store tends to cool all over as water is drawn off whereas the normal cylinder keeps hot water at the top until it is all used.   On the plus side the store is very versatile and can easily  incorporate additional heat sources in the future.   

It should be relatively easy to  exchange the present pump for a more normal twin motor pump that pumps both hot and cold water to the same pressure but both must be fed from the overhead tank, not direct from mains.  Motors will always be a bit noisy but they could be sound proofed to some extent if necessary.   You may also need to  increase the size of the existing cylinder but it may be possible to increase the  heat transfer from the stove by limiting heat to the radiators when the cylinder needs heat.

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
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« Reply #2 on: January 30, 2017, 11:42:04 PM »

Thanks the response. I'll have a look at a new pump first and how the noise could be reduced.
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