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Any plumbers in the house? Buffer tanks
tegwin - 25/9/07 at 02:31 PM

Im yet again looking at the heating system....

Im looking at fitting an Air source Heatpump, the manufacturor recomends fitting a "buffer tank" in the circuit to help maintain a more even flow and to basically encourage the heatpump to run for longer rather than stopping and starting all the time...

Now my confusion starts.... Are they suggesting that the buffer tank is installed like a capacitor so the water from the heatpump flows through the buffer on its way to the radiators..

Or, are they suggesting that the heatpump feeds the buffer and then returns to the pump and there is a seppreate loop inside the buffer tank to take the heat away to the radiator system....

NS Dev - 25/9/07 at 03:07 PM

no its like a capacitor, they only have one port, with a diaphragm inside and a schrader valve on top to recharge them with air above diaphragm.

screwfix sell em pretty cheap

Digger Barnes - 25/9/07 at 03:39 PM

quote:
Originally posted by NS Dev
no its like a capacitor, they only have one port, with a diaphragm inside and a schrader valve on top to recharge them with air above diaphragm.

screwfix sell em pretty cheap


I think what you are talking about is an expansion vessel, which is required in a closed heating circuit.

What they mean by a buffer tank I would imagine is a vessel that has a hold up of water that the circulates through the heat pump so that there is a reservoir for the energy to be stored in. This would stop the heat pump from modulating on and off all the time as there is a large sink for it to charge. I would imagine you would then have a separate pumped circuit from this tank for your radiators or it may even be part of one single circuit either would work (with slightly different characteristic response time).

Well with about 30 seconds thought that’s how I would design it (process engineer).

tegwin - 25/9/07 at 05:58 PM

Yup, thats pretty much how I would do it...

But..If the heatpump is just heating the buffer tank, would you simply pump the water from the tank around the house, or run the central heating water through a coil inside the buffer tank?

I guess its a case of suck it and see...the company who makes the heatpump sells various buffer tanks..Guess I have to buy one and see how best to connect it up..

Digger Barnes - 25/9/07 at 06:13 PM

You could do it in a number of ways.

Is the heat pump designed to keep the tank hot most of the time? Is the heat pump just providing hot water for the radiators, or is it to be used for domestic hot water too? What is the energy output from the heat pump? how many radiators are you running? what is the overall heat output for the radiators in KW or BTU etc?

With a little more information we should be able to get to the best way to plumb your system with a correctly sized buffer tank.

[Edited on 25/9/07 by Digger Barnes]

tegwin - 25/9/07 at 07:03 PM

I calculated the total heatloss of the house to be around 19Kw including hot water...

The heatpump I am looking at produces 24Kw at max, but will proberably average about 19Kw at very low temperatures...

Currently there is a sepperate imersion type hot water cylinder and a 17 radiator loop switched using a three port valve.....