Two Separate Pumps
- Thread starter Munroast
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If you mean can you have a pump for heating and a separate one for dhw yes at one point very common on oil systems .
Wired with relays to stop both pumps running together.
Low head pumps are available.
Wired with relays to stop both pumps running together.
Low head pumps are available.
Yes, use zone valves to isolate the circuits.
Yes - the valve can be used to switch power to the pump. It has 2 power channels - one that powers the valve motor to open and another that will switch a 240V power feed in to a 240V power feed out (switched live - SL), once the valve opens, that SL could be used to power the pump.
Just to clarify for the OP in this arrangement the call for heating or hot water goes to the brown wire on the valve and also to the respective pump.
The orange wire from the microswitch only supplies the switched live to the boiler
The orange wire from the microswitch only supplies the switched live to the boiler
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I have two pumps, the problem is to supply the pump independent to the boiler, I have a relay, ideal would be a motorised valve with two micro switches, but they only have one, so the relay allows feed to the boiler with no back feed to pump.
And yes pumps pass when switched off, clearly who ever put in my system did not realise that, so one pump was for flat and the other for main house, and running one pump causes reverse flow in the other one. I used motorised valves, but would think non-return valves would have also worked.
I have C Plan, and the flow to hot coil, can't sink the energy from the boiler, so if central heating not running, after 20 minutes boiler turns off due to return water temperature. By experiment, I found needed to run 4 times a week, and 20 kW boiler, so around 25 kWh to keep DHW warm to wash hands, using the immersion which is supplied with an iboost+ it shows how much energy used, this never exceeds 5 kWh, so need 5 times the power from oil as to using electric.
Cost of electric is either 8.5p/kWh or 15p/kWh depending on if heated during day or night, so in summer far cheaper to use electric, winter no option as can't turn DHW off. I had been told so many times gas was cheaper to electric, I had just believed what I was told, but it is simply not true, as I would guess the heating of the boiler and pipe work boiler to cylinder had not been taken into account.
And yes pumps pass when switched off, clearly who ever put in my system did not realise that, so one pump was for flat and the other for main house, and running one pump causes reverse flow in the other one. I used motorised valves, but would think non-return valves would have also worked.
I have C Plan, and the flow to hot coil, can't sink the energy from the boiler, so if central heating not running, after 20 minutes boiler turns off due to return water temperature. By experiment, I found needed to run 4 times a week, and 20 kW boiler, so around 25 kWh to keep DHW warm to wash hands, using the immersion which is supplied with an iboost+ it shows how much energy used, this never exceeds 5 kWh, so need 5 times the power from oil as to using electric.
Cost of electric is either 8.5p/kWh or 15p/kWh depending on if heated during day or night, so in summer far cheaper to use electric, winter no option as can't turn DHW off. I had been told so many times gas was cheaper to electric, I had just believed what I was told, but it is simply not true, as I would guess the heating of the boiler and pipe work boiler to cylinder had not been taken into account.
Just looking to clarify, any reason it's couldn't be run from the SL? I would always want the pump to run once the valve was open rather than the pump running against a restricted head whilst the valve is opening and potentially causing noise/wear on the valve/pump or if there's a valve motor failure then it would be running against a closed head? Using the SL could avoid all of that. As is the case when the boiler gets the SL it then goes through its startup and the pump then runs or the boiler sends a switched live out to the remote pump.
You make some good arguments as to why you should power the pump from it but it doesn't work like that.
Lets assume the wiring is correct and the orange wire has been used as SL
The various orange wires meet at the wiring centre then send demand to the boiler.
The microswitches are there to act as relays preventing voltage going back through the system.
So in essence whenever anything calls for heat all of the orange wires on the two ports become live but it doesn't usually matter because the power only goes back as far as the microswitch which is open.
If you put the pumps on the orange terminals whenever one zone called for heat it would bring all the pumps on.
If you feed the pumps from the brown wires they will only run when the 2 port gets a call to open.
The pump plan G112 referenced used a control box with relays in to switch the pumps and prevent this. Haven't seen one for about 15 years!
Ah right, of course - DOH! - as there's only one SL @ the boiler then at some point they will all connect up regardless of how it was wired.
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Thanks for the advice so far - just to clarify a bit more in what I want to do, and why!
Our HW heating has always been noisy,, lots of whooshing and gurgling noises, (it has been like that since we moved in 25 years ago), it is quiet when the CH is on at the same time (presumably all the energy from the pump is used pumping water around all the radiators!
Recently our pump broke and it became apparent our HW tank barely needs a pump, it must just set p a natural convection current?, , struggled to fill a bath out of it, but there was still plenty hot water
So it occurs to me that if I just had a very gentle pump for the HW, then I could cure this (sometimes very irritating HW heating noise)
so if you feel this is still doable - what sort of pump should i be looking for
Our HW heating has always been noisy,, lots of whooshing and gurgling noises, (it has been like that since we moved in 25 years ago), it is quiet when the CH is on at the same time (presumably all the energy from the pump is used pumping water around all the radiators!
Recently our pump broke and it became apparent our HW tank barely needs a pump, it must just set p a natural convection current?, , struggled to fill a bath out of it, but there was still plenty hot water
So it occurs to me that if I just had a very gentle pump for the HW, then I could cure this (sometimes very irritating HW heating noise)
so if you feel this is still doable - what sort of pump should i be looking for
What is the setup now.
Have you a gas or oil fired boiler and have only one pump and is it installed internally in the boiler or externally, if external, can you post the make/model/mode and setting?, it may be possible to run it at a lower head which will still satisfy the CH requirements with less noisy HW only operation.
Have you a gas or oil fired boiler and have only one pump and is it installed internally in the boiler or externally, if external, can you post the make/model/mode and setting?, it may be possible to run it at a lower head which will still satisfy the CH requirements with less noisy HW only operation.
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