Two circulating pumps on a vented CH system with open vented HW cylinder

[burt64]

Hi,

I just moved into a new house (built 1996) and struggling to work out why I have two circulating pumps on a vented central heating system with open vented hot water cylinder.

Circulator 1: Permanently running (even when the boiler is not running) and is hard wired to an on/off switch. This circulator is located on the hot water supply coming out the top of the hot water storage cylinder (below the vent pipe to the cold water cistern).

Circulator 2: Runs only when the boiler fires for hot water recirculation in the storage tank (coil) and for heating the radiators.

Circulator 1 is the issue here, if I turn it off, I still get hot water out the taps, just the flow drops very slightly (almost no difference). For showers I have a shower pump that draws off hot water at a faster rate (going through the same pipe as Circulator 1). I thought this Circulator 1 was a preload to the shower pump but it doesn’t effect the shower pump, hence why its running 24/7. However, it doesn’t seem to affect it.

So, my question is, what is this circulator for and can I turn it off to save electricity and noise?

A picture is attached of the two circulators and general setup.

Thanks in advance.

Burt

 

[Elsa TLC]

Pump 1 is a secondary return pump for your hot water.

I take you live in a big ish house.
This should give you hot water in far flung places quickly.

 

[burt64]

Thanks for the quick reply. The kitchen was extended by the previous owners and is the furthest away, but all other taps are close to the hot water tank. Since this tank is located on the second floor the gravity feed is fairly good to the kitchen with the circulator 1 turned off.

So if its adding pressure to the hot water line, is it not likely to damage the circulator 1 when most of the time the taps are closed and its just wirling away trying to pump nothing?

 

[Elsa TLC]

It's there so that the hot water is quick so as to eliminate cold long legs, hence saving water usage.

In some cases secondary pumps are used to protect against bacterias such as Legionella.

 

[Elsa TLC]

So if its adding pressure to the hot water line, is it not likely to damage the circulator 1 when most of the time the taps are closed and its just wirling away trying to pump nothing?

If its plumbed in correct then it pumps in ring back to the cylinder.

Putting a timer on it would be wise

 

[burt64]

Thanks, the timer is a good idea. I will investigate this to help reduce cost and noise.

From what i see it doesnt pump back in a ring. Its just continually presurising the line ready for someone to open the tap.

Very grateful for the feedback. Thank you.

 

[Exedon]

On some cylinders without a dedicated return connection the secondary return was connected into cylinder cold feed.

 

[Elsa TLC]

While on the Subject.

This is why Poly should never be used in the ring of a secondary return.

There may be exceptions but to be sure copper pipework is the best material.


This was cut from a hot water system This morning.

 

[burt64]

Hi, i followed the copper pipes from the Circulator 1 and it does not seem to return to the HW cylinder, it disappears through the floorboards in the direction of the hot water delivery pipes. All pipework appears to be copper, it changes at the kitchen extension to poly close to the kitchen taps.

Basically i dont think i have a return system.

 

[Exedon]

Yes been banned for quite a few years now by plastic pipe manufacturers for quiet some time. Have found secondary pumps blocked with bits of plastic in past.
We use the tectite metal tube (aluminium core) on secondary circulation systems.

 

[Elsa TLC]

Hi, i followed the copper pipes from the Circulator 1 and it does not seem to return to the HW cylinder, it disappears through the floorboards in the direction of the hot water delivery pipes. All pipework appears to be copper, it changes at the kitchen extension to poly close to the kitchen taps.

Basically i dont think i have a return system.

Best way to tell is:
Turn the pump off.
Leave for an hour or so.
Don't draw off any hot water in that time.
Turn the pump on. And feel if the pipework either side of the pump fluctuates in temperature.

If the Poly is branching off the main circuit, then that should be fine..

 

[burt64]

Thanks for the tips. I tried this and cant detect a difference in temperature either side of the pump with or without the pump on. Its just permenantly hot before and after the pump (even when no water is being drawn off the tank for hours). I did follow the vent pipe up towards the cold storage cyclinder and discovered its hot before it goes through the ceiling. However, its cold at the curve into the cold tank. So its likely its partially full with hot water and this is driving a pressure to the hot water system. The pump on should reduce this head in the vent pipe.

So considering no hot water use, and the pipework is permanetly hot, perhaps you are correct that there is a recirculation system in effect but this is maybe flowing by gravity based on changes in the cycliner temperature when the boiler heats the coil as Circulator 2 kicks in. I cant explain why the hot water pipework near the cycliner is hot if no-one is using it. Unless its just thermal conduction through the pipework from the hot water exit at the top of the cylinder.