Second pump to boost upstairs heating?

[LesE]

Recently bought a house which may well have a central heating system cobbled together from two earlier systems. I know that the system originally had a back boiler off the living room fire which was removed and a new oil fired boiler was fitted in a different location at a later date. All of the downstairs rads work fine but there is little heat upstairs. I have tried bleeding all the upstairs rads to no avail.

The boiler is on the ground floor with a pump close by that is fitted on the inlet to the boiler i.e. on the side that draws the cool water from the system back into the boiler.The hot water from the boiler goes straight up to the first floor where it branches off to the hot water cylinder and then goes immediately down through the central wall to underneath the ground floor where it feeds the downstairs rads. Mid way along the pipes under the ground floor a branch comes off and goes back upstairs to feed the upstairs rads where the pipework ends up within a couple of feet of (but not joined to) the initial feed from the boiler! It seems to me that there is perhaps not enough pressure to force the hot water back upstairs as well as feeding the downstairs rads.

There is a second pump under the ground floor on the hot (out) pipe where it comes down from the first floor before it feeds any of the rads but it is not working. There is an electric connection to this pump but it is not live (the feed may well have been accidentally disconnected when the kitchen was rewired). Testing the pump with a separate feed, however, indicates that the pump itself is dead. Now I am not sure if this pump is intended to be part of the current system or whether it is a remnant of an earlier system that has been deliberately disconnected. My first question is - if I replace this pump and wire it up to the CH controller so that it operates alongside the present working pump, is that likely to provide enough boost in flow to feed the upstairs rads?

If the above is not an answer (or sensible) would it be possible to put a tee junction on the 22mm pipes to/from the boiler to the pipes on the upstairs rads (which as I have said are within a couple of feet) and then close off the feed to upstairs that runs from under the ground floor? My concern with this is that I might end up reversing the situation i.e. having full heat upstairs and little heat downstairs.

Any advice?

 

[Nuttyboy]

Put a plug on the pump lead and try what it does first.

 

[LesE]

Already done that

Testing the pump with a separate feed, however, indicates that the pump itself is dead.

Point is I don't want to buy and fit another pump if it is not going to achieve anything.

 

[Best]

What size are the pipes - main branches & rad pipes?
If you turn all the downstairs rads off, does the upstairs rads then work?
Does the pipes to hot cylinder have any type of thermostatic valve or motorised valve or some sort of gate valve for balancing the system?
Does the oil boiler shut off after a while, or does it fire constantly when heating is on?
You could have overloaded pipes, or system needs balanced, or the pump may be faulty.

 

[Centralheatking]

Its not a bad idea - I bought a Wilo c/h 3 setting pump 4 £30 brand new so its not a
big investement even if if dont work. However if you can put up a plan of how u think the system is organised I am sure we can all help.

It is not unknown for c/h pumps to connected on to so called dead legs on systems
to make them work properly without any controls at all - just powered all the time
because they are so cheap and reliable .

Of course Father Christmas would never do this - i just know about the practice

centralheatking:29:

 

[LesE]

Best - pipes to/from boiler and 1st floor hot water cylinder are 22mm which then go into 28mm to drop down the central wall (which is what leads me to be believe that it is two systems cobbled together) then back to 22mm to "central" out/return pipes below ground floor, 22mm up to first floor and 22mm "central" out/return pipes on 1st floor. All feeds/returns to rads on both floors are 15mm.

Haven't been able to shut down ALL rads on ground floor due to a rather cranky 90 year old mother-in-law occupying half the ground floor! Will try this if opportunity arises but I do know that shutting off half the downstairs rads makes no difference.

There appears to be a motorised valve near the hot water cylinder shutting off the feed down through the central wall (i.e. to all rads) but it has been disconnected. This means that we can't have water only but that hasn't proved to be a big problem since running the whole system for an hour in the morning provides enough hot water (showers are instant electric) and keeps m-i-l happy!

Boiler shuts off, presumably when sufficient temperature is reached, and then comes back on when temperature drops. It is NOT on all the time.

Pump by the boiler is brand new, the original (probably 10 years old) having failed a couple of months ago so it is not a faulty pump.

 

[LesE]

Father Christmas - for £30 I might just give it a go, the new pump by the boiler cost me £95!

Will try to work out a diagram and post it.

 

[LesE]

Okay, attached is a diagram of the system

 

[Best]

The cylinder is the first thing on the circuit & cylinders have a coil inside them - normally 28mm, which the flow goes to & straight through it & out to the return. In other words, a bypass. While your system stays just pumping around cylinder & rads, the cylinder will rob most of the flow of water & miss the hardest rads to heat. A gate valve fitted on the pipes to cylinder to enable it to be turned down greatly to balance system is essential but needs a heating guy to make sure it will be okay. Shouldn't be a problem if it is a sealed system.
The old pump should be removed & make sure there are no other restrictions like check valves & have the mv at cylinder checked to see that the body part is full open to rads.

 

[LesE]

Many thanks. Not sure what you mean by a sealed system. There is a feed & expansion tank in the loft which I omitted from the drawing as I am not sure where it connects. Does that make it an 'open vented' system? If so what difference would that make?

 

[Best]

Yes LesE, that means it is an open vented system, if the f & e tank is still connected. (a sealed heating system is a closed system & would have a red vessel & filling loop, pressure relief valve & gauge, sometimes all built in to oil & gas boilers).
With an open vented system, which you probably have, there can be a risk of the pump pumping water up the vent & down the feed pipe, but depending on way it is piped. Balancing the system can make this more likely. It would introduce oxygen & destroys the rads, boiler etc, very rapidly. If on oil or gas heating, a system was sound enough for to have it changed to a sealed system, then it is the way to go.

 

[Dannyparty92]

Wouldn't the pump on the return side mean the system is under negative pressure?

 

[Best]

Wouldn't the pump on the return side mean the system is under negative pressure?

If the vent & feed pipes are on the flow & return pumped circuit somewhere after the boiler, then it won't matter if the pump is on the return or flow at boiler (basically no difference), as there will be a risk of pumping up. Combining the vent & feed will prevent this, or better a sealed system with oil or gas boilers.

 

[Dannyparty92]

Because the feed is the neutral point? And the static head of the f and e tank?

 

[SimonG]

Sounds like you need an experienced engineer to look at it. If it was a circulation issue then I wouldn't expect the rads downstairs to get warm.