Pump direction

[gabutt95]

Would the direction of water flow from a pump in a system have any effect if it was incorrect?

I am having problems with my radiators becoming warm when hot water is only selected. It cannot be the diverter actuators on the danfoss valves as I have replaced these. It cannot be the valve itself associated to the central heating as I have replaced this (danfoss HPV22B). The 22B gives 100% shutoff. My thoughts are that I have placed the valve in the correct orientation as indicated on the valve body. If the flow was incorrect and was then pumping against the closed valve with enough pressure to overcome the spring pressure on the actuator and thus slightly pass through then the circuit for the radiators would be complete and slight heating would occur on the radiators with this minimal flow.

Would there be issues with the boiler if the pump flow was in the wrong direction or is this a common event.

Would anybody have any thoughts?

Kind regards

 

[mogget]

The water should flow from boiler, to pump, to motorised valves, and then on to the rads / cylinder.

It could be reverse circulation, which can happen if the radiator returns are plumbed incorrectly. All the rad returns should come together before they join the cylinder return. A forum search for 'reverse circulation' should turn up some more information.

With the motorised valves, the flow should be against the spring pressure, ie trying to force the ball off its seat. If they are fitted the wrong way round you're liable to hear a very loud and annoying clunk when they close. The pump can only create a pressure of up to 0.6 bar in your average domestic system, and the motorised valves will be able to resist this without letting by.

 

[AlanE]

I replied to this question on the Ask the Plumber forum. Waiting for a reply there from you!

 

[Paul Barker]

Yes issues. Simple to check of pump is orientated correctly. Arrow on body.

 

[gabutt95]

Sorry AlanE I will use this thread. Thanks for the replies. The pump is in the correct orientation. again the radiators are getting warm(not hot) when the hw is required.

I have gone round and closed all the thermostatic valves and the pipework from the ch diverter has cooled. What I can't understand is if the diverter for the CH is closed then there is not a path to generate a flow the would heat the radiators?

The system consists of an oil fired boiler,pump, two diverters one for the HW tank and the other for the CH and a bypass leg with a gate valve.

The tank has a cold water feed and there is a common return to the boiler for I think both the CH and the HW.

Cheers

 

[Boilerman2]

Mogget's advice is probably spot on, it is likely that a heating return has been inserted between the cylinder return and the boiler, this will cause a reverse circulation, have any radiators been added to your system? it may be the cause, just one incorrect return will cause havoc to the system

happy hunting

 

[doitall]

Sorry AlanE I will use this thread. Thanks for the replies. The pump is in the correct orientation. again the radiators are getting warm(not hot) when the hw is required.

The system consists of an oil fired boiler,pump, two diverters one for the HW tank and the other for the CH and a bypass leg with a gate valve.

The tank has a cold water feed and there is a common return to the boiler for I think both the CH and the HW.

Cheers

Two diverters ??

And a bypass ??

Clearly the system has been installed by a wannaby

As AlanE asked for a pic or drawing

 

[gabutt95]

Thanks for the help everyone.

Work has me away for a couple of weeks will get the drawing on the system as soon as I am back.

Cheers

 

[Paul Barker]

As we can't get a picture I'll start he guesses off for fun.

My money is that you don't have two diverter valves (mid position valves) but two 2 port valves.

Your dhw cylinder return is quite likely to be in the correct place (nearest one to boiler).

You most likely have sludge in your system. the cure is a new 2 port valve for central heating a magnaclean a powerflush and replace gate valve with an automatic bypass.

If my guess is right, then whilst curing the system for future as above I would as a precaution and while IU have it drained down anyway, cut out the entire cold feed open vent pipework and renew (using an expanding T for the open vent) or replace with an air jec.

 

[gabutt95]

Paul,

spot on, I do have two 2 port valves (controlled by actuators), sorry for the confusion everyone.

I have replaced the two port valve for the central heating prior to asking for everyones help as I thought this was passing and indeed on stripping it down the seat was worn.

I still have the same problem of the radiators becoming warm when selecting hot water.

Cheers

 

[gabutt95]

Hello everyone,

I still have the same problem and have taken it a little bit further. I have changed the divertor for the central heating and I have proven the bypass is not passing.

I think it is reverse circulation as per moggets comments and I have attached a drawing of my system for the experts to confirm this.

I have a couple of questions.

How does reverse circulation occur if there is no flow?

How do I fix it!

Regards

Untitled

• gabutt95
• 6 Oct 2009
• 1

 

[D_Hailsham]

I think it is reverse circulation as per moggets comments and I have attached a drawing of my system for the experts to confirm this.

If your return pipes are as you say, you will get reverse return. Some of your diagram is not relevant to the problem, so could you do a diagram concentrating on just the return pipes? Make sure you can actually trace the pipes; don't guess what happens.

How does reverse circulation occur if there is no flow?

It's gravity circulation as in un-pumped hot water systems. Hot water has a lower density than cold water, so it will rise. When the hot water in the return from the cylinder comes to a return from the radiator circuit some of the water will flow down the radiator return and the rads will get warm.

How do I fix it!

Change the cylinder return so it comes after all radiator returns. But check your pipe work first to make sure it is connected wrongly.

 

[doitall]

The return is wrong as DH said, assuming the drawing is correct.

All the heating returns must connect together before the common return from the cylinder.

Reverse circulation is when it is connected wrong and the flow travels cown the return via an open circuit.

Easy to check by running the boiler in hot water only mode, and checking which end of each rad gets hot, then put the heating on and check if any swap over to the other end.

 

[gabutt95]

Hello all,

Thanks for the help, it is much appreciated.

I have a loft space above my garage so I can see the pipework from the boiler into the roof space and the connections to the tank etc in the cupboard below so I am reasonably certain that the diagrams I have posted are accurate.

I have added another diagram as requested with I hope the relevant detail.

I have another question the return from the tank is 6 inches above the ground and I think where the pipe disappears into the floor is part of the radiator return. The other return is then in the roof space. What would he easiest job to get this system straight?

Regards,

Untitled

• gabutt95
• 6 Oct 2009
• 1

 

[AlanE]

Which forum will you use this time? Or keep trying until you like the answer!!