Secondary Pump not pumping

[vetinry]

Hello all

I recently posted a question about controlling the bronze pump on my hot water system.

After taking some advice, I purchased a single channel honeywell timer, which I have programmed to work alongside my main DHW / CH controller.

The problem I have is that although the timer is switching the pump off and off ok, I'm not getting hot water at the taps.

I have set the bronze pump to run for about 1 hour in the morning and evening and to come on about half an hour after the boiler has started.

Am I not allowing enough time for the pump to push hot water around the system, or could something else be causing the problem?

I have drained down the system a couple of times to remove sinks etc and as yet, haven't finished plumbing in new facilities. I wonder whether I may have a major air lock somewhere.

Any thoughts?

Thanks

Steve

 

[picasso]

The pump should pump towards the cylinder with a check valve, what kind of cylinder do you have and where is the secondary connection on the cylinder?

 

[vetinry]

Hey Picasso

I've not touched the pump itself; just added a new digital timer to replace the manual one which was previously there.

When we moved in, the secondary pump was running continuously but I was running out of hot water very quickly and figured it was pretty inefficient.

My cylinder is just a standard one with a coil within to heat the water. Not sure what a check valve should look like, or whether the pump is towards the cylinder or not?

Steve

 

[picasso]

When you took off the sink ect you may have inadvertantly stopped the circuit for the secondary hot water, the pump would overcome any airlock in the pipes.

 

[vetinry]

I'm pretty sure I haven't touched any of the loops for the return circuits but I will have another look.

I guess it might be another job for an expert if I can't work it out.

As a matter of interest, how quickly should the secondary pump get hot water round the system.

Every sink has flow and return and there are 7 sinks.

Am I asking a bit much in an hour of pumping?

Steve

 

[picasso]

When you say your cylinder is just an ordinary one , is it an unvented cylinder (your hot water under mains pressure) ?

 

[vetinry]

Sorry for delay - broadband problems

It's a standard vented cylinder

 

[mysteryman]

Is your pump actually pumping? They can airlock very easily especially if they are pumping downwards - a common mistake.

 

[vetinry]

Access to the pump is not great - it's in a restricted loft space behind the cylinder

So, I'm not absolutely sure that it is pumping - would certainly account for it not seeming to work.

It's whirring though

Can I bleed it by using the main screw on the front of it?

 

[mysteryman]

Now then, Mr 'Erriott,

You can try venting it. If it is noisy, it may well be airlocked, or blocked with scale or other debris.

 

[vetinry]

Thanks Mysteryman

The pump is able to be isolated from the system by a gate valve either side of it.

To vent it, should I be just using the bleed screw, or would I be better to islolate it, remove it and give it a flush through?

Cheers

Steve

 

[mysteryman]

Bleed screw first. Pump gate valves are notorious for not shutting off completely. You may find also that the pump union nuts are very tight to remove - usually because some plonker has put Boss-White all over the threads even though they are a face seal. If you are confident that the gate valves are tight shut, you MAY be able to remove the pump motor and impellor from the volute - this is not for the faint-hearted though. None of it is!

 

[vetinry]

Quick update
Bled the secondary pump yesterday - it's a complete bitch to access but there was certainly a lot of air coming out.

And now the circulation appears to be working fine.

Thanks for all the help

Steve