Help! - Air lock problems

[GrahamT]

Hi

I've found a real bugger of a job.

I installed a new shower onto existing pipework from the old shower. The customer wanted a pump but didn't want me to redo all the pipework so that the shower had independent supplies so she decided on a Salamander RHP whole house pump.
I installed this in the airing cupboard along with a Surrey flange. A few days later I had a call saying that the pump was "revving". On investigating I found the pump was sometimes activating & deactivating in quick succession sounding like "revving". I put this down to air in the pipework that was triggering it, then because the taps were closed was deactivating.
I then installed an AAV in the loft on the highest point of the hot supply pipework. I also put one on the highest point on the cold, after the pump as it goes back up into the loft and over to the bathroom from above.
I then had a call again saying it was still "revving". After talking to Salamander I was recommended to fit a single check valve after each pump outlet. I did this and it cured the revving.

However, now the hot taps still get air in them but because of the check valves it can't escape. So, when the hot taps are turned on it take about 10secs before any water comes out and the pump kicks in. Opening the cold tap makes the hot work immediately but obviously isn't ideal.

The hot outlet from the pump seems to dissapear under the floor under the airing cupboard rather than going up into the loft - so I'm confused as to why it's locking ?

Any suggestions anyone????

much appreciated,

Graham

 

[cider]

whats the static head on the pump? could the pump be pulling air in from vent when running even though you have fitted flange? try holding thumb over vent when starting pump.
worth a try good luck

 

[Softus]

I installed this in the airing cupboard along with a Surrey flange.

What size SF is it?

Have you connected the pump inlet to the correct SF port?

How big is the cylinder cold feed?

Is the valve on the cold feed fully open, and not broken?

Is this a neg or pos head pump?

 

[GrahamT]

I installed this in the airing cupboard along with a Surrey flange.

What size SF is it?

Have you connected the pump inlet to the correct SF port?

How big is the cylinder cold feed?

Is the valve on the cold feed fully open, and not broken?

Is this a neg or pos head pump?

Size - not sure

Correct inlet - yes (on the horizontal)

cold feed - 22mm

valve - fully open

pump - positive

 

[GrahamT]

whats the static head on the pump? could the pump be pulling air in from vent when running even though you have fitted flange? try holding thumb over vent when starting pump.
worth a try good luck

I would approximate 3m

 

[cider]

aavs on domestic are bad news because the will scale quickly also could this be where the air is entering? if they are exposed to a negative pressure for a second or so ?
try running for a few days with vents manually closed

 

[GrahamT]

aavs on domestic are bad news because the will scale quickly also could this be where the air is entering? if they are exposed to a negative pressure for a second or so ?
try running for a few days with vents manually closed

I tried that already. I'm going there tomorrow - I'm going to open all taps then turn off pump at isolation, whilst they're running. hopefully this will rid any air in the hot pipework. See if it still continues to lock.

 

[cider]

what was the idea behind fitting non return valves?

 

[GrahamT]

what was the idea behind fitting non return valves?

as mentioned in the original post - was recommended by salamander technical help to stop pump from continiously triggering

 

[GrahamT]

Can anyone else add to this??

 

[Softus]

Going back to you first post, there are three things that confuse me.
______________________

1. These two statements seem to conflict:

I then installed an AAV in the loft on the highest point of the hot supply pipework.
.
.
.
The hot outlet from the pump seems to dissapear under the floor under the airing cupboard rather than going up into the loft...

Does the hot pipework go into the loft then down again before entering the point? If so, why? If not, then what do your statements mean?
______________________

2. This:

However, now the hot taps still get air in them but because of the check valves it can't escape.

(a) How is air getting it, and (b) how do you think it used to 'escape'?
______________________

3. This:

So, when the hot taps are turned on it take about 10secs before any water comes out and the pump kicks in. Opening the cold tap makes the hot work immediately...

How does opening the cold tap overcome the air problem on the hot?

 

[GrahamT]

Going back to you first post, there are three things that confuse me.
______________________

1. These two statements seem to conflict:

I then installed an AAV in the loft on the highest point of the hot supply pipework.
.
.
.
The hot outlet from the pump seems to dissapear under the floor under the airing cupboard rather than going up into the loft...

Does the hot pipework go into the loft then down again before entering the point? If so, why? If not, then what do your statements mean?
______________________

No, hot doesn't go back up into the loft - AAV in loft on cold feed to hot cylinder (highest point) - I know this is probably not going to do anything but I'm trying everything I can.

2. This:

However, now the hot taps still get air in them but because of the check valves it can't escape.

(a) How is air getting it, and (b) how do you think it used to 'escape'?
______________________

Still no idea how air is getting in. Sorry, bad terminology with "escape". What I mean is it's now trapped between the single check valve and the tap outlet.

3. This:

So, when the hot taps are turned on it take about 10secs before any water comes out and the pump kicks in. Opening the cold tap makes the hot work immediately...

How does opening the cold tap overcome the air problem on the hot?

Opening the cold triggers the flow switches on the pump, causing it to pump the hot out, clearing the airlock. When the hot is airlocked, the flow switch on the hot part of the pump isn't triggering on it's own.
Having said that , after about 10secs the hot does trigger - but no idea why - you'd think it would either trigger or not.

 

[Softus]

No, hot doesn't go back up into the loft - AAV in loft on cold feed to hot cylinder (highest point) - I know this is probably not going to do anything but I'm trying everything I can.

Oh, ok. Thanks for explaining.

However, now the hot taps still get air in them but because of the check valves it can't escape.

(a) How is air getting it, and (b) how do you think it used to 'escape'?

Still no idea how air is getting in. Sorry, bad terminology with "escape". What I mean is it's now trapped between the single check valve and the tap outlet.

So, before you installed the check valve, where did you think the air went to, bearing in mind that you don't know where it came from?

Opening the cold triggers the flow switches on the pump, causing it to pump the hot out, clearing the airlock.

So I would expect that the water splutters from the hot outlet when the pump first runs, and that it does this whether or not you open the cold first. Is that what is does?

When the hot is airlocked, the flow switch on the hot part of the pump isn't triggering on it's own.

Having said that , after about 10secs the hot does trigger - but no idea why - you'd think it would either trigger or not.

I get the impression that you haven't consider the possibility of a faulty flow switch on the hot side. It's worth eliminating this.

What size is the Surrey Flange? And is it a Surrey or a Salamander 'S'?

 

[GrahamT]

Hi Softus

Firstly apologies for not getting back sooner.

In order of your questions

1. I didn't think the air went anywhere as the pump was "pulsing" and I assumed air was trapped in between the tap outlet and the pump, causing the pump to keep triggering.

2. No, when you open the hot there is about 5-10 secs of nothing, then the flow starts normally - you can here the pump start.
If you open the hot, then open the cold immediately it will start the pump and start the hot also.

3. I can't remember exactly which flange but it is quite likely to be a Salamander S flange. Is there a difference with this and normal Surrey flanges in your experience? And I think s flanges are 1" - certainly 22mm outet

When I went back recently, I opened all hot taps with the pump switched off to bleed the system and noticed that when all taps were open, the shower cut out?? perhaps air being drawn in??

 

[Razor900]

Is air being drawn in down the cylinder vent pipe? Try proving it with a glass of water.