Air lock?

[goaty_man]

Hi guys,

Wonder if you might be able to help me.

I went to do a job recently involving the addition of 2 radiators in a house. The job was easy enough, however when I came to recommission the system I’ve hit a couple of fairly major problems. These are:

- The newly installed radiators aren’t heating
- One of the originally installed radiators isn’t getting hot

I thoroughly checked the system and believe that an air lock is probably the cause. After a couple of hours the flow to the radiators was slowly getting warmer, however I had to leave before any improvement in heat was experienced. I’ve fully bled the system including the pump and have not changed any of the other system settings other than turning off the timer and boiler during installation. In case it matters, it’s a Glow Worm Hideaway100B boiler.

One thing I noticed was that the system had been generally poorly installed, an example of which being the 2-way motorised port valve was located on the return of the hot water cylinder coil, pipes into soldered fittings not fully inserted, and the layout could have been better planned. Drain cocks are present on all of the radiators.

The customer called yesterday to say that there was still no heat. I’m due to go and investigate but to be honest I’m at a total loss. I have produced some diagrams to show the problem (and set-up)

Old set up

New set up

Any assistance would be great, let me know if you require further information. I’ve posted on other forums but not had too much luck!


Graham

 

[oilman]

Have you balanced the rads since the additions?

 

[masona]

Have you also tried shutting all the radaitors instead of the one you're having problems with?

 

[goaty_man]

Thanks for the reply guys,

I've shut off the majority of radiators as well as attempting to balance the system, this appears to have had little effect.

I don't believe that there are any blockages in the pipework. It really is starting to confuse me!

The flow to the radiator that was once working but no longer does is scalding, however this isn't transferring into the rad itself! Likewise where the flow pipe tees off to the new radiators the heat just stops. All the radiators appear to bleed properly

G

 

[mickw]

Sounds like a blockage or an air lock in feed or return ..... you could try closing both valves on the two existing and two new radiators, drain each radiator in turn then open the bleed valve, open one valve to half fill the radiator then close this valve and open the other, you should get an idea of the flow via each route from the hiss at the bleed valve.

 

[goaty_man]

Mick,

I'll give it a go, do you think it likely that a blockage in the flow (or return) pipework to the new radiators would affect the radiator that has suddenly stopped working? I suppose there is a possibility that there may be a blockage there as well, probably on the return if the flow pipe to the radiator is hot.

In general the addition of those two new radiators looks ok doesn't it?

G

 

[Tomas]

What Pipe size are the flow & return from upstairs? And the size to the radiators(flow & return?

 

[goaty_man]

The flow and return pipework is in 22mm upstairs, as this tees off (leading to the downstairs radiators) this reduces to 15mm, the piepwork to the existing radiators and new ones is all 15mm.

Each radiator situated downstairs is spurred from the ring circuit upstairs (hope that makes sense). The diagrams show the spur for two of the original radiators (with the addition of two more).

 

[Tomas]

If I follow correct, You have 15mm comming from the main 22mm circuit upstairs. This may have to be upped to 22mm, With the new 22mm in an upside down T to the down stairs rads. Carry the 22mm as close to the wall on the diagram and as far as you can on the left hand rad, Tee in the new rads and existing rads to the 22mm(leaving at least 350mm between each rad connection).

 

[goaty_man]

Tomas, thanks for the advice.

Before I go ahead and change the pipework is it likely that there is a blockage, afterall there is no warmth in the radiators at all or would a lack of flow due to pipework be enough to cause this?

once again cheers,

G

 

[Tomas]

Check for the blockage first, but I think asking 15mm to supply heat to 4 rads may be at bit much in this configuration.

I visited a job last week, The owner of the house had added two new rad to the system that would'nt heat up. Everything pointed to a blockage (if he closed all the rads down except the new ones, the boiler would start to bang). Water in the sytem was crystal clear.The new rads would only get luke warm (only when the locksheilds were opened full). After going under the floor we found that the 2 existing rads were running off a 15mm spur from the main 22mm circuit with the new ones tee'd in to the exsiting rads pipework (similar to your customers)

Totaling up the btu of the 4 rads on the spur came to about 17500. 15mm is supposed to cope with about 13500 btu max, but in practice 12000 is nearer the mark unless it's brand new pipe. The problems associated with this are similar to lack of flow probs, so it can be hard to diagnose between the two. Basically customer had the old 15mm spur changed to 22mm with the 4 rads comming off this and we now have one happy and toasty customer.

Tom

 

[goaty_man]

Tomas, thanks once again,

Can I ask one or two final questions?

Would the addition of thw two new radiators cause one of the original two to stop working altogther?

Should I experience some warmth from the new radiators (even if it was only slight?)

I'll check for blockages but I kind of feel you may have hit the nail on the head with the pipe sizing, what I'll look into doing is changing the piep to 22mm up until the wall, how does this sound?

G

 

[Tomas]

Would the addition of thw two new radiators cause one of the original two to stop working altogther?


Could do. I would expect it to get some heat though after a bit of time. It is possible that the existing rad that's not heating may have air lock and is unrelated to the new pipework going by the diagram.
Try turning off the hot rad and see if their's any improvement (however slight) across the other 3. If there is, I doubt it's airlock.


Should I experience some warmth from the new radiators (even if it was only slight?)

Probably after some time, Lukewarm or hot up the edges/top of the rads.


what I'll look into doing is changing the piep to 22mm up until the wall, how does this sound?

Sounds good,you could just add the new rad's circuit to the end of the 22mm using str reducers and tee the existing into the new 22mm section.

 

[goaty_man]

Cheers Tomas,

I'm gonna give it a shot tomorrow, it's being bugging the hell out of me. One thing that I thought was that the new part of the circuit joins the existing circuit using a tee (as would be common), however as the diagram shows the part where the flow tees in uses the bottom of the tee as it's join point and a certain amount of resistance may be felt.I wasn't sure whether this would have caused part of the problem (I know it sounds a little silly but you just never know).

Do you know the maximum recommended pipe length is when using 15mm?


G

 

[Tomas]

Doubt that the join in that position is doing any harm.

A few factors determine the max lenght, have a look here

Should answer a few questions