Pump struggling after bleeding radiator?

[DMC88]

Hello

My son's bedroom radiator has been cold at the top since the start of the cold spell recently so tonight I decided to bleed it. I've done this before on various radiators in this and my last house, thought I knew what I was doing.

Let the air out, of which there was quite a lot, it was hissing away for a good 2-3 minutes (long enough to read him a bedtime story!) at which it began weeping so I tightened it back up. Since then, 3 hours ago, the central heating system has been gurgling away (it's normally silent) and the Grundfos Alpha 2 25 60 pump seems to be struggling. In the || or ||| position it will struggle for breath at 9w then jump to 25-35, with a with a whooshing sound (sounds like relatively gentle waves hitting a beach) followed by the sound of lots of water gushing, then it struggles again, rinse and repeat.

The boiler is a Baxi Solo 2 60PF, seems to be acting normally, mounted in the kitchen, I have a cylinder upstairs in an aering cupboard and 12 radiators throughout the house, 2 are turned off however and have been since I moved in 8 months ago. Some have TRVs.

I've tried running the pump at full pelt, no better, I've just tried turning it off, once it stopped fully or sounded like lots of air bubbles rising through the system.

I'm also guessing the attached image is a problem, only just got up on a ladder to look in there tonight as a consequence of this issue?

Any help appreciated!

 

[JohnD]

Look in that F&E tank and check it has water in it. Tie up the float so you can see if the level drops when you bleed the radiator again, with the pump and boiler turned off.

If the noise from the pump doesn't clear after you've done that, and especially if the pump gets very hot, you can bleed the pump by loosening the silver screw in the middle (again, when turned off).

If the level doesn't drop, you have a blockage. This is common on systems like yours, and quite tiresome to fix.


The lid on your F&E tank should be flat, and clipped onto the sides, with a hole in it that the vent pipe goes through, so water doesn't splash out. If it is too short to go through the hole you can use a big funnel through the hole until you have time to lengthen the pipe. It should not touch the water in the tank. Adjust the float so the water level will be only two inches above the exit hole near the bottom. If there is brown mud in the tank, tie up the float, bale it out and wipe clean with bleach, then add a corrosion inhibitor such as X100. For better results find the drain cock downstairs and draw off a bucket of water before you untie the float.

If there is much sediment, or if water comes out of that vent pipe in normal use, you can do a chemical clean. You will need to have found the drain cock first.

If you have a blockage, it's worse, so check that first and don't add inhibitor yet. Have you got a magnet?

 

[DMC88]

Hi John, I will attempt it again in the morning when he is awake, I did try to bleed it again tonight but it is now fully hot and there was no air in it anymore, however this was while the system was on (how I've always done it... Googling seems to reveal 2 different schools of thought on that topic)

Also this pump doesn't seem to have a screw on it anywhere as I did think about trying to bleed the pump, it's just got it's LCD face on it with the wattage displayed?

 

[JohnD]

photograph the pump please when you have time.

I am not a heating engineer.

p.s.
I have updated my earlier post.

 

[terryplumb]

What was the water level like in the f&e tank in the loft ? It seems to me that when you bled a lot of air from sons rad, water has not gone into the system to replenish. You may have a blocked feed. The pump you have ,alpha 2 ,should self bleed but it wont if theres no water getting to it.

 

[DMC88]

I've attached a picture of the pump.

There is a small black tank in the loft but it is bone dry, or was in the summer when I went up there for the first time. I thought it may just be redundant and the previous owner couldn't be bothered to remove it? The tank I've pictured above is in the same cupboard above the cylinder. I don't know what the level in that tank was like before I bled the radiator as I wasn't expecting that much air to come out. I also came from a new build so spent a fair amount of time searching for a filling loop that doesn't exist!

I've read your updated reply John, thanks very much, all makes sense in theory however sounds a bit involved for me to take on, might have to get a local guy in to sort

 

[JohnD]

how big is the tank in your first pic?

where does the pipe, coming out of the bottom of it, go? Be precise.

And the one in the loft?

Is there a bigger tank somewhere?

If the tank in the loft is about 2ft x 1ft x 1ft, and is not redundant, it should have water in it to refill the radiators. It has a float valve in it like in an old WC cistern. This may have jammed, or somebody might have turned off its isolating valve. There will such a tank, somewhere in your house.

If the tank above the cylinder is much bigger, and there is no other small tank, go and put a bucket of water in the small tank.

 

[DMC88]

The cupboard tank is approx H50 X W40 X D60 cm

The loft tank is probably half that size.

The pipe exits the tank, there is a turn valve (assume turning that opens closes the feed) and then I snakes down the bottom of the cylinder as pictured. Is that the drain cock in the picture?

Many thanks

 

[terryplumb]

The tank above cylinder feeds cold water into the cylinder. A smaller one in the loft is likely the f,&e tank for central heating ,and if its empty its the cause of your problem and needs sorting out.

 

[DMC88]

Sounds like I have inherited multiple problems here then, that mucky, possibly broken, tank in the cupboard needs sorting so the cylinder doesn't become blocked and I am now starving the heating of its water replenishment supply. Thanks both for your kind and responsive help tonight

 

[JohnD]

that drain cock is to empty tapwater from the cylinder. it will not drain the radiators or boiler.

there is probably another one downstairs, at or near the lowest point. It might be by the radiator near the back door so you can throw a hose out.

if the little tank is bone dry, clean out any dirt you can from it before you tip a bucket of water into it (or turn on its supply). Dirt may cause a blockage.

the bucket will be quicker than trying to repair the ball valve or fix whatever the problem is, you can look at that tomorrow.

With luck, the absence of water in the F&E tank will be the cause of your problem, and you do not (also) have a blockage.

Running the pump when short of water may cause damage or excessive wear.

btw the big tank is very heavy when full of water.

pps
don't put any chemicals in the big tank! you clean your teeth in it! It will probably be pretty clean. It's the little F&E tank that is liable to be dirty.

I mistook your first photo for the F&E.

 

[DMC88]

Update, called a local plumber as it was beyond my ability, last thing I wanted to do was try to fix it myself, cause a water problem and then end up with ceilings down and electrics fried.

He came out and found the stop cock for the F&E tank had been turned off, hence it being empty. Once he turned it back on he found it was leaking at the stop cock (likely reason for it being turned off in the first place) so he tightened it up and everything back to normal. Best £40 call out I've ever spent for the peace of mind.

Thanks again for your help on this, I learnt a lot about how everything works.