No hot water since drain-down

[mpirie]

Hi guys,

I have a Glowworm Ultimate gas boiler supplying CH and hot water.

It supplies 4 radiators and the hot tank upstairs and 2 radiators downstairs.

A couple of nights ago, I drained the central heating down from one of the downstairs rads to replace a bathroom rad. Once the replacement was done, I refilled the system and bled all the rads.

However, my hot water system won't ignite now. I've reset the boiler cut-out and turned the boiler temp down. I suspect it's overheated due to an airlock, but can't find a way to get rid of the airlock. I read in another post that you can place your thumb over a tap and turn the hot tap on, then open the cold tap to back pressurise the system, and although I could hear the cold water entering the hot system, I'm a bit wary of knowing when to stop (before the ceiling comes down )

I can find no filling loop to vent the boiler.

Any suggestions?

Thanks,
Mike

 

[corgiman]

look for air vents on the main flow or return to the cylinder

ensure that you havent turned of the cylinder balancing valve if it has one (it is usually on the reutrn, bottom pipe from the cylinder and many people turn them off for some reason)

ensure that the ballvale in the feed and expansion pipes is fully functional, it may be stuck but the system may be just full enough to work in central heating (unlikely I know but it does happen)

try running hot water only (ensuring that you have turnedoff any by pass rads, do you have a rad that heats up all the time? if so turn it off) and turn off the boiler stat.

if the above dont work try (again with the boiler stat turned off) turning the CH pump around so it is pointing the other way as this does clear airlocks.

PS I am assuming you have tried the central heating as well as the hot water??

 

[JohnD]

you say you drained it and then refilled it.

When you bleed the upstairs radiators, does water squirt out forcefully?

Is this a system with a Feed & Expansion tank in the loft, which supplies water to the boiler and radiators?

Or is it supposed to be filled with a filling loop that has been mislaid?

The hot tap/cold tap trick will not refill the boiler or radiators.

Turn the boiler OFF until you have refilled it successfully.

 

[ChrisR]

The taps aren't connected to boiler water.
Look here, vent at V:

 

[corgiman]

The taps aren't connected to boiler water.
Look here, vent at V:

see if I was a fancypants like chris I would have drawn something like that

 

[JohnD]

How did you refill it?

 

[JohnD]

see if I was a fancypants like chris I would have drawn something like

 

[corgiman]

Now thems FANCY PANTS



I cannot wait to get home and get the wifes knickers off



























They dont half cut into me knackers

 

[mpirie]

Guys,

Some of you have a wicked sense of humour........

Once I'd replaced the radiator, I turned all the water back on and it gradually refilled after bleeding each one. There are large and small tanks in the loft.

I also have pipework like Chris's, but when I tried venting at point V, there was only water, and no air.......

Looking at the boiler, there are 4x20mm pipes coming out of the top of the boiler, and the gas supply at the bottom.

 

[JohnD]

How long did it take to fill?

go and have a look at the small tank in the loft. It should have about two inches depth of water above the outlet pipe at the bottom. See if it contains sludge, and what colour it is. It should have a ball valve like you find in a WC cistern. Does that valve work freely?

When you drained, did you get black water and sludge out? I am thinking you may have a blockage.

If no blockage, and the system is full (check if water squirts strongly out when you bleed the upstairs radiators) then try the CH pump on high speed (with the boiler thermostat off) which should circulate the water and blow out any air bubbles

 

[mpirie]

Hi John,

Yes, there's water in the small tank...it's clear with a small rust deposit on the bottom, but nothing much.

It took about 20 minutes to get all the air out of the rads.

The water that drained out was rusty, but nothing like as bad as I've drained from some car radiators !

I can't say the water coming out of the rads is forceful, but it never has been.

 

[JohnD]

you mean rusty brown water drained out? that's a bad sign.

You should be able to get water from an upstairs radiator to squirt up your sleeve in a fine jet, not just to ooze and trickle. What does yours do?

 

[Dan Robinson]

This one does sound like a blockage where the feed joins the system. I am assuming the OP has checked his pump hasn't seized.

 

[bobthebender]

Now thems FANCY PANTS

They dont half cut into me knackers

They look rather large to cut

.........revolting picture removed

 

[namsag]

Bob if thats what the women look like around your way no wonder you became a Bender..