Heating but no hotwater, and yes I have searched the forum!

[Space cat]

Look for a bleed valve somewhere on the pipes feeding the heating coil in your hot tank. It'll be at the top. Open it and check that water squirts freely. With the zone valve in the closed position, close the gate valve on the return pipe as well. Those gate valves don't always provide a perfect seal so some water may still come from your bleed valve.

Now for the important test. One way or another, get the zone valve into what should be the open position. Does water squirt freely from the bleed valve like it did before? If there's no change your zone valve never opened.

 

[metis1419]

Thanks guys, I now know it is air in the system, it was just a coincedence that the air started from the gate valve making it seem like the gate valve was at fault by not passing the hot water through.

I have tried bleeding all the radiators and the bleed valve near the gate valve on the cylinder but cannot get rid of all of the air in the system, the water will now get warm but not what you would call hot.

Whats the best way of completely bleeding the system to flush out all the air, I think a hose pipe is involved?

 

[dal5band]

Before doing something too complicated, try turning on the HW only so all the pump pressure goes to the HW circuit and bleed the air near the HW valve, with the valve open so the air can get past the valve.

Is the bleed valve at a high point so you can see that all the air will go that way ?

 

[Space cat]

Getting all the air out of a system can be a tricky business. Depending upon the position of the pump you might find that air is sucked into bleed valves when you open them. It's a good idea to always switch the pump off. On the other hand you might have air trapped in loops of pipe that only pump pressure will shift and so begins a merry dance of pump on, listen for air moving, pump off, bleed, pump on, etc, etc.

In your case the important question is this: why won't the air in your cylinder coil come out through the bleed valve? Here are some possible answers:

1) The bleed valve is blocked.

2) The gate valve and zone valve below the coil are both shut.

3) The pump is running and sucking at the cylinder coil.

4) The feed pipe from the header tank is blocked.

5) There is an upward sloping section in the feed pipe and it's created a monster airlock below.

You can test (4) if you are able to bleed radiators though its a messy test. Bleed water out until you hear the ballcock running. Alternatively, look for a drain cock somewhere and open that. If the ballcock opens to top up the tank your pipe isn't blocked. Do this with the pump and boiler off.

An airlock in the feed pipe will be an absolute pig to shift. The same thing can happen with the feed from your cold storage tank and the result is no hot water. This is where the hosepipe trick comes in. You connect the hot and cold taps together (don't tell the water board) and blow the air back up the pipe. To do this with your heating tank you'll need a point to attach the pipe. A drain cock will do nicely.

Personally I don't believe the airlock theory because every time the heating comes on the water expands up that pipe and this would push a little air out.

Check out that cylinder coil bleed valve first.

 

[metis1419]

Just a little update on this old thread, problem now solved!

I decided to cut the return pipe from the HW cylinder so I could plug a hose pipe on that particular section to flush it through - on cutting the pipe I found it to be completely blocked with sludge - thus not letting any hot water into the coil to heat the water....

My pump is now so much quiter too - there was very little water flowing down the return pipe which I think was causing the pump so suck in air too - which is why I was forever bleeding radiators.

Time to flush out the crap from the system me thinks....