No HW after powerflush to CH


Postby Jen_new_house » Tue Nov 25, 2008 9:07 am

Hi,

Plumber powerflushed through the CH system (removed lots of gunk) and it now works fine....

- however HW now does not!

HW pipes in cupboard get very hot - and leading up to the HW cylinder they start hot when we first switch HW on...but then as they reach the cylinder they irregularly turn hot / tepid / cold / tepid again.

Have checked thermostat on side of cylinder. Boiler is up to max and is firing fine. Have CH turned off to encourage HW to work. Have released any air from sump radiator and valve on hot water pipe leading into the cylinder.....

At a total loss as to what is going wrong inside the cylinder.

Any clues as to what to do next?

Many thanks for your help.
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Postby htg engineer » Tue Nov 25, 2008 12:05 pm

After draining and refilling there'll probably be an airlock in the primaries. Get the plumber/engineer back.


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Postby Jen_new_house » Tue Nov 25, 2008 12:49 pm

Hi - thank you for your reply; he is now going to come back this evening (but didn't seem to like the airlock idea!).

Just so I know what to ask for - what are the primaries?

(Is it the coil inside the cylinder? Or the cold water exit pipe?

We tried the valve on the hot water in pipe and that seems fine...)

Many thanks
Jennifer
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Postby htg engineer » Wed Nov 26, 2008 11:52 am

No-one likes airlocks they can be a nightmare to clear. The (primaries are the pipes from the boiler to the cylinder (yes the coil in the cylinder).

You can remove the thermostat and boil the air from the system, there's not many people like doing this - but it will clear it.


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Postby Jen_new_house » Thu Nov 27, 2008 2:40 pm

Hi, thank you for your explanations!

The plumber came back yesterday - but cannot solve it. He tried the nuts on the primaries but no joy. He confirms boiler, valves, thermostat etc are all fine.....

....and he has now given up! (He says he has tried his best but cannot spend any more time on it.)

So.

Do you think the best approach is now to investigate the other pipes - i.e. to start pullnig the cupboards & flooring up to try and release the airlock inside them?

Or can airlocks just work themselves loose over time if we continue to try & run the HW?

(NB we now have no CH either.)

Many thanks for your continued advice.

Regards
Jennifer
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Postby Steve the gas » Thu Nov 27, 2008 6:28 pm

Get him back again,to a degree he has a responsibility.
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Postby Dave From Leeds » Thu Nov 27, 2008 8:03 pm

Some plumber!!! He just seems to be making things worse.

Re. the possible airlock in the cylinder coil. Do you know where the Feed & Expansion tank for your CH system is? If you have an indirect system as it seems from your posts, there should be two cold water storage tanks, possibly in the loft. The bigger one is to replace water in your cylinder when drawn from hot taps and the smaller one is the Feed & Expansion tank (or Central Heating Top-up Tank).

If you can easily access the smaller tank, fit a hosepipe onto the vent pipe that goes over the top of the tank with the other end attached to a mains water fed cold water tank. Then get an assistant to gradually open the cold tap whilst you look inside the tank. If any air bubbles come up through the bottom keep the cold tap running until they stop. This may get the hot water working. You may then have to bleed your radiators in turn to get the CH going again.

Good luck. By the way, I'm not a plumber, just a DIY person.
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Postby Dave From Leeds » Fri Nov 28, 2008 12:32 pm

Hi Jennifer,

To update my previous post, where I said connect the hose to a mains water fed cold water tank, I meant cold water [b]TAP.[/b]
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