No Hot Water


Postby StoneAgeSteve » Tue Aug 05, 2008 5:44 pm

Hi, I hope someone can help out with a problem I've been unable to solve thus far.

I get no Hot water, only cold at normal flow rate , when boiler set to Central Heating & Hot Water, or Hot water only. The Central Heating (rads) work.
Its a 20 year old system, indirect hot water system, with Potterton(Gloworm) Fuelsaver 60F boiler on ground floor, pump & cylinder on 1st floor, expansion feed tank in loft.
There is 1 dual port motorised valve (MV) which is working & is not part of the cylinder supply.
The pipe feeding the cylinder coil is hot going into cylinder, but cool on the pipe coming out of cylinder coil (at HWCyl>---V1).
V1 is a valve (lockshield I think) that is turned on.
If I close the Gatevalve gV1, then the pipe at V1 does get hot so I believe there is water flowing through it at least some of the time. If I then reopen gV1, pipe at V1 goes cool again, but after say 4 minutes will get hot again, then cool again.
It sounds as if there is air swishing through the pipes & pump.
Every few minutes I can hear banging noises (air?) from pipes.
I really thought this was a problem caused by air in the primary circuit/cylinder coil.
I closed valve V1 and opened the cylinder side connection of V1, letting some water out hoping this would clear any air in coil. (Perhaps there is a vacuum).Also I noticed that the water which came out of V1 connection was clean with no sludge.
I have also been opening up the bleed valve which never releases any air.
The expansion tank is full & I dont think there is a problem with the water feed from the tank.
Can anyone tell what it seems like the problem is, & if it is air in the system how on earth do you purge it out effectively.

(I've tried to do a diagram which I know is very difficult to read.
The asterisks (ie. *) should be viewed as spaces cos the spaces get trimmed out! )

***********************BleedValve
**************************I
HWCyl<-----TRV-----------------I----------I
**************************I****** I
**************************I****** I
********************______I***** MV
********************I***** I****** I
********************I***** I****** I--->ToRads
*******************gV1**** I
********************I***** I
********************I***** I----------
HWCyl->-- V1------------I***** I
********************I***** I
********************I**** Pump******** VentPipe
***************_____I***** I************* I
***************I**** I***** I------------------I
***************I**** I***** I
***************I**** I***** I******** FeedfromExpTank
***************I**** I***** I************* I
***************I**** I***** I-------------------I
***************I**** I***** I
***************I**** I***** I
******************Boiler ***From
******************Return **Boiler

Any advice greatly appreciated
Steve
StoneAgeSteve
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Postby htg engineer » Wed Aug 06, 2008 10:48 am

Gave up when I got to the 'diagram'.

It sounds like there may be an airlock in the primaries. As the hot water is getting to the cylinder but nor returning to the boiler.

You need to clear the airlock and that should solve your problems.

htg
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Postby StoneAgeSteve » Wed Aug 06, 2008 6:15 pm

Whats the best way of clearing an airlock in the primary. I dont get why there is no air in the bleedvalve ever. I thought the circulating air would end up in the high vertical pipe with the bleedvalve.
And if there was a big air pocket in the cylinder coil then why do the cylinder flow & return pipes get hot when I force water through by closing the cylinder bypass gatevalve gV1.
And I tried clearing air from the cylinder by opening the cylinder side connection of the lockshield valve V1 (in cylinder coil return pipe), letting some water out hoping this would clear any air in coil- it didnt. Should I open up the cylinder coil flow & return connections at the same time.
I cant see a drain plug either anywhere around the cylinder & pipes except one in the Hot water supply pipe to cylinder.

Do I have to drain & refill. I'd like not to lose all the corrosion inhibitor if poss. It was pretty expensive when I last bought some, dread to think how much now.
Thanks for your help,
Steve
[I'm not sure why BBCode cant be switched on, then I might be able to post a proper diagram]
StoneAgeSteve
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Postby htg engineer » Thu Aug 07, 2008 8:58 pm

Best and most effective way - is to pull the boiler stat and boil the air out of the system.


htg
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Rank: Project Manager
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Joined: Tue May 22, 2007 5:22 pm

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