No hot water, but CH works fine - PLEASE HELP!!!
David Archbold
There is a real porblem getting hot water in our house.
I moved into a house about a year ago that has an old heating system
(25 years approx). The radiators are fed by a pump located next to
the boiler (downstairs) and the hot water is gravity fed from the
boiler. There are two radiators in parallel with the hot water tank
coil (both upstairs - towel rails). When the boiler is running the
towel rail radiators get piping hot and most of the time so does the
hot water tank (upstairs). However, every now and then the towel rail
radiators get hot but no matter what I do the coil in the hot water
tank does not get hot so we just get tepid at best water. When this
happens the feed to the coil is only tepid at best warm rather than
piping hot like the radiators.
There is a vent in the inlet to the coil in the tank so any trapped
air there should dissapate. The coil entry point to the tank does
seem a little low, but I would not imagine anyone is silly enough to
design a coil that has a vertical run inside the tank allowing either
air to be trapped (if going up), or sludge (if going down). There is
some sludge in the CH feed tank in the loft but not an excessive
amount.
There is no hot water tank thermostat. I have tried turning the
boiler thermostat up and this works sometimes but not always. There
does time to time seem to be some air in the towel rail radiators
which I bleed off, but this is not excessive and I bleed it off every
2 months or so (maybe 1 litre of air max). Also to get hot water we
seem to need to set the hot water to run continuous. I guess this is
because of this problem and if the water has momentum and is moving
its keep going. The CH system seems to work fine and gets hot with no
problems. It does sound as if there is some air in the CH system, but
all radiators are bled - no regular air build up - and there is only a
short clunking sound and swooshing shown (1 min) when the heating
comes on (not sure if this is related to the hot water issue or not).
There appears to be no NRV on the hot water system either at the
boiler or hot water tank. I have tried turning off the towel rail
radiators and this does not help. All that happens is that the boiler
reaches temp and shuts off quickly. When this problem occurred last
night I switched the HW off overnight and switched it on again with
the towel rail radiators off. This seems to have worked but I don't
know why. The boiler and boiler control system seems to work OK.
I can only think that this is either a trapped air, built up sludge or
a no NRV problem, but I am really stuck and getting it in the neck
from my wife when we keep getting caught without hot water.
Any tips or suggestions an what the problem is and how to overcome it
would be VERY VERY gratefuly received.
Thanks,
David
Dave Baker
>From: david_a...@agilent.com (David Archbold)
>Date: 21/01/03 17:54 GMT Standard Time
>Message-id: <6c4aee1b.03012...@posting.google.com>
>
>I wonder if anyone can PLEASE help.
>
>There is a real porblem getting hot water in our house.
>
>I moved into a house about a year ago that has an old heating system
>(25 years approx). The radiators are fed by a pump located next to
>the boiler (downstairs) and the hot water is gravity fed from the
>boiler.
If the boiler is downstairs and the hot water tank upstairs I don't see how the
hot water can be gravity fed from the boiler. The "heated" water in the tank
i.e. that outside the heating coil will be gravity fed from the loft tank but
the "heating" water inside the coil must surely be pumped from the boiler by
the same pump that feeds the radiators.
On the assumption that the above is correct I don't think we can give you any
further information than when you last posted this. There is either an air lock
or a blockage and you aren't going to fix it without taking things apart and
finding out what's wrong.
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
David Archbold
Hi Dave,
The gravity fed system really refers to the hot water rising from the
boiler to the hot water tank forcing the cold water down. I think
this system is fairly standard for older ystems, but most are pumped
CH and hot water nowadays.
I think that air could be the problem, but I am not sure why it works
sometimes and not others. If I don't get any suggestions I think I
will be forced to replace the tank (big job as it is bult into the
airing cupboard) and also fit a NRV on the feed to the hot water tank
coil.
Hopefully there are some CH wizards out there who can give me some
tips as to things I could try or even confirm that they agree with my
proposed cause of action if there is no easy fix.
Cheers,
David
fweefeww
periodically getting too low to reach the HW cylinder?
"David Archbold" <david_a...@agilent.com> wrote in message
news:6c4aee1b.03012...@posting.google.com...
baz
"David Archbold" <david_a...@agilent.com> wrote in message
news:6c4aee1b.03012...@posting.google.com...
David.
I had a similar problem. What had happened was the ball cock in the CH top
up tank had stuck and over time the water level had dropped below the level
of the top coil connection on the tank, as the water tank is heated by
convection the loop was not complete so no flow. Freed the ball cock and all
was well.
Good Luck
Baz
M. Damerell
1. As suggested by Baz, check the header tank.
2. Check for sludge or limescale.
3. Does the HW work better or worse if the CH
pump is running?
4. Has the system been altered since it
was installed? How long have you been in the house?
how long have you had this problem?
5. You say that the coil entry pipe is low on the
HWC. Your pipes might be wrongly connected: I
would expect the coil entry to be about half
way up & coil exit near base.
David Archbold
1. Have checked and cleared out the header tank. Just the usual rust
deposits in there and not an unexpected amount (need to add some
inhibitor when this gets sorted). Tried turning off the rising main
feed to the header tank and draining the system from drian tap on the
boiler. Some water came out of the drain but not much (one bucket).
Tried opening bleed valves on the towel rails (to relaese any air
lock) but this only released the water in the towel rails not the rest
of the system. I then refilleed the header tank and then turned the
rising mian feed off again to see (with the builer drain tap open) if
the system would refil. The header tank water drained extremely
slowly i.e. 1cm evey 15 mins. It looks like there is a blockage
somewhwre in the system most likley after the towel rails.
2. Only rust as above in the header tank, but I am worried about
sludge/limescale in the rest of the system I do not think it is just
an air probelm.
3. Does not seen to make any difference.
4. I do not think the system has been changed apart fom the
controller, but this works fine. When we moved in it seeed a little
tempramental, but turning up the boiler thermostat worked. System has
worked fairly consitently up till now (had to increase the thermostat
again once), but now hot water only get luke warm. From day 1 had to
have boiler on 24hrs to get hot water. CH is fine and water from
boiler is hot enough as judged by scorching towel rails.
5. Looking further at the coil it is fed correctly just they chose to
tap off the feed pipe (which is also a vent) quite high and then run
the pipe down to the coil feed. Presumably this to to let any air
vent rather than get in the coil. There is about 1'-1.5' between to
top of the coil feed on the boiler and the return (near the botton of
the boiler).
My synopsis thus far is that there is ablockage that is causing the
water not to get to or more likely return from the coil. It is either
this blockage that is directly restricting flow OR it is causing air
to be in the circuit in or just before the coil causing the issue.
Next step is to try connecting the rising main to the CH header tank
system feed pressurising the sytem to see if I can blast any blocakge
around the system and out of the vent pipe. Seems a bit brutal and
may cause issues if there are any potential leaks in the boiler or hot
water system, but needs must. If this does not work I am out of ideas
and wil have to bow to professionals.
Any other thoughts on things I could try, or what may be causing the
issue are welcome.
Cheers,
David
Andy Hall
Archbold) wrote:
>My synopsis thus far is that there is ablockage that is causing the
>water not to get to or more likely return from the coil. It is either
>this blockage that is directly restricting flow OR it is causing air
>to be in the circuit in or just before the coil causing the issue.
>
>Next step is to try connecting the rising main to the CH header tank
>system feed pressurising the sytem to see if I can blast any blocakge
>around the system and out of the vent pipe. Seems a bit brutal and
>may cause issues if there are any potential leaks in the boiler or hot
>water system, but needs must. If this does not work I am out of ideas
>and wil have to bow to professionals.
>
>Any other thoughts on things I could try, or what may be causing the
>issue are welcome.
>
This is starting to sound like heavy sludging.
As a test, try taking off a radiator that is relatively close to the
pump/boiler/valve. If you scan through Google, I've written a
procedure for cleaning radiators by taking them off, outside and
flushing them. Take care, sludge stains. If it looks like there is
a lot of sludge, then I would suggest doing all of the radiators in
the system.
Close the radiator valves when the radiators are off
and then open one at a time with water in the header tank.
This is going to be a better way to flush than in and out of the tank.
Ultimately, a radiator position is going to be a better place to hook
on a mains hose to try and clear the blockage. I suspect that the
pipework is full of sludge as well, or it could be something like a
piece of stray loft insulation that has found its way into the tank
and down the feed pipe.
Either way it's probably time for a good clean out. Don't buy into
the professional power flush game. It's a money spinner (especially
if you call BG) of several hundred pounds with questionnable results.
Taking radiators off takes longer and you have to be careful to avoid
mess, but you can do the job in half a day.
Once the system is pretty clean and flowing, use a chemical cleaner
such as Fernox Superfloc, hot for a week, then thoroughly flush again.
Then (please) add some inhibitor like Fernox MB-1 or Sentinel.
Total cost about £40.
M. Damerell
Another possibility is to flush with mains water. I dont think this
will be as effective as Andy Hall's method, but you dont need to
remove radiators. It should get things clean enough to last until
summer. You may need to cut some pipes & insert fittings.
Drain the system as far as possible.
** temporarily ** stop the fill pipe and vent pipe. It is essential to
unstop these pipes before you turn the boiler on again, you will do
serious damage otherwise.
Attach a hose from the cold main to fill the system on one side while
draining it from the drain cock on the other. Then by opening & shutting
taps around the house, you should be able to send a strong stream of water
through each radiator and the HW coil in turn.
Start gently, have family watch for leaks.
Continue with desludger, then inhibitor as described by A.Hall. Dont
forget to unstop the fill & vent pipes. Check for over pumping.
If cleaning-out fails, you may need to convert to fully pumped.