heating but no hot water - not combi


Postby beesley121 » Mon Mar 16, 2009 1:13 pm

hi guys,

for some reason i have no hot water. water is coming through the hot taps but it is stone cold.

my radiators are working fine and so is the pump.

ive even tried my immersion heater but still no luck.

not to sure what system i have but i have a tank in the loft and a copper cylinder on the secound floor. my boiler is on the ground floor.

when i switch the controller on for hot water, the boiler fires up so thats ok.
??

thanx
im thinking it could be an air lock!! what do you think? how do i fix this
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Postby stoneyboy » Mon Mar 16, 2009 10:04 pm

beesley121,
Have a look in the loft and see if the vent pipe end is dipped into the water, if yes lift it up, fix it and all should be OK.
end
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Postby rosebery » Mon Mar 16, 2009 10:29 pm

I'm thinking its your three port valve. Check the actuator.

Cheers
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Postby beesley121 » Tue Mar 17, 2009 4:00 pm

ive tried to locate the three port valve but cannot find it!!!

where abouts would it be??? would it be near the programmer in the kitchen were i select either hot water/ central heating or both???

will my system definatly have a 3 port valve
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Postby rosebery » Tue Mar 17, 2009 10:26 pm

I'd expect a three port motorised valve to be fitted adjacent to your hot water cylinder. It directs heated water from the boiler to the coil in the cylinder when the cylinder stat calls for heat and to the floww for the CH system when the room stat calls for heat. This is known as a Y plan system and you can find a diagram at "ultimatehandyman.co.uk/y_plan.pdf"

No your system will not definitely have a 3 port valve. You MAY have two valves which will be two port zone valves. One for the heating circuit and one for the HW circuit. This is known as an S plan system and you can find a diagram at "ultimatehandyman.co.uk/s_plan.pdf

HTH

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Postby beesley121 » Wed Mar 18, 2009 8:55 pm

thanx very much.

ill keep looking..............
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Postby beesley121 » Thu Mar 19, 2009 7:16 pm

hi guys,

i still cannot find this valve and ive looked every where :oops:

looking at my boiler again closer (glow warm space saver 38) i can seee that there are 4 pipes in total running to and from the boiler. i can set there is a central heating inlet and outlet which get hot when the ceentral heating is on but the other 2 which im sure is the hot water inlet and outlet are cold.

i guess this means my system wont have a three port valve or am i wrong??

the inlet and outlet pipes get warm close to the boiler when the hot water is turned on, but the rest of the pipes is stone cold. i guess this is just residual heat from the boiler when the central heating is on.

does this boiler use some kind of pump to push the hot water through the coil in the cylinder???
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Postby rosebery » Sun Mar 22, 2009 9:14 pm

"glow warm space saver 38"

This is a 30 year + old boiler. When was it last serviced?

If the boiler is that old and you can't find the valve then the chances are there isn't one and you have gravity HW and pumped heating. In that case the HW circuit is NOT pumped.

Does the system look anything like the first diagram on this

Google "gasman.fsbusiness.co.uk/gravity_hot_water_pumped_heating.htm"

page?

Cheers
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Postby beesley121 » Mon Mar 23, 2009 12:57 pm

i looked at that diagram and it is similar to that except the water that is heated for the central heating is not used to heat the heat exchanger in the cylinder.

this glow warm boiler has an inlet and out let for the central heating which has a grunfos pump on the line. The pump kicks in when the heating is switched on. There is no problems with this side.

but the boiler also has also 2 other pipes. one an inlet and one an out let. this. This is like a ring main. for HW, the boiler heats the water in this 'ring main' it flows through the heat exchanger in the cylinder and returns back to the boiler.

what i cant figure out is how the water is pumped from the boiler, through the heat exchaanger and then back to the boiler. i cant find/see and pump anywhere on this line.
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Postby beesley121 » Mon Mar 23, 2009 1:10 pm

just found a diagram to show what the system is like

take a look, its the fisrt diagram on that page.

http://images.google.co.uk/imgres?imgur ... 6%26um%3D1

i
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Postby rosebery » Tue Mar 24, 2009 7:13 am

If it looks like that then you DO have a gravity HW system. The HW system is NOT pumped and there is NO 3 port valve.

You have a blockage in your primaries. Its either scale or its air.

Trouble is with a gravity system just adding descaler won't help 'cos it doesn't get pushed round the HW circuit by a pump. Trace the blockage with your hand on the pipework. Where it suddenly goes cold its there!

If its air then the quick way is to boil it out but don't attempt this yourself. Get an RGI in as although its not a gas related problem he will know the limits of how far he can push this boiler / cylinder to do that.

Methinks you may also have reached the time where, medium term, you need to be considering a boiler replacement. As I said this one is over 30 years old!

Cheers
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Postby beesley121 » Tue Mar 24, 2009 1:24 pm

thanx rose!!

i understand that i should get a new boiler but im thinking of putting an extension on the side of my house. it will be quite a big extesion. this means that i will want the boiler in the new extension

i dont want to have a new boiler installed, only to have it moved in 12 months time.

i would prefer if i could get the existing boiler to run another 12 months
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Postby rosebery » Tue Mar 24, 2009 8:37 pm

Well I did say medium term and it looks like thats on your plan anyway.

So find the cold/hot point in the pipework and that will tell you where the blockage is. If its scale you could then cut that piece of pipe out and replace it.

If its air (and I can't tell if its air or scale from here) and you are going to consider boiling it out please do get an RGI in.

Actually thats probably the best solution whatever - get him to sort it either way.

Cheers
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Postby PaulthePlumber » Fri Mar 27, 2009 4:40 pm

Hi, you def have a gravity hot water system and pumped heating, first thing to check is the expansion tank (the small tank in loft) has it got water in it or is ball valve stuck? iif so free ball valve end of problem, if not could be blocked cold feed as already suggested or air, would not advise removal of boiler thermostat yourself to boil the primaries however if you find a drain point fill it up off the mains water pipe, this will take push the water through system and up into expansion tank, if tank fills first then overflows cold feed to system is probably fine and it is air which should now have been pushed out, if water comes through vent pipe over tank first cold feed is probably blocked, you could combine the two in the loft and see if that works otherwise cold feed should be the smaller pipe (15mm) going into the 1" primary return off the cylinder good luck Paul
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