Central Heating Circulation Problems


Postby Kerryt » Sun Jul 19, 2009 4:32 pm

Hi - Please can someone help. I have a Central Heating system that was put in 11 years ago. For the first couple of years it worked fine, then we found that the upstairs radiators were getting hot even though the heating was off - and the cause of that problem was the heat was creeping back up the return from the boiler over run radiator, (which was the bathroom). We fitted some Non return valves and this seemed to fix the problem for a while. For the past few years our heating has been getting worse and worse, and we found out that our pump was on its way our - so we got a new pump. This again worked for a while and I had 9 hot radiators (4 upstairs and 5 downstairs). Then we stopped getting heat upstairs - so we removed the non return valves. Now I only have heat upstairs even though the raditors are turned down so that they are only 1/8 switched on. We have applied a sludge remover and then flushed it all out. We have taken each individual radiator off the wall and jet washed them out. I have no air in any radiators, but still can only get heat upstairs. The only way I can get heat downstairs is if I turn all the radiators upstairs fully off, and even then only 4 out of the 5 get warm downstairs. We are at our wits end and really want this sorted before the winter as I have 2 very young children. I have a potterton Boiler which is in a bedroom on the 1st floor, my cylinder is in the kitchen on the ground floor and my tank is in the loft. Any help anyone can give would be appreciated. My dad is the plumber doing all this work and he has never come across this problem before in his 30 years+. Thanks you in advance,
Kerryt
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Postby htg engineer » Sun Jul 19, 2009 8:07 pm

When was the pump changed ?

It could be the pump again.

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Postby Kerryt » Sun Jul 19, 2009 8:20 pm

Hi - Thanks for replying.

The pump was changed in March. Its the same make as our previous one, but a higher power one. Its a Grundfos Super Selectric.

I also have the same problem now that I initially had - that the heat creeps backwards through the return pipes upstairs from the bathroom radiator which is the over run?

One other thing i forgot to mention - when we drained down the system and caught the fernox to re-use, when we tried filling back up again with the saved water, it wouldn't all go back in even though it had all come out??
Kerryt
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Joined: Sun Jul 19, 2009 4:19 pm


Postby Kerryt » Sun Jul 19, 2009 8:53 pm

Hi - Thanks for your reply.

The pump was changed in March. It is the same make as previously used but is a higher power one - a Grundfos Super Selectric.

I forgot to mention previously, that I now have the same problem back of the radiators getting hot upstairs when the heating is off, when the boiler runs for the hot water. Apparently its only my bathroom radiator that should get hot for the pump over run - but I have another 3 radiators that are getting hot.

I also forgot to mention that when we drained the system down and collected the water in 3 containers as it contained fernox, when we tried to re-fill the tank on the loft, we could only get 1 and half back in. Why?

My Dad says we may need to higher the tank in the loft to get more "weight of water" - but my roof is quite low so it can't be highered that much. Would this help?
Kerryt
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Joined: Sun Jul 19, 2009 4:19 pm


Postby htg engineer » Mon Jul 20, 2009 5:46 pm

What type of system ?

if it's a gravity hot water system, it's not unusual for all upstairs radiators to get warm, unless you trap the boiler flow.

'I also forgot to mention that when we drained the system down and collected the water in 3 containers as it contained fernox, when we tried to re-fill the tank on the loft, we could only get 1 and half back in. Why?'

I was also wondering why ? why collect the fernox ? it's only £15 to renew.

Who knows, if all radiators get hot and the hot water works, then the system is full - i wouldn't worry, you obviously refilled with fresh water too.

'I have a potterton Boiler which is in a bedroom on the 1st floor, my cylinder is in the kitchen on the ground floor and my tank is in the loft'

Do you mean your cylinder is in the bedroom and your boiler is in the kitchen ?

If only part of the heating system, works and there's no air or sludge, there's either a restriction/blockage or the pump is knackered.

'My Dad says we may need to higher the tank in the loft to get more "weight of water" - but my roof is quite low so it can't be highered that much. Would this help?'

Not really, it's worked for 11 years.

htg
htg engineer
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Postby Kerryt » Mon Jul 20, 2009 6:30 pm

Hi - Thanks again for replying.

I have a Fully Pumped Gravity System.

The Cylinder is in the kitchen (as the airing cupboard wasn't big enough).
The Boiler and pump is in the bedroom.

When the system was drained down it wasn't refilled with any clean fresh water as the stopcock was turned off. So surely the amount of water that came out must be able to go back. Would this suggest that there must be an airlock somewhere? Maybe in a pipe under the floor - and if so, how do we remove that.

Not sure if I mentioned previously, but all the radiators have been removed individually and jet washed through as this was a cheaper option than getting them powerflushed by an outside compay.

I'm not sure why my Dad said we should keep the fernox - maybe because it was a new one that had only been put in a few weeks earlier. We had a few weeks before used Sentinel cleaner to losen any sludge.

Its the return from the downstairs heating going up to the boiler in the bedroom that isn't getting hot, along with the downstairs radiators.

Any help you give is greatly appreciated.
Kerryt
Posts: 5
Joined: Sun Jul 19, 2009 4:19 pm


Postby htg engineer » Tue Jul 21, 2009 4:37 pm

'I have a Fully Pumped Gravity System'

No such thing, it's either fully pumped or gravity.

'The only way I can get heat downstairs is if I turn all the radiators upstairs fully off'

So the system is full, if you only got 1.5 out of 3 barrels back in, then the system would only be half full, and there would be no way upstairs radiator would heat.

The info you give is not accurate and is making the situation more complicated than it actually is, ie it can't be a fully pumped gravity system.

An airlock can be cleared easily, try draining and refilling, to see if ti fills properly this time, don't bother trying to keep the inhibitor, if it fills up and all gets warm, then add the inhibitor. If that doesn't work I would recommend getting someone out to try to get the system working for you.


htg
htg engineer
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Postby Kerryt » Tue Jul 21, 2009 5:06 pm

I have just spoken to my Dad - it is Fully pumped to central heating and cylinder and has a gravity fed tank. I have 2 Motorised Valves.

My Dad is going to back fill the feed in the next few days to see if that clears any blockage. He has already done the flow by linking it up to the mains in the loft.

To be honest - this is all complicated stuff for me and i'm just typing what i know has happened and what technical info i need from my Dad.

Thanks for all you help.
Kerryt
Posts: 5
Joined: Sun Jul 19, 2009 4:19 pm


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