Central Heating Struggling in the Cold

[JohnD]

The pipe at the bottom is 15mm, which has half the capacity of 22mm, so reduces the flow.

Unlike a gate valve, it will not leak or break.

BTW, if you clean off the green and other stains with a pan scourer and soapy water and polish off with a rag, any new marks will tell you you still have a leak.

You might consider lagging the pipes.

 

[DIYDisaster987]

The heating worked fine last night with the hot water on at the same time. All radiators nice and warm and actually got up to thermostat temperature of 18Deg C. There were lots of gurgling noises around pump though.
This morning there was plenty of hot water but radiators were only starting to get warm after about one hour and only got hot to the touch after the whole 3 hours of the morning timed cycle. Didnt get up to the thermosat temp of 18Deg C but house much warmer than it has been. Also noticed the frost guard kicking in just prior to timed cycle which is as expected as freezing conditions outside.
I checked the header tank to make sure it was full and would fill which was fine but it was full of black sludge.
Not sure what rating the Flamingo is. It has Potterton Flamingo on the outside and RS 50 under the front cover.

I think the deterioration is probably a build up of sludge in the system which has brought the performance down which is more apparent when its very cold. The house is arond 35 yrs old so some insulation but high on my todo list is improving the 100mm insulation in the loft.

Not sure where to go from here though. I see 'PowerFlush' seems to be the way to go for these kind of issues but are they any good or just marketing hype? I remember doing a chemical flush many years ago and that found several leaks which werent there before. Perhaps a gate valve would help but am I just putting off the inevitable that my old boiler just isnt up to it anymore?

 

[DIYDisaster987]

The pipe at the bottom is 15mm, which has half the capacity of 22mm, so reduces the flow.

Unlike a gate valve, it will not leak or break.

BTW, if you clean off the green and other stains with a pan scourer and soapy water and polish off with a rag, any new marks will tell you you still have a leak.

You might consider lagging the pipes.

Funily enough I did just lag all the pipes as they leave the boiler which is in the garage.

 

[JohnD]

You mention sludge. As you have an old open vented system a chemical clean is likely to help, especially if you add a Magnaclean or similar.

X400 is unlikely to cause leaks and you can safely leave it circulating while the system runs normally for a few weeks.

Bale out the feed and expansion tank and remove all its sludge before you start, so it does not wash down into the pipes.

It will work if you do it before there is an actual blockage.

A powerflush done properly is better, but a lot more expensive.

 

[DIYDisaster987]

You mention sludge. As you have an old open vented system a chemical clean is likely to help, especially if you add a Magnaclean or similar.

X400 is unlikely to cause leaks and you can safely leave it circulating while the system runs normally for a few weeks.

Bale out the feed and expansion tank and remove all its sludge before you start, so it does not wash down into the pipes.

It will work if you do it before there is an actual blockage.

A powerflush done properly is better, but a lot more expensive.

I had wondered about a magnetic cleaner with a filter and clean regularly at first to try and clear out the sludge.

I have a couple of weepy radiator valves that need changing too. I saw a technique where bungs were used in the header tank to create a vacuum so the valves could be changed without draining down the system. Would that work for fitting a filter or would it be best to drain it down in any case to try and get rid of some of the sludge?

 

[JohnD]

When you fit a filter you have two open pipes, so air can go up one and water down the other, so you need to drain.

X400 is so cheap that you could afford to run it for a week or so before draining down to fit the filter, then add it again during the refill. While you have it drained, change your valves or fit TRVs

You will be delighted and amazed to see how much sludge the magnet catches when you add X400.

 

[DIYDisaster987]

When you fit a filter you have two open pipes, so air can go up one and water down the other, so you need to drain.

X400 is so cheap that you could afford to run it for a week or so before draining down to fit the filter, then add it again during the refill. While you have it drained, change your valves or fit TRVs

You will be delighted and amazed to see how much sludge the magnet catches when you add X400.

That sounds like a plan!

Many thanks Jon and to all others that have offered advice, its much appreciated!

 

[MeldrewsMate]

If your hot water cylinder is taking more flow than it should (and without that restricting gate valve you can't adjust it) AND your boiler flow temperature (at 59C) is lower than your cylinder 'stat setting (typically 60C) then you'll never satisfy the hot water 'stat and you'll continue to 'short circuit' the boiler output....the boiler will run for just a short period at a time.

The solution is to turn up the boiler temperature to about 70C, this will increase the heat outputs from your rads and hasten DHW generation; the cylinder 'stat will be satisfied and the 3 port valve will divert to heating only mode...result? Your problem goes away.

You may have been ill informed that a boiler runs at a higher efficiency with lower flow temps, but that applies only to condensing boilers; your 40+ years old Potty Flamingo boiler is NOT of the condensing type.

MM (press thanks, you're welcome)

 

[DIYDisaster987]

If your hot water cylinder is taking more flow than it should (and without that restricting gate valve you can't adjust it) AND your boiler flow temperature (at 59C) is lower than your cylinder 'stat setting (typically 60C) then you'll never satisfy the hot water 'stat and you'll continue to 'short circuit' the boiler output....the boiler will run for just a short period at a time.

The solution is to turn up the boiler temperature to about 70C, this will increase the heat outputs from your rads and hasten DHW generation; the cylinder 'stat will be satisfied and the 3 port valve will divert to heating only mode...result? Your problem goes away.

You may have been ill informed that a boiler runs at a higher efficiency with lower flow temps, but that applies only to condensing boilers; your 40+ years old Potty Flamingo boiler is NOT of the condensing type.

MM (press thanks, you're welcome)

My Boiler Temp is already at Maximum (now 5 out of 5).
The original Temp 3 out of 5 was set by my plumber.

 

[DIYDisaster987]

One last question (hopefully!). If I'm draining down my system I'd turn off power to the controller but is there a risk of the frost guard kicking in and firing up the boiler when it has no water? If I isolate power to the boiler does the pilot light go out?

 

[JonathanM]

My Boiler Temp is already at Maximum (now 5 out of 5).
The original Temp 3 out of 5 was set by my plumber.

One thing isn't quite making sense to me. When you were following the suggestions early in the thread, you said that when the boiler was on heating only, it ran continuously. But you also said the flow only reached 59 degrees. I would have thought if the boiler was running continuously, rather than cycling on and off, the flow would be reaching over 80 degrees with the boiler thermostat turned to 5. All that heat has to go somewhere. Did you check how long it runs for continuously on heating only?

 

[JohnD]

One last question (hopefully!). If I'm draining down my system I'd turn off power to the controller but is there a risk of the frost guard kicking in and firing up the boiler when it has no water? If I isolate power to the boiler does the pilot light go out?

Frost guard? On a 30 yr+ Potterton Flamingo?

If you turn off the electrical supply to the boiler, it cannot start up.

I don't remember about the pilot light

But even if you drain the radiators, the pilot light is under a big block of cast iron full of water.

 

[DIYDisaster987]

Might be my terminology (DIYer not plumber1 ) but theres some sort of thermostat on the return pipe to the boiler (looks like the termostat on the hot water storage tank) and when its v cold at night (or actually after morning cycle this morning) the heating comes on outside the cycles on the timer.

 

[DIYDisaster987]

One thing isn't quite making sense to me. When you were following the suggestions early in the thread, you said that when the boiler was on heating only, it ran continuously. But you also said the flow only reached 59 degrees. I would have thought if the boiler was running continuously, rather than cycling on and off, the flow would be reaching over 80 degrees with the boiler thermostat turned to 5. All that heat has to go somewhere. Did you check how long it runs for continuously on heating only?

I didnt keep checking the temp to see what it reached and also my temperature checking could be suspect tbh. I have a cheap Infrared thermometer but that doesnt like shiny things like copper pipe so was just holding an electronic cooker termometer against the pipe. No very scientific!

 

[JohnD]

Might be my terminology (DIYer not plumber1 ) but theres some sort of thermostat on the return pipe to the boiler (looks like the termostat on the hot water storage tank) and when its v cold at night (or actually after morning cycle this morning) the heating comes on outside the cycles on the timer.

Post photos please.