Heating system

[Cosd]

Been in this house just over two years. The house is around 30 years old and the boiler has definitely been changed prior to us buying the house  

Heating system consists of an ample floor standing Worcester boiler and a Megaflow. 

Ive changed 8 radiators so far as we do the house up slowly, but will eventually change them all  

 

During this really cold spell the downstairs isn’t heating up adequately, it’s fine during normal winters. The upstairs gets really hot. 

 

Today I balanced the system having followed some guides on the net but some of my new rads are cooler down the bottom than they are up top. Reading about this symptom, there’s suggestion that it could be sludge in the system. 

 

Does this sound right? Why are the new rads, not all, affected and not the old ones?

 

Rads are good quality and I went over the recommended for BTU per room. The kitchen diner is quite large with lots of glass and that is suffering mostly. But the hallway is also not getting hot enough. Bothe of these have new rads 

 

Is is it worth having a power flush, is that likely to make a difference? What would I expect to pay?

 

Apologies for the long winded post; Any other suggestions welcome. 

 

 

Cos

[Winston72]

powerflush about 450 get a magna clean fitted at same time about 150 fitted if done at same time as flush

[silver pigeon69]

Hi, not a plumber, but IMO as you replaced the rads and re-prssured the system you could have moved some of the sludge from the older rads and pipework around and into the new rads. Are the rads that are cooler at the end of the "run", furthest away/last rads to get hot from the boiler?

[Cosd]

1 minute ago, Winston72 said:

powerflush about 450 get a magna clean fitted at same time about 150 fitted if done at same time as flush

The system has a Magnaclean. 

1 minute ago, silver pigeon69 said:

Hi, not a plumber, but IMO as you replaced the rads and re-prssured the system you could have moved some of the sludge from the older rads and pipework around and into the new rads. Are the rads that are cooler at the end of the "run", furthest away/last rads to get hot from the boiler?

I don’t know the system design but from what I’m reading on the net the pipes go upstairs first, so the downstairs rads are probably the end of the run so to speak. 

[TIGHTCHOKE]

If it was a build up of sludge I would expect the bottom middle of those affected radiators to be cold, not just cooler than the top of the radiator.

When you changed radiators did you drain down and re-fill with a suitable treatment added to the new water?

[silver pigeon69]

I would say it is a build up of sludge, but i'm sure someone more knowledgeable will be on here with advice soon.

[Cosd]

1 minute ago, TIGHTCHOKE said:

If it was a build up of sludge I would expect the bottom middle of those affected radiators to be cold, not just cooler than the top of the radiator.

When you changed radiators did you drain down and re-fill with a suitable treatment added to the new water?

The plumbers drained down more than once as we did the rads in stages, but I’m not sure any chemicals were used to flush the system. 

[Medic1281]

I’d say you need to try balancing them again. Or open the cold one right open and close the others down. If it gets hot all over then it’s not full of sludge. 

[aga man]

It would be nice to think the system was properly flushed when the new boiler was installed but this is rarely the case, even when the top 'companies' fit the boiler.

With a magnaclean fitted, it might be worth trying to re-balance the system again.

Shut off all the upstairs rads and get the downstairs rads nice and hot. Then open the upstairs rads a quarter of a turn at a time.

[Flyboy1950]

It may be worth having a check of the c/heating pump, some time the speed mechanism fails and puts the pump to low speed. if it appears ok try turning it up a notch. I have known pumps have the rotors disconnect internally and they will sound ok but not push the hot water around. The fact that the upstairs rads are heating well indicates that they may be working on convection alone, this will still show some heat in the down stairs rads.

It dosen`t sound like the system needs flushing as its been drained so often.

As previously mentioned try balancing the system. Best way is to use thermostatically controlled radiator valves then it does it its self. Remember to leave one radiator with out a trv so the hot water has the ability to flow and not pressurise the pump and seals.

[Cosd]

45 minutes ago, aga man said:

It would be nice to think the system was properly flushed when the new boiler was installed but this is rarely the case, even when the top 'companies' fit the boiler.

With a magnaclean fitted, it might be worth trying to re-balance the system again.

Shut off all the upstairs rads and get the downstairs rads nice and hot. Then open the upstairs rads a quarter of a turn at a time.

I turned all the upstairs rooms off and opened them just over a quarter turn. Downstairs rads are open fully. 

14 minutes ago, Flyboy1950 said:

It may be worth having a check of the c/heating pump, some time the speed mechanism fails and puts the pump to low speed. if it appears ok try turning it up a notch. I have known pumps have the rotors disconnect internally and they will sound ok but not push the hot water around. The fact that the upstairs rads are heating well indicates that they may be working on convection alone, this will still show some heat in the down stairs rads.

It dosen`t sound like the system needs flushing as its been drained so often.

As previously mentioned try balancing the system. Best way is to use thermostatically controlled radiator valves then it does it its self. Remember to leave one radiator with out a trv so the hot water has the ability to flow and not pressurise the pump and seals.

All the rads but one have thermostatic valves. 

[aga man]

I would concentrate on getting the ground floor rads hot before opening any upstairs rad valves. If you cant get the ground floor rads hot with the pump set at max then there is sludge in the lower circuit.

[Cosd]

4 minutes ago, aga man said:

I would concentrate on getting the ground floor rads hot before opening any upstairs rad valves. If you cant get the ground floor rads hot with the pump set at max then there is sludge in the lower circuit.

Ok

Will try that tomorrow, I’ll turn all upstairs off and see how downstairs reacts to that. 

 

I wasnt aware ware you could change the speed of the pump!!

[aga man]

On many combi boilers the speed is factory set with no adjustment. on some systems you have 3 water pump speed settings.

Sorry but this is the best video I can find to describe the speed setting.{not the best}.

https://www.bing.com/videos/search?q=central+heating+water+pump+speeds&&view=detail&mid=548DF1CA88EB1B742188548DF1CA88EB1B742188&&FORM=VRDGAR

 

[figgy]

Close All the other trv,s and let the water flow through the coldest radiator make sure it gets hot. Do this for all the radiators down stairs then re-balance your system.

Backflushing with a hose always cleared sludge and trapped air from a system.

[Tim Kelly]

If you've changed some of the radiators, you must know what the state of the water in the systems is. If it's brick red and like liquid mud, then yes, it will be a sludge build up, and you should probably have addressed the problem when you started changing radiators. If it's generally clearish, with some black at the very end when you drain a radiator, the system is probably fine. I think you should probably re-balance the system, opening the rads that are cool at the moment a bit and closing down some of the ones that heat up first. 

If you've replaced radiators with fancy looking radiators, especially the tall thin ones, they are sometimes directional, so the flow must go through them the correct way. If you have the flow going through from the wrong side, they will only heat partially. Fancy radiators are almost always dreadful, don't do the job they are supposed to do, and corrode very quickly, so be warned.

[B725]

You can hire a power flush for around  £100 and do it yourself it's fairly straight forward you then will know the system is clean. 

[Cosd]

39 minutes ago, Tim Kelly said:

If you've changed some of the radiators, you must know what the state of the water in the systems is. If it's brick red and like liquid mud, then yes, it will be a sludge build up, and you should probably have addressed the problem when you started changing radiators. If it's generally clearish, with some black at the very end when you drain a radiator, the system is probably fine. I think you should probably re-balance the system, opening the rads that are cool at the moment a bit and closing down some of the ones that heat up first. 

If you've replaced radiators with fancy looking radiators, especially the tall thin ones, they are sometimes directional, so the flow must go through them the correct way. If you have the flow going through from the wrong side, they will only heat partially. Fancy radiators are almost always dreadful, don't do the job they are supposed to do, and corrode very quickly, so be warned.

 

I’d like to think if the water was that bad my plumbers would have told me and done something to clear it . 

I don’t know if bleeding  the rads is a way to tell, but water runs clean. I haven’t looked at the magnaclean since I moved in so will also check that also . 

 

Should I add some inhibitor in the magnaclean?

No fancy rads, these are the usual white panel radiators; Going from memory the y are made by Kartell or K-Rad.  

 

Thanks for all all the advice guys, some things for me to try. 

Edited March 4, 2018 by Cosd

[Cosd]

8 hours ago, aga man said:

On many combi boilers the speed is factory set with no adjustment. on some systems you have 3 water pump speed settings.

Sorry but this is the best video I can find to describe the speed setting.{not the best}.

https://www.bing.com/videos/search?q=central+heating+water+pump+speeds&&view=detail&mid=548DF1CA88EB1B742188548DF1CA88EB1B742188&&FORM=VRDGAR

 

Wow, I had no idea there was a switch for the speed on these pumps. 

There are a load of rads in this house, so guessing a higher speed to get hot water to the end of the line quickly before it cools too much is what I’m after? We have 21 rads. 

[Tim Kelly]

Combi pumps, if speed selectable, should be left on the highest setting.

[TIGHTCHOKE]

4 hours ago, Cosd said:

Wow, I had no idea there was a switch for the speed on these pumps. 

There are a load of rads in this house, so guessing a higher speed to get hot water to the end of the line quickly before it cools too much is what I’m after? We have 21 rads. 

Every day is a learning day!

[Tim Kelly]

If you have 21 rads, you definitely need to balance the system well. You might well need a bigger pump too, something like a 25-50 as the resistance of the system might be too much for a standard pump. Has the heating system ever worked well?

 

If you don't have them, TRVs (thermostatic radiator valves) if used correctly will help balance your house heating as the upstairs rooms which heat up well will shut down the radiator once the room is warm enough, which sends more heating potential to the cooler parts of the house.

Edited March 4, 2018 by Tim Kelly

[JohnfromUK]

I have about 30 rads in a 4 zone system, completely renewed (all rads, all pipework, boiler, 42KW Worcester Bosch condensing gas boiler, all hot water system) 2 years ago. It is in a rambling old house and some of the pipe runs are long and complex, with lots of bends getting round beams and walls.   I have a few comments based on experience.

1. Room calculations are a reasonable guide, but some rooms are naturally cold, some naturally warm.  Wind exposure, windows, drafts, insulation, doors left open all make a difference.  I have 50% extra radiator capacity in some places that I know to be 'cold' and it is still a bit marginal in cold windy weather.  Big rooms in particular seem to need more than calculations show unless you are prepared for  very slow warm up time.
2. Rads work by convection, so the top will always be hottest, and the water falls down the rad as it gives up its heat.  Generally modern condensing boilers have a 20ºC difference between flow and return (older boilers were less, 11ºC in some models if I remember right).  In modern systems, a 'two pipe' system is used where all of the radiators have a 'flow' sourced from the boiler, and a 'return' going back to the boiler.  Therefore, on average each rad inlet should be at boiler 'flow' temperature, which will be around 65-70ºC , and return about 50ºC which allows the boiler to condense correctly.  Flow water goes straight to the top of the radiator and the water sinks down the radiator, giving up its heat before flowing out, roughly 20ºC  cooler.  The top will therefore be about 15 - 20ºC  warmer than the bottom.
3. If a rad is dropping more temperature than this, the flow through it is too slow.  If there is little temperature change between flow and return, the flow is too fast.
4. Balancing the rads in a big system is hard to get right, (more so in a multi zoned system), but generally, each rad should drop about 15 - 20ºC between flow and return.  Note that TRVs should be open when balancing, or you may end up chasing your tail, because as you try and increase flow on the lockshield, the TRV may be reducing it at the other end!
5. Small rads therefore need less water flow than big rads.
6. Rads close to the boiler will tend to naturally get a higher pressure/flow as pipework looses pressure with distance (and bends, thin pipes etc.)
7. The method I have found works best in practice (starting from scratch) goes a bit like this;
8. Fully open the lockshields and TRV/Flow valves on all radiators.
9. Close down the lockshields on smaller rads (and those closest to the boiler) which get hot very quickly and have no apparent temperature drop between flow and return. I use a cheap eBay infra red thermometer (about £10) to get about 15 to 20ºC  drop across rads.  An investment you should recoup in savings when all is set up right.
10. Big rads you will probably leave the lockshields fully open, and only balance down those that clearly have a very fast flow.

It is quite hard to get right in a big system, and you have to be patient.

[Flyboy1950]

I think that JohnfromUK has given you sound advice. I have reread your original post and quote "Rads are good quality and I went over the recommended BTU per room." New rads are likely to have less resistance to water flow and hot water takes the least line of resistance, also as they are bigger you are compounding your problem further. You must also now consider whether your boiler is man enough for the extra requirement placed on it in its present and future forms as you replace even more radiators. Possibly having reached the point of the straw breaking the camels back.

Maybe depending on your home layout and requirements you could divide your house into 2 zones with the upstairs running at a cooler temperature and times? Cheaper than a bigger boiler that you wont need in the summer, so more fuel efficient.

Every time you replace a radiator you will upset the balance of the system.

Edited March 4, 2018 by Flyboy1950

[daveboy]

I balanced mine using a meat thermometer that I found in the kitchen draw.