Boiler Flow Temp Low?

Mutton_Geoff

Ectophile said:

Unless all the radiators are off, and the water is flowing through a bypass valve instead.

They did say they were trying to balance the system so I assumed not. It could be the boiler stat, it's quite possible that this has partially failed, come loose, moved etc and overreading.

piperm87

for me to get a 10-12 degree difference between the flow and return at the rads im having to turn the valves right down on 4 rads, to the point they aren't working properly as there isn't enough flow, As soon as i start opening the valves to get more flow the furthest 3 radiators stop working properly as they aren't getting enough flow. 

Mutton_Geoff

piperm87 said:

for me to get a 10-12 degree difference between the flow and return at the rads im having to turn the valves right down on 4 rads, to the point they aren't working properly as there isn't enough flow, As soon as i start opening the valves to get more flow the furthest 3 radiators stop working properly as they aren't getting enough flow. 

If you adjust the lockshield so you've got a 12 degree drop, the radiator is working most efficiently. This is how it's designed. If the rooms are too cold then, the rads are too small. If you increase the flow rate, the rads won't be as efficient and nor will the boiler. The secondary effect of some radiators allowing too much flow is other radiators then don't get any water. As you discovered. Stick with the 12 degree balancing, it's how it's meant to be done and you will notice a drop in your energy costs.

The principle of balancing is to restrict the flow sufficiently to let the energy from the heated water dissipate through the radiator and into the room. Fully open, the water rushes around, the rad still gets hot but the return temperature to the boiler is too high and the boiler will shut down thinking there is no demand for heated water and the whole system runs a whole lot less efficiently.

Have a look at any radiator specifications, you will see references to their output based on the temperature drop across the rad, called "delta t" for difference in temperature, eg 12∆T is a 12 degree drop between inlet and outlet. Balancing is always done with the system & house just coming up to temperature (but stats not satisfied so as to keep the boiler & pump running) and with the opposite side to the lockshield fully open (whether it's a manual valve or thermostatic type) and then adjust the delta with the lockshield. A handheld digital thermometer is best and taking your time a bonus. It could take half a day to balance a 4 bed house since each adjustment then has a knock on effect on the other radiators. As you found. 

piperm87

Mutton_Geoff said:

piperm87 said:

for me to get a 10-12 degree difference between the flow and return at the rads im having to turn the valves right down on 4 rads, to the point they aren't working properly as there isn't enough flow, As soon as i start opening the valves to get more flow the furthest 3 radiators stop working properly as they aren't getting enough flow. 

If you adjust the lockshield so you've got a 12 degree drop, the radiator is working most efficiently. This is how it's designed. If the rooms are too cold then, the rads are too small. If you increase the flow rate, the rads won't be as efficient and nor will the boiler. The secondary effect of some radiators allowing too much flow is other radiators then don't get any water. As you discovered. Stick with the 12 degree balancing, it's how it's meant to be done and you will notice a drop in your energy costs.

The principle of balancing is to restrict the flow sufficiently to let the energy from the heated water dissipate through the radiator and into the room. Fully open, the water rushes around, the rad still gets hot but the return temperature to the boiler is too high and the boiler will shut down thinking there is no demand for heated water and the whole system runs a whole lot less efficiently.

Have a look at any radiator specifications, you will see references to their output based on the temperature drop across the rad, called "delta t" for difference in temperature, eg 12∆T is a 12 degree drop between inlet and outlet. Balancing is always done with the system & house just coming up to temperature (but stats not satisfied so as to keep the boiler & pump running) and with the opposite side to the lockshield fully open (whether it's a manual valve or thermostatic type) and then adjust the delta with the lockshield. A handheld digital thermometer is best and taking your time a bonus. It could take half a day to balance a 4 bed house since each adjustment then has a knock on effect on the other radiators. As you found. 

Thanks, I get what your saying and i totally agree but to achieve the 10 -12 degree difference on the closest rads the lockshields are almost closed which is restricting flow to the point where only the top half of the radiators get heat, the bottoms half stay cold or take an age to warm up - if i open the valves more then the whole rad will get hot but im losing rads further down the line. It feels like a lose lose situation really.. I've lost count of the amount of hours i've spent going around the house with my digital thermometer trying to get everything balanced up but once done im only getting use of half the capacity of each radiator.

FreeBear

piperm87 said:

Mutton_Geoff said:

piperm87 said:

for me to get a 10-12 degree difference between the flow and return at the rads im having to turn the valves right down on 4 rads, to the point they aren't working properly as there isn't enough flow, As soon as i start opening the valves to get more flow the furthest 3 radiators stop working properly as they aren't getting enough flow. 

If you adjust the lockshield so you've got a 12 degree drop, the radiator is working most efficiently. This is how it's designed. If the rooms are too cold then, the rads are too small. If you increase the flow rate, the rads won't be as efficient and nor will the boiler. The secondary effect of some radiators allowing too much flow is other radiators then don't get any water. As you discovered. Stick with the 12 degree balancing, it's how it's meant to be done and you will notice a drop in your energy costs.

The principle of balancing is to restrict the flow sufficiently to let the energy from the heated water dissipate through the radiator and into the room. Fully open, the water rushes around, the rad still gets hot but the return temperature to the boiler is too high and the boiler will shut down thinking there is no demand for heated water and the whole system runs a whole lot less efficiently.

Have a look at any radiator specifications, you will see references to their output based on the temperature drop across the rad, called "delta t" for difference in temperature, eg 12∆T is a 12 degree drop between inlet and outlet. Balancing is always done with the system & house just coming up to temperature (but stats not satisfied so as to keep the boiler & pump running) and with the opposite side to the lockshield fully open (whether it's a manual valve or thermostatic type) and then adjust the delta with the lockshield. A handheld digital thermometer is best and taking your time a bonus. It could take half a day to balance a 4 bed house since each adjustment then has a knock on effect on the other radiators. As you found. 

Thanks, I get what your saying and i totally agree but to achieve the 10 -12 degree difference on the closest rads the lockshields are almost closed which is restricting flow to the point where only the top half of the radiators get heat, the bottoms half stay cold or take an age to warm up - if i open the valves more then the whole rad will get hot but im losing rads further down the line. It feels like a lose lose situation really.. I've lost count of the amount of hours i've spent going around the house with my digital thermometer trying to get everything balanced up but once done im only getting use of half the capacity of each radiator.

I had a similar problem with one radiator here. Adjust the lockshield for a 10-12°C drop, and the radiator just wasn't getting hot. Ended up with an 8°C drop to get enough flow through the darned thing and heat out. I suspect part of the problem is that it is close to the end of a run of 15mm pipe - Plan on replumbing the whole system next year and using 22mm pipe apart from the short tails coming out of the floor to each radiator.

Mutton_Geoff

piperm87 said:

Thanks, I get what your saying and i totally agree but to achieve the 10 -12 degree difference on the closest rads the lockshields are almost closed which is restricting flow to the point where only the top half of the radiators get heat, the bottoms half stay cold or take an age to warm up - if i open the valves more then the whole rad will get hot but im losing rads further down the line. It feels like a lose lose situation really.. I've lost count of the amount of hours i've spent going around the house with my digital thermometer trying to get everything balanced up but once done im only getting use of half the capacity of each radiator.

It may need a little more time to settle down. As I said it took me forever to do mine. You can approximate, after all, something is better than nothing but in my experience balancing, the lockshields closer to the boiler are almost closed (within 1/4 to 1/2 turn of fully closed) whilst the furthest are almost fully open. Then give it all time to work.

chris_n

Pump isn't working properly or blocked magnaclean filter assuming you have one. If both of these are OK then system flush. I'm assuming you have done the balancing correctly.