CH Pump Speeds

Just had my pump replaced in my heating system. Boiler is an Ideal e type CF60N, replacement pump is a three speed Grundfos with a 5m head. This was the the recommended equivalent to the Myson unit 3 that was on there before. Can someone tell me what speed the pump should run at 1, 2 or 3. I live in a three storey house if that is relevant. I am also getting a bit of noise from the rads as though pump is running too fast. Before I reduce speed just thought I'd ask first. any advice appreciated. Jim.

2 or 3 depending on the size of the system and the pipe diameters.

Pumps often quieten down soon after they're put in.

You won't do any harm. So try speed 2 and check that the furthest rads get thoroughly hot about as quickly as the closer ones.

Turning the speed down from 3 to 2 will help a lot with the noise, but like said before it depends on the size of the pipework, and amount of pipe. It is quite common to get a noise like a harrier jump jet taking off with a grundfos pump set to speed 3, when the heating switches on! Also, you can help the radiators all getting hot regardless of the length of the runs by making sure that they are all correctly balanced. This invloves removing the plastic valve top on the side of the radiator that has the valve that seems to do nothing but turn round and round, and adjust it downwards until nearly off, and then out a bit at a time using the plastic knob off of the other side of the rad temporarily. Then when all the radiators are balanced correctly they will all get hot at the same time. There is a more technical way of doing it by comparing the water temp leaving and returning back to the boiler, but by basically turning down the rads that are hot, and up the ones that are cold, will get the desired result. The other side of the radiator, which has the knob that turns can then be used to turn on and off any rads as required. Hope that this helps.

Thanks for info. Pipework is 10mm smallbore if that helps. What do you think should I turn the pump speed down? Jim.

Try turning the pump down, and check that all gets hot and works OK. 10 mm is quite a small bore and trying to run the pump too fast will cause back pressure and lead to premature pump failure, the pump will be working hard for no benefit.

My own system is micro bore, 10mm to the front of the house and 8mm to the rear. I have had the same pump in for about 23 yrs now and (touch wood) it is still running on the 1st speed slow as it can go. all the rads still get hot fairly quickly (second hand back boiler make unknown).
I was warned that smaller tubing is more prone to blockage, I have found, so far, the opposite is true.