Pump Speed?

[J3nkinso]

Hi,

It’s my first post on this forum so go easy on me

My home CH heating system is an OV type that includes a heat bank (thermal store). My condensing boiler is mounted half way up my garage wall and the heat bank is directly above it on the above floor. There’s a pump in the return circuit from the store to the boiler and the boiler returns directly to the store. There’s approx 1m of pipe work in each direction and probably around 1.5m height diff between the boiler and store. The system has a separate pump for the CH.

The pump in the boiler circuit has 3 speed settings. How do I know which pump speed to select? Obviously I’d prefer to use the slowest speed to minimise running costs but don’t know how to choose the right setting to ensure the system works properly. I guess there’s some way of calculating or figuring this out?

Is anyone able to offer some advice?

 

[muggles]

Slightly confusing post. Are you using "heat bank" and "store" interchangeably? Is it actually a thermal store, or a hot water cylinder? Generally condensing boilers want slow pump speeds but this can be affected by your system setup. Post a few photos if you can

 

[J3nkinso]

Sorry about my lack of technical understanding! It’s a thermal store (Gledhill Torrent T170 IND-OV). My boiler is an Ideal Icos M3080. Both are a good few yrs old.

Here’s a diagram of my system I recently drew to help me understand how it works: (don’t laugh!):

 

[sirocosm]

I'm just a DIY guy, but I do have a heat bank (thermal store with external plate exchanger). There should be 3 pumps on such a setup.

1. One for the boiler to heat the store. This should be set on high, although you might get away with a lower setting. If it is too low, the boiler will cycle/modulate more towards the end of heating the store. Not much point turning the pump down just to have the boiler cycle/run longer. Also your boiler should be set to the max temperature for the same reason.
2. One for the primary side of the plate exchanger for the hot water. I would start out with this in the middle setting. You might be able to get away with a lower setting, perhaps in the summer. If it is too low, your hot water will not be as hot as you require.
3. The third is for the radiators. This depends a bit on how your system is set up, but again, if it works fine on the middle, or lower speed, then it should be fine.

Edit: Pump 1 might be located within the boiler itselft, and if your system is vented, this may limit how high you can set it.