Can I install a pump on horizontal pipes?

[nomad]

I have a DAB circulating pump attached to horizontal pipes in my basement. It is located about 3 feet below the boiler, and on the floor underneath it are 2 old Grundfos pumps. From this I deduce that the previous owners have had pump problems in the past. The reason I had to check it out is the pump stopped working. I managed to start it by spinning the bit in the middle with a screw-driver, but the next day it stopped again.

I am wondering if it needs replacing, but also wanted to figure out if there is a more serious issue (due to the 2 old pumps on the floor!). So, I have 2 questions: First, is it OK to have the pump mounted on horizontal pipes, and secondly, is having the pump at the lowest point in the entire sytem part of my problem? Thanks.

 

[doitmyself]

First, is it OK to have the pump mounted on horizontal pipes,

Yes. But the pump shaft must be horizontal. Grundfos say:

Where pumps can only be installed in horizontal pipework, it is imperative that the pump shaft is horizontal, or slightly higher at the vent plug end. The shaft must not fall below the horizontal plane, even by a few degrees, as this causes premature wear of the top bearing and shaft.
Pumps should not be installed with the shaft in a vertical plane, as this may lead to dry running of the top bearing, noise and possible pump failure.

is having the pump at the lowest point in the entire sytem part of my problem?

Shouldn't cause any problem.

It might be worthwhile stripping down the old Grundfos pumps (four Allen screws) and finding out what the damage is (jammed/broken impeller etc).

 

[Toddyplumb]

Basic central heating design . You do NOT put the pump at the lowest point ! As you have correctly observed your pump has been changed before. Sludge , sediment etc . I would have a look at cleaning / flushing and if possible move the pump. This is usually easy in a cellar.