Pump advice on pressurised system

[b21playa]

Hi all

Following some advice earlier this year on here, I finally have new boiler due to be fitted soon. I’ll be fitting a low loss header as advised due to loss in Vaillant 637.

I currently have a Grundfos usp2 on my open vent system which I was planning on using for the time being until the correct pump is selected. I have 3 zones; dhw, upstairs heating (plus loft) and downstairs heating. I’m wanting to have a single pump in the secondary circuit.

Any recommendations? Many thanks in advance

 

[John.g]

Which exact 637 model are you installing?.
What is your heating load ~ in kw/ how many rads in each zone.

 

[b21playa]

Hi

I just know it’s an ecotec plus 637. Heating load when last calculated was around 27kw not including hw coil. There are currently 7 rads on downstairs zone (will eventually be 11/12) and upstairs has 8 but will extend to 11.

Many thanks

 

[John.g]

A UPS3 (6M) which has a very high capacity for a 6M pump should do the job for you IMO, even if your heating demand is say 35kw then that pump will deliver almost 2m3/hr at a dT of 15C with a 4.5M head, for camparison, most other 6M pumps will only deliver 2m3/hr at 3.3M, 3.3M head hight not be sufficient if you are trying to heat 23 rads at one time, your UPS2 is similar, 2m3/hr at 3.3M.
If you do opt for another make you may have to choose a 8M, whatever you opt for ensure that its output is similar or greater to the UPS3.

 

[b21playa]

A UPS3 (6M) which has a very high capacity for a 6M pump should do the job for you IMO, even if your heating demand is say 35kw then that pump will deliver almost 2m3/hr at a dT of 15C with a 4.5M head, for camparison, most other 6M pumps will only deliver 2m3/hr at 3.3M, 3.3M head hight not be sufficient if you are trying to heat 23 rads at one time, your UPS2 is similar, 2m3/hr at 3.3M.
If you do opt for another make you may have to choose a 8M, whatever you opt for ensure that its output is similar or greater to the UPS3.

I was just speaking to a friend and he has an Alpha2 with auto adapt he has I can have. Is this similar to ups3?

 

[John.g]

No, much of a much as the others, 2m3/hr @ 3.1M head, also I have rarely if ever heard of anyone where the Auto Adapt works on any Grundfos pump, they seem to sit at 9W which will pump absolutely nothing, If you can "have it" literally, then maybe worth a try, also its PP (proportional pressure) settings are hopeless with a max of 3M on PP2, all grundfos pumps have very poor/low PP settings which would be useful for the secondary (heating side) circulation, the UPS 3 PP2 has a head of 3.8M at 2.45m3/hr so much better and would stand a good chance of working well IMO if you choose to use this mode.

 

[b21playa]

Much appreciated John. No point me even trying the alpha2, might as well just buy the UPS3. Reading the docs it suggests PP mode for 2-pipe systems unless your experience shows another setting would be better

 

[John.g]

Is yours a one pipe system?

 

[b21playa]

Is yours a one pipe system?

No, 2-pipe

 

[b21playa]

Had a quick look on eBay and managed to get a UPS3 for £25. I can use this to see if it’s the right pump, if not it’s only £25.

It’s about 18months old according to tag and removed due to combi swap.

Can this be wired directly from boiler or better from switched live to boiler?

Thanks