pump head over 10m

[petthebuilder]

Hi,
I am having issues to size a pump for a large house. Boiler is in the basement, UVHW cylinder in the loft. the property is a 2 story + ground floor.
At the moment the boiler is a Vaillant 637 (integrated pump). Flow and return 22mm to cylinder (mind that partially it is plastic - so diameter reduced internally at fittings). Also there is an additional pump on the ground floor. However, it is enclosed so I don't now if it is for heating or hot water side.
I found it helpful to have it connected to the sw/live of the boiler,as it seemed to help prime the hw cylinder - primary.
The issue I am having is 2 fold , but related to the same issue.
To prime the cylinder primary took me 3 hours last time (secondly) it has an air lock again 2 weeks later.
As you know the pump in the 637 is 15-60 variable (2 stage) pump, I had it set to high speed permanent.
In my opinion the pump head is 10m at least so the internal pump not enough. I am thinking to use a WH40 low loss heather with a wilo Yonos maxo 30/0.5-12 or a g/foss Magna 1 32/120 pump. leaving the existing unknown pump wired in series with the new pump.
My concern is the high velocity in the pipes.
Should I be worried, does anyone has a better solution. please note the property has been renovated 2 years ago, so I should avoid routing pipes and cables (ie additional pump near the cylinder not acceptable) , however I could fit an additional pump on the hw primary flow next to the boiler as the Honeywell zone valve is next to the boiler.
I presume it would be a suitable option to fit 15 - 60 pump in series with the existing internal one to provide 12m head, without increasing the volume of the water (velocity should be the same).
Thank you
Peter

 

[Gasguru]

Join the CC or are you really a builder playing with heating systems?

Have you calculated the index circuit, hope you're not thinking the 10m pump head is anything to do with the height of the property.

System boilers have their place but this is not one of them....pump and vessel will almost certainly be very underszied. Manufactures are too dumb and continue to produce high output system boilers...and ignorant installers fit them. LLH might be the way to go but it's a complex way to go.

 

[Dan Robinson]

+1 - especially in view of this:

I don't now if it is for heating or hot water side.

 

[petthebuilder]

Hi,
I am domestic gas engineer, mostly repair and and service.
I try to keep away from plumbing installation as it is hard work.
You are correct the Exp vessel was undersized. I had to fit an additional 18L (from top of my head).
I wont be able to calculate the index circuit as the property is already finished and the pipes are concealed. The heating system is a mess I have at least 1 reverse circulation on 3 rads - this I have sorted by Evohome a few months ago.
I am trying to use some common sense method to avoid unnecessary disruption and minimise the possibility of my failure.
As of the height of the property relating to the pump head I always thought that a 6m head is only capable to create excess pressure up to 6 m height from the pump. Of course the pressure loss through the pipe is the main concern.
Thank you
Peter

 

[MJGas]

"Hope your not a builder"

Petthebuilder

 

[petthebuilder]

Yeah
I am on gas for a few years now, I made this user name when I had a building company. I know I should change it.

 

[Dan Robinson]

Register for the Combustion Chamber.

 

[Gasguru]

...I wont be able to calculate the index circuit as the property is already finished and the pipes are concealed.
...As of the height of the property relating to the pump head I always thought that a 6m head is only capable to create excess pressure up to 6 m height from the pump.

Peter it appears you've not grasped the concept of the index circuit and are confusing maximum pump head with the height of a system. The height of a system has ABSOLUTELY nothing to do with pump head. The only relevance of the system height is to set the expansion vessel pre-charge and system pressure....nothing to do with the pump. The pump is sized purely on pipe/heat exchanger friction at the required flow rates.

I suggest you get to grips with index circuits and pump (circulator) performance curves. Also the head loss diagrams in the Vaillant MI.

Join the combustion chamber....there's a wealth of info with very knowledgable installers.

 

[petthebuilder]

Thank you,
I will look through my books to see what I missed.
Regards
Peter