Pump Sizing

[Chester]

Hey guys long time since I have posted here but know some of you know your salt. I've got a job in a townhouse and currently the boiler sits on the second floor of a three story but I'm moving it to the ground floor as per client request, problem is, its got ridiculously high ceilings, I'm going to double check but suspect at the very least top floor rads are 7 meters up.. so I'm concerned about a standard 15/60 or whatever being man enough, I've been looking at the 25/80 as a viable alternative but I'll be honest I really don't have a great deal of experience in pump sizing, I'm usually just whacking in combis and forgetting about it so I keep hearing that it'll make the system noisy and all these horror stories, just wondering if anyone could give me some advice basically. Current system is 22mm flow + return, currently open vented, 10 rads overall, I'm going to seal it and putting in a 180l unvented indirect. Also, client is a bit of an eco warrior so they want me to put in electric, electric boiler needs 12lpm minimum according to Mi's. Cheers

 

[ShaunCorbs]

Can you seal it ?

 

[Chester]

Can you seal it ?

yeah i will be

 

[ShaunCorbs]

Should be fine with a 15-60 then

 

[Chester]

Should be fine with a 15-60 then

Okay thanks Shaun, any chance you could you explain why that is? I always thought the height mattered whether its sealed or not

 

[ShaunCorbs]

As it’s sealed and the return will equal out the flow so your pump won’t have to work as hard

with open vent it will hep but not as much

 

[Chester]

As it’s sealed and the return will equal out the flow so your pump won’t have to work as hard

with open vent it will hep but not as much

I see, so in theory the weight of the water coming back down the return contributes to the force of propelling it up. At what point would it be worth uprating the pump given this effect?

 

[ShaunCorbs]

When the internal resists exceeds the pump spec or you need more flow

 

[Chester]

When the internal resists exceeds the pump spec or you need more flow

nice one thanks, so if the 15/60 doesn't work here that means i have a badly designed heating system

 

[ShaunCorbs]

Yep / not pipedsized correctly

 

[cjg]

but electric is not eco friendly, and to run c.h. off is going to cost them a pritty penny.

 

[Chester]

Yep / not pipedsized correctly

so, the pressure is on - I'm here all night gents

 

[Chester]

but electric is not eco friendly, and to run c.h. off is going to cost them a pritty penny.

I know, depends who your supplier is i guess, 12kw gonna run some fat bills in winter. I have explained this to them considering they have gas in house, i cant wrap my head around it.

 

[cjg]

gas is miles cheaper, even when on a course about heat pumps they had to admit gas is best.

 

[Chester]

gas is miles cheaper, even when on a course about heat pumps they had to admit gas is best.

yeah gas is like 4 times cheaper or something on average