CH Pumps - stupid questions (?)

[PumpIt]

Possible stupid newbie question coming up!

Q1. I've always wondered... WHY do Central Heating Pumps have such huge couplings on them?

I doubt many homes use pipes bigger than 22mm - but the couplings on all the pumps I've ever seen have about 40mm threads.
My guess is so you can change the pump by just shutting off valves either side and take it out without having to drain the system down - but how often is that needed! Just seems silly to me.

Q2. Do any pumps have 22mm (or even 15mm) couplings on them?

Cheers!
Mark.

 

[PlumbBobBob]

because the bore of the pump itself is that much larger to allow adequate flow

 

[happyflyer]

Look very closely at domestic heating pump and tell me how you think you could make the connections smaller
I am sure the manufactures would love any comments you could come up with to make them small and save money
you would be their hero, yes as you say, stupid question, can you think of another one.

 

[rpm]

The inlet and outlet bore sizes along with the size of the impeller within the impeller bowl and the length of the shaft are all taken into account regarding the required output when designing a pump and it`s expected life span.

 

[Ray Stafford]

95% of pumps are sold as replacements. Why would you market a pump that wouldn't fit 95% of existing valve sets?

 

[Killy Bing]

I think i would cry if i had to change a pump directly on 22mm. That five minute job has just turned into having to cut a section out when the pipes rigid...

 

[Best]

Pumps are not necessarily very reliable, especially on systems with corrosion, so they can fail at any age. Besides, even if a pump lasts 20 years, you don't want a engineer coming out on a snow covered Christmas Eve & (if he could be bothered) having to spend 3 or more hours draining & refilling your heating system just to do a 10 minute pump replacement - do you? You wouldn't want the bill either!

 

[AWheating]

why would you limit the pump to one size?

 

[jase158]

more to the point, why didn't they think to put isolators on 2 port and 3 port valves as they are more likely to fail then pumps, were designed after pumps and they should of learnt from pumps and thought "what happens if this breaks??""

 

[snowhead]

more to the point, why didn't they think to put isolators on 2 port and 3 port valves as they are more likely to fail then pumps, were designed after pumps and they should of learnt from pumps and thought "what happens if this breaks??""

They did, that's why the heads are removable without having to isolate water.

 

[AWheating]

more to the point, why didn't they think to put isolators on 2 port and 3 port valves as they are more likely to fail then pumps, were designed after pumps and they should of learnt from pumps and thought "what happens if this breaks??""

worked on a number of council/HA jobs where we put gate valves on the plan so any part could be isolated and removed without drain down. One way to cut labour costs of repairs when you have alot of houses to maintain i guess.

 

[jase158]

They did, that's why the heads are removable without having to isolate water.

but I find its usually the valve that goes, especially on the cheap models

 

[happyflyer]

more to the point, why didn't they think to put isolators on 2 port and 3 port valves as they are more likely to fail then pumps, were designed after pumps and they should of learnt from pumps and thought "what happens if this breaks??""

Come Jase, most 3 port valve won't come out unless you drain down, or do some serious damage tugging at the pipework, they will be making little flanged ones next, hey that's and idea for a daft question
why don't they make 22 mm flanged 3 port valve, easy to change when they go, BTW do they go that regularly, I didn't think they did.