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Discuss Use shower pump for whole house in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

R

Ric2013

Plumber
The problem with closed head running is temperature rise so a inbuilt PRV would just recirculate the water which would get hotter and hotter, if the pump has brass impellers as well and if the pump seals are high temperature design and if the pump has dry running protection then maybe that's their answer as a 2 bar pump will have to reach 135C before the water starts vaporising.
Why would the water get hotter and hotter?
 
J

John.g

Because all or most of the pump power required at that closed head is converted into heat as the pump efficiency is very low, probably only a few %, if it were (impossibly) still 100% then there would be no heat rise. The efficiencies of very large industrial pumps is often checked/monitored by actually measuring this temperature rise during normal operation.
 
R

Ric2013

Plumber
Because all or most of the pump power required at that closed head is converted into heat as the pump efficiency is very low, probably only a few %, if it were (impossibly) still 100% then there would be no heat rise. The efficiencies of very large industrial pumps is often checked/monitored by actually measuring this temperature rise during normal operation.
Yes. The friction and motion will degrade to heat. Surely the solution would be to run the water through a loop of pipe (or uninsulated section of the pump body) such that as the heat rises the heat losses would eventually equal the heat gain and no further increase in temperature would result? Which is presumably something the pump manufacturers have achieved if they say their pumps can be run against a closed head?
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Physics. Is it Boyles law?
No, that's to do with the pressure and volume of a gas. And, yes I did look that up.
 
J

John.g

It would be interesting to run one of these pumps with say the hot side pumping only and then just feel the cold pump and also along the pipe as the pipe is open for some of its length at least and will absorb and dissipate heat along here.
 
J

John.g

Maybe we should stick to Boils law!

P1V1/T1 = P2V2/T2 is a combination of Boyle's & Charle's law but don't think this much help in choosing a whole house pump, personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.
 
rpm

rpm

Esteemed
Plumber
Why would the water get hotter and hotter?
The water having nowhere to go and the increased pressure raises the temperature is the short answer. There would be a world of difference in the design of a shower pump compared to the design of a whole house pump. A quick look at the sizes and prices tells a story.
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personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.
Thermal cuts outs, are they fitted to expensive versions?
 
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J

John.g

Perhaps with an inbuilt PRV?
Salamander seem to employ a form of PRV alright, in the form of a by pass tube.

"" The technology behind Salamander’s shower pumps
Pumps, explains the technology inside the products that helps to make them powerful, quiet and compact…

Crossover technology

Salamander’s crossover technology allows its pumps to boost both hot and cold water at the same time, or independently of each other. In situations where a thermostatic shower is running, both hot and cold water will be supplied to the shower. However, as the pump only has one common driveshaft, if only a hot or cold tap is used, both sets of impellers would be turning but only one side of the pump would be supplying water, meaning one side of the pump would be running ‘closed head’. This causes an increase in temperature and pressure in that side of the pump, leading to severe damage.

However, most Salamander pumps have an innovatively placed bypass tube found in bathroom, universal and whole house variants, which allows the excess pressure to be relieved into the open side of the pump, which also brings fresh water into the closed head chamber, stopping the pump from overheating ""
 
SimonG

SimonG

Plumber
Maybe we should stick to Boils law!

P1V1/T1 = P2V2/T2 is a combination of Boyle's & Charle's law but don't think this much help in choosing a whole house pump, personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.
The seals will go on the non used/less used side. Seen it a handful of times.
 
J

John.g

I'd like to see how that Salamander crossover tube technology works.
Stuart Turner give a 5 year warranty on their Monsoon which isn't bad even when used for whole house use bearing in mind all the above, wonder if they use anything to prevent seal failure etc for closed head conditions.
 
rpm

rpm

Esteemed
Plumber
Salamander seem to employ a form of PRV alright, in the form of a by pass tube.

"" The technology behind Salamander’s shower pumps
Pumps, explains the technology inside the products that helps to make them powerful, quiet and compact…

Crossover technology

Salamander’s crossover technology allows its pumps to boost both hot and cold water at the same time, or independently of each other. In situations where a thermostatic shower is running, both hot and cold water will be supplied to the shower. However, as the pump only has one common driveshaft, if only a hot or cold tap is used, both sets of impellers would be turning but only one side of the pump would be supplying water, meaning one side of the pump would be running ‘closed head’. This causes an increase in temperature and pressure in that side of the pump, leading to severe damage.

However, most Salamander pumps have an innovatively placed bypass tube found in bathroom, universal and whole house variants, which allows the excess pressure to be relieved into the open side of the pump, which also brings fresh water into the closed head chamber, stopping the pump from overheating ""
Could you add a link to where you found this John. It makes interesting reading and like you I would like more intel on this cross over tube.
TIA
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The seals will go on the non used/less used side. Seen it a handful of times.
Are we talking rubber lip seals or proper mechanical seals Simon.l
 

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