Grundfos Home Boster Pump

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The check valve is to stop reverse circulation to the taps, not anti-gravity, which would be a bonus anyway.
 
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An interesting theory but I think you'll find it won't work as you expect it to. If it only operates once the tap is switched on, you will still have to draw off the same quantity of cold water before you get hot to the tap, as the amount of cold water in the pipe between the cylinder and your tap will not change. It would reduce the time required for the hot water to reach the tap by increasing the flow rate, but it would do this whether you installed the secondary loop or not, making the loop redundant. In fact the loop may hinder you as some water would be forced back to the cylinder rather than out of your tap, and you would also end up with a loop of warm water that then goes cold, thereby wasting energy heating water you're not going to use.


So, in short, it depends what you're trying to achieve. If you're trying to save water you need a properly-installed secondary loop with a bronze pump. This would either run constantly or you could feasibly have it running off a timed switch that you operate by the desired outlets before you open the tap, although to my mind that's a bit of a faff.

If you're just trying to increase flow to the taps then the whole house pump would be a good option but it's not going to save you any water and the secondary return is pointless.

Hope this helps

Thank for the input Muggles. What I am trying to achieve is to reduce the time for hot water to get to the taps. You state, "you will still have to draw off the same quantity of cold water before you get hot to the tap," This I disagree with. If a tap 20 foot away is opened then the pump kicks in and it can shift 23 litres of hot water a minute around the loop. This is around 0.4 litres a second. It will be a matter of seconds before hot water is at the taps, and a saving of water and the pump only run when needed, so saving electricity. Simple installation as well. This means a permanently hot/warm loop is not required. OK there will be more of lag than having a permanently hot loop, but not that much to worry about.

These pumps are quite cheap, about £80-90 cheaper than Comfort or normal bronze pumps and are not brass bodies being cataphores coated. Why aren't the rest of them made this way to get the prices down? The flowswitch can be switched out and run as per a normal switched pump. That means it can be fitted as a normal secondary circulation pump switched by a pipe stat.

20 foot of pipe contains the same volume of water regardless of whether there's a pump on it or not, and this water will be cold. As the pump only kicks in after you've turned on the tap, this cold water will almost certainly be pushed out of your tap rather than around the loop. Therefore the quantity of cold water coming out of your tap will be roughly the same, it will just take less time as the flow rate is higher. Hence you save very little water. Any flow around the loop would just decrease the pressure gain at the taps, therefore the loop is not necessary.

However, let's consider the possibility of you being correct for a while, and that a lot of water is forced around the loop. I strongly suspect that, if this is the case, there will be sufficient velocity in the water in the loop to keep the flow switch in the 'on' position when you turn your tap off, and that the pump will therefore run continuously until you go and switch it off manually. Either way, dispensing with your idea of installing a loop and just installing the pump on your existiing system would be a more effective, faster and cheaper option.

I know your original question was about whether the pump is any good, and I will come to that shortly, but I'm pointing out these potential pitfalls to stop you wasting money on something that I don't think will actually work.

Now to the pump...Grundfos have a very good reputation in general for pumps and I would suspect that this uses the same running gear as their domestic heating circulators. It should therefore be very reliable. HOWEVER, whilst you correctly state that it is capable of shifting 23 litres per minute, if you turn your attention to the graph provided in the technical information you will note that this is at a pressure rise of just 1m head (0.1 bar) or in technical terms 'bugger all'. To achieve the maximum pressure of 8m head (0.8 bar) the flow rate must be reduced to 2.4 litres per minute, and I can **** faster than that.

Once again, hope this helps
 
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You make a very good point there Muggles, once the flow is started there's nothing to stop it.

Perhaps it could be wired into the light switch.
 
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morrismini

muggles, thanks. Your points are

1. The pumps will keep pumping.
(A cheap pipe stat will solve that)

2. To get the maximum pressure rise a low litre per minutes is achieved.
(The object is not to raise the pressure but to push wash around the loop. An open loop will give few restrictions and give high flow rather than pressure rise.)

I reiterate, the prime aim is to get a high flow through the loop when the pump switches in, other gains are low electricity usage and low energy wastage on the loop. This may mean a 22mm loop to give low resistance to the pump. It will work, as I described.
 
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I still don't see HOW a pipe stat, cheap or otherwise, will stop the pump pumping when you don't want it to.

My point is also that the loop is rather a waste of time, if you just pumped the water to the taps you'd achieve the effect of getting hot water to your taps quicker without having to faff around installing a loop then having to cure the potential problem of constant pumping. I really don't see what the loop would gain you.
 
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Grundfos make good quality pumps, so I have no doubt that it will be a very good pump.. I see the point that you make about reducing the quantity of water before the hot comes out as some will come from the tap and some will continue through the loop and back to the cylinder.... But what a palava!! I thought you liked to keep things simple... Hows about a bronze pump wired to the light switch of each bathroom that you have? Light on and pump runs.. By the time you have done your business, the water at the tap will be instant
 
M

morrismini

I still don't see HOW a pipe stat, cheap or otherwise, will stop the pump pumping when you don't want it to.

My point is also that the loop is rather a waste of time, if you just pumped the water to the taps you'd achieve the effect of getting hot water to your taps quicker without having to faff around installing a loop then having to cure the potential problem of constant pumping. I really don't see what the loop would gain you.

muggles, you are not thinking it through. A 22mm pipe loop (It will be threaded plastic) with taps teed off it. That is easy so far. A tap is turned on and the pump switches in, sending water quickly around the loop reducing the time to get DHW at a tap maybe 20 foot away. That will happen. When the loop is hot the pipe stat cuts out the pump. If the loop is hot then no need for the pump to cut in. The loop cools and the pipe stat switches in the pump. the internal flow switch keep the pump off.
 
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Aaahhh, now I see where you're coming from with the pipe stat. Still think a decent whole house pump would achieve the effect of getting hot water to the taps more quickly without the loop though, but you seem set on doing this and nobody's going to change your mind so maybe we should just end the discussion here...
 
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Aaahhh, now I see where you're coming from with the pipe stat. Still think a decent whole house pump would achieve the effect of getting hot water to the taps more quickly without the loop though, but you seem set on doing this and nobody's going to change your mind so maybe we should just end the discussion here...

Except,

If you have a pump in line it will severely restrict the flow when it's off.
 
M

morrismini

Grundfos make good quality pumps, so I have no doubt that it will be a very good pump.. I see the point that you make about reducing the quantity of water before the hot comes out as some will come from the tap and some will continue through the loop and back to the cylinder.... But what a palava!! I thought you liked to keep things simple... Hows about a bronze pump wired to the light switch of each bathroom that you have? Light on and pump runs.. By the time you have done your business, the water at the tap will be instant

The pump wired to a bathroom light is a very good idea if the bathroom has no windows. It is similar to the infra-red detector in a bathroom. When you walk in, the pump starts up so it It will start up even if you are only wanting a towel, but overall it will still use less electricity, waste less energy and and waste less water. It works on ships.

The idea is simple. One pump only £112 and one cheap pipe stat around £10. Bronze pumps, which this is, are about £200 and you still need and pipe stat and timer. Grundfos Comfort pumps are always around £200. This Home booster saves £80 installation costs, reduces electricity usage and less energy wasted.
 
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When the loop is hot the pipe stat cuts out the pump.

So this pump is on the flow and whilst someone is needing water at the taps , it is suddenly switched OFF by a pipe stat!

What happens?
Ans = Severly reduced flow through the pump impeller!
 
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Aaahhh, now I see where you're coming from with the pipe stat. Still think a decent whole house pump would achieve the effect of getting hot water to the taps more quickly without the loop though, but you seem set on doing this and nobody's going to change your mind so maybe we should just end the discussion here...

Except,

If you have a pump in line it will severely restrict the flow when it's off.

Excellent point. Still won't work minimorris...
 

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