Indirect unvented and secondary return pump

[Beverly27]

We've just had a boiler and unvented indirect cylinder fitted and the time lag before we get hot water in the loft (the cylinder and boiler are on the ground floor) is sometimes over 1 minute. A secondary return pump has been mentioned to speed things up. Our knowledge is purely theoretical and minimal, so we wanted to ask a couple of questions to those of you here who have much greater experience and understanding. Is there a way that such a pump can be fitted so it's activated by turning on the hot water, so we don't have to worry about timers and wasting energy and money? If not what's the best way to set up? What brands and models of pumps would you recommend? Thanks!

 

[ianmcd]

I have fitted a few that the customer didnt want the pump always running so fitted PIR sensors say in the hallway next to the bathroom or what ever, that trigger the secondary pump when someone approaches that room and goes off again when they leave that space

 

[JohnD]

good idea. Should save energy and heat wastage as well as water. I suppose there's a way of estimating time per length.

I formerly had a Grunfoss bronze for that, it was incredibly expensive.

 

[Beverly27]

I have fitted a few that the customer didnt want the pump always running so fitted PIR sensors say in the hallway next to the bathroom or what ever, that trigger the secondary pump when someone approaches that room and goes off again when they leave that space

Thanks, that's helpful to know. Is there a brand of pump you'd recommend please?

 

[ianmcd]

Thanks, that's helpful to know. Is there a brand of pump you'd recommend please?

I like Grundfoss, but that is strictly a personal choice, there are lots on the market, a secondary pump has to be Bronze as opposed to a CH circulator which will be cast iron, they are a lot more expensive, but offer a great service compared to not having a secondary circuit

 

[Beverly27]

I like Grundfoss, but that is strictly a personal choice, there are lots on the market, a secondary pump has to be Bronze as opposed to a CH circulator which will be cast iron, they are a lot more expensive, but offer a great service compared to not having a secondary circuit

Thanks, that's good to know. Could I trouble you with one more question please? How do I work out which size pump we need?

 

[oldbuffer]

1. They are often fitted on a timer so that they don't run at night, but I do like the PIR idea and think its much better.
2. All the pipework, new and existing, must be insulated.
3. Don't forget that you can't run the pipework in plastic, and that includes any existing pipework which will form part of the circuit. Plastic is not certified for the temperature domestic hot water can reach.

 

[ianmcd]

a standard domestic one would do your requirements

 

[Dan Robinson]

Not entirely sure how Martin and Des are going to get a 15mm copper pipe back down the house now.

Remember it needs to run from the top of house into the top of the cylinder and connect into the safety group:

Controlling it is easy enough, my personal preference is the Grundfos Comfort UP 20-14 BXT, but it's not the cheapest.

 

[Beverly27]

Not entirely sure how Martin and Des are going to get a 15mm copper pipe back down the house now.

Remember it needs to run from the top of house into the top of the cylinder and connect into the safety group:

View attachment 161524

Controlling it is easy enough, my personal preference is the Grundfos Comfort UP 20-14 BXT, but it's not the cheapest.

Thanks Dan. Martin and Des (and yourself of course) have been excellent so far in figuring out solutions, so hopefully they can figure one out! A few questions - Would we need you to install as you're gas registered and I'm not sure Des is? We'd found a Grundfos Comfort pump which is a wee bit cheaper than the one you've recommended, the Grundfos Comfort 15-14 BAPM GB Hot Water Re-Circulation Brass Pump With AutoAdapt. Would there be any benefit of choosing one over the other? Would you suggest running the additional pipework to any of the other hot taps in the house too? How would you suggest we control the pump best? Thanks! V&B

 

[Dan Robinson]

The model I referred to has an integrated thermostat and learns when you use your water. It will be more efficient but whether it justifies the extra cost of the unit its hard to say.

Des should be able to do it as you don't need to be gas registered, and it can be wired into the nearby heating spur.

The route up to the top of the house ( except the kitchen ) will mean that the family bathroom will benefit anyway.

 

[Beverly27]

The model I referred to has an integrated thermostat and learns when you use your water. It will be more efficient but whether it justifies the extra cost of the unit its hard to say.

Des should be able to do it as you don't need to be gas registered, and it can be wired into the nearby heating spur.

The route up to the top of the house ( except the kitchen ) will mean that the family bathroom will benefit anyway.

Wonderful, thanks Dan.

 

[Beverly27]

I have fitted a few that the customer didnt want the pump always running so fitted PIR sensors say in the hallway next to the bathroom or what ever, that trigger the secondary pump when someone approaches that room and goes off again when they leave that space

Our electrician has suggested that if we have more than 1 PIR sensor wired to the pump that this may be an issue. This, he informed us, is because when the 1st PIR is triggered it activates the pump, but if a 2nd PIR is then triggered shortly after the 1st, for example if people enter both bathrooms at around the same time, then the 2nd PIR activation will then switch off the pump. How did you overcome this?

 

[ianmcd]

just use a relay with a timer they are not expensive, low voltage from the PIR will switch the 240V supply on from the relay to the pump, I would be using a different electrician if he cant work that out, @Dan Robinson loves these things , I have tagged him for you he has a lot of experience doing this

 

[Dan Robinson]

I installed the cylinder