Anyone reccomend an instant inline water heater?

[Bob Hill]

Hello,

So the situation is as follows,

The building has a pumped hot water circulating loop.
The system is vented.

At the very end of the loop where the pipe work turns round to go back the way it came it tees off into 15mm and goes to a hand basin tap in a shower room. The length of this leg of pipework is probably about 10-15m. The upshot of all this is that it takes ages for the hot tap to actually get hot (17 minutes to get to the requiered 50 degree C).

It has been suggested that we could fit an inline water heater to the HOT side in order to bridge the gap between when the tap is turned on and the hot water from the boiler eventually arrives. In effect to heat all the cold draw off from the leg of pipework back to the circulating loop. We would be using the heater as a booster so to speak.

Has anyone ever used an inline heater in this way?
Does anyone know of anything designed to work like this?
I've seen that the Zip instant heaters say that they can handle up to 70 degrees incoming water temp so maybe they are designed to work like this.

Any helpful thoughts or alternate ideas welcomed.

Ta

 

[Ray Stafford]

If its only a handbasin tap, why not disconnect it from the system altogether, and supply it from a 10 or 15 litre unvented unit?

Or fit a Strom instant hot water tap.

 

[ShaunCorbs]

why not remove and refit the secondary return closer to the basin

 

[snowhead]

There is no way it should take 17 minutes to draw off 15mtrs of water down a 15mm pipe.
Is it more than 50 at the point the return joins back to the flow?

What type of tap is it supplying?

Does it have a thermostatic mixer on it, does it have mains cold to it and if so it's probably crossing over and cooling the Hot down.
Are there any TMV's elsewhere in the building?

You need someone with experience of DHW with Secondary return systems to look at it.

 

[Sparkgap]

Why fit a water heater? Why not extend the circulation? One option for long dead legs is to trace heat it if you can't.

 

[stevetheplumber]

extend the loop as its just the one tap it could be run in microbore

 

[Bob Hill]

Thanks for the feedback.

Sounds like some sort of pipe re routing is the best option.

On further investigation it seems like there is a length of at least 28mm pipe which the 15mm runs off before it gets back to the loop. This would explain why it takes so long to get hot.

The tap is just a standard 1/4 turn one. There is a TMV before it but I was taking temperature measurements off the pipe before the TMV.

Thanks for your help I'll have to work out the best option for rerunning the pipe.

 

[snowhead]

This would explain why it takes so long to get hot.

No it doesn't, it wouldn't take 17minutes to run off all the water in a 15mtr length of 28mm.

The tap is just a standard 1/4 turn one. There is a TMV before it but I was taking temperature measurements off the pipe before the TMV.

If its tank fed Hot as you say and the Cold is mains then it's crossing over Cold into Hot at the TMV.

If it's tank fed cold it wont cross, the pressure is the same both sides so it can't cross over.

Confirm if it's mains cold into the TMV, then I'll tell you an easy way to check for cross over.

 

[Bob Hill]

It's tank fed cold but i'm interested to know the easy way to check for crossover for future reference.

I've traced the pipe all the way back to the loop and it is cold when the tap hasn't been running and it gets hotter as the tap runs so it seems like the hot water just isn't in that part of the loop. Got a chap coming in tommorrow to advise to I'll let you know what he says.

 

[snowhead]

The system should have balancing valves on the returns on the branches off the main run.

These need closing down on the branches closer to the source to give better flow at the more remote branches.

 

[Bob Hill]

The chap came in today and we came to the conclusion that there was a massive air build up in the return side of the loop as the air vents had failed. This meant that this particular part of the circulation loop simply wasnt circulating so the water near the tee that goes to the tap was only hot via one pipe circulation so to speak. Plannng to install air vents to resolve the issue as we managed to clear some of the air today and that improved things.

Thanks for all the adivce, Ive learnt a good bit by working though this problem.

 

[ShaunCorbs]

The chap came in today and we came to the conclusion that there was a massive air build up in the return side of the loop as the air vents had failed. This meant that this particular part of the circulation loop simply wasnt circulating so the water near the tee that goes to the tap was only hot via one pipe circulation so to speak. Plannng to install air vents to resolve the issue as we managed to clear some of the air today and that improved things.

Thanks for all the adivce, Ive learnt a good bit by working though this problem.

tbh there shouldnt be air getting into the system and i would check pump