How to reduce flow rate?

[danbr]

Hi,

Just looking for abit of info please.

I have an outdoor combi boiler and the plumber when he installed the system used 22mm pipe to hot and cold water.

The boiler has an issue with supplying hot water when in demand for more than 5 minutes. After 5 minutes the temperature begins to drop.

Is there a restrictor i could put on the 22mm inlet pipe that would restrict the flow to less than 15l per minute?

 

[Dan Robinson]

//www.diynot.com/diy/threads/flow-reducer-restrictor.437093/


Nothing like looking to see if an answer has already been given - this week -

 

[muggles]

Welcome to the joys of oil combi ownership...

The boiler might well have a built in restrictor that you can adjust (Grants do) but failing that buy yourself a Calflow

 

[DeletedUser]

Turn your tap down.

 

[danbr]

Thank you, sorry i should have searched.

Its a mixer shower and just turning the pressure down doesn't seem to solve the issue. I have changed the heat plate exchanger on the boiler and replaced the little plastic flow regulator on the inlet.

I have a grant vortex outdoor combi 26. Should have been 15mm pipe installed to hot water.

Most of the pipework to the taps/shower etc is 22mm with 15 mm tails. Would it be best for me to chop into the 22mm cold pipe from the stop cock and put a 22mm wondervalve on at this point restricted to 15l pm ? Or to place a wondervalve on the shower tail?

 

[Agile]

The only difference the 22 mm should make is to take longer for the hot water to get to the tap.

I will help too if you turn the tap on at half flow for the first 25 seconds or until it starts to warm up.

Lagging the hot water pipes will also help.

You seem to be saying the water cools down after 5 minutes. That would imply a possible boiler fault. But what happens next after it gets cooler?

Tony

 

[danbr]

The only difference the 22 mm should make is to take longer for the hot water to get to the tap.

I will help too if you turn the tap on at half flow for the first 25 seconds or until it starts to warm up.

Lagging the hot water pipes will also help.

You seem to be saying the water cools down after 5 minutes. That would imply a possible boiler fault. But what happens next after it gets cooler?

Tony

All the pipes are lagged, it's a new build. It's like the oil combi boiler can't keep up with the demand. I think it's because the flow rate through the heat exchanger needs to be below 15l per minute to keep the hot water store heated. Would that be right?

 

[Agile]

If its a storage combi it will give a higher flow rate to the taps for a few minutes and then reduce to the capability of the boiler.

That's about 11 li/min raised 35° if its 30 kW power.

Tony

 

[Razor900]

He could always try crushing the pipe in a vice eh Tony?

 

[easyflow]

Adjust the flow rate from the stop cock.