My New Hot Water Pump (Evosta 3) is over pumping

[PaulInEssex]

Hi, I'm a DIY plumber and new to the forum, and would appreciate some advice.

I have an oil fired boiler heating a smallish house. I just took out my old (20 years) copper hot water cylinder and replaced it with a new stainless steel Indirect Unvented cylinder.

The old system had a pump on the central heating (still there) but no pump on the hot water circuit, and it flowed pretty well via I assume the principles of hot water rising. It is a very short distance from boiler straight up to the cylinder.

With the new cylinder however it just would not flow, so I had to fit a pump, namely the Evosta 3. I'm sure it is a great pump, but it seems just over the top for the job, to the extent that even on the lowest pump setting it is pushing water into the vent.

Is there a known fix for this, eg do I have to add another pressure tank, or is there another setting on the pump to reduce the head (and hopefully make it quieter). Any ideas welcomed. Many Thanks.

 

[ShaunCorbs]

Any pictures of the install ?

 

[exedon2]

Pictures and a diagram of pipework would be useful.
You need to be G3 registered to fit unvented cylinders !
And pumping what is basically a gravity circuit is a big no as well.

 

[PaulInEssex]

Any pictures of the install ?

Hi, I'm not sure they would help.....the pump is on the return pipe, 1m above the top of boiler and 1m beneath the bottom of cylinder on the floor above

 

[exedon2]

Needs properly converting to fully pumped ie S plan

 

[ShaunCorbs]

Hi, I'm not sure they would help.***.the pump is on the return pipe, 1m above the top of boiler and 1m beneath the bottom of cylinder on the floor above

Can we have some please

 

[PaulInEssex]

Can we have some please

Hi, Pictures attached.

In answer to an earlier well made point, I am guided in all of this by a professional plumber. The current plan is to add an expansion vessel, but I/we would welcome other thoughts, and if anyone knows why a gravity fed system that worked fine for years now won't flow with the new cylinder, that would be interesting too! Cheers.

 

[ShaunCorbs]

Because your feed and vent placement is wrong it’s set up for a gravity hot water system (teed into the cylinder return and vent off the flow)

 

[EvilDrPorkChop]

You've basically put the cylinder on the gravity circs, I really hope you've installed the two port valve as per the manufactures instructions. It would never work on gravity as it isn't designed to, they are for fully pumped systems only.

As other's have said the system needs converting to an S plan system, with motorised valves for heating and hot water, the Feed and Vent correcting.

 

[John.g]

Hi, I'm a DIY plumber and new to the forum, and would appreciate some advice.

I have an oil fired boiler heating a smallish house. I just took out my old (20 years) copper hot water cylinder and replaced it with a new stainless steel Indirect Unvented cylinder.

The old system had a pump on the central heating (still there) but no pump on the hot water circuit, and it flowed pretty well via I assume the principles of hot water rising. It is a very short distance from boiler straight up to the cylinder.

With the new cylinder however it just would not flow, so I had to fit a pump, namely the Evosta 3. I'm sure it is a great pump, but it seems just over the top for the job, to the extent that even on the lowest pump setting it is pushing water into the vent.

Is there a known fix for this, eg do I have to add another pressure tank, or is there another setting on the pump to reduce the head (and hopefully make it quieter). Any ideas welcomed. Many Thanks.

What starts/stops the Evosta, Paul?
That pump should also display the Head (M), the Flowrate (M3/hr) and the power ((W), what are they?, Night give some clue as to reason for pump over apart from the other stated reasons.
One reason for your new cylinder not performing on gravity may be that it has a corrugated coil.

 

[SJB060685]

As mentioned above the position of the cold feed and vent is on the old gravity circuit. No matter where the additional pump is situated on the HW flow or return you will get pumping over.
You need to remove the pump, convert the system to an S plan and either repipe feed and vent or seal the system.

 

[PaulInEssex]

What starts/stops the Evosta, Paul?
That pump should also display the Head (M), the Flowrate (M3/hr) and the power ((W), what are they?, Night give some clue as to reason for pump over apart from the other stated reasons.
One reason for your new cylinder not performing on gravity may be that it has a corrugated coil.

Hi John,
The pump is controlled by the cylinder thermostat, currently set at 55. The pump is set at the lowest rate I could find......6W, 1.1m head and 0.5m3/hr, sometimes showing a little higher.

My thanks to everyone for the generous and clear advice. I'm sure S plan would be the best solution....given where I am would another be to remove the current open vent tank and add an expansion vessel to the hot water loop?

 

[ShaunCorbs]

You have to go s plan for a unvented there’s no ifs or butts

But the plumber doing the unvented should know this so suspect diy

Thread closed due to you need to be qualified to install an unvented else it’s a bomb and your home insurance is invalid