Firebird condensing Boiler issues help needed

[sherylryan]

Hi there

Well after my last posts, we have a new ufh manifold and return temp is good. But we still have an issues with the water being blown out the condensate trap when the boiler starts up and melting the condensate pipe. We have a .65 80s nozzle, pump pressure 12 bar, air set to 5, co2 12.4, flue temp of 135 degrees, excess air 43%. can someone please tell me why this keeps happening. the boiler is set to 35KW. how do we get the flu temp down? thank you

 

[ShaunCorbs]

Is it a plastic trap or metal one ?

As they have upgraded to a metal / stainless trap because of this issue

 

[sherylryan]

Is it a plastic trap or metal one ?

As they have upgraded to a metal / stainless trap because of this issue

It’s the metal trap. It’s almost like there’s to much pressure and bit enough air. Could there be a blockage or restriction somewhere?

 

[ShaunCorbs]

It’s the metal trap. It’s almost like there’s to much pressure and bit enough air. Could there be a blockage or restriction somewhere?

What size boiler as that would give you around 35kw ish

 

[sherylryan]

What size boiler as that would give you around 35kw ish

It’s a 35 kw boiler. I wonder it we need to use a smaller nozzle, less pressure. It operates 2 UFH manifolds 70% of the time, 15 rads & trench heating on cold cold days.

 

[ShaunCorbs]

It’s a 35 kw boiler. I wonder it we need to use a smaller nozzle, less pressure. It operates 2 UFH manifolds 70% of the time, 15 rads & trench heating on cold cold days.

Combi boiler ?

 

[sherylryan]

Combi boiler ?

no Condensing boiler. sounds like the water inside the boiler is boiling. The burner is shutting of at 65 degrees but flow water continues to climb to 75

 

[oz-plumber]

Have you got a hydraulic separator ( low loss header ) installed on the system.
What is the heat load of the UFH or M2 of underfloor heating?

If you've got 15 radiators + trench heating on a 35 Kw boiler the UFH may be under the lowest turn down ratio the boiler can operate at. Particularly if the UFH is being mixed from 75C down to 45C.

There is also a condensate drain baffle ( in the instructions ) that I assume would have to be in place to stop the situation that you are experiencing. Check if it is in place.

We may need pics of the installation and piping setup to give you any further information.

 

[sherylryan]

Have you got a hydraulic separator ( low loss header ) installed on the system.
What is the heat load of the UFH or M2 of underfloor heating?

If you've got 15 radiators + trench heating on a 35 Kw boiler the UFH may be under the lowest turn down ratio the boiler can operate at. Particularly if the UFH is being mixed from 75C down to 45C.

There is also a condensate drain baffle ( in the instructions ) that I assume would have to be in place to stop the situation that you are experiencing. Check if it is in place.

We may need pics of the installation and piping setup to give you any further information.

No low loss header installed on the system. Condensate drain baffle is in place. The boiler is turned down to 60 degrees flow, return when on UFH manifolds is 48/49 return.

The heat load on one manifold is 13 kw the other is 9kw.

 

[ShaunCorbs]

Long flue run and you maybe able to get the burner down rated to 26kw depending on the model

 

[sherylryan]

Long flue run and you maybe able to get the burner down rated to 26kw depending on the model

We have the standard horizontal flue suggested from firebird on the condensing boiler. The burner can be downrated to 26kw but on a cold day would that have enough output to heat both UFH manifolds, trench heating & rads.? The other option is to possibly open 1 rad zone permanent?

 

[oz-plumber]

Are you running the UFH @ 60C?
I've never run it over 50C maximum.

I'm not sure how that flow temp ( 50C ) will have an effect on the output of your heating panels & trench heating, but if they were sized for 75C flow, it would reduce their heat output considerably.

Do you have a mixing valve setup on each manifold?
- does each manifold have a pump connected to it.

Does the boiler short cycle?
- Starts and stop regularly.

All these things can point to where the boiler is over shooting its temperature setting and causing the problems you have.

Do you have any pics to show the boiler and the boiler piping, manifold piping and radiator / trench heating setup?

Something doesn't sound right with the system you have installed.

 

[sherylryan]

Are you running the UFH @ 60C?
I've never run it over 50C maximum.

I'm not sure how that flow temp ( 50C ) will have an effect on the output of your heating panels & trench heating, but if they were sized for 75C flow, it would reduce their heat output considerably.

Do you have a mixing valve setup on each manifold?
- does each manifold have a pump connected to it.

Does the boiler short cycle?
- Starts and stop regularly.

All these things can point to where the boiler is over shooting its temperature setting and causing the problems you have.

Do you have any pics to show the boiler and the boiler piping, manifold piping and radiator / trench heating setup?

Something doesn't sound right with the system you have installed.

Hi there
The boiler is set to 60 degrees flow, but shuts off at 68 then rises to 72. Both UFH manifolds are set to 45 degrees flow, there is mixing valves on both manifolds with a bypass, each manifold has there own pumps.

The boiler when operating everything does not reach set point until the kitchen manifold shuts off. The boiler is short cycling all the time when operating both manifolds, as in 1 min on 1 min off. It also sounds like there is air building up inside the heat exchanger.

Everytime the boiler starts there is a big woosh and the condensate blows out the trap.

We are at a loss as to what is happening.

 

[oz-plumber]

It sounds to me like a flow issue.
There is not enough flow of water through the boiler.

The mixing valves on the manifolds will be drawing very little heated water from the boiler.
Technically, only trying to raise the entering water into the manifold by 10C from the return water.
The boiler will be trying to punch out water @ 60C and not having anywhere for that water to go , when only one or both of the manifolds are operating.

As for the wooshing sound, when the boiler starts, it sounds like the boiler is kettleing when the boiler fires up.
The initial flame from the burner will be too much for the boiler to take with too little flow.
You may be even boiling the condensate ( to a degree - well heating the condensate enough to get out of there quickly,
Residual heat may also try to escape through the condensate pipe also


Try setting the boiler to 45C - 50C and see if that helps.

It wont fix all your problems, but it may help in trying to work out a solution.

The boiler cycling as it is, is not good.
I'm not sure if those boilers have a setting that you can set for the boiler to come back on.

eg: Set boiler temp: 60C - Set temp for boiler to come back on: 50C
(10C differential )

I'm not familiar with those boilers, just referring back to the days when we had problems with non condensing boilers and having flow issues, initial boiler fire ups that didn't have time to reduce the gas valves to low flame before the boiler went off.

Hope this helps and keep us posted.

 

[sherylryan]

It sounds to me like a flow issue.
There is not enough flow of water through the boiler.

The mixing valves on the manifolds will be drawing very little heated water from the boiler.
Technically, only trying to raise the entering water into the manifold by 10C from the return water.
The boiler will be trying to punch out water @ 60C and not having anywhere for that water to go , when only one or both of the manifolds are operating.

As for the wooshing sound, when the boiler starts, it sounds like the boiler is kettleing when the boiler fires up.
The initial flame from the burner will be too much for the boiler to take with too little flow.
You may be even boiling the condensate ( to a degree - well heating the condensate enough to get out of there quickly,
Residual heat may also try to escape through the condensate pipe also


Try setting the boiler to 45C - 50C and see if that helps.

It wont fix all your problems, but it may help in trying to work out a solution.

The boiler cycling as it is, is not good.
I'm not sure if those boilers have a setting that you can set for the boiler to come back on.

eg: Set boiler temp: 60C - Set temp for boiler to come back on: 50C
(10C differential )

I'm not familiar with those boilers, just referring back to the days when we had problems with non condensing boilers and having flow issues, initial boiler fire ups that didn't have time to reduce the gas valves to low flame before the boiler went off.

Hope this helps and keep us posted.

Hey there

Thank you vey much for your reply. The boiler is set to the lowest it can go down to 60C. The differential set boiler point between on and off is +- 4C. We have a high flue temp of 134C, the trap is blowing and when doing the analyser setup we have high pressure . Just a nightmare. Maybe a buffer tank is the option.

 

[oz-plumber]

Try to increase the differential to 10C - 15C and see if this helps. If you can.
Looked through specs for boiler online and all very limited.
Can't even find boiler modulation specs.
Your boiler is acting like an old On / Off boiler with no modulation.

Best contact NZ Agent or contact manufacturers directly for their assistance.
The boiler should be operating much better than yours is currently operating for you.

 

[ShaunCorbs]

Try to increase the differential to 10C - 15C and see if this helps. If you can.
Looked through specs for boiler online and all very limited.
Can't even find boiler modulation specs.
Your boiler is acting like an old On / Off boiler with no modulation.

Best contact NZ Agent or contact manufacturers directly for their assistance.
The boiler should be operating much better than yours is currently operating for you.

It’s an oil boiler so no modulation on or off

 

[oz-plumber]

Ok. - never dealt with oil boilers. - you may have already figured.

On off boiler with 4C differential?

Problems occur when only 1 UFH zone is on.
Understandable now

 

[John.g]

IMO, the boiler should be derated to ~ 20kw, there are plenty of Firebirds, including my daughters, running 1 UFH zone with no problems whatsoever, it does cycle ON about every minute or so and OFF for 2 to 3 minutes minutes or well more as the boiler HEX temperature rises to 75C/80C even with the circ pump still running. This boiler has a stat hysteresis of 8/10C.
Oil boilers do have some buffering as the HEX contents are 20 to 25L, it requires 0.291kwh to raise 25L by 10C so the minimum on cycle time with a 20kw boiler should be around 0.291/20*60, 0.873 minutes, the off time will be far greater because the HEX temperature must now fall from ~ 80C to 45C before the burner refires.