What size boiler needed

[sherylryan]

Can't show calcs just now but 60C does tally with manifold flow and temps, try and measure that 76.5C boiler temp as far away on the pipe as you can but before any T off to anywhere, the only way that it's a tue temperature is if the boiler is cycling rapidly but with the off time way longer than the on time, the temp will then certainly reach very high temps especially if no pump overrun installed. The boiler circ rate at 4.1kw manifold requirement will mean/should result in a lot of cycling especially with a boiler flow rate of less than 5LPM.

Ok, I’ll move the thermostat to the flow pipe before it tees of into the valves for UFH manifolds. Thank you.

 

[sherylryan]

Can't show calcs just now but 60C does tally with manifold flow and temps, try and measure that 76.5C boiler temp as far away on the pipe as you can but before any T off to anywhere, the only way that it's a tue temperature is if the boiler is cycling rapidly but with the off time way longer than the on time, the temp will then certainly reach very high temps especially if no pump overrun installed. The boiler circ rate at 4.1kw manifold requirement will mean/should result in a lot of cycling especially with a boiler flow rate of less than 5LPM.

So I ran the boiler and watch, flow directly out the back of the boiler 75 degrees on 2 different thermometers, temperature before 2 way valve for UFH manifold was 60 degrees.

This could possible explain the short cycling and the boiler re firing again when the flow water is still reading 66 degrees at the boiler.

I also ran the same experiment with the Kitchen manifold, flow temperature directly out of the boiler 54 degrees, flow temperature before 2 way valve for ufh manifold was 54 degrees. Never reached boiler setpoint.

 

[John.g]

Boiler not cutting out on kitchen manifold probably because heat demand greater than boiler output?

When boiler cycles on laundry manifold the circ pump should continue to run continuously even when the burner cuts out and should only stop when room stat shuts the boiler down, check this out, also monitor boiler temp while burner off and note the temperature that it cuts in at again, should normally be a 10 deg hysteresis before cut in, my 20kw Firebird has 10/12 deg.

 

[John.g]

Also check boiler return temp when burner cuts back in but I think you have posted trends on this previously?

 

[sherylryan]

Boiler not cutting out on kitchen manifold probably because heat demand greater than boiler output?

When boiler cycles on laundry manifold the circ pump should continue to run continuously even when the burner cuts out and should only stop when room stat shuts the boiler down, check this out, also monitor boiler temp while burner off and note the temperature that it cuts in at again, should normally be a 10 deg hysteresis before cut in, my 20kw Firebird has 10/12 deg.

Yes circ pump continues when boiler cuts out and stops when room starts reaches temperature.

When the boiler is off the temp on return rises and flow drops and boiler cuts in again when flow temp is 66/67 degrees. Return temp is 57 degrees.

 

[sherylryan]

Yes circ pump continues when boiler cuts out and stops when room starts reaches temperature.

When the boiler is off the temp on return rises and flow drops and boiler cuts in again when flow temp is 66/67 degrees. Return temp is 57 degrees.

Today we found this damage on the top baffle mount inside the firebox.

 

[John.g]

Definitely not low temperature corrosion!

What do Firrebird say? Ask them what they think of the nozzle selection and especially their thoughts on the 14 bar pump pressure.

Saw damage similar to this but not as bad where the circulation was wrong way round and had been for 8 years, boiler used to trip occasionally on its hi limit pstat.

 

[sherylryan]

Definitely not low temperature corrosion!

What do Firrebird say? Ask them what they think of the nozzle selection and especially their thoughts on the 14 bar pump pressure.

Saw damage similar to this but not as bad where the circulation was wrong way round and had been for 8 years, boiler used to trip occasionally on its hi limit pstat.

I’m trying to get some answers out of firebird now to see what they have to say. Will let you know

 

[ShaunCorbs]

I would say overfired

 

[sherylryan]

I’m trying to get some answers out of firebird now to see what they have to say. Will let you know

Can’t get any answers 🤷🏼‍♀️

 

[exedon2]

I'm not surprised your having difficulty getting answers from firebird.
In general I've found them to be evasive often useless.
Plus the minute boiler out of warranty they totally refuse to even talk to you.
Plus unfortunately you have a installer who to put it politely ain't up to speed.

 

[sherylryan]

H

Definitely not low temperature corrosion!

What do Firrebird say? Ask them what they think of the nozzle selection and especially their thoughts on the 14 bar pump pressure.

Saw damage similar to this but not as bad where the circulation was wrong way round and had been for 8 years, boiler used to trip occasionally on its hi limit pstat

Have tried to get some answers from Firebird but no one is interested to answer questions.