What size boiler needed

[sherylryan]

If UFH is the main form of heating this can lead to very low boiler return temperatures and high condensing rates which just may lead to excess sooting if combustion settings are not spot on as per FGA. This "melting" problem was very well known here but seemed unique to the downward firing Firebird, it also be interesting to see any flue gas temperatures and also I think the temperature can be measured after the primary heat exchanger.

Yes John the UFH is the main hesting, during the day, in the evening the tench and Rads run if really cold. How can I measure the flue gas temperatures? Do you have any photos of where these temperatures can be taken please? Thanks John you are very helpful and I appreciate the time you have given to answer all my questions.

So to clarify, if boiler is changed back to 35kw it has enough capacity to heat UFH, Rads, trench & DHW if all calling for heat as these have an output of 44kw or is a 35 kw boiler to small?

 

[John.g]

You will probably have to get someone with FGA, I don't know where the sampling points are on the condensing firebird, the condensate trap float must surely be melting as well (or maybe there is no float)so this is why important to check these temperatures. I know that the flue gas temperature on my SE Firebird is ~ 230C so would expect similar if a measurement can be taken between the primary and secondary Hxs on yours, Is that baffle damage due to corrosion.

 

[John.g]

Re boiler output, seeing that you can run continuously at outputs as low as 6 to 10kw I think 35kw should be more than enough and even 26kw should do once the house is up to temperature?, your total heat loss shows 929.2 watts so only 18.5kw (blr output of 21.8kw) required at a dT of 20C?.

 

[sherylryan]

You will probably have to get someone with FGA, I don't know where the sampling points are on the condensing firebird, the condensate trap float must surely be melting as well (or maybe there is no float)so this is why important to check these temperatures. I know that the flue gas temperature on my SE Firebird is ~ 230C so would expect similar if a measurement can be taken between the primary and secondary Hxs on yours, Is that baffle damage due to corrosion.

View attachment 76600

Baffle damage is due to heat in boiler apparently, The boiler was installed in September 2019 and baffles damaged September 2021.

 

[John.g]

If that baffle was near the bottom then unlikely heat damaged, did Firebird determine this?, and wonder why no one suggested taking any temperatures.

 

[sherylryan]

If that baffle was near the bottom then unlikely heat damaged, did Firebird determine this?, and wonder why no one suggested taking any temperatures.

If that baffle was near the bottom then unlikely heat damaged, did Firebird determine this?, and wonder why no one suggested taking any temperatures.

Yes as per your above pic these baffles were at the bottom of the boiler, our firebird agent who replaced them said it was heat that caused the damage. Interesting considering boiler was only 2 years old and was turned off for the summer, so boiler only operated approx 12 months of the 2 year period. If not heat what would cause the baffles to do that?

 

[John.g]

COLD would corrode them due to the gas temperature being too low leaving the primary HX, the concern I think is that the primary Hx is mild steel and could corrode/leak. I have put those photos up in our local Boards.ie website with a few general questions, there are some very experienced Firebird people there that will soon confirm the above, or not.

 

[sherylryan]

COLD would corrode them due to the gas temperature being too low leaving the primary HX, the concern I think is that the primary Hx is mild steel and could corrode/leak. I have put those photos up in our local Boards.ie website with a few general questions, there are some very experienced Firebird people there that will soon confirm the above, or not.

Hi John thank you very much, it would be nice to know what happened.
Tonight I put a thermostat under the silver insulation ( see attached photo white arrow) and the temperature was 10 degrees higher than the flow water. Yellow arrow is pocket where firebird thermostat sits 🤷🏼‍♀️

 

[John.g]

Is the white arrow the flow temperature?
The condensate trap does not have a float and is installed correctly a Firebird Tech guy from the home of Firebird here in Co Cork told me, ensure its filled with water and/or check hose regularly to ensure water dripping constantly. Also ensure return temp doesn't fall below 45C, you might measure this (except the white arrow is the return?)

 

[sherylryan]

Is the white arrow the flow temperature?
The condensate trap does not have a float and is installed correctly a Firebird Tech guy from the home of Firebird here in Co Cork told me, ensure its filled with water and/or check hose regularly to ensure water dripping constantly. Also ensure return temp doesn't fall below 45C, you might measure this (except the white arrow is the return?)

Is the white arrow the flow temperature?
The condensate trap does not have a float and is installed correctly a Firebird Tech guy from the home of Firebird here in Co Cork told me, ensure its filled with water and/or check hose regularly to ensure water dripping constantly. Also ensure return temp doesn't fall below 45C, you might measure this (except the white arrow is the return?)

Yes the white arrow is on the flow side. Both arrows are on the flow side. Condensate trap does have water in it. I’m not sure how to get the return temp above 45 as the return flow is the same temp as manifold around 35.

Maybe the boiler needs to be turned up as it is set to 60 degrees, now I’m really confused 🙂)

Does the manifolds need a bypass on it to send the flow water back to the boiler that is not being mixed with the return, or should there be a bypass between flow and return after the pump.

 

[John.g]

Turning up the boiler stat/flow temp is no good as the manifold TMV will still hold its setpoint, you can turn up the manifold(s) TMV setpoint by 5C (as long as no damage to your flooring), if you get a return of 38/40C then IMO should be OK and I know of of a few condensing boilers that are running this way for years with no major problems.
If you really want control of the boiler return temp then a bypass of some sort between the flow and return is required (or maybe a low loss header). Don't know if its a regular method but I think a two port TMV (between the flow & return) with a capillary sensor on the return set to 45c or whatever should do the job with the minimum of trouble.

 

[sherylryan]

Turning up the boiler stat/flow temp is no good as the manifold TMV will still hold its setpoint, you can turn up the manifold(s) TMV setpoint by 5C (as long as no damage to your flooring), if you get a return of 38/40C then IMO should be OK and I know of of a few condensing boilers that are running this way for years with no major problems.
If you really want control of the boiler return temp then a bypass of some sort between the flow and return is required (or maybe a low loss header). Don't know if its a regular method but I think a two port TMV (between the flow & return) with a capillary sensor on the return set to 45c or whatever should do the job with the minimum of trouble.

I’ll try for a start to turn the TMV up by 5 degrees to see what that does. We did have a bypass on the side of the boiler that actually came off the flow and feed back into the boiler, but the plumber removed it,

 

[John.g]

Have you got any Flue Gas Analysis (FGA) printouts?

Some good feed back from Boards.ie

"usually with these boilers when you come across the top 2 baffles damaged in this way over airing plays a big part most likely boiler wasn't commissioned after install."
if they are the bottom two the state of the condensate hose would suggest a blockage from the bottom of the boiler.
Blocked trap or poor flow from the condensate pipe could also cause excess heat
where is that pipe discharging and does it have a fall from the outside of the boiler case
I have often come across the pipe rising sharply outside the case
Can your pour water into the flu and see does the water discharge through the turbulator holes"

"Drain baffle made of stainless steel and positioned as shown. Seems to be there to stop crud getting into and blocking condensate outlet. Some times the trap isn't screwed properly to the boiler outlet or sealing washer missing or misaligned. Then the condensate trap doesn't fill properly and allows hot gasses to flow through to damage the plastic pipe."

Re baffle damage caused by overheat or cold end corrosion (sulphuric acid attack)
"Hard to say really without seeing, the scaling on the baffles is more common that you might think"

Re Flue gas temperature.
"Depends on what boiler re the temp
enviromax temp up to 90 at flue
silverpac up to 130 at flue"

"Regular servicing and baffle rotation will also help this boiler looks like it has never been open before"

 

[sherylryan]

Have you got any Flue Gas Analysis (FGA) printouts?

Some good feed back from Boards.ie

"usually with these boilers when you come across the top 2 baffles damaged in this way over airing plays a big part most likely boiler wasn't commissioned after install."
if they are the bottom two the state of the condensate hose would suggest a blockage from the bottom of the boiler.
Blocked trap or poor flow from the condensate pipe could also cause excess heat
where is that pipe discharging and does it have a fall from the outside of the boiler case
I have often come across the pipe rising sharply outside the case
Can your pour water into the flu and see does the water discharge through the turbulator holes"

"Drain baffle made of stainless steel and positioned as shown. Seems to be there to stop crud getting into and blocking condensate outlet. Some times the trap isn't screwed properly to the boiler outlet or sealing washer missing or misaligned. Then the condensate trap doesn't fill properly and allows hot gasses to flow through to damage the plastic pipe."

Re baffle damage caused by overheat or cold end corrosion (sulphuric acid attack)
"Hard to say really without seeing, the scaling on the baffles is more common that you might think"

Re Flue gas temperature.
"Depends on what boiler re the temp
enviromax temp up to 90 at flue
silverpac up to 130 at flue"

"Regular servicing and baffle rotation will also help this boiler looks like it has never been open before"

Thanks john, that’s a lot of information. I will find the I initial printout on install of commission.

Interesting that they mention the fall from boiler, because I have mentioned to the plumber when he installed it the condensate trap pipe rises outside of the casing. I pointed out to him that in the instruction manual it clearly say is must fall 1:40 minimum.
They blamed the baffle damage on our flow and return pipes saying they are undersized. I will go find printouts and get back to you.

 

[sherylryan]

This is the only information I have on commissioning Re the flue gases, very hard to read printout, although can see flu says 97.8 c.

I have attached an image of the condensate pipe, you can clearly see how much it runs uphill.

 

[John.g]

Is the condensate pipe rising up vertically after it joins that "T" or what?? Is it flowing left to right or right to left?
What model of Firebird?.

 

[sherylryan]

Is the condensate pipe rising up vertically after it joins that "T" or what??

No runs outside, the PRV overflow pipe also runs into it

 

[John.g]

When it goes outside (to the left) does it then fall downwards?.

(What is Boiler Model)

 

[sherylryan]

When it goes outside (to the left) does it then fall downwards?.

(What is Boiler Model)

Certainly no fall, it runs uphill through that brick wall.

Boiler model is a environmax C35 condensing boiler, run by a Riello 2.2, 21-41.5kw burner with a .55 80s nozzle giving out 26kw. ( This burner was changed October 2021 from below)

Orginal burner on install was a Riello 2.2R 33-54Kw with a .65 80 S nozzle giving out 35kw

Just found the below photos, Air setting was clearly changed when new burner install. Also blast tube, and damages baffles and door panel.

 

[John.g]

To be clear, it flows from right to left as I indicated? and then runs uphill? but where (at what height relative to the condensate outlet) does it finally level out as it could just mean that the condensate is being evaporated in the boiler and causing untold damage.

The oil pressure at 14bar seems very excessive if burning Kerosene?., should be ~ 9bar.

 

[sherylryan]

To be clear, it flows from right to left as I indicated? and then runs uphill? but where (at what height relative to the condensate outlet) does it finally level out as it could just mean that the condensate is being evaporated in the boiler and causing untold damage.

The oil pressure at 14bar seems very excessive if burning Kerosene?., should be ~ 9bar.

To be clear, it flows from right to left as I indicated? and then runs uphill? but where (at what height relative to the condensate outlet) does it finally level out as it could just mean that the condensate is being evaporated in the boiler and causing untold damage.

The oil pressure at 14bar seems very excessive if burning Kerosene?., should be ~ 9bar.

It doesn’t level out at all

 

[John.g]

So, how can, or does, the condensate drain from the trap??

 

[sherylryan]

So, how can, or does, the condensate drain from the trap??

Well I believe it doesn’t, as the pipe clearly runs uphill but our plumber keeps telling me it’s fine, it does clearly state In the manual it must have a 2 degrees full from the boiler. Possibly why baffles damaged inside boiler, after a years operation. When the boiler fires up all you hear is gurgling noises.

 

[John.g]

It's hard to imagine why your plumber thinks this is OK, the only way that the condensate can be discharged to a higher level, if required, is via a pump.

 

[sherylryan]

Well I believe it doesn’t, as the pipe clearly runs uphill but our plumber keeps telling me it’s fine, it does clearly state In the manual it must have a 2 degrees full from the boiler. Possibly why baffles damaged inside boiler, after a years

It's hard to imagine why your plumber thinks this is OK, the only way that the condensate can be discharged to a higher level, if required, is via a pump.