What size boiler needed

[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.

 

[sherylryan]

I know, they just keep blaming our pipe sizes, but they are all ok. When he pulled the damaged baffles out I asked how did they get like that, his reply was the return water is to low at 46 c

So I guess we need to replace condensate pipe work

 

[sherylryan]

Boiler is set up for light oil,

 

[sherylryan]

Went and checked the condensate trap and found this:
Condensate trap was full and water had been leaking out on to the ground also found a lot of water lying inside on the bottom of the boiler.

 

[John.g]

No surprises there!!, just run the drain properly. Have you any spec on that light oil, not 100% sure if suitable for a condensing boiler but if so may require the burner to have a preheater somewhere, it might be in the specs.

 

[sherylryan]

No surprises there!!, just run the drain properly. Have you any spec on that light oil, not 100% sure if suitable for a condensing boiler but if so may require the burner to have a preheater somewhere, it might be in the specs.

No surprises there!!, just run the drain properly. Have you any spec on that light oil, not 100% sure if suitable for a condensing boiler but if so may require the burner to have a preheater somewhere, it might be in the specs.

It’s run on diesel, don’t think it has a pre heater. Sometimes when it’s behaving it’s self when the boiler starts up the pump will run first before the boiler fires up but not all the time.

 

[John.g]

Didn't think diesel allowed with condensate.nsing Firebirds.
The fan and direct coupled pump should run for ~ 7 sec purge time. The oil solenoid should then energise with ignition spark.

 

[exedon2]

Certainly all the Firebird boilers sold here are 28 sec fuel only .
Plus your plumber is a idiot to think that condensate waste is ok.
Manufacturer asks for minimum of one in two hundred fall.

 

[sherylryan]

Didn't think diesel allowed with condensate.nsing Firebirds.
The fan and direct coupled pump should run for ~ 7 sec purge time. The oil solenoid should then energise with ignition spark.

I wonder because they have taking the pump off from the inside of the boiler and fitted an external one that’s why it didn’t purge anymore.

 

[sherylryan]

Certainly all the Firebird boilers sold here are 28 sec fuel only .
Plus your plumber is a idiot to think that condensate waste is ok.
Manufacturer asks for minimum of one in two hundred fall.

Everytime I question him about the condensate waste he says it’s not a problem and the reason the pipe melts is because of our flow and return pipes, he thinks I’m an idiot .

 

[John.g]

I wonder because they have taking the pump off from the inside of the boiler and fitted an external one that’s why it didn’t purge anymore.

I'm talking about the oil pump not the water pump that's connected to the fan, the boiler fan runs for around 7 seconds to purge the combustion chamber of any explosive gases before allowing ignition. The original boiler circ pump may have been programmed to overrun for awhile when all zone valves close.

I think you should think about getting someone familiar with oil boilers if changing boiler output or whatever, the original burner didn't need changing as its rated down to 26kw with the appropriate nozzle.

 

[sherylryan]

I'm talking about the oil pump not the water pump that's connected to the fan, the boiler fan runs for around 7 seconds to purge the combustion chamber of any explosive gases before allowing ignition. The original boiler circ pump may have been programmed to overrun for awhile when all zone valves close.

I think you should think about getting someone familiar with oil boilers if changing boiler output or whatever, the original burner didn't need changing as its rated down to 26kw with the appropriate nozzle.

Ok Re the fan. A quick rundown on what the plumber (who is supposedly a firebird agent installer) has done.

New 35 kw boiler installed August 2019 (sized by installer after doing all calculations)

October 2019 first melted condensate trap hose (Steel trap)

May 2020 another melted condensate trap hose

June 2020 another melted pipe

June 2020 new pump installled ( as installer advised us flow and return pipes to small hence condensate trap hose melting)

July 2020 another melted pipe

August 2020 air vent added to flow pipe (installer now advised us air is in the system and this is causing melted pipes.

September 2020 another melted pipe, pump pressure turned down by installer as apparently pressure to high.

October 2020 another melted pipe, pump pressure turn up by installer as apparently to low

March 2021 another melted pipe, pump pressure turned up again as apparently to low.

April 2021 another melted pipe, pump pressure turned up again as to low.

October 2021 installer decided to downsize boiler from to 23 kw as now the boiler is oversized hence melted pipes and pump pressure turned up.

November 2021 boiler downsized to wrong kw output so now sized to 26 kw from 35kw.

April 2022 boiler still not operating correctly.

 

[John.g]

OK, what's done is done.
There may have been little if any corrosion damage done to the boiler while operating in the fashion it was, a good clean out and service by some one who knows what they are doing is maybe all that is required.
You say the same boiler installer did the house heat loss calculations which look professionally done, on paper, at least. Can you ask him what the heat losses are, ie watts/dT difference between required room temp & ambient or whatever.

What have you done with the condensate waste just now?,, does it have to be discharged to that higher level?, if so you need a pump set which firebird can advise on, you may be able to run it temporarily into a container, it will only be a liter or so daily.,
Are you running the boiler just now?.

 

[sherylryan]

OK, what's done is done.
There may have been little if any corrosion damage done to the boiler while operating in the fashion it was, a good clean out and service by some one who knows what they are doing is maybe all that is required.
You say the same boiler installer did the house heat loss calculations which look professionally done, on paper, at least. Can you ask him what the heat losses are, ie watts/dT difference between required room temp & ambient or whatever.

What have you done with the condensate waste just now?,, does it have to be discharged to that higher level?, if so you need a pump set which firebird can advise on, you may be able to run it temporarily into a container, it will only be a liter or so daily.,
Are you running the boiler just now?.

So apparently heat loss calcs are Area/R value = watts/C.

I have the condensate waste going into a container at a lower level. Yes the boiler is still running.

 

[John.g]

The above whole house loss is 929.2 watts, you gave a average dT of 11C, 11C/22C, which means a required boiler output of 10.22kw, I know the rads output is 15kw but with zoning/roomstats one would think that a boiler output of 23/26kw should be sufficient even if the ambient was 5C, dT 17C, required boiler output 15.8kw.

For interest, how many litre(s) of condensate are you collecting daily?.

 

[sherylryan]

The above whole house loss is 929.2 watts, you gave a average dT of 11C, 11C/22C, which means a required boiler output of 10.22kw, I know the rads output is 15kw but with zoning/roomstats one would think that a boiler output of 23/26kw should be sufficient even if the ambient was 5C, dT 17C, required boiler output 15.8kw.

For interest, how many litre(s) of condensate are you collecting daily?.

Re zoning/roomstats the floorplans I sent through the other day the trouble manifold controls the w/c, entry, dining, kitchen. stairs, Office, living all in one thermostat.

To be honest I have no idea how many litres of condensate we are collecting per day. I am picking from what i saw yesterday with the condensate trap full (that has has not been checked since last October) not a lot of condensate.

 

[sherylryan]

The above whole house loss is 929.2 watts, you gave a average dT of 11C, 11C/22C, which means a required boiler output of 10.22kw, I know the rads output is 15kw but with zoning/roomstats one would think that a boiler output of 23/26kw should be sufficient even if the ambient was 5C, dT 17C, required boiler output 15.8kw.

For interest, how many litre(s) of condensate are you collecting daily?.

Hi John , I’ve have checked the condensate trap again today and it is full with excess water lying in the bottom of the boiler under the baffles. The condensate trap has 220 mls in it, last checked it 48 hours ago. Also noticed some has flown out pipe but I’m wondering now if some of this is from the PRV as it flows into the same outlet pipe. Water full of soot.

 

[John.g]

The condensate trap should always be full of water even with little/no condensing, if the boiler is fully condensing (and it won't be) then based on your fuel consumption of ~ 23 LPD would result in ~ 22 LPD of condensate in your container but you should possibly be collecting ~ 6 to 10 LPD or ~ 0.5 to 1 liters/hr if firing continuously for 1 hour and pro rata. The PRV waste pipe should not be teed in with the condensate waste pipe and the PRV should not in any case be lifting, try and collect the condensate before any T.

In view of the the continued and sooted water would advise getting someone in ASAP who knows what they are doing to clean out and inspect boiler for any damage, take FGA etc, the condensate baffle is possibly perforated so all/most of the condensate will flow into the bottom of the boiler.

What is the flexible hose in the boiler flue for?. (post #33)

 

[ShaunCorbs]

The condensate trap should always be full of water even with little/no condensing, if the boiler is fully condensing (and it won't be) then based on your fuel consumption of ~ 23 LPD would result in ~ 22 LPD of condensate in your container but you should possibly be collecting ~ 6 to 10 LPD or ~ 0.5 to 1 liters/hr if firing continuously for 1 hour and pro rata. The PRV waste pipe should not be teed in with the condensate waste pipe and the PRV should not in any case be lifting, try and collect the condensate before any T.

In view of the the continued and sooted water would advise getting someone in ASAP who knows what they are doing to clean out and inspect boiler for any damage, take FGA etc, the condensate baffle is possibly perforated so all/most of the condensate will flow into the bottom of the boiler.

What is the flexible hose in the boiler flue for?. (post #33)

Air intake from the double wall flue

 

[sherylryan]

The condensate trap should always be full of water even with little/no condensing, if the boiler is fully condensing (and it won't be) then based on your fuel consumption of ~ 23 LPD would result in ~ 22 LPD of condensate in your container but you should possibly be collecting ~ 6 to 10 LPD or ~ 0.5 to 1 liters/hr if firing continuously for 1 hour and pro rata. The PRV waste pipe should not be teed in with the condensate waste pipe and the PRV should not in any case be lifting, try and collect the condensate before any T.

In view of the the continued and sooted water would advise getting someone in ASAP who knows what they are doing to clean out and inspect boiler for any damage, take FGA etc, the condensate baffle is possibly perforated so all/most of the condensate will flow into the bottom of the boiler.

What is the flexible hose in the boiler flue for?. (post #33)

Yes bottom of the boiler is full of water. That Flexi hose goes from the air damper into flue

 

[adomas]

When we are discussing the size of a boiler, we aren’t referring to its physical dimensions. Instead, we are referring to the output in kilowatts (kW), the unit that is used to measure how much energy is output by the boiler in the form of heat. It is important to choose the right size boiler for your home because it will mean you are not wasting energy and money you don’t need.

Generally speaking, the more heat and hot water you require, the higher the output you will need, although other factors also play a part in choosing the right size.