What size boiler needed

[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.

 

[sherylryan]

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.

Hi there, yes I understand we are referring to the output in kw. As I mentioned we need 23 kw/h for ufh, 15 kw/h for radiators. 3 kw/h for DHW and 3.5 kw/h for trench, total 44.5 kw/h. If all of these were calling for heat at once a would boiler with 35kw/h output would struggle?

 

[John.g]

How are the heat loss calculations reconciled with that 44.5kw, presuming they were carried out before sizing rads etc?.

 

[sherylryan]

How are the heat loss calculations reconciled with that 44.5kw, presuming they were carried out before sizing rads etc?.

Yes all heat loss calculations were carried out before sizing Rads etc. we’ve taken out a 24kw gas boiler, 16kw & 9 kw heat pump and replaced with 35 kw boiler 🤷🏼‍♀

Also on another note Re expansion vessel. I have today calculated 214 litres of water in the whole of the central heating system, not counting the 310 litres of DHW. (Total water content of system with DHW Is 524 litres)

Also the PRV is lifting in the boiler releasing water into the condensate pipe.

 

[John.g]

With precharge & filling pressures of 1.0bar/1.5bar a 12L EV = final pressure of 2.92bar when system hot. (too close to the bone of 3.0 bar safety valve lift).
A 18L EV will give a final pressure of 2.29bar under the same conditions.

Check EV size/volume, precharge/filling pressures should then be checked, requires system drain down but quick test of diaphragm can be done by pressing the EV air end schrader valve with finger nail or whatever, if water issues, diaphragm failed, if air pressure (or none), requires pre/filling pressures checked.

 

[sherylryan]

With precharge & filling pressures of 1.0bar/1.5bar a 12L EV = final pressure of 2.92bar when system hot. (too close to the bone of 3.0 bar safety valve lift).
A 18L EV will give a final pressure of 2.29bar under the same conditions.

Check EV size/volume, precharge/filling pressures should then be checked, requires system drain down but quick test of diaphragm can be done by pressing the EV air end schrader valve with finger nail or whatever, if water issues, diaphragm failed, if air pressure (or none), requires pre/filling pressures checked.

This is in my firebird instruction manual, our EV is set to 1 bar