Thank you for the calculations they are very handy.
I am totally stumped over the whole system 😂😂😂 but have quite a bit more knowledge now thanks to you.
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What size boiler needed
- Thread starter sherylryan
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View the thread, titled "What size boiler needed" which is posted in Boiler Advice Forum on UK Plumbers Forums.
I am totally stumped over the whole system 😂😂😂 but have quite a bit more knowledge now thanks to you.
This Laundry Manifold/TMV is a mystery to me as all the indications are that the return temperature to the boiler is the mixed flow temperature but havn't figured out if this is thermodynamically possible.
You might please take the (4) temperatures where indicated and also take the return temperature to the boiler; at the boiler.
You might please take the (4) temperatures where indicated and also take the return temperature to the boiler; at the boiler.
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Ok, will do. I’ll get back to you.
Boiler set point 60
Boiler flow temp 72
Boiler return 59
Ufh at points 2 72 into mixing valve 50 going into pump.
Point 4 45 degrees
Point 8 57 degrees
Wow temps are all over the place. Return is high into boiler as that manual bypass is open.
I have attached a graph of the laundry manifold with boiler flor and return temps taken when boiler was set at 35kw. (Blue is boiler firing flow , Red is pump only pumping)
Oh sorry, I’ll check again
Oh sorry,
Awesome, sorry have been away for back tomorrow and then I’ll have temps. Thank you.
Ok so I have checked all temperatures and what a shambles, they are
Boiler flow 76.5 degrees
Boiler Return 46.3
Temp 1 - 60
Temp 2 - 46
Temp 3 - 38
Temp 4 - 34
Temp 5 - 48
Yes, it's working as I thought it might, apart from temp 1 at 60C which should be the same as the boiler flow at 76.5C or vica versa. The TMV is controlling (first mixing) the temp at 48C = temp 5, this is then (second) mixing with the manifold return of 34C to give a final mixed manifold temperature of 38C, there is only a dT of 4C across the loops so do your calc, LPM*60*dT/860, to give the loop output, kw.
The TMV mixed flow temp of 48C is returning to the boiler which is very good from a balanced corrosion and efficiency point of view, obviously if you require the manifold flow temp of 38c increased then you have to increase the TMV setting.
Its quite a clever control system IMO especially for a oil fired system as it obviates the need for recirculation if the manifold return was returned to the boiler.
The TMV mixed flow temp of 48C is returning to the boiler which is very good from a balanced corrosion and efficiency point of view, obviously if you require the manifold flow temp of 38c increased then you have to increase the TMV setting.
Its quite a clever control system IMO especially for a oil fired system as it obviates the need for recirculation if the manifold return was returned to the boiler.
Out
It’s a shame the kitchen manifold doesn’t run like this. I ran it after this manifold and could not even get the flow temp out of boiler up to 55, but yet this got to 76.5 at boiler
Another thing I noticed today, if you reduce the pressure on the pump while radiators are calling for heat the flow temp rises and so does the return temp.
But if you reduce the pump pressure when the UFH is calling the flow temp rises and the return temp drops.
Yes I can’t work out why the flow temp at 1 isn’t the same as the boiler. Output of 4.1kw.
It’s a shame the kitchen manifold doesn’t run like this. I ran it after this manifold and could not even get the flow temp out of boiler up to 55, but yet this got to 76.5 at boiler
Another thing I noticed today, if you reduce the pressure on the pump while radiators are calling for heat the flow temp rises and so does the return temp.
But if you reduce the pump pressure when the UFH is calling the flow temp rises and the return temp drops.
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Heatloss on pipework?
Yes possibly. should the pump be set to flow rate instead of constant pressure?
A headscratcher Shaun, the return from the manifold to the boiler is a measured 46C (but is possibly 47C/48C) and its 46.3C measured at the boiler so very little loss in this pipework. The heat loss based on 76.5C/60C and a boiler flow of ~ 4.2LPM = loss of 4.57kw, no way IMO. (Boiler flow 76.C measured at the boiler, 60C measured at the manifold)
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Problem with setting it as flow is that’s ok if you have no controls and the load is matched eg your Heatloss is the same as your rads/ufh
But as you have multiple zones and on off controls I would leave it on pressure
The other way to do it is temp difference but you require a sensor if the pump is capable
Op can you go round and when the system is on measure all of the flows and see if there’s any difference in temp etc ?
Very confusing, I believe something is happening inside the boiler as the setpoint was 65 degrees but the flow leaving the boiler is high.
Flow gets well above setpoint with laundry UFH & Rads
Flow does not reach set point for Kitchen ufh manifold.
If you press the right arrow on the pump should show the flow rate
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.
I tried to find it the other day but I’ll get the instruction manual out and have a look.
Ok, I’ll move the thermostat to the flow pipe before it tees of into the valves for UFH manifolds. Thank you.
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.
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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.
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.
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.
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.
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I’m trying to get some answers out of firebird now to see what they have to say. Will let you know
I would say overfired
Can’t get any answers 🤷🏼♀️
exedon2
Esteemed
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.
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.
H
Have tried to get some answers from Firebird but no one is interested to answer questions.
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