Ivar 3 Loop UFH

[John Carroll]

This setup is apparently working fine for the past 10 years, its set to give a UFH temp of 30C from a oil fired boiler running with a 65C flow temp. I havn't seen it in action yet but just can't figure out how it actually works, the manifold pump is pumping downwards but I can't see how any cold (UFH manifold return) water is returned to the boiler.

 

Edited October 4 by John Carroll

[Nickfromwales]

Erm..... deja-vu?

[JohnMo]

I posted all the manuals for this last week (ish). Have a look under underfloor heating section 

Edited October 4 by JohnMo

[John Carroll]

Apologies to all, thought I was on another web site!.

[JohnMo]

33 minutes ago, John Carroll said:

Apologies to all, thought I was on another web site!.

Ok, obviously our answers not good enough, I won't bother next time

[Nickfromwales]

14 minutes ago, JohnMo said:

Ok, obviously our answers not good enough, I won't bother next time

Easy, tiger.

 

It's OK that we can see other people  

[Nickfromwales]

49 minutes ago, John Carroll said:

Apologies to all, thought I was on another web site!.

Just make sure you use protection, ok.

[John Carroll]

36 minutes ago, JohnMo said:

Ok, obviously our answers not good enough, I won't bother next time

 

I appreciate all answers John, the nearest arrangement I can find is the one below which makes perfect sense.

 

[John Carroll]

Glad to report that after viewing it, I can see that this UFH is operating fine. The manifold pump is pumping downwards, the 3 flowmeters are reading a total of (2.5+2.7+2.5), 7.7LPM, the UFH loops are operating at a dT of, (25.5-19.5), 6.0C, this gves a calculated Boiler/UFH output of (7.7*60*6.0/860), 3.22kW.

The downside of this set up is, one, that the mixed water is returned to the boiler and not the UFH outlet water which means that returned water temperature is higher, in this case, returned at 25.5C and not 19.5C, resulting in a slight loss in condensing efficiency, and, two, the manifold circ pump is circulating at twice the UFH loops flowrate resulting in greater pump power required.

[JohnMo]

21 minutes ago, John Carroll said:

The downside of this set up is, one, that the mixed water is returned to the boiler and not the UFH outlet water which means that returned water temperature is higher, in this case, returned at 25.5C and not 19.5C, resulting in a slight loss in condensing efficiency

Is it really a down side? If you only allowed UFH return back to boiler the flow through the boiler would be very low and most likely just short cycle.

[John Carroll]

No John, not really, the oil fired boiler here has a TMV to maintain 40C return to prevent corrosion but I've omitted it for simplicity, but I suppose gas fired boilers on UFH only can be run with very low flow/return temps and some can now modulate down to ~ 2.0kW, so some  impact here, still it seems a very unconventional way of implementing the UFH and took me a long time to realize that the mixed water can also be used to reduce the UFH flow temperature. I think this schematic might show how this system was  running when I noted the data.

 

 

 

 

 

 

 

 

 

 

Edited Saturday at 22:38 by John Carroll

[John Carroll]

Upnor apparently sell (or did, in 2023) a system something like the subject one and don't even use a TMV, they simply use a Tapstat with some the mixed water also returning to the boiler/ASHP. First screeshot below shows a live system with a ASHP. The manifold pump is pumping Upwards.

 

 

 

 

Edited Monday at 07:22 by John Carroll

[Sumo]

Hello John Caroll. I hope you are well. I am the poster/owner of that uhf loop. Not sure this will help.

I have one question for you, to see if we can improve your efficency?

Can your floor surfaces tolerate more than the 30 centigrade that your ufh TMV is set at? The closer your tmv is to your boiler flow, the less the loss, John Cantor did a youtube on it.

As you say you need your boiler return at a minium of 40, it would make sense to target an ufh return of at least 40. Also that way you are reducing the loss through mixing at the manifold. Can your boiler target lower than 59, or is that needed for elsewhere.

[Nickfromwales]

This is a candidate for a low loss header or 4 port buffer imo.

 

In most instances I’ll put a TS instead of an UVC, with the TS providing DHW, if it’s an oil boiler.

 

I do this when there’s mixed temp heating or multiples of zones of heating, but always if there’s UFH.

 

Is it possible to at least add a LLH here? 

[John Carroll]

2 hours ago, Sumo said:

Hello John Caroll. I hope you are well. I am the poster/owner of that uhf loop. Not sure this will help.

I have one question for you, to see if we can improve your efficency?

Can your floor surfaces tolerate more than the 30 centigrade that your ufh TMV is set at? The closer your tmv is to your boiler flow, the less the loss, John Cantor did a youtube on it.

As you say you need your boiler return at a minium of 40, it would make sense to target an ufh return of at least 40. Also that way you are reducing the loss through mixing at the manifold. Can your boiler target lower than 59, or is that needed for elsewhere.

I don't know how how you can reduce  the heating loss through the manifold, the only heating loss that I'm aware of is radiation losses which can be improved by insulating the manifolds?, In my (daughter's) case, as long as the water returned to the boiler is less than 40C then it doesn't matter whether like your set up its at 36C or 26C (if you had a conventional UFH where some of the UFH loop outlet water is returned to the boiler. Her boiler has a TMV set to keep the boiler return at 40C, it just mixes some of the boiler flow water with the return water, obviously more HW required if the return is 26C vs 36C, there are also no losses associated with this TMV.

For example, if her system had a UFH total flow of 7.5LPM, then its output (and the boiler's) at a dT of, 36-26, 10C,  is 7.5*60*10/860, 5.233kW..

With a boiler flowtemp of 54.5C and a return of 36C, then the boiler return (before the TMV) flowrate is 7.5*(36-26)/(54.5-36), 4.05LPM, 1.12LPM of water at 54.5C must be added to give a boiler return flow of 5.17LPM at 40C,  if the return is 26C, then the return (before the TMV) flowrate is 7.5*(36-26)/(54.5-26), 2.63LPM, 2.54LPM of water at 54.5C must be added to give boiler return flow of 5.17LPM at 40C, boiler output 5.17*60*(54.5-40)/860, 5.23kW, equals UFH output?. You can see it doesn't matter what the mixing ratios are, same with the UFH mixing.

 

What have you done to improve your own ASP COP? You can theoretically run that at 36C/26C, flow/return with no mixing to improve it, this has nothing to do with the mixing though.

Edited Monday at 11:27 by John Carroll

[John Carroll]

2 hours ago, Nickfromwales said:

This is a candidate for a low loss header or 4 port buffer imo.

 

In most instances I’ll put a TS instead of an UVC, with the TS providing DHW, if it’s an oil boiler.

 

I do this when there’s mixed temp heating or multiples of zones of heating, but always if there’s UFH.

 

Is it possible to at least add a LLH here? 

 

No LLH required here (oil fired boiler) the TMV (Tapstat) does the job.

Edited Monday at 11:44 by John Carroll

[Sumo]

29 minutes ago, John Carroll said:

I don't know how how you can reduce  the heating loss through the manifold, the only heating loss that I'm aware of is radiation losses which can be improved by insulating the manifolds?, In my (daughter's) case, as long as the water returned to the boiler is less than 40C then it doesn't matter whether like your set up its at 36C or 26C (if you had a conventional UFH where some of the UFH loop outlet water is returned to the boiler. Her boiler has a TMV set to keep the boiler return at 40C, it just mixes some of the boiler flow water with the return water, obviously more HW required if the return is 26C vs 36C, there are also no losses associated with this TMV.

For example, if her system had a UFH total flow of 7.5LPM, then its output (and the boiler's) at a dT of, 36-26, 10C,  is 7.5*60*10/860, 5.233kW..

With a boiler flowtemp of 54.5C and a return of 36C, then the boiler return (before the TMV) flowrate is 7.5*(36-26)/(54.5-36), 4.05LPM, 1.12LPM of water at 54.5C must be added to give a boiler return flow of 5.17LPM at 40C,  if the return is 26C, then the return (before the TMV) flowrate is 7.5*(36-26)/(54.5-26), 2.63LPM, 2.54LPM of water at 54.5C must be added to give boiler return flow of 5.17LPM at 40C, boiler output 5.17*60*(54.5-40)/860, 5.23kW, equals UFH output?. You can see it doesn't matter what the mixing ratios are, same with the UFH mixing.

 

What have you done to improve your own ASP COP? You can theoretically run that at 36C/26C, flow/return with no mixing to improve it, this has nothing to do with the mixing though.

With loss I was meaning that you have had to heat your water upto 54.5 when you could say heat it to 44.5, is that not a potential 20% saving?

With mine, it was realising that the 9l/min through the loops, was only using say 4.5l of water from the ashp. The 9l through the loops always has to be more than the water returned to the ashp, for seperation?(sorry in advance if i am a, wrong novice). Seen as the ashp needs a flow of 20l/min minimum, if we just ran the ufh we would short cycle. So to improve cop I have balanced the whole house (7 double rads and 70m sq of ufh) as one, all operating on there check valves alone, so no tmv or trv or zone actuators. The largest heat loss room on the ufh loops dictates the ashp run time. I have made it so well balanced that the ashp permenantly modulates and never cycles on or off, no choking through lack of demand and no aggressive ramping up/short cycling through too much demand and the return temp not been reached. It is always running untill the coldest room is happy. My bill is down 30% along with a warmer house. My ashp targets 46c, water que's at the manifold entrance at 50c and leaves at 41c, the 3 loops now run at 37 return and 41c flow. Three of my radiators have a flow of 46 and return of 41 and four are around 39/34.

I still have not got around to re doing the manifold to run without mixing, the flow and return need swapping over, a new pump and an auto bypass valve to handle the unused 11l/min, are at the ready, meaning hopefully I can run the ufh on its own occasionaly and use 9l/min of un mixed 46c water, though I have not done it as I am worried I will mess it up.

[John Carroll]

No, its the boiler return temperature that primarily determines the Boiler efficiency, the colder the return temperature, the colder the boiler flue gases are, leading to greater efficiency, if you could lower the retur temperature to say 20C then you would have a almost 100% boiler efficiency.

 

The flow through the loops will always and only be greater than the ASHP return flow when the required Loop flow temperature is less than the ASHP flow temperature, for example,  with loop flow/return of 36C/26C and ASHP flow/return of 48C/26C, the % ASHP flow is (36-26)/(48-26), 10/22, 0.4545, 45.45%, a loop flow of 7.5LPM will return 7.5*45.45%, 3.41LPM to the ASHP and recirculate/mix , 7.5-3.41, 4.09LPM with the 3.41LPM from the ASHP at 48C to give the 7.5LPM at 36C loop flow temp, (3.41*48)+(4.09*26) = 7.5*36. If, both the  flow/return temps are the same for both the loops and the ASHP, then both flowrates exactly the same.

The bottom, 4th fom top screenshot below shows this, the 3rd from top screenshot shows the bypass required to give your required ASHP flowrate of 20LPM.

The 2nd from top screenshot shows the data if you run with loop and ASHP flow/return the same at 36C/26C and the top screenshot just below shows the bypass required to give that required ASHP flowrate of 20LPM.

 

Hope this is of some help.

 

 

 

 

 

 

 

 

 

 

Edited Monday at 15:44 by John Carroll

[John Carroll]

Have attached two files which combine the UFH+Rads, the other just shows UFH only but you or anyone  can play around with the values and you can see the effect, hopefully,  more easily.

You can configure any one of S.Sheets for UFH only, Rads only or UFH+rads. by just changing the values in yellow.

UFH ONLY Sumo Extract Rev0.xlsx UFH + Rads Sumo Extract Rev0.xlsx