Better way to control water UFH system?

[JohnMo]

Just now, Munchincocopops said:

Really interesting that you reduced gas consumption by over 50%, that is impressive and of course you know what you are doing.

Didn't at the time, all I knew was the heat loss of the house was supposed be x, but I was actually using twice that.  From there it was a voyage of discovery and learning. Plumbers weren't interested, it just the way it is!  I soon realised the boiler as in cycle on off mode continually.

[marshian]

7 hours ago, JohnMo said:

Didn't at the time, all I knew was the heat loss of the house was supposed be x, but I was actually using twice that.  From there it was a voyage of discovery and learning. Plumbers weren't interested, it just the way it is!  I soon realised the boiler as in cycle on off mode continually.

 

Similar in my case - data is the key - once you have data you can make better decisions or changes to the system

 

Few years back I was using 16,500 kWh of gas to heat my house on a schedule it was never just right it was too hot or too cold and I was using manual weather compensation (ie i changed the boiler flow temp) - the 24kW boiler was massively oversized for a 6 kW heat loss with a 10 kW minimum and it cycled like a B1tch in the shoulder seasons and not that much better in a really cold snap.

 

Then we had the shock of gas prices rising rapidly and I knew I needed to both improve the house and manage the energy costs. Got it down to 8,500 in the end (CH and HW) but now I'm at 9,500 heating 24/7 with a much more suitable boiler - it's 16 kW with a min of 4 kW and is set up with weather compensated flow temps - house is always comfortable in every room - rads are sized to room heat loss and flow temp is managed by the outside temp sensor - the whole system runs low and slow - it so much nicer to be in the house.

 

Not a heating engineer just someone who wanted to improve/optimise what I had 

 

I've not totally finished but I'm pretty damn close..................

[marshian]

7 hours ago, Munchincocopops said:

Thanks for the guide on what to do it is really helpful. I realise these systems are complicated to understand and get the best out of them and I'm no expert in this area but the comments and advice will help me understand better.

 

No probs with trying to help

 

Actually systems aren't very complicated at all - it's just warmer water in pipes or rads providing an increase to room temps (or maintaining the temps)

 

7 hours ago, Munchincocopops said:

<snip> just wanting to make the best of what I have if at all possible and if (as it appears) I have 2 conflicting requirements of a boiler, then if savings would be reasonable I'm open to spending a bit now to save long run...not too long run as I'm an OAP...LOL.

 

One of the reasons I changed my boiler before it had reached end of life is I'm 4 - 5 years away from retirement - Need to ensure I minimise "extraordinary" expenditure when my income drops significantly so I'm very much in the camp of invest now to reduce risk of large capital items hitting me when I'm retired.

 

7 hours ago, Munchincocopops said:

Thanks for all the comments and help everyone. Looks like I have some work to do....I wonder if I can fit a radiator next to the boiler to keep me warm when looking at this...LOL.

 

Electric fan heater??

 

There is a lot to be said for a boiler in a kitchen even if it does rob a cupboard space (much to Mrs Aliens annoyance)

[Munchincocopops]

Early days and not spent much time on this yet but just been in garage for about 20 mins and boiler cycled 3x.

UFH only is on and I turned up stat to ensure it asks boiler for heat when I'm in garage.

 

What I find confusing is that the boiler heats (thought it was set at 70 but its set at 60 deg c) up to reading of 60-64 deg C and stays there for a while but return temp is about 15 deg c (read with chatty ir gun....it  also reads output as 45 dec C but it feels hotter....but 15 deg c feels about right).

 

As this is only feeding UFH manifold (CH & HW turned off) and pipe to UFH manifold is about 15ft or so I was expecting hotter return?

 

Anyhow....return feels 15 deg or so when boiler is running then when boiler shuts down it does not take long for the boiler out temp (was reading 60 deg or so on boiler temp guage) to drop to about 38 deg at which point boiler fires up again. Return still feels like 15 deg or not much less (skin meter).

 

I'm waiting for a new multimeter with temperature measurement so will pull insulation box around manifold kit once I get it as I have to move a lot of stuff and shelving to get to it so not a 5 min job.

 

Will spend an hour counting cycles and timing on off maybe later in the week though would be nice to do when I get my temperature meter so I can record temperatures too.

 

Just thought...I did have CH on but turned it off and I know its was off as relay was off in garage. But I guess CH mororized valve could be leaking and allowing pass through so return water to boiler is being mixed with return water from UFH?

 

Will look at this again ensuring CH is off.

 

Thats my update so far.

Edited yesterday at 17:53 by Munchincocopops

[JohnMo]

3 minutes ago, Munchincocopops said:

return feels 15 deg

15 degs will feel cold.

 

5 minutes ago, Munchincocopops said:

20 mins and boiler cycled 3x.

That is worrying already. It basically says the boiler cannot get rid of its heat quickly enough. As the system heats up it will most likely not worse, as every time boiler senses it's tripped on over temperature it starts a timer before firing up again.

 

11 minutes ago, Munchincocopops said:

ir gun

They are rubbish with copper pipe,if you paint or stick some white tape on it it will read better.

 

13 minutes ago, Munchincocopops said:

What I find confusing is that the boiler heats (thought it was set at 70 but its set at 60 deg c) up to reading of 60-64 deg C and stays there for a while but return temp is about 15 deg c (read with chatty ir gun....it  also reads output as 45 dec C but it feels hotter....but 15 deg c feels about right).

A few loops have very little flow, with a mixer a small amount hot water is let in to the mixer and it's mixed with return water from the floor loops. The only water going down the return is return water from the floor equal to the hot water let in via the mixer.  The rest of the flow back to the boiler will a min flow valve in your heating.

[Munchincocopops]

5 minutes ago, JohnMo said:

A few loops have very little flow, with a mixer a small amount hot water is let in to the mixer and it's mixed with return water from the floor loops. The only water going down the return is return water from the floor equal to the hot water let in via the mixer.  The rest of the flow back to the boiler will a min flow valve in your heating.

 

I understood the mixer would not take much hot water so I was expecting the return to the boiler to be the unused hot water mixed with a little UFH return.....so to heat up as hot water is delivered to the manifold and "most" returned to boiler?

 

I can reduce boiler temperature and see if its any better.....as I watch it for a while.....later in the week.

And (?) for the moment pull CH relay and manually open CH motorized valve so CH comes on when UFH demands heat.....is that worth doing?

[Munchincocopops]

I think I got it.......basically hot water from boiler is going to a dead end and only mixer valve consumes the water and only excess return water from UFH to manifold that is not recycled is returned to the boiler? Up to now I thought manifold was like a heat exchanger with a mixer valve to take hot water as required.....my mistake. Blimy - ran like this for past 2 years!

 

Think I will pull CH relay and manually open CH motorized valve.

 

Buffer tank looks like a good idea. OK 4 min or so run but boiler will cycle much less I expect.

Edited 23 hours ago by Munchincocopops

[JohnMo]

I would engage a few radiators in the main living space. This will do a few things

 

Give the boiler an open route for flow, provide a temperature dump for excess heat. Should result in longer run times. You may actually find your energy consumption stays the same, may even go down.

[marshian]

30 minutes ago, Munchincocopops said:

I think I got it.......basically hot water from boiler is going to a dead end and only mixer valve consumes the water and only excess return water from UFH to manifold that is not recycled is returned to the boiler? Up to now I thought manifold was like a heat exchanger with a mixer valve to take hot water as required.....my mistake. Blimy - ran like this for past 2 years!

 

That doesn't seem right - no circulation pump is going to like being almost dead headed 

 

What confuses is me is why it appears the return temp is so low - Avg human skin temp is 33 to 36 deg C so anything cooler than that is going to feel colder.

 

I can only "just" feel the difference between my 30 deg flow and 24 deg return on my rads but they both feel cool.

[JohnMo]

45 minutes ago, Munchincocopops said:

Buffer tank looks like a good idea.

No h you need good stable running, 4 mins is pretty rubbish

[JohnMo]

1 minute ago, marshian said:

What confuses is me is why it appears the return temp is so low -

The return water is at floor temperature, as the system runs longer the return temp increases. 

 

         Hot Water In

              |

          [ Mixing Valve ] ---> Mixed Flow to UFH

              |

     Cool Return from

UFH

 

So makes sense

[Munchincocopops]

flow to manifold and return has me confused....ok my15 deg return is a guess...its warm but not as hot as flow at 60 deg....its a lot cooler.

 

So I'm still wrong about "heat exchanger" manifold...still learning....I agree boiler pumping to dead end does not seem right....but at a loss where the heat is going...the boiler runs for quite a few minutes.

 

I'm thinking with buffer tank boiler runs for longer than I see now (in my quick investigation) and stays off for a long time as it takes for the UFH to cool the buffer tank (ok plus heat losses).

Anyhow.....will give boiler some radiators to heat as well as UFH and see if its better.

 

Thanks for the replies.

[JohnMo]

11 minutes ago, Munchincocopops said:

agree boiler pumping to dead end does not seem right...but

Your system will have either a valve like this, this is to prevent pump dead heading

Or you will have a radiator always open - bathroom or hall?

[marshian]

14 minutes ago, JohnMo said:

The return water is at floor temperature, as the system runs longer the return temp increases. 

 

         Hot Water In

              |

          [ Mixing Valve ] ---> Mixed Flow to UFH

              |

     Cool Return from

UFH

 

So makes sense

 

I get above but if the boiler is throwing out 60 deg C I find it really hard to understand a return temp of 15 deg - in fact I'd struggle with a return less than 40 if the UFH is only taking a little heat out of the circuit via a mixer unit. Unless there is heat being removed elsewhere??

[Munchincocopops]

Yes forgot....I have 2 ensuite bathrooms without Trv's and a main bathroom with cast iron radiator and trv.....all permanently on...i.e no motorized valve in circuit.

Edited 22 hours ago by Munchincocopops

[marshian]

6 minutes ago, JohnMo said:

Your system will have either a valve like this, this is to prevent pump dead heading

Or you will have a radiator always open - bathroom or hall?

 

Resulting in a lot hotter water returning to the boiler if the bypass has opened due to system pressure being higher than the bypass is set to

 

Either way until we get some "firmer" temps it's probably not much point.

 

It looks like the boiler running just UFH is cycling a lot more than is desirable - chucking heat out the flue on every start and nit running long enough to stabilise

[marshian]

4 minutes ago, Munchincocopops said:

Yes forgot....I have 2 ensuite bathrooms without Trv's and a main bathroom with cast iron radiator and trv.....all permanently on...i.e no motorized valve in circuit.

 

Bingo - so the heat is going somewhere

 

So if the boiler is firing and running for a short period of time you aren't going to get warm water back to the boiler very quickly the rads will take that without giving a higher return temp

 

If the boiler hits temp limit and shuts down then it's going to send "unheated" water round the circuit 

 

What does surprise me is that the boiler doesn't shut down because the flow temp exceeds the return by a large margin - many boilers don't like to see difference between flow and return that exceeds 20 deg after a certain period of running.

 

Good example of this was my my old glow worm that faulted out if flow and return went above 20 deg after 5 mins - I had to run the downstairs toilet rad at a high flow to feed back return water to the boiler - the room quickly warmed up and the TRV shut down but by that time the boiler was getting a warmed return from all the other rads