UFH - Its Broke Me....

[Toppers]

I was going to fit water fed UFH from a standard boiler, through a manifold with the pipes fitted between joists set on top of insulation in a biscuit screed mix - so far so good. I have then had that much conflicting information (loads of it) its totally put me off the idea and think of going for a double panel radiator with possibly an electric UFH mat to take the cold edge off the tiles.

 

So frustrating.

[scottishjohn]

having done what you are proposing  -close to 20 years ago  

yes fitting rads will be simpler -no argument 

does what you propose to do  work -- absolutely  YES

but what are your parameters of this change --cheapest system to install or different comfort level -cheapest to run 

simplest way is to fit on top of floor you have  now -you can get a system which will only add 50mm to floor height 

how well insulated is the fabric of the house ?- that should ALWAYS be first thing to address

what don,t you like about system you have now --cost to run   or rads blocking walls ?

Edited July 11, 2019 by scottishjohn

[ProDave]

I thought you had all the advice you needed here?

What has now put you off?

[Toppers]

2 hours ago, scottishjohn said:

having done what you are proposing  -close to 20 years ago  

yes fitting rads will be simpler -no argument 

does what you propose to do  work -- absolutely  YES

but what are your parameters of this change --cheapest system to install or different comfort level -cheapest to run 

simplest way is to fit on top of floor you have  now -you can get a system which will only add 50mm to floor height 

how well insulated is the fabric of the house ?- that should ALWAYS be first thing to address

what don,t you like about system you have now --cost to run   or rads blocking walls ?

 

Its not a change its a new build extension.

[Toppers]

2 hours ago, ProDave said:

I thought you had all the advice you needed here?

What has now put you off?

 

Quite a few factors, i'm getting conflicting info on:

 

• Where the manifold needs to be fitted and do I need one at all
• If I do fit one does it have to be connected to the boiler directly
• Do I use PUG (25mm) or ali spreader plates
• What does the floor then need to consist of (the final floor finish will be tiles)
• Will it be effective to heat the room (approx 17m2) well insulated with bi-fold doors

[Onoff]

UFH? Just wing it...I am.

[Toppers]

I've got some of the above questions answered by a local UFH supplier, next question:

 

As the UFH is to go in a new extension what is the best way to get a connection to flow and return pipework from the boiler to the UFH pipes, our boiler is in the loft and is not easily accessible from the extension.

[Carrerahill]

7 hours ago, Toppers said:

I was going to fit water fed UFH from a standard boiler, through a manifold with the pipes fitted between joists set on top of insulation in a biscuit screed mix - so far so good. I have then had that much conflicting information (loads of it) its totally put me off the idea and think of going for a double panel radiator with possibly an electric UFH mat to take the cold edge off the tiles.

 

So frustrating.

I am still going with mine. Not sure which parts of the UFH system are giving you grief but I am sure it can be solved, or you will end up convincing me not to fit it either!

 

For the record I am going to buy one of these for the kitchen as it will be tiled: 

https://www.thefloorheatingwarehouse.co.uk/acatalog/Small_Room_Radiator_Add-on_System.html

 

OR a pumped option:

 

https://www.thefloorheatingwarehouse.co.uk/acatalog/Single-Room-Warm-Water-Underfloor-Heating-Complete-Packs-10m---28m.html

 

Suspended timber floor, 450 mm c/c, batten bottom edges, 100mm PIR to top of joists, pipes fastened across the top of it all, batten out tops of joists with gaps for pipes to pass over top of joist, biscuit screed over the lot, then I will worry about the next stages when I get that far. One additional layer may be to put 11mmOSB over the top of the insulated joists, then fit pipe to that and batten over the joist positions - need to check my details book as I sketched it up from info on here and the internet.

 

I will fit rad's elsewhere.

 

 

 

 

Edited July 11, 2019 by Carrerahill

[Carrerahill]

4 hours ago, Onoff said:

UFH? Just wing it...I am.

Sort of my plan too! But with good guidance and advice.

[Carrerahill]

4 hours ago, Toppers said:

 

Quite a few factors, i'm getting conflicting info on:

 

• Where the manifold needs to be fitted and do I need one at all
• If I do fit one does it have to be connected to the boiler directly
• Do I use PUG (25mm) or ali spreader plates
• What does the floor then need to consist of (the final floor finish will be tiles)
• Will it be effective to heat the room (approx 17m2) well insulated with bi-fold doors

I am learning all of this too, I am in no way saying this is right but here are my thoughts and or findings:

 

Manifold goes somewhere that suits - for me that will be against the original house wall nearest the current boiler pipes which then lets me start my UFH run from a convenient corner.

 

Connected directly to the boiler - I am going to extend my 22mm pipes under my house and out into the kitchen - this is best practise for fluid dynamics as far as I am concerned, I will look at the dimensions of the unions on the valve and make a decision then. I think you really do need a valve or manifold - for a single room the one I am looking at is a Danfoss FHV - they seem to market it as a radiator add on kit. Without a valve of any sort you would get full flow into the system from the boiler which could get a bit warm if the boiler is on a lot. I do suspect I could develop my own system using just UGH pipe and then connect it up using an electronic solenoid and an electronic thermostat (of which I have several for some reason in a box in the old garage!).

 

I am not using spreader plates, I will insulate, vapour barrier wherever it goes (under PIR, over PIR?) then screed - mainly as I have 1/3 ton of cement and tons of sand spare!

 

Over screen and battens I think I will just fit 9mm ply then tile over it. If this floor is changed in the future the ply can be unscrewed and replaced without interfering with the screed or UFH.

 

I am confident it will heat well - I worked out the expected BTU's of my system and it's far more than a radiator would be.

 

 

 

 

[daiking]

Its taken 4 years to get this far...

 

 

An example of how (or not) to connect to a conventional gas central heating system. The radiators operate at a hot water temperature, the UFH will need tepid water so you're going to need some further plumbing to mix the hot water with colder water to get it to the right temperature - which is what the TRV  and curly wire on the UFH manifold is for. Mine is also for a single room - 1 zone - but its about 40m2 and been split into 4 loops with the manifold, 3 in the slab, 1 small loop in a suspended floor with insulation between joists and spreader plates topped with plywood and some tile backer board + tiles. Not exactly the best make up for UFH but its only a small area in the whole room - 6m2

 

It was planned that the manifold would be in the same room as the boiler so it has been relatively easy to get a full 22m pipe feed to the UFH manifold. As your boiler is in the loft, is there a suitable point in your existing radiator pipework where you can conveniently tee into the 22mm flow and return pipes for the boiler?

 

[Toppers]

On 12/07/2019 at 09:18, daiking said:

Its taken 4 years to get this far...

 

 

An example of how (or not) to connect to a conventional gas central heating system. The radiators operate at a hot water temperature, the UFH will need tepid water so you're going to need some further plumbing to mix the hot water with colder water to get it to the right temperature - which is what the TRV  and curly wire on the UFH manifold is for. Mine is also for a single room - 1 zone - but its about 40m2 and been split into 4 loops with the manifold, 3 in the slab, 1 small loop in a suspended floor with insulation between joists and spreader plates topped with plywood and some tile backer board + tiles. Not exactly the best make up for UFH but its only a small area in the whole room - 6m2

 

It was planned that the manifold would be in the same room as the boiler so it has been relatively easy to get a full 22m pipe feed to the UFH manifold. As your boiler is in the loft, is there a suitable point in your existing radiator pipework where you can conveniently tee into the 22mm flow and return pipes for the boiler?

 

 

There are some boxed in vertical 22mm pipes in the kitchen which I aim to investigate, I think they potentially could be the answer.

[Toppers]

On 11/07/2019 at 17:28, Carrerahill said:

I am learning all of this too, I am in no way saying this is right but here are my thoughts and or findings:

 

Manifold goes somewhere that suits - for me that will be against the original house wall nearest the current boiler pipes which then lets me start my UFH run from a convenient corner.

 

Connected directly to the boiler - I am going to extend my 22mm pipes under my house and out into the kitchen - this is best practise for fluid dynamics as far as I am concerned, I will look at the dimensions of the unions on the valve and make a decision then. I think you really do need a valve or manifold - for a single room the one I am looking at is a Danfoss FHV - they seem to market it as a radiator add on kit. Without a valve of any sort you would get full flow into the system from the boiler which could get a bit warm if the boiler is on a lot. I do suspect I could develop my own system using just UGH pipe and then connect it up using an electronic solenoid and an electronic thermostat (of which I have several for some reason in a box in the old garage!).

 

I am not using spreader plates, I will insulate, vapour barrier wherever it goes (under PIR, over PIR?) then screed - mainly as I have 1/3 ton of cement and tons of sand spare!

 

Over screen and battens I think I will just fit 9mm ply then tile over it. If this floor is changed in the future the ply can be unscrewed and replaced without interfering with the screed or UFH.

 

I am confident it will heat well - I worked out the expected BTU's of my system and it's far more than a radiator would be.

 

 

 

 

 

Just be cautious of using ply to tile on, hardiebacker would be much better, even ply manufacturers are not recommending its use these days.

[Carrerahill]

17 hours ago, Toppers said:

 

Just be cautious of using ply to tile on, hardiebacker would be much better, even ply manufacturers are not recommending its use these days.

Thanks - I will sort this detail soon and allow for this.

 

I am going to lift the temp joists and see what I have - been a while since I just stared at it all - I may now backfill with type 1, sand, DPM, 150-200mm PIR then crete!

[Toppers]

Can anyone confirm thats it ok to connect UFH to a conventional boiler?

[daiking]

1 minute ago, Toppers said:

Can anyone confirm thats it ok to connect UFH to a conventional boiler?

 

Probably

 

tag @Nickfromwales and @PeterW

 

Also tell us what model boiler you have. (mine is a Baxi duotec 33 which is a reasonably modern combi boiler)

 

[Triassic]

14 minutes ago, Toppers said:

Can anyone confirm thats it ok to connect UFH to a conventional boiler?

Absolutely, in our old house we simply connected our ground floor UFH direct to the Combi and it worked fine.

[Toppers]

1 minute ago, Triassic said:

Absolutely, in our old house we simply connected our ground floor UFH direct to the Combi and it worked fine.

 

Its not a combi its a tank fed system.

[Triassic]

Can’t see any reason why it wouldn’t work 

[Onoff]

46 minutes ago, Toppers said:

Can anyone confirm thats it ok to connect UFH to a conventional boiler?

 

I believe that without a buffer tank the boiler can suffer from short cycling?

[Carrerahill]

32 minutes ago, Onoff said:

 

I believe that without a buffer tank the boiler can suffer from short cycling?

I may not be a UFH buff but I know enough about boilers to answer this one. It can do but depends on the UFH loads and boilers modulation ratio - a buffer tank is a mitigation measure but an inefficient one at that. So the best way to engineer out short cycling is with with things like a towel rad on the circuit on full flow or heat a central colder area like a hall with a rad which can consume enough to consume enough of the boilers minimum capacity. This of course is only an issue when other rads on the system are drawing very little from the system - if the house is being heated and the system demands enough it won't be an issue. Sometimes having a slightly smaller boiler is actually better than a bigger boiler in these circumstances. 

Edited July 18, 2019 by Carrerahill

[Ed Davies]

OTOH, it's likely that a lot of radiator systems short-cycle, too. Here's my rented house for New Year's day this year. Blue line is the overall household electricity consumption and green line is the temperature of the flow to the radiator in the bedroom I use as a study.

 

The heating comes on at 07:00. It runs steadily for about 20 minutes then starts to short cycle as you can see from the castellated power consumption as the blower and oil pump switch on and off. The spike at 08:30 would have been the kettle for tea with breakfast. Not sure why the flow temperature to the radiator changed at about that time, maybe removing something left on a radiator to dry? It continues to cycle until 09:30 when the the thermostat in the living room was satisfied and both the boiler itself and the circulation pump turn off. Some of the other pulses of heating needed early in the day also have a few short cycles.

 

I think there's a problem that plumbers are motivated to oversize boilers. No customer is likely to call them back for a bit of short cycling but if the boiler is underpowered for the coldest days they'll get it in the neck. When the boiler here was replaced I showed a graph like this to the plumber and suggested if he had a choice to round down on the boiler power compared with the previous one. He didn't seem much interested.

[Toppers]

1 hour ago, Carrerahill said:

I may not be a UFH buff but I know enough about boilers to answer this one. It can do but depends on the UFH loads and boilers modulation ratio - a buffer tank is a mitigation measure but an inefficient one at that. So the best way to engineer out short cycling is with with things like a towel rad on the circuit on full flow or heat a central colder area like a hall with a rad which can consume enough to consume enough of the boilers minimum capacity. This of course is only an issue when other rads on the system are drawing very little from the system - if the house is being heated and the system demands enough it won't be an issue. Sometimes having a slightly smaller boiler is actually better than a bigger boiler in these circumstances. 

 

Our radiators are in regular use, would I need to fit something else?

[Carrerahill]

6 minutes ago, Toppers said:

 

Our radiators are in regular use, would I need to fit something else?

Should be good, the load on the boiler from the rads would probably stop short cycling - it's easy enough solved to be honest so I would not worry. 

[Carrerahill]

8 minutes ago, Ed Davies said:

OTOH, it's likely that a lot of radiator systems short-cycle, too. Here's my rented house for New Year's day this year. Blue line is the overall household electricity consumption and green line is the temperature of the flow to the radiator in the bedroom I use as a study.

 

The heating comes on at 07:00. It runs steadily for about 20 minutes then starts to short cycle as you can see from the castellated power consumption as the blower and oil pump switch on and off. The spike at 08:30 would have been the kettle for tea with breakfast. Not sure why the flow temperature to the radiator changed at about that time, maybe removing something left on a radiator to dry? It continues to cycle until 09:30 when the the thermostat in the living room was satisfied and both the boiler itself and the circulation pump turn off. Some of the other pulses of heating needed early in the day also have a few short cycles.

 

I think there's a problem that plumbers are motivated to oversize boilers. No customer is likely to call them back for a bit of short cycling but if the boiler is underpowered for the coldest days they'll get it in the neck. When the boiler here was replaced I showed a graph like this to the plumber and suggested if he had a choice to round down on the boiler power compared with the previous one. He didn't seem much interested.

You keep producing lots of good graphs from your house, it makes me think you have a control room and lots of sensors and a home management or at least monitoring system that I suspect you made, can you elaborate if you do?

 

I love metrics, I am looking at an Arduino based BMS for my house just because I can and I love this sort of stuff.