A simple underfloor heating layout system? Advise please!

[micketherton]

I have just fitted 7 underfloor heating pipe loops of my 3 floored Victorian house. I have the idea to make up a simple "natural" system without any auxillary items, using two manifolds made with 22mm push-fit copper tee pipes and locate it under the ground floor staircase in cupboard.

2 upper floors of wood with 4 loops on spreader plates; and 3 ground floor on screeded loops, with 2 convential rads serving existing area.

I intend to use a combi condensing boiler, and run the supply heating pipe first directly to two in-line conventional radiators, then return that flow to the input manifold for the 4 underfloor wooden upper floor heating loops. That return manifold will go an input manifold supplying the 3 underfloor concrete ground floor heating loops. Then this return manifold will go back to the boiler!


I figure the conventional radiators will lower the water temperature down for the wooden floor manifold, then this lower temperature water return will go into the concrete floor manifold, which will then return to the boiler at a much cooler temperature! Thus making a very efficient condensing system. I will monitor the temperature drop with temporary thermometers at each return manifold to see how it works out !


I will balance the loops with gatevalves on their returns (or what else do you suggest).

I intend to only use the inbuilt boiler water temperature thermostat and timer, to control the whole house's heating temperature, and to only use the inbuilt boiler pump to circulate the system. I can always retro fit thermostatic radiator valves in-line on each loop in each of the rooms if the heating is uneven.

Q.1. Do I need to put in any Automatic Airbleed Valves on the upper storey loops, or is there enough water pressure in the system to force any air bubbles back down to the manifold AAV on the ground floor? If not, where does the AAV go? -Just before the return pipe goes vertically down to the ground floor manifold?

Q.2. Do I put AAV,s on BOTH the inlet AND return manifolds?

Q.3. Is the inbuilt combi pump strong enough to do this job? 6m head. Any recommendatations of a good boiler! Is a Smart Pump a good idea?


Q3. Is this workable? and what else should I consider. All your thoughts are most welcome- good or bad! mant thanks

 

[SimonG]

You need temperature control of the loops. Get the proper gear and do it properly, more expensive in the short term but will save you money down the road.

 

[micketherton]

many thanks for your advice Simon. But I am more concerned at the moment as to whether I need to put an air bleed in the loops on the upper floors, as I am about to lay the T&G floorboards down and it will be a difficult retro fit. Is there enough water pressure in the heating system to purge the air out down to the manifold on the ground floor? Can you advise?

I can easily retro fit your suggested heating water mixing contollers if my experiment does not work. many Thanks

 

[Bartdude]

As above,actuators on the manifold controlled by thermostats are essential to control the room temperatures. You will also need a mixing valve on the manifolds to ensure the right temperature to the UFH.You can't rely on the radiators to lower the temperature,that's just guesswork I'm afraid.

AAV's should be on every manifold too.

One thing that could be a problem is the age of your house,have you had up to date insulation installed?Because without it underfloor heating is a waste of time. It's not usually suitable for older houses,unless major refurbishment is done and the whole house is brought up to modern insulation standards

 

[SimonG]

Apologies but won't give advice for something that shouldn't be done.

 

[micketherton]

Thanks for your advice.

Many thanks for your interest in my project. I have completely refurbished the house with loads of insulation on walls floors and roof, hence the underfloor heating idea. It's ideal for my a small roomed house to eliminate the radiators!

Can you answer me this though.

Is there enough water pressure, either within the combi pump system( or using mains pressure) to purge any possible future air build up in the upper floor loops, down the the ground floor maifold AAV. Or do I need to add additional air bleed points on the high points on each of the upper loops . (I'd rather not do this if possible, as it would be difficult aesethitically to put in place in the rooms).

As said in the previous reply, I can easily retro fit a conventianal manifold system if my plan doesn't work out. But it would be very difficult to add air bleed valves to the upper floor loops under the T&G engineered oak floor if required!

So I need to know now if I will be able to get rid of any air in those upper loops by isolating at the manifolds and purging each loop with either the boiler heating water pressure, or even using a mains feed into the system?

cheers Mick

 

[Blackcatgas]

To hell with it Mick, just put it in how you like with no aavs etc, its all part of the fun of an "experiment", if it all goes wrong you could always make a homemade crack pipe with the spare bits.

 

[micketherton]

I never said not using AVVs. Of course they will be on the manifolds.

What I would like to know from someone in the heating engineering profession is ' Is there sufficient water pressure in a combi-boiler wetunderfloor system to force any air 6 meters vertically down a 15mm pipe to the ground floor manifold bleed valve'.

Failing that, will a mains pressure supply purge the sytem?

Or do I need and additional vent at the high point of each loop?

It should be relatively easy to answer for any jobbing professional I would have thought!!

 

[tweakyboy]

To hell with it Mick, just put it in how you like with no aavs etc, its all part of the fun of an "experiment", if it all goes wrong you could always make a homemade crack pipe with the spare bits.

Hahah best reply ever!

 

[tamz]

Your whole concept of how it should work is totally wrong. By the sound of it you will soon learn an expensive lesson in plumbing.
Better to read up a bit more or better employ the services of a local firm even on a consultation basis.
It will be cheaper than ripping the place apart to alter everything.

 

[SimonG]

It should be relatively easy to answer for any jobbing professional I would have thought!!

It is a very easy question to answer.

Questions for you -

1. Do you know the maximum floor temperature for an underfloor heating system?

2. Do you know why this temperature was decided on?

3. With no thermostat or mixing device how do you envisage to maintain the temperature at or below the maximum?

 

[micketherton]

Many thanks for your advice.
But how can the concept be TOTALLY wrong! Surely the principal is correct and simple. It's only hot water!!

At each stage the supply feed water is getting cooler, serving each floor type temperature requirement,and ending with a final return temperature to the boiler that should work perfectly in condensing mode.(Yet to be discovered)

It won't really be an expensive lesson in plumbing, as it will be easy to reftro fit any parts at the manifolds and boiler.

The only thing I need to know now is the potential air purge problem, as the manifold (and AVV) is 6m below the floor level,

As yet, no one seems to be know the answer to the simple question of whether combi heating water supply pressure can purge a 15mm pipe of air from 6 meters high. Surely mains pressure can shift the air down 6m. ( As doesn't that mean that over 6Bar is needed to force the air downwards?)

If, from this forums' advice, I am told air won't go downhill, I can always fit an AVV up top on the loops.

Simples! But would just like an answer to the physics!

All comments still greatly appreciated!!! honestly

 

[micketherton]

Hi Simon, thanks for getting back

As you well know, screeded floors will require around 25-30 degrees input ( to give 16-20 degree output)
The uppers wooden suspended floors require a slightly higher heat input of 30-35 degrees to get through the wood etc.

The initial two conventional radiators on the feed, I intend tosupply initially at around 50 degrees (or whatever the min boiler temperature output is)

I will control the floor temperatures by monitoring the temperature of the supply and return manifolds (4 total) and using the boiler heating output thermostate and timer as controls.

I figure I can always retro fit a mixing valve on one of the manifold supplies if needed.

What about the air purge thing though!

 

[Gray0689]

Firstly how do you know if you have the correct centres for the required heat in each circuit (or is this part of your so called experiment)

It is called warm water underfloor heating for a reason the temps you are planning on using are to high
How are you planning on controlling these circuits??

As tamz says your concept is all wrong
Underfloor heating is not justices simple as running pipes with water in then there is a lot of calculations to take in to account
Even down to the floor covering
Not all types of insulation is acceptable in floors Some may need spreader plates
You need to get someone in to look just to make sure your not making a complete mess of the job and to be honest from what you have wrote I think you are

 

[micketherton]

Thanks for your advice Gray

It is based on 300mm centres on floor areas giving 100w/m2 screed and tiles, and 60w/m2 ouput for suspended floors. The flooring pipes are all laid out and either screeded, or have spreader plates with engineerd oak T&G.

re. my initial question- Do you know if air go downhill then?

 

[tamz]

Air rises

 

[Gray0689]

Thanks for your advice Gray

It is based on 300mm centres on floor areas giving 100w/m2 screed and tiles, and 60w/m2 ouput for suspended floors. The flooring pipes are all laid out and either screeded, or have spreader plates with engineerd oak T&G.

re. my initial question- Do you know if air go downhill then?

300mm spacing your house better be super insulated
If you got this spacing on a sand cement screed hope you got plenty of money as going to cost a lot to heat
What your suggesting is to be honest ridiculous you need it done properly with separate pumps mixing valves manifolds actuator heads room stats

You don't need air vents as the system should of been purged of air and pressure tested on laying of the pipes if you put the screed on empty pipes it is possible to crush the pipe

Underfloor needs a correct working temp your going to shock the floor with to much heat and can make a mess of your flooring

 

[tamz]

If you had asked any underfloor manu and supplied plans of your house they would have designed it for free.

 

[unguided1]

oh dear

 

[Toddyplumb]

Before you go any futher speak to your floor supplier and ask what they think, before it all goes Bannana shaped

 

[micketherton]

oh dear

Many thanks for your informed opinion

Can you answer me this though. As every other response is also so full of wisdom, but the question is still not answered !

Is there enough water pressure, either within the combi pump system (or using mains pressure) to purge any possible future air build up in the upper floor loops, down the the ground floor maifold AAV. Or do I need to add additional air bleed points on the high points on each of the upper loops . (I'd rather not do this if possible, as it would be difficult aesethitically to put in place in the rooms).

As said mant times in my previous replies, I can easily retro fit a conventianal manifold system if my plan doesn't work out. But it would be very difficult to add air bleed valves to the upper floor loops under the T&G engineered oak floor if required!

So I need to know now if I will be able to get rid of any air in those upper loops by isolating at the manifolds and purging each loop with either the boiler heating water pressure, or even using a mains feed into the system?

Many thanks

Mick

 

[Gray0689]

No you don't need aav if done properly but as yours is an unorthodox way to do things then non of us can answer that question but I see you have what you think is an airlock from previous post
If itis airlocked mains pressure will get rid of it
But as I said the pipes should of been purged of air and water lett in pipes under high pressure till the flooring ie screed laid
You could have a crushed pipe or a kink
Love to see a drawing of how you have done this (job)
Where the cuircits are running

 

[micketherton]

Many thanks for this information!

I do not have any airlocks at the moment, as the system is un-connected and un- pressurised. I don't imagine that 30mm of sharp sand gently screeded over the plastic pipe would crush it, so I didn't screed with pipes under pressure. There are no joins inder the screed, so what could go wrong? It's not a biulding site, with steel toe-capped chippies clambering all over it!

The upper floor are clipped to the side of the joists with aluminium spreader plates wrapped around them made from printers litho plates! It works I've experienced it!

PIPE LAYOUT
There are 2nos. conventianal vertical rads to serve existing conventional concrete floored front room (13m2). This room is open planned to a rear UFH dining room (13m2)
The whole ground floor has three 15mm loops in 50mm screed with slate tiles at 250mm centres serving this diningroom,and kitchen/bathroon/hall (30m2 total UFH ground Floor area)

The 1st floor has 2 bedrooms rooms, each with a loop (300mm spacing) running between joists, serving the two rooms and corridor. It will be boarded in 20mm Engineered Oak T&G

The second Floor is one large bedoom (25m2) laid out as 1st floor on two loops (80m run length each)

All manifolds are located on ground floor in centre of building under stairs

A combi-boiler (5m away from manifold) will first directly supply the two ground floor rads then return into 4 way manifold to supply 2 upper wooden floors. Then that return manifold will run the 3 way concrete loop supply manifold at the lowest temperature; and then via a return manifold to the boiler.

The biulding is very well insulated floor, walls ceiling, and the room heating will be controlled by the boiler heatring output temp and combinations on 15 minute intervals on the timers.

In the past we usually have had our heating on constant low from October to April anyway; and none of our TRVs, or room thermostats have ever worked, so I have always controlled the heating only from the boiler controls quite satisfactory. yes I know it is against regulations!

If my experiment does not work out, I can alway fit TRVs in-line in some of the bedroom loops and re-gig the manifold layout in the proper manner as everyone suggests.

What I needed to know, and what you have kindly answered me, is if I needed to put AAVs on the above the manifold height loops.

Any other problems I can easily rectify at the manifold.

Manny many thanks for you interest in the project and I will post you the outcome when it is up and not running!!!

Any suggestions still welcome too!

regards Mick

 

[Bartdude]

You have to have room thermostats,it will not work properly without them.You have to have mixing valves to control the temperature to the loops from a boiler. I know it's not what you want to hear but I think you should seek an expert opinion before floors are finished,planning is everything with UFH and it's difficult to fix later on. You should have tested the pipework before you screeded too,I've had pinholes in pipe before,it's unusual but it does happen.

What pipe have you used?

 

[Gray0689]

I'm sorry but I think what you are planning is a joke

 

[Dotty]

Mick.

Word of advice cocker.

STOP! NOW!

You have had many replies telling you what you're attempting is not only not going to work, but also in contravention of current regulations and that it will all cost you dearly in the long run.

The reason you've not had the answers you think you're looking for is because you need to walk before you can run.

We all speak from years of training and experience in our chosen field, it's not because we won't help but rather recognition of the fact you're in way over your head here my friend.

Please call a local company in. Yes, it will cost.

But how much is that worth against peace of mind of a job done properly.

And Gray was actually restrained there then.

 

[Gray0689]

Croppie I think you know me too well lol

 

[PlumbingSucks]

You should have a secondary pump for the UFH and if using a combi you need to check MI's that you can have a secondary pump. So you're retro fitting of mani and pump idea if it doesn't work properly (which it won't) will go out the window if you can't have one on your particular boiler. Just do it properly INHO or not at all.

 

[Howsie]

It's only hot water. It's only gas....

 

[dontknowitall]

Why don't you install electric? Piece of cake in comparison ...