underfloor heating advice

[beesley121]

Hi guys,
Been asked to install some undefloor heating for a house thats been completely renovated. House is a 3 bed semi, customer wants the boiler in the loft and the whole of the down stairs installed with underfloor heating. she does not want any radiators upstairs in bedrooms etc other than maybe a towel rad in the bathroom
now, ive never installed a underfloor heating system but have been doing alot of reading. Apparently, each circuit is limited to 120m in length. I under you can buy kits that show you how the lay the heating pipes to give you the best out of the system but If i buy all the kit seperatly to save money, I wont get these plans so how do i know which way to lay the pipes?
im also worried that the under floor heating will not be enough to heat the whole house as they dont want rads upstairs, is there someway this can be calculated?
thanx in advance, you help is really appreciated

 

[Cds]

You need to undertake a heatloss calculation and then size the underfloor heating (UFH) to match the heatloss loads. UFH outputs are limited and any shortf all will have to be made up.

UFH suppliers will do the work for you but only if you buy their equipment. You can also get the design done by an independent designer that will charge you for the design and provide enough information, including layout drawings, for you to purchase the equipment and install it.

Not sure how much of a saving can be made but I do a number of designs for heating engineers.

 

[SimonG]

Get in touch with speedfit. They'll do all the calcs and plans. I was told they will even send an engineer out foc for the day for your first install.

 

[chris watkins]

or Polyplumb much easier to lay than Speedfit
Has anybody looked at the groundfloor construction, you are going to need 75mm of insulation + 65mm of screed on the existing floors if solid ??

 

[Destroyer2813]

Downstairs floor structure will need to be determined first to see what you will need to regarding insulation and as mentioned go to a manufactuer for the design. I tend to prefer polyplumb

 

[SimonG]

or Polyplumb much easier to lay than Speedfit
Has anybody looked at the groundfloor construction, you are going to need 75mm of insulation + 65mm of screed on the existing floors if solid ??

Will have to try polyplumb, not the first time I've heard that.

 

[mike-c]

If the whole house is being renovated is there any chance of fitting the pre piped chipboard flooring? I have fitted it a few times and it is quite effective. I think poly plumb do it.

 

[beesley121]

This boiler is only going to be running the underfloor heating, maybe a towel rad in the bathroom and obviously the ho****er

do i have to buy a manifold with a pump and mixer attatched or can i just run the whole thing straight of the boiler via a manifold with pump and mixer


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[Gray0689]

or Polyplumb much easier to lay than Speedfit
Has anybody looked at the groundfloor construction, you are going to need 75mm of insulation + 65mm of screed on the existing floors if solid ??

You can get thinner insulation and thinner screeds if needed

 

[Gray0689]

This boiler is only going to be running the underfloor heating, maybe a towel rad in the bathroom and obviously the ho****er

do i have to buy a manifold with a pump and mixer attatched or can i just run the whole thing straight of the boiler via a manifold with pump and mixer


​

No you don't have to have a manifold with mixer attached
Just run flow return to mixer then pump to manifold you can buy the stuff separate or as kit your choice

 

[chris watkins]

You can get thinner insulation and thinner screeds if needed

Gray0689 please be careful with advice, as we don't know details of floor construction, if lesser insulation is used 1. it is likely it will not meet the Building reg's over here & 2. the system may not give the outputs sated as more losses through floor.
Don't understand what you are asking beesley121 re the manifolds, pump & mixer linked to boiler ?? Is the boiler got to heat the a HW cylinder ??

 

[beesley121]

Gray0689 please be careful with advice, as we don't know details of floor construction, if lesser insulation is used 1. it is likely it will not meet the Building reg's over here & 2. the system may not give the outputs sated as more losses through floor.
Don't understand what you are asking beesley121 re the manifolds, pump & mixer linked to boiler ?? Is the boiler got to heat the a HW cylinder ??

I've never laid or seen anyone do a underfloor heating job. I've watched a few vids on utube but that's it. I understand what the mixer does on the manifold by keeping temp low enough not to break screed but some manifolds have pumps on, why is this? The combi boiler I'm putting in is only running this underfloor heating so it has a pump of it's own, y the need for a second pump

 

[chris watkins]

Hi beeley121
The pump on the U/F manifold is always required its job is to solely circulate water around the U/F system which can have a high resistants with up to 12 loops each up to 100M long depending on which system is installed. The system pump in this case in the combi will be used to circulate water through the boiler & out to the manifold/s only this is also likely to have a high resistance to the flow of water. The pump in the boiler would not have the power to do both.
Most of the systems you may have seen come with a thermostatic mixer valve which blends in fresh hot water as required to maintain, normally 50deg C, going around the pipe coils. As fresh water is allowed in of cause cooler water must flow out back to the boiler to be reheated. If the boiler is serving hot water via indirect cylinder or a heating system that requires higher than 50deg C water then a blending valve will be required but if the boiler is only serving the U/F then so long as the boiler heating output temp can be limited (set & fixed) to give 50deg water then one wouldn't be required & the boiler would be very efficient as it would always be in condensing mode.
Hope this helps ? Tip - make sure the customer is fully aware of the facts around having & using U/F heating it is NOT like having rad's & must be left on for much longer or all the time when cold outside.

 

[Cds]

With a three port thermostatic mixing valve there will betimes when no additional hot water is required and thus the valve will beclosed to the boiler side of the circuit. When this happens the boiler pumpwill not provide circulation (even if it was capable of overcoming the UFHpipework resistance) to the UFH part of the system thus the requirement for theUFH pump after the mixing valve.

 

[Gray0689]

Gray0689 please be careful with advice, as we don't know details of floor construction, if lesser insulation is used 1. it is likely it will not meet the Building reg's over here & 2. the system may not give the outputs sated as more losses through floor.
Don't understand what you are asking beesley121 re the manifolds, pump & mixer linked to boiler ?? Is the boiler got to heat the a HW cylinder ??

I didn't mention a lesser insulation I said you can get thinner insulation and thinner screed
Still has same u value property's to 100mm high density insulation
And the liquid screeds are put in thinner than sand cement
And both will meet building regs do don't think I need to be careful with advice

 

[chris watkins]

I didn't mention a lesser insulation I said you can get thinner insulation and thinner screed
Still has same u value property's to 100mm high density insulation
And the liquid screeds are put in thinner than sand cement
And both will meet building regs do don't think I need to be careful with advice

Gray I stand corrected with the liquid screed, not so sure about the insulation, would be interested in any details.
My point in responding was without any details beesley121 may have been tempted to use the thinner boarding designed for suspended intermittent floors on a ground floor in this renovated house. Sorry if you took offence.

 

[Gray0689]

No offence taken mate the insulation is a multi layered foil designed for this purpose and it's more expensive than 100mm insulation

 

[chris watkins]

Do you know the manufacturer, as any saving in the thickness could be very handy in refreb's ?

 

[Gray0689]

Can't remember stuffing used but actis do one
[DLMURL]http://www.solarcrest.co.uk/proddetail.asp?prod=FOIL015[/DLMURL]

 

[beesley121]

right guys, this job is going ahead but ive not heard back from the likes of nu-heat regarding plans/cost. Problem is customer wants a price as shes waiting for kitchen to be fitted and floor to be laid so all this underfloor heating needs to be done by then.

ill upload some plans of the house so you get a better idea whats going on. Customer now wants both the ground foor and the 1st floor fitted with underfloor heating. no rads apart from a towel rad in each of the bathrooms. Im guessing im goind to need 2 x 3 port manifolds with pump and mixer as theres 3 rooms on each floor. so im thinking it would be good to give each room its own circuit. ground floor is approx 26sqm in total. 1st floor is 34sqm

what im unsure how to do is the layout of the piping in the floor? can anyone edit the plans i will try to upload to show me how its done. Im a complete newb to this so any help really appreciated. Also what size boiler would be needed to run this? not sure how many watts in total the heating system will be? and what controls should be put on the system?

sorry for all the questions but if yer dont ask, yer dont get. hopefully you nice guys will help me out

just to note, ground floor will be tiled, 1st floor will be carpeted and tiles in bathrooms. 1st floor has joists running from to back at 350mm centres as does the kitchen on ground floor. The louge and dining room will be concreted to bring the floor level up to the level of the kitchen floor. Can the pipes be laid in concrete or does it have to be screed?

 

[beesley121]

here you go

 

[beesley121]

and again

 

[Mike Jackson]

The manufacturers will deal with all of this for you. Just give them a set of the plans and they size it and tell you the layout required.

 

[wetdrip]

Great thread guys, keep it up.

 

[SimonG]

right guys, this job is going ahead but ive not heard back from the likes of nu-heat regarding plans/cost. Problem is customer wants a price as shes waiting for kitchen to be fitted and floor to be laid so all this underfloor heating needs to be done by then.

ill upload some plans of the house so you get a better idea whats going on. Customer now wants both the ground foor and the 1st floor fitted with underfloor heating. no rads apart from a towel rad in each of the bathrooms. Im guessing im goind to need 2 x 3 port manifolds with pump and mixer as theres 3 rooms on each floor. so im thinking it would be good to give each room its own circuit. ground floor is approx 26sqm in total. 1st floor is 34sqm

what im unsure how to do is the layout of the piping in the floor? can anyone edit the plans i will try to upload to show me how its done. Im a complete newb to this so any help really appreciated. Also what size boiler would be needed to run this? not sure how many watts in total the heating system will be? and what controls should be put on the system?

sorry for all the questions but if yer dont ask, yer dont get. hopefully you nice guys will help me out

just to note, ground floor will be tiled, 1st floor will be carpeted and tiles in bathrooms. 1st floor has joists running from to back at 350mm centres as does the kitchen on ground floor. The louge and dining room will be concreted to bring the floor level up to the level of the kitchen floor. Can the pipes be laid in concrete or does it have to be screed?

Don't assume that because you have three rooms it will be a 3 port manifold, due to maximum loop lengths you may have multiple loops per room. But as Mike Jackson said the manufacturer will sort all that for you.

 

[310]

hi uf heating is as only good as insulation be sure to put 100mm insulation on floor lay pipe on also 40mm on outside walls also a small buffer would be good

 

[tweakyboy]

Contact Osma Wavin UFH, I use alot of it. Their tech line is pretty good, they will sort out plans for you and do all of the sizing etc.