Can my boiler handle underfloor heating?

[freddyq]

Hi all,

Needing some advice on underfloor heating please. I have an approximately 4 year old Vaillant ecoTec Plus 838 combi boiler which is currently serving 11 radiators around the house which includes 2 towel rails. I've heard that if you want underfloor heating you need to ensure the boiler can handle it so how can I determine that?

The area I am wanting to put underfloor heating in is roughly 29m2 but will be split into 3 rooms and I'd be looking for 3 zones of the underfloor heating for each room so it can be controlled individually.

Thanks!

 

[oz-plumber]

I doubt your boiler will have any problems with the extra load.

Just ensure that you have a mixing manifold in the UFH. This is to get the water temperature down to @ 45 C.

 

[snowhead]

Is that 29m2 additional floor space or to replace existing radiators?

 

[Stu-B]

Are you removing 3 rads and fitting underfloor heating or adding to the system?
You’ll need to work out your existing heat output/radiator sizes then subtract that from your boiler heat output in CH mode.
Calculate the heat output from your underfloor heating, and see if the figures match up.
It’s not enough to say 11 rads cos we don’t know if you live in a small house with loads of rooms or a massive house with huuuge rooms and rads.
Get in touch with an underfloor heating manufacturer, they’ll do you drawings and calculations.

 

[freddyq]

Is that 29m2 additional floor space or to replace existing radiators?

Additional floor space. It's a new extension.

 

[IND_Nick]

If you contact an underfloor heating supplier and send them plans most will work out the layout and provide the heat input in kW required. You then need to work out the rest of the house and see if the boiler has sufficient capacity. Your current boiler has a high out put, so should be ok, but I would definitely do the calculations first.

 

[freddyq]

If you contact an underfloor heating supplier and send them plans most will work out the layout and provide the heat input in kW required. You then need to work out the rest of the house and see if the boiler has sufficient capacity. Your current boiler has a high out put, so should be ok, but I would definitely do the calculations first.

OK thank you. I'll contact a specialist. If I give them details of my existing rads will they also be able to work out existing house stats?

 

[EvilDrPorkChop]

You will have more than enough with that boiler.

 

[freddyq]

You will have more than enough with that boiler.

That's good to know! Thanks..
[automerge]1575810141[/automerge]
I've done some more checking as I can't call around until Monday morning. My boiler has 38.7kW output. How do I measure the kW required by my existing rads?

 

[EvilDrPorkChop]

That's good to know! Thanks..
[automerge]1575810141[/automerge]
I've done some more checking as I can't call around until Monday morning. My boiler has 38.7kW output. How do I measure the kW required by my existing rads?

That'll be for HW only. Underneath there is a label with all the details. It's the KW output next to the Radiator symbol you need to look at - it'll be about 28kw for CH. Which as I said earlier should be more than enough for what you require.

 

[freddyq]

That'll be for HW only. Underneath there is a label with all the details. It's the KW output next to the Radiator symbol you need to look at - it'll be about 28kw for CH. Which as I said earlier should be more than enough for what you require.

Here is what the label underneath says..

 

[centralheatking]

Hi all,

Needing some advice on underfloor heating please. I have an approximately 4 year old Vaillant ecoTec Plus 838 combi boiler which is currently serving 11 radiators around the house which includes 2 towel rails. I've heard that if you want underfloor heating you need to ensure the boiler can handle it so how can I determine that?

The area I am wanting to put underfloor heating in is roughly 29m2 but will be split into 3 rooms and I'd be looking for 3 zones of the underfloor heating for each room so it can be controlled individually.

Thanks!

UFH wet systems rely on a constant drip feed of blended ch water and a large thermal mass , usually
concrete heavily insulated and are not really suited to. retro fit in older buildings is problematic. Also
you need to examine your home lifestyle to be sure its ok for this type of system. UFH in the correct building for suitable homes is absolutely ace, get it wrong and its misery and big bills
centralheatking

 

[freddyq]

UFH wet systems rely on a constant drip feed of blended ch water and a large thermal mass , usually
concrete heavily insulated and are not really suited to. retro fit in older buildings is problematic. Also
you need to examine your home lifestyle to be sure its ok for this type of system. UFH in the correct building for suitable homes is absolutely ace, get it wrong and its misery and big bills
centralheatking

By retro fit do you mean that its not running around the whole house? Because otherwise what I'm looking to install the UFH in is a new extension rather than under an existing floor so the extension has a cavity wall with insulation and insulated roof. The concrete of the new extension floor hasn't been laid yet but will be in the next couple of days along with insulation so it should be a much more thermally efficient space than the rest of the existing house.

In terms of usage, the area won't be used all the time so neither will the UFH but the idea was that when we do use the space we turn it on and the UFH would heat the room evenly and the heat would last through the day. I am in two minds about it to be honest but a neighbour has said he has it, albeit with a mega flow system, and it works really well and heats up in a couple of hours.

 

[centralheatking]

By retro fit do you mean that its not running around the whole house? Because otherwise what I'm looking to install the UFH in is a new extension rather than under an existing floor so the extension has a cavity wall with insulation and insulated roof. The concrete of the new extension floor hasn't been laid yet but will be in the next couple of days along with insulation so it should be a much more thermally efficient space than the rest of the existing house.

In terms of usage, the area won't be used all the time so neither will the UFH but the idea was that when we do use the space we turn it on and the UFH would heat the room evenly and the heat would last through the day. I am in two minds about it to be honest but a neighbour has said he has it, albeit with a mega flow system, and it works really well and heats up in a couple of hours.

My take on UFH is its a whole building set up, with heavily insulated concrete floor slabs that need to be drip fed with heat 24 7 to operate effectively and efficiently.
If you are wanting a walk in and heat up heating system going from o 2 60 in an hour then look eleswhere. Others on PF will comment ..chking

 

[EvilDrPorkChop]

By retro fit do you mean that its not running around the whole house? Because otherwise what I'm looking to install the UFH in is a new extension rather than under an existing floor so the extension has a cavity wall with insulation and insulated roof. The concrete of the new extension floor hasn't been laid yet but will be in the next couple of days along with insulation so it should be a much more thermally efficient space than the rest of the existing house.

In terms of usage, the area won't be used all the time so neither will the UFH but the idea was that when we do use the space we turn it on and the UFH would heat the room evenly and the heat would last through the day. I am in two minds about it to be honest but a neighbour has said he has it, albeit with a mega flow system, and it works really well and heats up in a couple of hours.

It'll be fine in your newly built extension. Just beware you have to run it 24/7 as it doesn't work like radiators. You cannot turn it on and expect it to be hot within the hour like with radiators. It can take a good 8 hours for any heat to start coming through, and the most efficient way is to run it 24/7.

It has it's Pros and Cons as with anything, but all the systems we fit everyone seems to love it.

 

[freddyq]

It'll be fine in your newly built extension. Just beware you have to run it 24/7 as it doesn't work like radiators. You cannot turn it on and expect it to be hot within the hour like with radiators. It can take a good 8 hours for any heat to start coming through, and the most efficient way is to run it 24/7.

It has it's Pros and Cons as with anything, but all the systems we fit everyone seems to love it.

So then it's not really suited to rooms not constantly in use? I can see the use in a kitchen diner or living room but ours will be a dining room and office which will only be in use as needed not all the time...