Underfloor Heating and Viessmann Boiler Set up

[revelation]

Hi all

 

We have had the whole house set up for underfloor heating (no radiators)

 

The GF is in a 50mm screed, the FF and Loft is between joists on aluminium spreader plates. 

 

We have a manifold/pump serving the entire ground floor, and one manifold/pump serving the FF & Loft. 

 

We have a Viessmann 200W systems boiler, we were planning to run with a low temp from the boiler (to help with modulation) and let that be the temperature that the whole system runs on.

 

My plumber has done a few ground floor in-screed installs but hasn't done it where there are both screed and between joists installations.  I have realised that the FF manifold will need to run at a slightly different temperature than the ground floor due to the use of different materials.

 

What would be the best way to set this all up, so it worked as efficiently as possible? 

 

We were also looking at utilising Viessmann weather comp on the system is that as simple as just wiring the sensor in or is there more to consider?

[JohnMo]

The UFH pump would normally come with a temperature control valve, the different temperatures would be set at the manifold.  You just run the system at the highest temperature of two systems.

 

Some things to discuss with your plumber.  

 

Although your boiler has a good modulation range, will it short cycle, when several circuits have met their demand (no flow required) and the weather is say 10 to 12 degs.  Your demand for heat will be very low.

 

Do you need or have you already got a buffer tank.

 

If you are well insulated, it may not be worth installing weather compensation, we have it, but ended up turning it off, as it started to cause temperature under and over swings.  Instead we ended up setting a temp that gave the least over swing by trail and error.

Edited December 3, 2021 by JohnMo
Last sentence made no sense, do corrected

[Nickfromwales]

+1 on not bothering with WC’p in a well insulated, low energy dwelling. The house heating system and thermal time constant just cannot adjust linear to that being sensed from

outside. I have it going on atm with a very high-spec Steibel Elton ASHP ( aiming for a CoP of 6 ) but will likely have to make WC’p defunct after commissioning as I expect it won’t cope with a PH. 
 

18 minutes ago, JohnMo said:

You just run the system at the highest temperature of two systems.

In a nutshell, yes, but you should set the flow temp just a bit higher if there is to be a buffer or low loss header.

8 hours ago, revelation said:

My plumber has done a few ground floor in-screed installs but hasn't done it where there are both screed and between joists installations.  I have realised that the FF manifold will need to run at a slightly different temperature than the ground floor due to the use of different materials.

 

What would be the best way to set this all up, so it worked as efficiently as possible? 

I have just been called to retrospectively adapt an identical setup to yours, and I installed a 50L wall mounted buffer tank which was used as an energy buffer, to absorb the heat from a single heat cycle eg to stave off short-cycling.

Quick and easy job. 
 

 

[revelation]

On 03/12/2021 at 09:35, Nickfromwales said:

+1 on not bothering with WC’p in a well insulated, low energy dwelling. The house heating system and thermal time constant just cannot adjust linear to that being sensed from

outside. I have it going on atm with a very high-spec Steibel Elton ASHP ( aiming for a CoP of 6 ) but will likely have to make WC’p defunct after commissioning as I expect it won’t cope with a PH. 
 

In a nutshell, yes, but you should set the flow temp just a bit higher if there is to be a buffer or low loss header.

I have just been called to retrospectively adapt an identical setup to yours, and I installed a 50L wall mounted buffer tank which was used as an energy buffer, to absorb the heat from a single heat cycle eg to stave off short-cycling.

Quick and easy job. 
 

 

 

 

We have an old 1930, property which has been extended.  It has had the front and back re-built so has cavity insulation.  The side of the house has 50mm of EWI.

 

This is something that was suggested as a fairly cheap solution, but don't know if this is the best way? 

You will need hydraulic seperation. Standard mixers are not designed for low-temperature heating.

1 - Ditch the mixers on the manifolds

2 - Use ccts at the boiler

3 - Run weather comp with a Viessman emp1 and secondary flow sensor. 

4 - Retrofit room stats on any rooms you find gets too hot

This is simple and low cost and low running cost.

 

 

[Nickfromwales]

2 minutes ago, revelation said:

1 - Ditch the mixers on the manifolds

2 - Use ccts at the boiler

3 - Run weather comp with a Viessman emp1 and secondary flow sensor. 

4 - Retrofit room stats on any rooms you find gets too hot

This is simple and low cost and low running cost.

 

 

On 03/12/2021 at 01:23, revelation said:

The GF is in a 50mm screed, the FF and Loft is between joists on aluminium spreader plates. 

1. You categorically cannot ditch the thermostatic mixing valves on the manifolds. How else do you intend creating different temps for the differing disciplines??

2. Different circuits on the boiler? Different ccts will only be fed with the designated flow temp.

3. Good luck with making that work with an emitter that takes a long time to get the rooms up to temp. Honestly.

4. You would need room stats for all zones from the get-go, and these are not optional. This point makes no sense whatsoever, sorry.

[revelation]

I appreciate I don't know a great deal about the setting out of UFH etc.

 

However, it has actually been difficult to get consistent information in regards to the setup of the system.

 

The above advice was from an approved Viessmann engineer so thought it may have been possible, guess not.

[Adsibob]

On 05/12/2021 at 01:38, revelation said:

I appreciate I don't know a great deal about the setting out of UFH etc.

 

However, it has actually been difficult to get consistent information in regards to the setup of the system.

 

The above advice was from an approved Viessmann engineer so thought it may have been possible, guess not.

The modulation on your Veissman boiler is market leading. Something like 1:17. With a low loss header, you should be fine. I would keep space somewhere to install a buffer tank if necessary, but I wouldn’t necessarily install one from the get go, as you might not need one if you have a low loss header.

[SteamyTea]

If you have a buffer fitted, would there be any advantage in adding a low loss header, and visa versa?

A buffer is a simple, cheap and easy to understand bit of kit, I would have thought it was one, or the other, but both is, if correctly sized, unnecessary. 

[revelation]

23 hours ago, Adsibob said:

The modulation on your Veissman boiler is market leading. Something like 1:17. With a low loss header, you should be fine. I would keep space somewhere to install a buffer tank if necessary, but I wouldn’t necessarily install one from the get go, as you might not need one if you have a low loss header.

 

Thank you, is there a simple diagram anywhere that you are aware of that would simply show the arrangement.  As I think my plumber hasn't fully got his head around how he will do it.