Planned new UFH install in extension

[Milgo123]

We have a new ground floor rear extension being added to our Victorian mid terrace and the intention was to make the change to a single zone (2-Loops) wet UFH in the extension (concrete beam & Block) and the adjoining back room that will be knocked through (timber suspended floor) this will entail removing 2 radiators from the old kitchen and back room.

 

The more I investigate, the more concerned I get that is what I plan on doing is even possible...why you ask? 

 

My existing setup is a 15kW heat only Glow-worm 15r with a 200L UVC on S-Plan. Control is via a Drayton Wiser 3-channel (only 2-channels in use currently - DHW & radiators) The boiler is 7 years old and this setup has heated the house adequately for the past 7 years with the boiler output temp set at 58.

 

The builders "plumber" has indicated that I would need a new boiler! although to be honest I have not had a conversation with him yet to ascertain the reason/s why he thinks that this would be the case.

 

So in my head this all sounded easy! Control the new UFH as 1 zone from the spare wiser channel and the remaining radiators as 1 zone on the existing channel, DHW on its channel.

 

My concerns...

1. Do I need to use actuators on the 2 loops on the manifold for the ufh seeing as they will both be in the same zone? Room temperature will be controlled by a Wiser wireless stat!

 

2. Do I need to use a Wiser ufh controller to control this single zone? 

 

3. Water temperature differences required for UFH, radiators and DHW? Would the current 58 boiler output water temp be low enough for the UFH blend valve to lower it sufficiently to be the right temp for the UFH

 

Hope the above makes sense and I'm possibly over thinking but would be glad of your thoughts.

 

Thanks. 

[JohnMo]

You will need a heat loss calculations to determine if the existing boiler is ok or otherwise.  

 

No need for actuators, you will need a pump, mixer valve and wiring center.  Once thermostat is no longer calling for heat the pump will stop.

 

Wiser thermostat looks an expensive way to control a couple of loops and you possibly need to use the UFH controller instead of a simple wiring centre.

 

The mixing valves are designed for that.

[Milgo123]

With the new extension being built to current regulations regarding insulation would it be fair to assume that the amount of heat required for the house would be no more than it currently is? Point taken regarding heat loss calculations though. Is that something that I could do or would you suggest getting it done professionally? 

 

Yes I understand that a manifold kit comes complete with the pump, mixer valve and zone valve. Would these items be wired back to the same wiring centre that the existing zone valves and heating controls/thermostats are wired to so long as there are enough connections available? 

 

I have the Wiser 3-channel programmer, 2 room stats and some trvs already so was wanting to utilise them instead of having to purchase new equipment. 

 

Is there any guidance regarding how much the input temperature can be reduced by a mixing valve or would it more likely vary by manufacturer? 

 

Finally, could you say what might dictate me having to use the Wiser controller as opposed to the standard wiring centre that the other zone valves and controls are wired to? 

 

Apologies if any of the questions appear really dumb, I'm just trying to get as best an understanding as I can so that I can have a useful input to whatever is installed and of course other posters/readers might find the information useful. 

 

Thanks for your quick response. 

[Olf]

On 30/06/2022 at 01:13, Milgo123 said:

would it be fair to assume that the amount of heat required for the house would be no more than it currently is?

You remove (from heat loss at least, but to large extent physically) one wall of W width and replace it with a new one of W width (back wall), 2 side walls of L length and floor and roof of WxL area. So assuming your extension is a cube (the optimal shape from efficiency perspective), the losses through each of your new surfaces must be 1/5 of the existing one - and that's the best case. You assume Victorian = Very bad, but do check the numbers

 

 

On 30/06/2022 at 01:13, Milgo123 said:

Is that something that I could do

Yes, there are plenty of online U calculators to get idea of your current wall performance, search here of 'Jeremy Harris spreadsheet' to get new figures

 

 

On 30/06/2022 at 01:13, Milgo123 said:

 so was wanting to utilise them instead of having to purchase new equipment. 

I did something similar and ended up with a situation, where rads (existing building) typically call for heat for longer than the new UFH. So the UFH became a new 'radiator', than 'opens' (via pump rather than TRV) and shares circuit with the rest. So I did rely on the existing single stat in the old house, with UFH wiring centre completely independent. I replaced it now with a stat linked to the wiring centre, occasional cases where UFH calls for heat mean that rads heat as well, but the net result is only change in timing, rather than extra unnecessary output (and rads have TRVs, so would close if too hot). How you want to link and program your heat emiters is down to your preference of heating: stable temperature all day long on one end vs some rooms warmer and some colder over specific periods. 

 

On 30/06/2022 at 01:13, Milgo123 said:

Is there any guidance regarding how much the input temperature can be reduced by a mixing valve

It is specified on the valve and adjusted by the user to the required temperature. Typically they come in 35-70 flavour, in low heat buildings those blending down to 25 (or lower) are recommended though. 'Required' is combination of many factors: floor surface (some have limits), rate of temperature rise, risk of heat source short cycling etc.