UFH system queries

[d307hpo]

Hi,
Any help or opinions appreciated on this topic.

Summary - last year bought a 90’s build house that had a wet UFH heating system designed and fitted to downstairs by NU-Heat.

It’s the last of the santoprene rubber contra flo systems. The floor is a suspended timber type where the pipes are laid within a type of polystyrene bed. As far as I can see the old set up had a thermal store set up, it doesn’t now!

The house was empty for a couple of years and in that time sprang some leaks which corroded the boiler etc.( no leaks in ufh pipes)

When I bought the house I fitted ( /my plumber fitted);

Worcester style 35kw system boiler
300L indirect un-vented water cylinder
Grundfos magna 1
Low loss header (no idea why)
Radiators to the top floor
5 two port valves to create 5 different zones
1 - hot water cyclinder
2- 1st floor radiators
3- uFH manifold 1
4 - UFH manifold 2
5 - UFH manifold 3

heatmiser ufh8 control system and Honeywell evo home thermostats and programmer

Basically everything has worked ok until this real cold weather where the house struggles to get over 19 degrees.

After looking into UFH in more detail it’s clear I wasn’t aware of flow rates and temperatures etc. My initial logic was pump as much hot water as you can as fast as you can!

To increase the performance I need to alter the flow rates etc obviously, problem being this is an old type of system where the manifolds don’t have flow temperate or rate readings.

All I have on my side are 28mm gate vales all over the system to help slow the flow rates.

I have a couple of cheap digital thermometers and and infa red thermometer to measure temps.

At the moment I have the pump down as low as poss and am working on one zone only with the gate valve 70% closed on the flow side. The boiler is at 60 degrees and I’m only seeing a drop between flow and return of about 3 degrees, eg, 40 to 37

Any ideas from there? Pics attached so you can see the set up

 

[d307hpo]

 

[ShaunCorbs]

That’s normal for ufh to have a low delta on average you won’t get anything past 5 dc when the slabs warm

are you running the ufh all the time eg constant?

 

[Brambles]

You will probably get better performance if you replumb and take the radiator and hot water flows / returns direct from the low loss header - albeit you will need one or more additional pumps, depending on whether you take one or two circuits - I would take 2.

The issue you are probably having is that one or more of the ufh circuits are starving the rest of the system - when it is cold and all the heating zone valves are open - but I guess you knew that!

The plumber has fitted a low loss header to separate (hydraulically) the boiler pump from the circulating pump - but he / she could have have got more value from the cost of the bit of kit, rather than just having one secondary circuit

 

[Jerry]

are you running the ufh all the time eg constant?

I agreed with this.

Is the whole house not getting warm or only the UF heating zones?

If everything is getting up to heat and it's not warm when it's really cold, then it might be a heat loss problem. i.e the house loses heat faster than it can produce.

You also have a lot of zones which implies a larger property. It might be an idea to try and figure out your heat requirements (rads+uf+cylinder) and see if the kw of the boiler is sufficient. Chances are it is but it might help.



I wouldn't touch those UF pipes but... you might be able to retrofit the manifolds with their own mixing valve, pump etc like on a modern UF installation.