Oil boiler capacity and underfloor heating advice

[Jim63]

Would appreciate any advice please. I am trying to add some underfloor heating in the kitchen using the existing oil fired boiler and hot water system.

Have installed 10mm pipe loops around the floor (not yet covered over with the screed), but boiler is not coping with this.
If I turn off all 2 or 3 radiators the pipes get nice and hot. With all downstairs radiators on but upstairs off the pipes are only luke warm.

The boiler (Trianco 25kw, with grundfoss 15/50 pump) has always seemed ok before for size of house (5 beds) although rooms on one side sometimes cooler.

Some websites seem to suggest a larger boiler for this size of house, is this the problem or I am expecting too much from the new underfloor heating circuit, or any other suggestions?

 

[chris watkins]

Jim
This is not a DIY job get someone in who understands what they are doing before it ends in tears. What mixing manifold are you using, why are you using hight resistants 10mm pipe.
What insulation are you using, what is the existing pump head, are the controls linked / are you using thermostat so that it is Building regs compliant, should I go on ?????
Not trying to be clever just giving you a flavour or what U/F involves.

 

[Jim63]

Hi Chris
I have done this in conjunction with a heating engineer, he had done something similar and it seemed to work ok.
We have not used a manifold, it is connected to the radiator tails. The plan was to not to replace the radiator heating but just to get some circulation under the floor to take the chill off.
I appreciate that the subject can be complex but hoped to achieve a little extra heat in this one floor area.

 

[chris watkins]

Hi Chris
I have done this in conjunction with a heating engineer, he had done something similar and it seemed to work ok.
We have not used a manifold, it is connected to the radiator tails. The plan was to not to replace the radiator heating but just to get some circulation under the floor to take the chill off.
I appreciate that the subject can be complex but hoped to achieve a little extra heat in this one floor area.

Sorry but he does not know what he is doing, you should not run U/F directly from the heating the max water temp is around 50deg C. It will not work !!!!
Get someone who knows Jim.

 

[SimonG]

Jim, listen to Chris. Your heating engineer doesn't have a scooby doo. There are regulations with regard to maximum floor temps.

10mm pipe Made me chuckle.

 

[Bronze_tap]

Sorry but he does not know what he is doing, you should not run U/F directly from the heating the max water temp is around 50deg C. It will not work !!!!
Get someone who knows Jim.


10mm pipe Made me chuckle.

The "engineer" seems to have forgotten the Bernoulli law. 10 mm pipe...
It may be ok for the drip feed... :wink: not for the CH...

Use at least 15/22/25mm one (depending on loop length).
Also maximum system system design temperature should be <50 degrees.
You can do it without mainfold IF your radiators are BIG ENOUGH,

So they chunk out enough heat when the delta is <25 degrees.

Replace underfloor pipes with 22/25 mm one and put your boiler's thermostat at 45 degrees max.

Then make sure that it doesn't cylce (and there is enough flow through it).

 

[lame plumber]

hot feet hot feet hot feet, it will be like running across hot sand!!!!!!!!!!!!!!