Undefloor heating performance

[bigharj]

I have had our wet underfloor system running for about 6 weeks and am experiencing some performance problems.

Our system consists of a combi boiler - Feroli MAxima 35c running 16 rads and about 48 sqm of underfloor heating, split into 2 zones.

Zone 1 - 8 sqm gym
Zone 2- 40 sqm kitchen, dining room & wet room.

I have had no issues with the heating of the ch rads and hot water.

My problem is with Zone 2. The kitchen warms up to a very comfortable temperature, yet the dining and wet rooms do not warm up anywhere to the same level, although you can feel some heat.

The pressure at the manifold is approx 2 bar and the temperature guage reads 75 degrees. The two plastic pipes connecting at the manifold differ vastly in temperature, I take it that the floor is sucking up heat and by the time the water returns it is quite cool.

Should I be considering swapping the two ends over at the manifold so that hot water goes to the dining and wet rooms first, as they are part of a single storey extension and the kitchen being part of a 3 storey house?

Any help appreciated

Harj

 

[njk]

Hi Harj,


I have a few questions.

a) in zone 2, it sounds like you only have 1 loop. is that correct?
b) temprature gauge is 75 degrees. where is it? flow from boiler or mixed water?
c) is the ufh on a seperate time with a separate zone valve?
d) are the loops balanced?

zone 2 should be at least 2 loops, depending on where the manifold is.
mixed temprature should be from 40-45 degrees (if the floor is concrete).
the ufh should be on a seperate timer and have it's on zone valve.

Lolli

 

[bigharj]

a) in zone 2, it sounds like you only have 1 loop. is that correct?
Yes

b) temprature gauge is 75 degrees. where is it? flow from boiler or mixed water?
On the manifold

c) is the ufh on a seperate time with a separate zone valve?
Not yet, there are to be 2 zone valves fitted so that the uf and ch can be switched on independently however according to my plumber there are issues with the two systems energising each other, he has a fix which he should be completing after xmas

d) are the loops balanced?
no

too late to put zone 2 on 2 loops

 

[njk]

it looks like you have a faulty installation.

40 sqm for one loop means that you have a minimum apr 200m loop, the maximum length you should have (for a 15/16mm pipe) is 100 m.

75 degree flow into the floor far too high. do you have a mixing valve by the manifold? a circulation pump? are the pipes in screed or between joists?
what floor covering do you have, tiles, carpet, wood etc?

lolli

 

[bigharj]

There is a mixing valve and pump at the manifold.

I have just been looking at the system specification from the underfloor heating supplier and it DOES specify 3 loops, unfortunately I read it incorrectly and installed 2 loops. As it is concrete screed there is very little we can do about it now.

We have the following floor coverings

Gym - carpet & low tog underlay
Kitchen - tile
Dining Room - carpet & low tog underlay
Wet Room - tile

Apart from ripping up the screed and starting again (which is not an option), are there any 'make the best of a bad job' remredies out there?

 

[mointainwalker]

Unfortunately you are not in a good position and your technical problem is worsened by your choice of floor-covering.

I would first see what the temperature of the carpet surface is compared to the screed, to see exactly how much heat is being absorbed by carpet plus underlay.

I don't know if an ordinary thermometer would work, better would be an infra-red type ( non-contact.)

1)If you discover a significant difference - don't know how likely this is, you could consider replacing carpet with tiles or, possibly thin, engineered, parquet.

2)If the loop happens to run close to the manifold, you could consider cutting out a small channel, cutting into the loop, adding another feed and return pair of pipes to make two circuits out of one.

This is not something anyone would normally recommend however companies do offer repair couplings which would allow you to do this. You need professional advice on that. Contact your supplier for that.

Obviously whether that is something you find acceptable depends on layout, whether you have a good plan of what you laid whether there is space for another feed and return pipe etc etc

Best of luck

 

[mointainwalker]

Have just re-read your post and seen the floor-coverings of the three different parts of the big circuit.

What are the relative sizes ?

What is the actual length of the two circuits as shown on the suppliers plan ?

What is the spacing between the pipe as shown on the plan and is it the same for all three rooms ?

 

[njk]

there are no quick fixes for this one.

the 2 options mountainwalker mentioned are the only real options you have.
I would try first option 2. If you go for option 1, it might be worth looking at swapping the flow and return of the loop, depending on where the heat loss is greatest.

if you do cut into the loop and change it into 2 loops, make sure you use press fittings, not compression. ideal would be to contact the supplier of the system and get one of their recomended installers around to do it for you. they could then also set the mixing valve and set the flow rates.

Lolli

 

[bigharj]

Thanks for your replies.

I will be swapping over the return and flow, so to send the hottest water to the dining and wet rooms, the kitchen will run on the cooler return flow.

Having been through a six month build I am not in the mood to dig out a channel quite yet, although it is very feasable and would mean 2-3 days of discomfort. It will probably require the removal of about 5 linear meters of tile & screed to get to the pipes. I am not fazed about doing this.

As there is some heat in the effected rooms I am going to add some supplementary heating to the dining room and an electric heated towel radiator to the wet room (I presume this can run straight off a ring main).

Sometimes you make mistakes in life, the challenge is learning from them and putting them right. I just won't be able to live with the thought I should have read the specification and installed 3 loops.

Once again all is not lost, your comments have been very helpful. I will be returning for advice on how to get this repair off the ground in the summer.

But for now lets enjoy Christmas and look forward to the New Year!!!

Kind Regards

Harj Bains