HELP! UFH system causing boiler temp drop/excessive gas consumption

[kaye]

Hi all, first post on here - really hope you can help.

We have recently moved to a newly converted barn (single story) which has a Polypipe under floor heating system heated by an ideal system +24 boiler. It is quite a large property (the barn is 22x5x6.5) as well as a similarly sized extension. There are 3 manifolds in total - 1 x 5 port one that feeds the main barn, 1 x 9 port one that feeds the extension and 1x 2 port one that feeds the mezzanine floor area.

We have been experiencing astronomical gas consumption (£300+ per month 110000kwh usage per year projection!) and upon investigating we have established that when the system is calling for heat at the two furthest points (I.e through both the 5 port and 9 port manifolds) it is dropping the temp of the boiler like a stone (low 50 degrees ish) so consequently the boiler is working overtime to compensate for this and the rooms are the struggling to reach temperature (hence the high gas consumption!?). When the boiler drops temp the barn can take a good 4-6 hours to increase room temperature by 1.5 degrees yet when the 9 port manifold is isolated/not calling for heat the barn temperature will do this in around 1.5 hours.

The plumber who installed the system has been advised by the Polypipe dealer to fit a low loss header to the system to rectify the issue. The thing is, I have had a contradictory diagnosis from another plumber who has suggested that a low loss header is not necessary/will not fix the problem and in fact the route cause of the issue is due to the diameter of the feed pipes from the boiler to the manifolds (which is particularly relevant I guess given the 9 port manifold is approximately 12meters from the boiler) The pipe work is 22mm copper out of the boiler but then disappears into the loft in plastic speedfit connections (which apparently are also further reducing the flow).

This is our dream house that we have waited 2 years to be finished and poured all our money into, as well as our first experience of ufh; I really hope someone can help as we can’t continue to pay those sorts of bills and we don’t know who to believe / what to do for the best

 

[king of pipes]

Floor preparation and insulation is the most important thing here is it a project you had commissioned? I have experience of these type of systems and UFH is the only real way of heating such a space but the property needs to be able to hold that heat the usual way is to insulate the walls , ceiling and floors with Celotex type insulation was this done ? if not then the rooms will never reach there optimal temperature and the boiler will never turn off, can you post some pictures please . Regards kop

 

[kaye]

Hi Kop

Thanks for your reply. The system was designed by Polypipe and the insulation is to latest building regs (the ufh pipes are laid on 100mm insulation boards with 70mm screed if I recall correctly). I really don’t believe the issue is insulation as the barn holds the temperature for most of the day once it’s warm so - the issue is it struggles to reach temperature when there is this extra demand on the system from the extension and the boiler temperature plummets. If the boiler temperature doesn’t drop then the barn temperature can be lifted easily in around 11/2 hours?

 

[Aire]

How are you using your system? Are you setting your desired room temps and leaving it on constant or are you timing your heating to come on twice a day?

 

[Old Account]

How are you using your system? Are you setting your desired room temps and leaving it on constant or are you timing your heating to come on twice a day?

That was my question too. If the op turns it off it will take ages until he really reaches the desired room temperature.

 

[Old Account]

As KOP has mentioned above, it does make a huge difference on insulation. Furthermore it’s important to know what type of windows do you have single, double or triple glazing? Is there any insulation at the walls or ceilings? If so how thick is the insulation and what type did you use. The plumber who has suggested a low loss header is quite right. I personally would have used a low loss header too but in the same time I would have used a different boiler to reduce the gas consumption annually. With the right controller and boiler you could let the boiler run continuously. For example I installed a boiler which had over 9200 working hours but run on very low kilo watts. The boiler I installed was able to modulate itself and therefore reduced the amount of gas usage. But again, there are many factors which are very important to achieve that. You should not let the boiler switch off if you have only ufh. Once it’s cooled down it will take ages to get back to temperature.

 

[chris watkins]

You must have a LLH installed, it will never work correctly without one.
Do you heat your hot water via a cylinder ?

 

[snowhead]

Where in the Country is this, is it remote, exposed or part of a group of Barns?
What temperature are you trying to get to and what is the actual measured temperature?
Does it eventually get all areas up to temperature?

 

[chris watkins]

The plumber who has suggested a low loss header is quite right. I personally would have used a low loss header too but in the same time I would have used a different boiler to reduce the gas consumption annually. With the right controller and boiler you could let the boiler run continuously. For example I installed a boiler which had over 9200 working hours but run on very low kilo watts. The boiler I installed was able to modulate itself and therefore reduced the amount of gas usage. But again, there are many factors which are very important to achieve that. You should not let the boiler switch off if you have only ufh. Once it’s cooled down it will take ages to get back to temperature.

Beat me to it, UFH is likely to give a temp diff of 7deg C whereas the boiler is looking for 20deg C.

 

[Sharp Point]

Can I ask what the finished floor is and if it’s timber, is it solid or engineered?

Oh and thickness

Ta

 

[Sharp Point]

Oh and if it’s Polypipe, have the built in filters on the manifold been checked for blockages?

Ta

 

[ShaunCorbs]

You must have a LLH installed, it will never work correctly without one.
Do you heat your hot water via a cylinder ?

That's not the issue it's the temp drop that there asking about when they open up the furthest manifold/ zone set and how long it takes to heat up

Now not saying that wouldn't help when the zones started to shut off but depending on flow rate it might not be required

Op What's the heatloss of the barn and size of the boiler

 

[Aire]

Op What's the heatloss of the barn and size of the boiler

Barns 20x5x6.5, said it's single story so I'm taking that at 20m long, 5m wide and 6.5m high ceilings. And boilers a 24kw ideal system boiler.

 

[Aire]

Sorry, you said heat loss not size, ignore everything about my previous comment except the boiler size

 

[king of pipes]

I would have fitted a heating buffer vessel the boiler would charge this to say 70°c, the underfloor heating primary supplies to the heating manifolds are then pumped from the buffer to the UFH manifolds and pump sets to be blended down and circulated through the underfloor loops, this way it reduces your energy usage and run time of the boiler . Kop