Newbie question

[Munchincocopops]

Hi....I have just built a large garden room and opened up the kitchen into this area and fitted water based underfoor heating that works very well. My only concern is the run time of the boiler.

The boiler is new, a Baxi 32kW system boiler as we have a hot water tank.

As normal the hot water uses tank stat to open valve and call boiler for heat, same goes for heating though bathroom and en-suite radiators are connected to separate feed circuit so that they come on no matter if hot water or CH demand. We've had this for years and works fine.

 

Boiler temperature is set at 68 deg C.

UFH manifold is 6m from the boiler.

UFH pipes - 7 loops approx 75m each only in garden room extension as kitchen floor is T&G

 

Now, of course, whenever the garden room stat calls for heat the system opens valve to UFH manifold feed pipe and turns on manifold circ pump and UF water temperature is set at 35 deg c so I expect UFH mixer valve takes 68 deg C water and shuts off when manifold water reaches 35 deg C. I'm expecting this will take very little time as CH is not on at the moment but well controlled anyhow so takes little demand.

 

So to my question. Is there a better way to control the boiler for UFH demand? My thoughts are the UF manifold does not take heat so often as the boiler capacity is large and 68 deg C but the boiler remains in demand due to UFH stat so all it is doing most of the time (my guess) is heating bathroom and en-suite radiators which is unnecessary.

 

Ideally I only want the boiler to run if the manifold is less than 35 deg C. I'm thinking of fitting a stat to measure manifold temperature and shut off boiler but ideally I'd like a mixer valve with a volt free output that can be used to call for heat when the mixer requires it.....if there is such a thing?

 

Thanks for your help and any comments.

 

 

 

Edited December 2, 2021 by Munchincocopops

[ProDave]

I think the answer to this is a buffer tank. The plumbers will be along to explain I am sure.

[Munchincocopops]

Thanks - I know of the buffer tank - but here's a curved ball - for the cost of a buffer tank maybe I can buy a new small gas bolier, set its temperature to 34 deg c and replace mixer valve with a valve so this small boiler is for heating UFH only?

 

Just an idea?

[Munchincocopops]

So - buffer tank - what size?

 

But just to be sure before I buy....

Are my thoughts unreasonable?

 

Buffer tank

or Mixing valve with volt free contact to call for boiler when heat required......is there such a thing?

or add stat to manifold to call boiler if temp less than mixer valve setting

or Dedicated small boiler for UFH only to negate need for buffer tank.......and will it be more efficient?

 

Any thoughts or advice appreciated.

 

Many Thanks.

Edited December 5, 2021 by Munchincocopops

[SteamyTea]

22 hours ago, Munchincocopops said:

So - buffer tank - what size?

I a sure the Baxi boiler installer instructions will have a minimum volume requirements.

If you can find that figure, go to the next size up to reduce short cycling of the boiler.