Newbie help - water UFH Anti cycle with Valiant ecotech 831

[kash]

ok - same issue.

totally confused....

boiler gets to the temp set on the manifold thermostat then enters cycle mode. temp drops quicker now then fires up again.....

 

[kash]

Blending valve set to max
Bypass valve is almost fully open

I'll upload pics of the new pipe work shortly. Any suggestions?

 

[kash]

Here's todays pipework

 

[chris watkins]

Thermo blending valve will prevent this tho....

That boiler can only modulate down to a minimum of 5kW as above it sounds as if your UFH is less than this so causing cycling.

As above, you have a 2 pipe coil plastic UFH system, the chances are it can't loose the heat to the building structure as quick as the boiler on its minimum burn rate can produce it therefore it will have to stop for a while until the water temperature drops.

You can't square the circle you have a big boiler so that you can produce domestic hot water instantaneously (combi) it can't in the next produce heat at such a slow rate that you can just have the UFH on its own with no other load.

 

[kash]

ok cool -

so in its current working order, just want to make sure this isnt going to ruin the boiler?

 

[kash]

The plumber I used agrees too but said he would speak to vailant anyway just to get a better understanding. not that im hoping for anything more now - as long as its safe and wont break anything

 

[Worcester]

Buffer tank, simples.

Buffers started to be used before modulating boilers to stop short cycling, it can do the same here, probably only need a small 100 litre one and it'll work nicely, the ufh will still work just fine and the boiler won't short cycle as much

Buffer Buy online

You'll need an extra circulation pump for the central heating and or dhw, or you could just put it on the ufh circuit. then you might get away with a 50 litre buffer and no extra pumps - install it as a 4 port buffer.

They key thing here is that your builder is at fault under the Consumer Rights Act 2015 and he should be paying to correct it not you.

 

[kash]

Been quoted around £500 to supply and fit!?

Yikes...

 

[Worcester]

That's a reasonable price, however as above, it is your Builder's legal responsibility to fix this.

He is supposed to be an experienced person, so a mistake / error of this type is his problem to solve not yours

They key thing here is that your builder is at fault under the Consumer Rights Act 2015 and he should be paying to correct it not you.

 

[chris watkins]

That's a reasonable price, however as above, it is your Builder's legal responsibility to fix this.
He is supposed to be an experienced person, so a mistake / error of this type is his problem to solve not yours

Just playing devils advocate here Worcester but couldn't the builder simple claim that the UFH was never designed to work independently from the other parts of the heating heating ? and when the two were running together if the boiler then entered anti-cycling mode that this was acceptable for a medium 3 bed house.

I have installed single zone UFH to new kitchen / diners but never offered it as an independent zone.

I believe the OP had the UF system added to an existing system so I suppose it comes down to when you could ague that the UFH design should dictate the total design including the boiler.