2 gloworm boilers in parallel both producing fault codes f25

[Anwah]

35mm just from the boilers to the floor then 22mm.
The primaries are as you described although flow and returns are equal lengths.
Could i lower the return temprature by icreasing the differential ?
I have also got the return stat on the sequencer set at 50c which will hold the lag boiler off if we go on to light load also both of the boilers are condensing and modulating ok.

 

[Beerlover]

Why 35mm (single load) then 22mm (shared load)? If the other way round and 35 mm to first 25% of heat load I would understand. Then you may get away without a header stack - just.

I was taught 130K Btus +, then use a header stack or a LLH as it is now known.

 

[looneyfitter]

Pipework undersized for sure. Pump definately undersized. LLH will certainly cure your probs.

The heat from the boilers cant get away quick enough, you need to be carfull as you may warp the HEX's. If the house is in 22mm then it will not transfer 60kw away quick enough. The fact you have set them at 50 makes no difference as your still pumping 60kw in to get to 50deg. If you get my drift.

Turn 1 boiler off and fry that. Is it possible any of it is air locked?

 

[Biggles..]

hxi's have a massive internal resistance that a 15/60 will struggle to overcome on a large system(large index).
2 of them just compounds the matter.

id agree with LF you should have used vaillants/glowworms LLH to connect them with a decent shunt pump.

50kW requires a flow of 2.2m3hr whuch is from memory way outside what the alpha will shift for the suspected head on your system

 

[Anwah]

HI Loony i have adjusted the output of the boilers in the software. Their is also a megaflow just next to the boilers i think this is connected to the 35mm primaries. I think he didnt run 35mm under boards because of the amount of timber he would have had to cut out of the joists,
The system on the heating side is split into 3 zones with trvs on all the rads except towel rails , room stat on each floor.

 

[Anwah]

I have just checked the spec on the pump and it is 1.3m3h-2.7m3h
If we fitted a shunt pump would we fit it in plsce of the auto bypass valve
or as well as.

 

[looneyfitter]

how much m3hr will 22mm flow at say 1.5bar? cant find any charts

 

[looneyfitter]

I have just checked the spec on the pump and it is 1.3m3h-2.7m3h

We could really do with a pic/s mate tbh. Depenant on the size of the cylinder, that should take say 15-20k btu out of the equasion. How long do the boilers run for? Could well be suffering from reverse circulation.

22mm isnt big enough mate. The fact that he didnt want to notch the joists is no excuse for a poor installation.

How long are the 35mm runs? If say 4m long i would fit a by-pass between them with a shunt pump if you dont wanna go down the LLH route.

What does it do with 1 boiler on its own running?

 

[kevplumb]

havent the boilers got built in pumps

only asking never had much to do with gws

other thing that springs to mind does the 35 drop to 22 or is it teed

 

[Biggles..]

I have just checked the spec on the pump and it is 1.3m3h-2.7m3h
If we fitted a shunt pump would we fit it in plsce of the auto bypass valve
or as well as.

It doesn't shift 2.7 at 6metre head though.

Hxi 's are heat onlys and suffer the same as Vaillant 400's. That size has about a 30kpa heat exchanger plus your index making pump sizing very crucial for them to run without the deltat spread being to large.

The alpha just can't shift the heat quick enough.

 

[Anwah]

Thanks for all the input were trying to get the most cost effective solution
to make the system work properly. I will try and get pics asap thanks for
being patient.

 

[Agile]

As you have described the system you have two heat only boiler and ONE domestic pump but with 35mm pipework which reduces two sizes to 22 mm under the floor.

To addd to the amusement you have a proper boiler sequencer which cannot do its job because with a single pump that pumps the flow through BOTH boiler even when only one is firing.

Either you have to add a motorised valve to close the non operating boiler

OR fit two pumps with one per boiler. That will increase the flow through each boiler and go towards solving the problem.

Has anyone calculated the heat loss of the house before selecting 60kW of boiler power?

22mm tube is not expected to pass more that 30 kW so that in itself is an immediate problem.

Do as I suggested closing the isolating valves on one boiler and turning it off.

Tony

 

[Agile]

As you have described the system you have two heat only boiler and ONE domestic pump but with 35mm pipework which reduces two sizes to 22 mm under the floor.

To addd to the amusement you have a proper boiler sequencer which cannot do its job because with a single pump that pumps the flow through BOTH boiler even when only one is firing.

Either you have to add a motorised valve to close the non operating boiler

OR fit two pumps with one per boiler. That will increase the flow through each boiler and go towards solving the problem.

Has anyone calculated the heat loss of the house before selecting 60kW of boiler power?

22mm tube is not expected to pass more that 30 kW so that in itself is an immediate problem.

Do as I suggested closing the isolating valves on one boiler and turning it off.

Tony

 

[Anwah]

Hi everyone been to the site today to take pictures. I also got pipe size wrong
flow from boilers to pump=35mm then under floorboards to ground and first floor=28mm. If you can see pics flow comes out of left hand boiler and picks up flow from right hand boiler on its way to the pump. Boilers are located on the top floor of house/2nd floor this zone=22mm. Megaflow is a 300 litre unit with warm up time of 20 minutes. Flow and return for megaflow=22mm.
Return=28mm under floorboards then 35mm back to left hand boiler then onto right hand boiler.
We recently extended the bypass to 5 meters,
Upon arrival at the house both boiler displays were showing f25 i reset left hand boiler only this fired for about 20 minutes then modulated till it reached
67 degrees which is the flow temp that the owner has set it at. it then refired
after about 5 minutes then it went on and off for short periods.

 

[Anwah]

Tried to add pics tothe post they were showing when i typed it up but will not show with the text anyone know what im doing wrong ?