Problem with solid fuel heating system

Germar

Just wondering if anybody has any thoughts on the following.
Had a boiler stove installed at the end of March. Only just using it fully now as the weather got warm when we installed it.
Here is my problem. Our house is a two story with an attic conversion. Total amount of rads including attic is 9. The stove output is 18kw (15kw to the water and 3kw to the room). All the rads have TRVs except the one in the attic. We are having a problem getting heat to the attic and also downstairs. I have tried and succeed by turning off the TRVs but when I opened them up again, the rad in the attic and downstairs cool down. I should say that we also have a gas boiler which I have ran when stove is not lit and all rads come on, including the attic.
I was thinking of replacing the TRVs for regular values to let me balance the system better. Good idea or not?

John.G

Can you see what the make/model of the stove circulating pump fitted?.

Germar

Picture attached and it's set to the highest speed

Wearb

Height-wise, how does your expansion tank compare to your attic radiator?

Turbohymac

Possibly you will need to restrict the flow through the downstairs rads.. I had this issue with a very long run on a single story house where the water was simply taking the path of least resistance and the end of line /furthest away rads were only barely heating up.. before doing anything drastic turn off 5 or 6 of the rads nearest to the stove and I bet the one in the attic gets it fair allowance of hot water and will be as hot as the rest

Wearb

Turbohymac wrote: »

Possibly you will need to restrict the flow through the downstairs rads.. I had this issue with a very long run on a single story house where the water was simply taking the path of least resistance and the end of line /furthest away rads were only barely heating up.. before doing anything drastic turn off 5 or 6 of the rads nearest to the stove and I bet the one in the attic gets it fair allowance of hot water and will be as hot as the rest

He has already mentioned that in his original post.

John.G

Germar wrote: »

Picture attached and it's set to the highest speed

Is it on PP or FP control. even though the photo is clear enough, I cant see if its on PP (proportional pressure) control or FP (Fixed curve) control. There is/will be a huge difference, if its on PP3 setting then the maximum head is 3M but as it will be seeing a resistance it will probably modulate down to 2M or so BUT if its on FP on setting3, it will still give a flowrate of ~ 20 LPM at 4.5M head. Thats a pretty hefty pump so it should have no problem on FP setting 3 or even 2 in circulating water through all those rads even with no balancing.

Germar

Wearb wrote: »

Height-wise, how does your expansion tank compare to your attic radiator?

Bottom of tank is about 10cm above top of the radiator. Is this enough?

Wearb

Germar wrote: »

Bottom of tank is about 10cm above top of the radiator. Is this enough?

If (with pumps off) you can bleed water out of that rad bleed screw, then it’s most likely ok. Check to see if there is any water flowing through the pipe that hooks in over then expansion tank - when the stove is hot and pump running.

Dtp1979

I can’t remember the exact math but I think 2/3 the pump head is the min distance between the highest circulated point and the tank base

John.G

Dtp1979 wrote: »

I can’t remember the exact math but I think 2/3 the pump head is the min distance between the highest circulated point and the tank base

I have a similar set up, attic rad wise to the op. (oil fired boiler only) and have no problem with it, once or twice a year I do get a little air from it when I bleed it with the circ pump off as it runs with a slight negative head.
The OP has no problem when running on gas firing so I would suggest that its a circulation problem, that's why I asked if the stove pump is running on PP or FP control, if the pump is performing OK then it should have no problem if set to FP setting iii or even ii, these Grundfos pumps have a very low max PP setting of 3M, I don,t know why as all their competitors have max settings of at least 5 but no doubt Grundfos could answer this.

Germar

John.G wrote: »

Is it on PP or FP control. even though the photo is clear enough, I cant see if its on PP (proportional pressure) control or FP (Fixed curve) control. There is/will be a huge difference, if its on PP3 setting then the maximum head is 3M but as it will be seeing a resistance it will probably modulate down to 2M or so BUT if its on FP on setting3, it will still give a flowrate of ~ 20 LPM at 4.5M head. Thats a pretty hefty pump so it should have no problem on FP setting 3 or even 2 in circulating water through all those rads even with no balancing.

Is the fixed curve what I have outlined in red on the attached page of the manual as I have changed to this setting and the rads downstairs have started warm up a little. Am I right in saying that they will get warmer still and the one in the attic will eventually?

John.G

Germar wrote: »

Is the fixed curve what I have outlined in red on the attached page of the manual as I have changed to this setting and the rads downstairs have started warm up a little. Am I right in saying that they will get warmer still and the one in the attic will eventually?

NO, the setting that you have changed to is IMO the "worst" one as its the PP control and will only give a max head of 3M if I am reading the pump curves properly. I will just repeat that I am very surprised that the FP settings (iii) isn't giving adequate circulation. I just wonder if the stove pump is recirculating the water through the gas boiler when off because there is no NR valve fitted or if it is fitted and is defective.
IF you do change back to the FP, try it on i then ii then iii, you should hear the pump "revving" up a bit with each change.

However IF the attic rad is now heating up on the PP setting, I would let it there even though I don't know logically why it should.

Germar

John.G wrote: »

NO, the setting that you have changed to is IMO the "worst" one as its the PP control and will only give a max head of 3M if I am reading the pump curves properly. I will just repeat that I am very surprised that the FP settings (iii) isn't giving adequate circulation. I just wonder if the stove pump is recirculating the water through the gas boiler when off because there is no NR valve fitted or if it is fitted and is defective.
IF you do change back to the FP, try it on i then ii then iii, you should hear the pump "revving" up a bit with each change.

However IF the attic rad is now heating up on the PP setting, I would let it there even though I don't know logically why it should.

Seems to working on the setting that I marked on the PDF. All rads are heating starting in the attic and working it's way downstairs. Only thing is that as the rads have TRVs they go off as the rooms warm up. Should I change to standard vavles or not. Would they be better for balancing as I think I need to.
Thanks for all the help on this.

John.G

Germar wrote: »

Seems to working on the setting that I marked on the PDF. All rads are heating starting in the attic and working it's way downstairs. Only thing is that as the rads have TRVs they go off as the rooms warm up. Should I change to standard vavles or not. Would they be better for balancing as I think I need to.
Thanks for all the help on this.

If you need to balance then I would not change to standard valves, open all the TRVs fully, then on the valves that are not heating up ensure that the lock shield valves are fully open, these are the ones under a white plastic cap that doesn't do anything when you turn it, you have to remove it and adjust the valve stem with a adjustable spanner. On the rads that are heating up rapidly; shut them off fully and open them maybe a 1/2 to 1 turn each and see what effect this has. I have never had to do it myself so I am just suggesting this method.

BUT because the rads are all heating fine on the gas firing then I would think that there is something not quite right with the stove set up.
Have you just the two circ pumps on that system? (stove & gas fired) or have you a common manifold (systemlink) with one or more circ pumps feeding the heating system?. Are there two coils in the hot water cylinder, one from the stove and a separate one from the gas boiler?.

Germar

John.G wrote: »

If you need to balance then I would not change to standard valves, open all the TRVs fully, then on the valves that are not heating up ensure that the lock shield valves are fully open, these are the ones under a white plastic cap that doesn't do anything when you turn it, you have to remove it and adjust the valve stem with a adjustable spanner. On the rads that are heating up rapidly; shut them off fully and open them maybe a 1/2 to 1 turn each and see what effect this has. I have never had to do it myself so I am just suggesting this method.

BUT because the rads are all heating fine on the gas firing then I would think that there is something not quite right with the stove set up.
Have you just the two circ pumps on that system? (stove & gas fired) or have you a common manifold (systemlink) with one or more circ pumps feeding the heating system?. Are there two coils in the hot water cylinder, one from the stove and a separate one from the gas boiler?.

There is two circ pumps on the system and two coils in the hot water cylinder.
I assume I can balance the system with just the gas on.

John.G

Germar wrote: »

There is two circ pumps on the system and two coils in the hot water cylinder.
I assume I can balance the system with just the gas on.

I didn't realize you had balancing problems while gas firing but yes that's the best way of doing it as you will have constant heat output from the gas boiler.

When next you have the gas fired boiler running on its own see if you can feel the stove boiler's flow and return pipes as close to the boiler as you can and see if they are hot/very hot/cold.