Biomass domestic boiler issue

mountfarm

Member
Got a heat exchanger plumbed in a house which is fed directly from the biomass boiler. The flow pipe is hot and return pipe is warm so we are getting heat into the house. However there doesn’t seem to be enough heat being utilised as the house is just luke warm.
if we put the motorised valve into manual then we get more heat in the house but then the return pipe is also red hot so we are sending heat back to the biomass boiler. Our plumber who fitted and knows this stuff is not contactable so anybody seen this before.
The motorised valve seems to be working in auto as it opens and shuts but we don’t seem to be getting the full heat into the house.
Checked radiators for air etc and they are fine as it’s also luke warm in the shower/baths.
 

Still Farming

Member
Mixed Farmer
Location
South Wales UK
Lots of questions possibly?

Have you had work or replaced anything with the system recently?

Is biomass boiler lit and upto temp. 70 oC + or more?

Is Accumulator tank upto temp?

Are all pumps on and flowing ok?
How old is system?

What type of heat exchanger do you have?
Remember you never get the boiler temps in your house through the heat exchanger, think 60 to 70% generous possibly?
Is anything different recently or just happened?
 

mountfarm

Member
Lots of questions possibly?

Have you had work or replaced anything with the system recently?

Is biomass boiler lit and upto temp. 70 oC + or more?

Is Accumulator tank upto temp?

Are all pumps on and flowing ok?
How old is system?

What type of heat exchanger do you have?
Remember you never get the boiler temps in your house through the heat exchanger, think 69 to 70% possibly?
Is anything different recently or just happened?

No
Biomass kicks in at 65 and kicks out at 87
No accumulator tank - direct feed as the boiler has an auto fuel feeder so runs as soon as it hits 65.
Yes
2 yrs old
Nordec tec plate 32-20
 

mountfarm

Member
So all working ok upto today was it?

I’m not in the house and the person who is has said a few days but I’ve discovered about putting it in manual today.
It’s 17 degrees here today but I can tell come winter time it’s not going to be efficient unless run in manual which we can of course do, but sending heat back to the biomass boiler isn’t ideal!!
 
Last edited:

f0ster

Member
I presume the heat exchanger is a plate heat exchanger (phe) these have a hot end and a cool end so the flow has to be in opposite directions if you know what I mean, what has changed recently, anything? you should have a pump on both sides of the phe, one to feed the phe and the other to take the heat from the phe to the property, are these both working, put your ear right up close to see if it is turning or just humming, these phe can be prone to block up internally especially if you do not have a magnetic filter fitted, we usually remove them and fill them with hypochlorite for a couple of hours then pressure wash them out, do not leave the hypo in too long, it attacks the brazening,
 

rollestonpark

Member
Arable Farmer
Location
Burton on trent
Got a heat exchanger plumbed in a house which is fed directly from the biomass boiler. The flow pipe is hot and return pipe is warm so we are getting heat into the house. However there doesn’t seem to be enough heat being utilised as the house is just luke warm.
if we put the motorised valve into manual then we get more heat in the house but then the return pipe is also red hot so we are sending heat back to the biomass boiler. Our plumber who fitted and knows this stuff is not contactable so anybody seen this before.
The motorised valve seems to be working in auto as it opens and shuts but we don’t seem to be getting the full heat into the house.
Checked radiators for air etc and they are fine as it’s also luke warm in the shower/baths.
sounds like the motorised valve is opening properly when done manually, but not when in auto.
When in manual sounds like too faster water flow from boiler. You need to slow the pump down, or restrict it on a ball valve or something. So that the return is about 60 (+-5).

If its 1 of those domestic honeywell motorised valves, I have had them eat the teeth off inside. They are pretty poor I think (like most honeywell stuff).
Chris
 

mountfarm

Member
Nothing has changed to answer that question.

Update is we have temporarily swapped the plate heat exchanger for a coiled one out of an old swimming pool just to see if it’s any better which it is but it’s still not getting the house warm enough. It was 1 degrees yesterday outside and the house thermostat was at the top setting of ‘30’ on the dial. It wasn’t acceptably warm and the occupiers are retired so feel the cold much more than me.

I’ve come to the conclusion the 3scenarios:

1. the original heat exchanger was sized incorrectly and we need to just go bigger again?

2. the size of the underground pipes from the boiler aren’t big enough so there’s not the volume of hot water getting into the house system. The boiler to the house is 100m and all pipes are underground.

3. the biomass boiler running temp needs to be set higher to send more heat? I could change this to anything really such as kick in at 80 degrees and kick out at 98 degrees but as I’m not familiar with the system (already on site when we bought the place) then I’m unsure if this could damage the actual biomass boiler.

Lastly it’s not the house system because if we switch to kero from an old tank then the house gets to warm so it’s definitely biomass related.
 

dave mountain

Member
Livestock Farmer
what are the pipe sizes? if the flow is hot a return is warm (which is correct) then the problem is either the PHE size (unable to extract enough energy to heat the house) or the pipe size (not enough flow to provide enough energy to PHE)

may also be worth increasing flow temperature, as it may be losing a lot of energy in 100m of pipe before the PHE
 

Wisconsonian

Member
Trade
Is the automatic valve still in the system? I'm not familiar with what the function of an automatic valve would be in this system. Sending hot water back to the biomass boiler is not a waste, the boiler will heat it easier than cold water. 100m of pipe underground is a possibility for large losses, but that has not changed, has it?

Usually a new problem like this will be the result of poor circulation, either something is plugged, or airlocked, or the pump is failing. Need temperatures and pictures of the system to make any better guesses.
 

mountfarm

Member
Dave:
110 uno underground pipe swapping to 40 to get it into the garden shed next to the house where the heat meter is. It then is 25mm copper pipe into the heat exchanger.
To me the flow and return pipe in and out of the heat exchanger are very similar temps (to the touch). I need to get a clamp thermometer for some accurate readings but I dont think they’ll be anything in it.
100 metres away in the biomass plant room the temps for start up are 70 and shut down 85. This is measured accurately in their digitally. 100m in another direction we have a temp read out in a grain store fan house and it sits happily at 75 so there isn’t much heat loss. Obviously the grain drier is not on at this time of the year so not sapping heat.

Wis:
Auto valve is still in the system but it’s working correctly. If the biomass looses heat due to fuel supply the auto valve kicks in.
The underground pipe run has not changed.
The pump is new and the filters in the system are clean as we check every few days. The whole system has been bled for air numerous times.
 

rollestonpark

Member
Arable Farmer
Location
Burton on trent
at the heat exchanger:
what are the flow and return temps boiler side ?
what are the flow and return temps house side ?

Hard to get a handle on what's happening with the given information...
but sounds a bit like there is insufficient flow volume threw the heat exchanger on the house side to remove the heat, since you say return temps at the boiler remain high.
 

dave mountain

Member
Livestock Farmer
at the heat exchanger:
what are the flow and return temps boiler side ?
what are the flow and return temps house side ?

Hard to get a handle on what's happening with the given information...
but sounds a bit like there is insufficient flow volume threw the heat exchanger on the house side to remove the heat, since you say return temps at the boiler remain high.
I thought that but if it runs fine off Kero then it can hardly be a pump or flow rate problem, which is why I thought it must be either the pipes from the biomass or the heat exchanger itself. Perhaps the heat exchanger is piped in parralel flow rather than opposing?
 

rollestonpark

Member
Arable Farmer
Location
Burton on trent
Can't really get a handle how the kero boiler is plumbed in relation to the heat exchanger, biomass and the house network.
Is the kero boiler down the yard with the biomass boiler? using the same pipe work.
If not is there a different pump operating when the kero boiler is on? or valves etc
how is the plumbing different for the kero boiler, is there any valves that operate separately etc.
Is the water from the biomass bypassing somehow back to itself? through a valve somewhere or through the kero boiler.
 

dave mountain

Member
Livestock Farmer
Can't really get a handle how the kero boiler is plumbed in relation to the heat exchanger, biomass and the house network.
Is the kero boiler down the yard with the biomass boiler? using the same pipe work.
If not is there a different pump operating when the kero boiler is on? or valves etc
how is the plumbing different for the kero boiler, is there any valves that operate separately etc.
Is the water from the biomass bypassing somehow back to itself? through a valve somewhere or through the kero boiler.
good point, i assumed the kero boiler was in the house, as the biomass boiler will only be down the yard so as to be near the fuel source. so assume it will be one pumped circuit going through though an oil conventional boiler and the heat exchanger in series, possibly at different points in the system. is that correct OP?
Obviously will be a bypass for each heat source for when the other is working
 

Adeptandy

Member
Arable Farmer
Location
PE15
Sounds to me like it’s either short circuiting back to the biomass or the pump is knackered or airlocked, but that will depend I the way the kero boiler is spliced into the system imho 🤔🤷🏻
 

Bloders

Member
Location
Ruabon
if its been fine for 2 years id suggest there is nothing wrong with the design of the system, there is a component faiure. Most likely a pump or a divertor valve?
 

mountfarm

Member
Update. I turned the biomass boiler up so it now kicks in at 82 and out at 95. This has made a difference so it looks like not enough heat is being utilised through the plate exchanger? I.e. it’s still not big enough?
I also think the heat meter in the biomas boiler room isn’t clocking up as quickly which means heat is being returned? So the house isn’t removing enough heat?

Also re reading I have confused matters - so the biomass boiler and grain drier have been in place for 2 years. We have added the house in the autumn. So everything house wise is new.

The kero boiler is what the house previously used. The boiler itself is in the house and the kero tanks are about 10m away in an outbuilding.
 

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