Woodpellet boiler woes

lostinrates

Geotherm wrote: »

Think the problem is that you have the tank switched off from the morning, so you take the hot water for the bath, then the tank does not heat up again till later. I may be wrong, so hope someone els can comment.

Nope, the tank is on all the time (as is the boiler)

We turn the heating off so that no demand is made of the tank so to let some heat build up in it.

What we have been told is that once the tank gets below 55 degrees Celsius we are fighting a losing battle trying to draw heat for anything (rads or tap water) as the temperature in the tank /cylinder cannot be maintained or built up from below that point while doing a job. So that's why we turn the heating off!

lovesgshp

Only speculating here, but is the cold water flow through the tank for the DHW high, as that could be a problem?

lostinrates

Geotherm wrote: »

Only speculating here, but is the cold water flow through the tank for the DHW high, as that could be a problem?

When the tap is on its a possibility. That's why they have suggested not to turn taps fully on. The problem then is that the bath cools down while filling!

lovesgshp

lostinrates wrote: »

When the tap is on its a possibility. That's why they have suggested not to turn taps fully on. The problem then is that the bath cools down while filling!

Do you know how many bar the pressure is to the tank for the DHW, this may be why they suggest not opening the taps fully

lostinrates

Geotherm wrote: »

Do you know how many bar the pressure is to the tank for the DHW, this may be why they suggest not opening the taps fully

Hmm. Not sure. There is a pressure guage leaving the boiler and a pressure guage for the heating system, but not one separate for the cylinder. Would either of those two be relevant?

Ultimately, if it cannot run a bath that is got enough for whatever reason, or other washing facilities it was spec'd for it is not what we were told it would be.

I actually will check the pressure now to see what it is, I know it should be one leaving the boiler and 1 - 1 and a half on the ch system.

lovesgshp

lostinrates wrote: »

Hmm. Not sure. There is a pressure guage leaving the boiler and a pressure guage for the heating system, but not one separate for the cylinder. Would either of those two be relevant?

Ultimately, if it cannot run a bath that is got enough for whatever reason, or other washing facilities it was spec'd for it is not what we were told it would be.

I actually will check the pressure now to see what it is, I know it should be one leaving the boiler and 1 - 1 and a half on the ch system.

You need the pressure to the DHW system, heating system from the tank should be about 1.5 bar, and water about 2.0-3.0.

lostinrates

Geotherm wrote: »

You need the pressure to the DHW system, heating system from the tank should be about 1.5 bar, and water about 2.0-3.0.

Grazie mille per le tue risposte Geotherm. Buon Natale.

I will LO at the pressure gauges tomorrow now. Eight weeks of this from no interest in heating other than using it cheaply and having lots of hot bath water has made my head spin.

Alycidon

I installed a pellet boiler 4 years ago and also had issues. No bulk tank so that did not help but a boiler that was rated at 25kw with an advised actual output of 31kw would not produce the same heat or anywhere near that the elderly 19kw oil fired boiler it replaced did.

Adjustments to fan and feed auger speeds did eventually sort the problem, now it uses twice as much fuel as I was advised it would use when I ordered it. I was told 4-6 tones a year, in a cold year it was double ( 11 tonnes) that plus a ton or two of cereals, an average year is about 8 -9 tonnes. Put an additional wood burning stove into the lounge now, that has got the costs under control and cut pellet use significantly.

A

lostinrates

Alycidon wrote: »

I installed a pellet boiler 4 years ago and also had issues. No bulk tank so that did not help but a boiler that was rated at 25kw with an advised actual output of 31kw would not produce the same heat or anywhere near that the elderly 19kw oil fired boiler it replaced did.

Adjustments to fan and feed auger speeds did eventually sort the problem, now it uses twice as much fuel as I was advised it would use when I ordered it. I was told 4-6 tones a year, in a cold year it was double ( 11 tonnes) that plus a ton or two of cereals, an average year is about 8 -9 tonnes. Put an additional wood burning stove into the lounge now, that has got the costs under control and cut pellet use significantly.

A

We are advised we should be about nine tonnes a year of pellet. It's impossible really to judge this as we were heating the house up from very cold at first and now the weather is remarkably mild.

As it is the 'long weekend' hopper doesn't go a normal weekend, but at most a day and a half.


Geotherm has hit something interesting getting me to monitor the pressure. There is a largish variable which seems like it must be relevant.


The boiler Is holding temperature itself (working at highest recomended temps as maximum setting) but the cylinder and pressure for they seems to be the problem.

To clarify, the water IN the boiler and in the bulk of the cylinder are 'common', moving between both. The water in the coil in the cylinder is our hot water.

No progress on that has been made, but dialogue has reopened on a less fraught keel, whoch is half the battle. I know the suppliers are frustrated and tbh I think they feel out of their depth that it is not working, but we shall see.

If it doesn't work withing a reasonable parametre then we will have to go back to the drawing board for all our heating and hot water needs as which point we will ALL be significantly disappointed and out of pocket, so I am hoping by staying patient and allowing further tweaks to be made we can get there eventually. I think we will have to put a date in the sand by which we cannot keep procrastinating. The thing went in two months or so before Christmas and still hasn't reached sign off and official commissioning.

We have now involved an independant expert who is reviewing the communications and spec of the kit and who will probably come down week after next (we have purposely opted for a non local person).

Thank you for your response. It's good top know that someone else had had resolvable problems.

aelitaman

Manufacturer and model of tank would help a lot.

You say the tank and the CH water are common but there are different ways to "plumb" these in.

On method is to have a central ring of hot water from the boiler and spur the tank of the ring just like a radiator. You imply this is what you have. The other method is to have a ring, spurs the rads of but the tank is not on a spur it is an integral part of the ring.

Because you say that your heating works but the tank does not heat up this implies it is on a spur.

A 28 Kw boiler should heat up 500 litres of water from 55c to 75C in 30 to 40 mins if running full pelt but they do modulate, again do not know your boiler but it most proberly will modulate on return temperature of water. Which if the water is flowing through a tank of water at 55c will be no more that 55c.

Anyway the simple fact that your tank is not heating up quick when the boiler is producing hot water is because you do not have a high enough flow of hot water from the boiler through the tank.

So why? Again need to know how the hot water from the boiler and the return from the tank is plumbed in. If the hot water inlet is at the bottom of the tank and the return is at the top then you are trying to force hot water through 500 litres of water or 500KG of water. So the hot water could be taking the path of least resistance and flowing through the central heating ring (even with the radiators off) very little flowing through the tank (because of the resistance of 500Kg) the return water to the boiler gets up to a temperature that starts the boiler modulating and boilers kicks it output down and you think everything is ok because the boiler is doing what it should.

To check this you say that you can turn on and off the heating of the tank. I would turn the heating on after a period of not heating the tank and physically check the hot water inlet pipe to the tank. If you have a decent length of exposed pipe to the tank you can hold the extremity of the pipe and check for when the hot water the the tank starts to flow you can then trace its path heating up the pipe to the tank. This should not take very long a few minutes if the flow rate is good. Also if the flow rate is good this pipe should get to 80C very quickly ie too hot to hold. If this is the case then you have a good flow of hot water to the tank, if not there is your problem.

On the subject that when the tank is hot enough to provide hot water it does not provide enough and cools very quickly.

A bath is about 80 litres of water. the temp of the water from the mains will be about 10c at this time of year and outside temps and you want to raise this to 55c for use at the taps.

So the tank is 500 lites and 80 litres of water is 16% of the 500.

So if you want to raise the temp of the 80 litres from 10 to 55c is 45c then the 500 litres will drop in temperature by the corresponding % tage.

45c x 16% = 7.2C so your tank should drop in temp from 75C - 7.2C = 67.8C and then still be able to provide hot water for another 80 litre bath.

Seeing as you have a 20c drop before the bath is full there can only be one reason and that is that the 500l tank is not at a uniform 75c temerature. where the thermostat is it is but beneath the thermostat it is not maybe just room temp.

The technical term for this is stratification and the tank makers know all about it. I would get the tank manual out and make sure that the flow and return from the boiler have been connected correctly to the tank as per manufacturers specs. But again stratification could happen because not enough hot water is flowing to the tank.

Just for you information a lot of tanks on the market have coils in them to heat them as well as for the hot water. Solves the issue of 500KG of water pushing down on the inlet pipe and also of stratification.

Anyway this is where I would look and ties in with the pressure issues because if the tank is plumbed in with the hot water inflow at the bottom you have 500 Kg pushing down on the 22mm or 15mm inlet trying to get out hence pressure.