Viessmann Vitodens 100 poor heat

[WillFB]

The church that I am a member of, replaced on old boiler 18 month ago with a Vitodens 100 19kw Open Vent boiler.

The original boiler worked fine, apart from the pilot blowing out on occasions and spare parts becomming almost impossible to get. However, the church was always warm, even during the coldest winter.
Since the new boiler was installed we have never had the church as hot as it previously was, and during the winter people have to keep their coats on.

When the heating engineer installed the boiler, he flushed all of the system and fitted a "Magnaclean".

The heating engineer has attended several times to try and fix the problem, and he has had an engineer from Viessman out twice look at the system.

The Viessman engineer said that the system must be sludged up, even though it has been all flushed out once already. The next time he pronounced the pumb defective. The pump had been replaced two years previously, but to show good faith I replaced it with a new Grundfos pump and the problem is the same.

All along I have suggested that the boiler wasn't reaching a high enough temperature. It is only supplying water for the radiators and all of the radiators warm up quite quickly to the same temperature, but don't get hot.

Both engineers said to turn the temperature dial right up, past the higest setting, almost to the reset possition. Even doing that hasn't made any discernable difference. The display readout reaches about 68deg and sometimes flashes to 70deg.

I noticed on another thread someone saying they increased the boiler temperature to overcome a similar problem. Does anyone know if this is possible and how?

In another part of the church complex we have a Baxi Combi 80 which performs brilliantly and we have to turm the rad valves down, because it gets too hot. I'm beginning to wish we hadn't been persuaded to fit a Viessman for the main building.

Any help would be appreciated.

 

[Agile]

Unfortunately we cannot give a proper diagnosis without scientific information.

Flow and return temperatures at the boiler and what the power input is.

Does it cycle on/off or does it run all the time?

You can hear the pitch of the fan which is proportional to the power output. Is it running at full power all the time?

What was the power of the previous boiler? 18 kW for a church does not sound very much!

Tony

 

[thetman]

I would suggest the boiler is undersized for the load, that type of system should be running at about 82deg.

Is the new boiler the same size as the old one ?

 

[WillFB]

Unfortunately we cannot give a proper diagnosis without scientific information.

Flow and return temperatures at the boiler and what the power input is.

Does it cycle on/off or does it run all the time?

You can hear the pitch of the fan which is proportional to the power output. Is it running at full power all the time?

What was the power of the previous boiler? 18 kW for a church does not sound very much!

Tony

Hi Tony.

I can't give you much in the way of scientific information, but I can confirm that it runs all of the time.
With regards to the church, its not one of those big sandstone building with a high roof. It is a single storey brick building and the system runs 13 radiators. This part of the complex has the cloakrooms, main hall and a smaller room. It probably is equivilent to a large detached house.

Regards

Will

 

[alan999]

Hi
I'd be interested to find out if the radiators run too cool, or if they run at full temperature but this is still not hot enough to heat the church.

If you are unable to measure the temperature of the radiators I would establish whether or not the smaller room and the cloakrooms get warm enough FIRSTLY with all the other radiators in the church turned on and SECONDLY with all the others turned off (wait till the church is not being used of course).

If you cant heat the smaller rooms it suggests the radiators are too cool because the boiler isnt producing enough heat, the pipes going from the boiler to the radiators are losing heat or the radiators are blocked (assuming the radiators are big enough)

You may then establish if the main hall heats up with the cloakroom and smaller room radiators turned off. If it does this could indicate you have too many radiators on your system.

Perhaps you could then manage your system better by using different radiators at different times. Not ideal but it may help you through this cold spell.

 

[WillFB]

Hi
I'd be interested to find out if the radiators run too cool, or if they run at full temperature but this is still not hot enough to heat the church.

If you are unable to measure the temperature of the radiators I would establish whether or not the smaller room and the cloakrooms get warm enough FIRSTLY with all the other radiators in the church turned on and SECONDLY with all the others turned off (wait till the church is not being used of course).

If you cant heat the smaller rooms it suggests the radiators are too cool because the boiler isnt producing enough heat, the pipes going from the boiler to the radiators are losing heat or the radiators are blocked (assuming the radiators are big enough)

You may then establish if the main hall heats up with the cloakroom and smaller room radiators turned off. If it does this could indicate you have too many radiators on your system.

Perhaps you could then manage your system better by using different radiators at different times. Not ideal but it may help you through this cold spell.

This isn't scientific, but before this boiler was fitted all of the rediators got too hot to keep your hands on for more than a few moments. Now you can keep your hands on for as long as you like!

All of the radiators get to the same temperature. I have tried turning off the radiators in the smaller room and the cloakroom, but it doesn't appear to make any difference to the other radiators.

Tomorrow morning the heating will come on at 5.30am and will switch off at 12.30pm. The services start at 10.00am.and most of the people attending will need to keep their coats on.

What I can't grasp is that with the old boiler the place was steaming hot, and since the new boiler was fitted its been Baltic. Nothing else changed.

Do you know what temperature the boiler should achieve when its running? As I mentioned in my earlier post, this boiler gets to about 68deg and occasionaly 70deg. Surely that's not high enough?

Regards
Will

 

[Dan Robinson]

You haven't told what was taken out.

Nor (I believe) what controls are fitted to the new boiler.

Have you done a heat loss calculation for the property?

 

[WillFB]

I would suggest the boiler is undersized for the load, that type of system should be running at about 82deg.

Is the new boiler the same size as the old one ?

If I travel to London in a Fiesta and you in a Jaguar we'll both get there, but it would take me longer. Would it not be the same case with boilers? Both heating the radiators to the same temperature, but one taking longer than the other. Providing they ran at the same temperatue.

You have mentioned 82deg, but the one that has been fitted only reaches 70deg max. What I need to know is why this one can't reach 80deg and is there some adjustment at the boiler?

thanks
Will

 

[Dan Robinson]

Would it not be the same case with boilers?

No.

Look at it this way.

You are filling your petrol tank at 5 litres per minute. But the dirty great hole in the bottom is leaking the fuel onto the floor at 6 litres per minute.


How long to fill the tank.

Can you answer some of the requests for information, otherwise you won't get any answers.

 

[thetman]

I would suggest the boiler is undersized for the load, that type of system should be running at about 82deg.

Is the new boiler the same size as the old one ?

If I travel to London in a Fiesta and you in a Jaguar we'll both get there, but it would take me longer. Would it not be the same case with boilers? Both heating the radiators to the same temperature, but one taking longer than the other. Providing they ran at the same temperatue.

You have mentioned 82deg, but the one that has been fitted only reaches 70deg max. What I need to know is why this one can't reach 80deg and is there some adjustment at the boiler?

thanks
Will

The heat output of the radiator is based on the temperature difference between the radiator and the room. If the temperature of the radiator is reduced, the effective output will reduce.

Is the boiler fitted with the optional weather compensation sensor ?

With the system running I would be interested to see the temperatures of the flow and return pipework at the boiler.

 

[WillFB]

Would it not be the same case with boilers?

No.

Look at it this way.

You are filling your petrol tank at 5 litres per minute. But the dirty great hole in the bottom is leaking the fuel onto the floor at 6 litres per minute.


How long to fill the tank.

Can you answer some of the requests for information, otherwise you won't get any answers.

The original boiler I think was a Potterton Cowan, and was originally fitted about 1973.

The new boiler is a Vitodens 100 19kw open vent model.

There is a roomstat in the main hall.

When the new boiler was fitted and the system flushed, new thermostatic valves were fitted to all of the radiators.

Thanks

 

[Dan Robinson]

I think was a Potterton Cowan,

No it wasn't.

 

[WillFB]

I would suggest the boiler is undersized for the load, that type of system should be running at about 82deg.

Is the new boiler the same size as the old one ?

If I travel to London in a Fiesta and you in a Jaguar we'll both get there, but it would take me longer. Would it not be the same case with boilers? Both heating the radiators to the same temperature, but one taking longer than the other. Providing they ran at the same temperatue.

You have mentioned 82deg, but the one that has been fitted only reaches 70deg max. What I need to know is why this one can't reach 80deg and is there some adjustment at the boiler?

thanks
Will

The heat output of the radiator is based on the temperature difference between the radiator and the room. If the temperature of the radiator is reduced, the effective output will reduce.

Is the boiler fitted with the optional weather compensation sensor ?

With the system running I would be interested to see the temperatures of the flow and return pipework at the boiler.

Hi thetman

I don't know about the optional weather compensation sensor? But I'll send an e-mail to the guy who fitted the boiler and ask him

I don't know how I'll do it, but I'll try to check the temp of the flow and return pipes tomorrow.

Thanks
Will

 

[holty]

the 100 compact will get no higher than 70c in normal mode, end off.

 

[thetman]

the 100 compact will get no higher than 70c in normal mode, end off.

How do you get it out of normal mode, installation manual gives an output at 80/60.