Veissman Vitodens 100 Not Cutting The Mustard?

[DanJohnson]

Hi.

Would really appreciate some more opinions on this..

I have a veissman Vitodens 100 boiler that was fitted about two years ago. I've felt that recently it wasn't really getting the water hot enough in the bathroom and it's taking an age to heat the house.

Today has been a pretty mild day (approx 12 degrees outside). We had the thermostat set to 23 from 5pm onwards. It's now 8:45 and it is reporting the room temperature as 18.5. I'm thinking that it should know it has some work to do to get upto the required temperature but none of the rads are anywhere near too hot to touch. Looking at the panel on the boiler it's only showing level 1 (of 5 for gas flow). Am I right in thinking the boiler should be working hard until it gets to the temperature we want and then just working to top up when needed?

We ran a bath last night and although the water was warm, it was never 'hot'. Am pretty sure I don't have asbestos hands Any help or advice would be appreciated.

PS> I contacted the guy who fitted this boiler at the beginning of winter and he told me that modern day boilers should be left on most of the day to heat the house to the required temperature. Was I fobbed off here?

Any help or advice appreciated.

Dan

 

[holty]

could be a number of factors. what is the dial reading when ramping up to ch and hw? also is this weather comped. and when it does ramp up, how fast is it reaching its target temp.

 

[DanJohnson]

Cheers for the quick reply Holty,

The hot water hit 62.5 on the boiler display and sat there for 20 minutes while we ran a bath. Water was warm but not too hot

CH goes upto about 72 on the boiler display, sits there for about a minute and then dips down slowly to 50, then rebuilds.

This is fairly typcial if we have the thermostat set for 23 celcius. Room temp started at about 17 celcius at 5pm, 4 hours later it's on 18.5. Again this is fairly typical... Never seen it hit anywhere like 23 degrees

How would I know if it has weather comp?

 

[holty]

dont worry about wc at the mo. have you always had a problem with room temps. i ask as 72 is about right for a modern condenser. yet if your rads are undersized. no matter what it takes, the room wont get up to temp. even with the boiler working at max. but also if your system has a flow restriction. e.g sludge then the boiler will ramp up very quickly to 70. then it will cut out on this boiler and begin up around 54 degrees. etc. cycling.

 

[DanJohnson]

I can't honestly remember a time when the room temp has been up in the 20's. Unfortunately I was renting the house out in the first year that the boiler was fitted so can't comment there.

The cycling you suggested sounds about right though, I just checked now and it was droping down to 40 on the display, it'll work back up to the 72 now.

I have six rads in the house, all single panel

3 * 200cm by 60cm (all downstairs)
3 * 140cm by 60cm (all upstairs)

Boiler is also upstairs in bathroom

 

[holty]

really hard to say. it sounds as though your boilers doing as it should. bath taps can be the worst to judge a combis performance, especially if a conversion was done from an old system, were 22mm was used up to the bath taps from an old gravity hot water arrangement. only way to tell performance would be to test flow, test incoming mains temp and testing hot water temp at the tap.when was the boiler last serviced.

 

[DanJohnson]

holty, I haven't had the boiler serviced this year. Reckon that's probably the first thing I should do. Just wanted to check that what it's doing is what it's expected to do. Cheers for your input

 

[holty]

holty, I haven't had the boiler serviced this year. Reckon that's probably the first thing I should do. Just wanted to check that what it's doing is what it's expected to do. Cheers for your input

would recommend you do. to keep your warranty. funny if i missed a service on my new van, my warranty is void. shame customers dont feel the need with there boilers. i say this as some manufacturers wont entertain a callout fix if the boilers not been logged with a service. so be aware.

 

[JohnD]

holty, what do you think servicing a 100 will do to improve the heating?

 

[DanJohnson]

JohnD> interested to hear if you have any other comments on my situation

 

[holty]

nowt john. but its whats required if there is a problem with the boiler. p.s iv installed over 80-100 wb1bs and a service agent for viessmann. so i do know what is needed.

 

[JohnD]

On mine the "recommended" setting for the boiler stat equates to 60 degrees, turning the knob to max is 80 degrees.

What's yours set to? Might not be the same as mine.

It seems to like running gently, turning the knob up makes it run harder.

Mine modulates down as it gets nearer to the set temp, so it tries never to turn off on a cold day until the room stat is satisfied.

 

[DanJohnson]

There are two controllers on the boiler. From 1-6. Both set at 6.

Room stat temp is never satisfied.

 

[holty]

first get the thing serviced. a proper service on this would requre taking the burner out even if you do get a guy who says it can be done with a FGA and thats all. and the seal wont need replacing. then ask the guy about your problems. this will probably arise when he/she does a FGA test. if the system ramps up to quick from cold on service setting high. then this should be noted by your service engineer. and thus a service will help to your answer hopefully.

 

[DP]

Holty, any boiler should delivery stipulated hot water to the taps regardless of the age of secondary plumbing. A combination boiler will raise the hot water temperature by 35 degrees. If the cold is clocking 10 degrees C, hot will be 45. For this to happen, boiler must have correct size of gas pipe and cold water flow through the boiler must be what is stated in boiler specification.

A dirty system will not work well.

Insufficient gas pressure will result in poor hot water delivery

Too much water passing through the HW heat exchanger will result in tepid water at the hot tap

I think your installer needs to get his facts right. A smallest combi is rated at 24kw for hot water delivery of 9.5l/ min (approx). 24kw is there to heat the water but rarely is all this power required to heat the house. In fact this power could easily heat the house next door too, so your boiler will be man enough to heat the house unless there are other factors inhibiting correct boiler operation.