Voker Linea Max Hot Water

[marvin]

I've had a new Linea max floor standing combi boiler installed about 4 months ago along with all new pipework/radiators. Basically the whole system is new. Its been working fine and the pressure I'm getting is amazing compared to my last combi unit. Recently with the cold weather I put the central heating thermostat onto full,last night tried to run a bath, I opened the hot water tap and the water would not get up to the right temperature, the boiler was showing about 44 degrees.

Why would this happen ?

I'm wondering if it was because the CH was on at the time, that was perfectly running at the right temperature. Was I asking too much of the boiler ? I would have thought it would drop the flow rate so it could warm the water to the right temperature but the pressure never dropped.

Any ideas ?

 

[kevplumb]

dont turn the tap on as far

 

[marvin]

ok, i guess I can try that next time, not very scientific though

 

[DP]

Linea Max runs on HW priority. If the store temperature is low, it cares not what the CH thermostat is set at- it diverts the primary water to heat the store.

If the water temperature is 44 degrees, have you tried altering the HW stat setting?

 

[weargas]

snapped stem on the dhw temp selector switch?

first of all, get the installer back to look at it, then vokera. it's under warranty if it's 4 months old.

 

[kevplumb]

thermocouple never thought of that

 

[marvin]

I put the HW thermostat on full too but this didn't really make a difference.
I've turned down the CH a bit too, I'll see how it goes next time, if no better then I'll get the installer back.

 

[kevplumb]

listen to weargas he knows
weve had similar probs b4

 

[marvin]

Same happened again this morning, the CH was on, lovely and warm.
Had a shower, ok for a minute or so then the temperature dropped, tried to increase the shower thermostat but it wasn't happy at all.

I think I will have to call the installer back, weargas you said "snapped stem on the dhw temp selector switch?", is this visible if I remove the front of the boiler and I can take a look ?

Marvin

 

[ChrisR]

In ANY storage combi you can take the HW fast, which is fine until the store is depleted. I don't have thw figures to hand but if you have a 50 litre store and you take it at 20 litres/minute it'll last 2 1/2 minutes, plus a litle bit for theextra which has been heated in the 2 1/2 minutes.

I think the Linea Max is 80,000 Btu/hr, so on a continuous basis (after the store has emptied) you'll only get about 10 litres a minute of shower-temperature water. Remember the stuff in the store was hotter so you added cold so maybe had 30 litres/minute of shower water.

See?

 

[marvin]

Yes I see, but surely the boiler should still give me the water at the same temperature but just at a slower rate ?

Marvin

 

[ChrisR]

NO. Or at least, only if you adjust the flow right down. The store will be hot hot. The water temp coming out once the store is depleted depends on the flow rate. You get say 10 litres per minute with a 35º rise. If it lets 15 l/min through you'll only have a 24 rise. We all shower at 38-40. If the incoming water is at 10 you're cold in the shower at 34. And thats with NO cold added to the hot.

Your combi can't have a flow restrictor like normal ones do to assure water hot enough for a bath (45), cos it has to be able to let the stored stuff out fast.
Solution could only be to take the water slower.

 

[DP]

Linea Max will display about 55 degrees for minimum setting of HW stat to 70 when at max.

With boiler cold, run a hot tap and feel the flow and returns to the rads to see if they are getting hot. If they are suspect diverter problem.

Boiler does not have a thermocouple. It is a storage combi

 

[marvin]

I can not take the water slower when having a shower, it has an on/off button only , there is something in the loft though for the shower, I wonder if that could be adjusted

 

[marvin]

I just ran a test, I emptied the water store by putting the shower on, then watched the temp gauge on the boiler, within about 4 minutes it went down to 35 degrees.

I will run the test from cold as you suggest and see what happens to the rads.

If everything looks ok, can the boiler's flow rate be adjusted ? With my last combi, I could only run 1 tap at a time, nothing would come out any others if 1 was open, on the vokera with the store empty it comfortably runs the 2 open hot taps with good pressure.

Marvin