Unvented Water Heater - Problem All aspects of plumbing questions and answers, help, tips and information

[Carlusha]

We've had a Santon Premier Plus 150 ltr unvented water heater installed. This is to run off the economy 7. After 2 months, we have had problems from the outset. No matter what setting, all we are getting is enough hot water for 2 morning showers!

Santon have been on-site and found no problems with their heater but provided new elements and thermostats. The original fitters have been round too many times to count and found no problems. EDF have checked the meters and found all settings correct. We have purchased and fitted a new Horstmann Economy 7 Quartz switch. After all this, the problem persists and no one has a solution for each believes his part of the system is 100%.

We are having to use the expensive boost switch to get any hot water during the day and early evening. Since we are pensioners, this is proving very costly and totally defeats the object of the system.

We are at a loss here, so would any expert having encountered a similar problem and found the reason to be totally unexpected or was something that was a big surprise, kindly let us know?

Grateful thanks.

[roger196]

Not an expert in this area, but I would try the following as it might give a clue.
When should economy 7 meter come on.
Note reading at this time, take reading again one hour later, then again at next hour.
Work out how much electricity the water heater has used , assuming nothing else on economy 7. An a-level physics book should help you work out through what temperature 150 litres of water should have risen.
Are you using the hot water for anything else eg washing machine, dishwasher, bath etc.
Are you spending too long in the shower.

[Carlusha]

We have all the various temperatures, times required to heat 150 ltrs etc etc - all available from the Sadia / Heat Team website.

We timed our showers! 8 minutes for the two. Bear in mind that the shower is not delivering 100% hot water - that would be too hot. So, assume 75% flow is hot and 25% cold water. We are confident that 150 ltrs would provide 3 well-filled baths or perhaps 10 or more showers.

We cannot check the electricity usage as we have storage heaters too. The Economy 7 settings have been checked by EDF and all is fine, so we're told.

Washing and dishwashing machines are both cold-fill and fitted with delay systems so that they only function during the cheaper overnight economy period.