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Boiler short cycling

Issue with boiler short cycling in system with hot water tank.

We have an ideal heating logic heat2 h15 boiler which feeds a hot water tank upstairs in the house. We have an issue where if the boiler isn’t set to 80c then the boiler will short cycle, the hot water tank thermostat is set at around 60c however if we have the boiler at 65 or 70 it will short cycle constantly, it heats up to over the set temperature and drops immediately and then between 30-60 seconds will fire back up and repeat the process. The only way to stop this is to have the boiler set to 80c and at this point it seems to modulate a lot better and hold itself at that temperature which is fine other than it makes the radiators scolding hot, if we were to have children in the house I would be worried it could burn them. Is there an obvious reason for this or will we have to put up with having the radiators so hot all of the time?
 
What’s the coil capacity of the cylinder eg is it an old copper one
 
IME, 65°C should be (just) enough to heat a DHW cylinder to 60°C in a reasonable time without excessive cycling. The system does need investigating. As well a being hazardous, flow temperatures above 65°C will likely increase the fuel consumption of the boiler by preventing it from operating in 'condensing mode'.

A few extra questions to help diagnosis
  1. How long have you had this problem?
  2. Do you live in a hard water area?
  3. Can you post a photo showing the tank and the relevant pipework?
  4. What sort of pump does the system have and what setting is it on?
  5. Is there a balancing valve that controls how much flow the DHW cylinder receives?
Hot radiators are not only dangerous to children. If an elderly person falls, e.g. in a bathroom, lands against a hot radiator and is unable to move away, the resulting burn can be very nasty.
 
Chuck said:
IME, 65°C should be (just) enough to heat a DHW cylinder to 60°C in a reasonable time without excessive cycling. The system does need investigating. As well a being hazardous, flow temperatures above 65°C will likely increase the fuel consumption of the boiler by preventing it from operating in 'condensing mode'.

A few extra questions to help diagnosis
  1. How long have you had this problem?
  2. Do you live in a hard water area?
  3. Can you post a photo showing the tank and the relevant pipework?
  4. What sort of pump does the system have and what setting is it on?
  5. Is there a balancing valve that controls how much flow the DHW cylinder receives?
Hot radiators are not only dangerous to children. If an elderly person falls, e.g. in a bathroom, lands against a hot radiator and is unable to move away, the resulting burn can be very nasty.
Click to expand...

We have had this problem since we moved in back in March this year so the boiler and the tank are both brand new.

We live in a hard water area but as mentioned we’ve only been In since March and it is a brand new property.
 
Chuck said:
IME, 65°C should be (just) enough to heat a DHW cylinder to 60°C in a reasonable time without excessive cycling. The system does need investigating. As well a being hazardous, flow temperatures above 65°C will likely increase the fuel consumption of the boiler by preventing it from operating in 'condensing mode'.

A few extra questions to help diagnosis
  1. How long have you had this problem?
  2. Do you live in a hard water area?
  3. Can you post a photo showing the tank and the relevant pipework?
  4. What sort of pump does the system have and what setting is it on?
  5. Is there a balancing valve that controls how much flow the DHW cylinder receives?
Hot radiators are not only dangerous to children. If an elderly person falls, e.g. in a bathroom, lands against a hot radiator and is unable to move away, the resulting burn can be very nasty.
Click to expand...

Chuck said:
IME, 65°C should be (just) enough to heat a DHW cylinder to 60°C in a reasonable time without excessive cycling. The system does need investigating. As well a being hazardous, flow temperatures above 65°C will likely increase the fuel consumption of the boiler by preventing it from operating in 'condensing mode'.

A few extra questions to help diagnosis
  1. How long have you had this problem?
  2. Do you live in a hard water area?
  3. Can you post a photo showing the tank and the relevant pipework?
  4. What sort of pump does the system have and what setting is it on?
  5. Is there a balancing valve that controls how much flow the DHW cylinder receives?
Hot radiators are not only dangerous to children. If an elderly person falls, e.g. in a bathroom, lands against a hot radiator and is unable to move away, the resulting burn can be very nasty.
Click to expand...

Hi,

We’ve had this issue since we moved in in March of this year, we do live in a hard water area but the house, boiler and tank are all brand new as mentioned we have only been in since March.

I’ve put a picture in of the tank and the pipe work please let me know if you need any closer view etc.

I’ve also put in a picture of the pump, it’s been on Auto for the majority of the time although I did turn it up to it’s highest setting for only a short time to see if it made any difference which it didn’t seem to.

Finally I’m not too sure on the balancing valve it doesn’t look like there is but I unfortunately don’t have a lot of plumbing experience to go off.

Appreciate your response.
 

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jordanmakin_ said:
Hi Shaun,

It’s a brand new cylinder along with boiler on a new build property we moved into in March, on the label it says the coil rating is 15.9 kw

Cheers
Click to expand...

Wouldn’t do anything it’s brand new get them out to sort the issue the boiler should run for 10 mins plus easily

Could be the left brass valve is shut / nearly
 
ShaunCorbs said:
Wouldn’t do anything it’s brand new get them out to sort the issue the boiler should run for 10 mins plus easily

Could be the left brass valve is shut / nearly
Click to expand...
I’ve had the boiler company out previously and they ran tests on the boiler and said there was no issues. Makes me think it’s either the plumbing or to do with the tank itself, who would you recommend requesting first the plumber or the tank fitters coming in
 
jordanmakin_ said:
I’ve had the boiler company out previously and they ran tests on the boiler and said there was no issues. Makes me think it’s either the plumbing or to do with the tank itself, who would you recommend requesting first the plumber or the tank fitters coming in
Click to expand...

The boiler company? The people who installed the boiler or the manufacturers ?
 
jordanmakin_ said:
The manufacturer of the boiler, ideal heating engineer came and ran tests on it and said there was no issue with the boiler itself.
Click to expand...

No the installers need to come out
 

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