Will not fire at all, trys to light but get the e1 code . used to work intermitently or fire right of way but then go cold and back to hot for about five min. then stay hot now wont even light

Question edited for clarity.

This is not a make we know in North America. If you have a pump for the hot water and a pump for the heating, it may indeed be the pump. You can tell if they are working by putting a screwdriver onto the pump and putting the handle against your ear.

Call a different technician or ask the maker for someone local

https://www.google.com/search?q=Saunier+duval+isotwin+f24+e1+error

https://www.google.com/search?q=Saunier+duval+isotwin+f24+no+hot+water

F14 Error

F14 Central heating flow T° > 95°C System fault / Possible pump failure Check thermistor on flow

I suspect a faulty thermostat.

are you sure it is E1 not P1?
Error P1 is not enough water flow.
Clean water filter located on cold water inlet at top of cold pipe when cold enters unit
Test single handle faucets for crossover
Check if faucet can fill 1 gallon can in 30 seconds.


http://www.palomastore.com/paloma_error_codes.html

No hot water anywhere,or just one faucet,doesn't sound right if burner is working,if its coming on then your gas valve/thermostat on front is not working properly.Can be changed,but I would turn up temp. red dial see if she fires and watch to see if she stays on.Gas valve is threaded in and can be changed,depending on warranty.Could also be dip tube is cracked or broken in half,its a tube that forces cold water to bottem of tank,if not working you'll get a real short shower because cold water is in top of tank.Tube can be replaced,its on the cold water fill side which would have to be taken apart.Thinking now its your tube

There are several things I would look for:
-Flashing burner light (indicates an error code)
-Trying flowing more hot water. In the summer alot of times you'll flow less hot water because your cold water is warmer. If you flow additional hot water at your shower, it will ensure the unit stays firing
-If the unit doesn't fire at all, you may have debris in your cold water filter or a stuck flow sensor. Call tech support to help you with cleaning a flow sensor.

your gas supply may be to low to keep the unit firing while you are showering...especially if you have other gas appliances running while you are using the unit.

If this is happening after someone else has recently used the unit....then it may be a problem that some call stacking. The unit works on flow....not sure about that unit but they usually take between 1/2 - 3/4 gallon to turn the burner on. If someone recently used it and then you get in the shower...you will get the hot that is already in the line but then it takes that initial amount to fire again, thus loading the pipe with cold water.....it then comes out on you followed by the hot that has finally entered the line. Once it is past that point there should be no issue, unless it it a gas problem like I mentioned.

A few things you should check:

1. Cross Connections - this occurs when cold water leaks into the hot water system through a fixture. In order to check for a cross connection: 1) turn off the cold water to the tankless 2) open up hot water fixtures in the home. The water should shut off at all hot water fixtures; if there is a continuous flow of cold water, then you have a cross connection. The most common place to find a cross connection is on old shower cartridges.

2. Ask the customer to check to see if the burner indicator is continuously lit during operation.

3. When the water goes cold at one fixture, try another near by fixture to confirm it is also cold there. If its hot at one fixture but not the other, then you have some issue with you plumbing. Tankless heaters can't pick and choose which fixtures to deliver hot water to.

4. Tankless water heaters all have a minimum flow rate that must be maintained in order to continually fire (.5 gpm for Noritz). Ensure their hot water fixtures flow at least this amount, or that the customer isn't mixing too little hot water at their fixture.

5. If they see the cold spurt during initial firing, they may be experiencing a cold water sandwich. When the heater moves from a standing state to a firing state it takes a short period to ignite and heat water. During this time it will be passing cold water through the system. Usually this cold water mixes with hot water in the line as it travels through the plumbing system, but if their fixture is very close to the heater, there won't be enough time to mix.

6. If debris has gotten into the flow sensor, this can prevent the unit from registering flow and cause intermittent firing.

chances of a critter in the fan? Like a dead 4 legged critter?

I wonder if you have this problem below caused by a drop in water pressure from someone flushing a toilet or a washing machine. I would call the company to remedy this issue.

17. What is a cold water sandwich effect? The term “cold water sandwich effect” is a term that is used to describe the introduction of cold water into the hot water supply line during frequent on/off operation of an instantaneous water heater. The cold water sandwich effect, when present, appears as a momentary drop in hot water temperature as it is discharged from a hot water supply outlet (i.e. shower, tub, or faucet). This phenomenon is present in the operation of all instantaneous, tankless style, water heaters, but is minimized with the high tech design of Rinnai water heaters.
The technology built into the Rinnai water heaters is designed to minimize the cold water sandwich effect. Rinnai water heaters are microprocessor controlled and when water flow through them ceases, they remain in a “ready to fire state” for approximately 1 minute. If water flow through a Rinnai water heater begins within the first minute following water flow stoppage, the water heater will fire back up within 1 to 2 seconds. This minimizes the cold water sandwich effect that would otherwise be experienced with a low tech tankless water heater. It should be noted that the cold water sandwich effect cannot be removed completely from tankless style water heaters. The safety standards developed to insure the safe operation of water heaters require a delay in the ignition sequence of all gas water heaters.
While the cold water sandwich effect cannot be completely eliminated from standard plumbing systems, it can be eliminated from plumbing systems that have a supply and return hot water circulating system. Rinnai has developed 2 methods to eliminate the cold water sandwich effect in residential hot water circulating systems.
The first (and preferred) method to remove the cold water sandwich from circulating systems utilizes a small electric tank water heater (powered up) that is used with a dual purpose. The small water heater acts as a mixing tank to eliminate the cold water sandwich effect from the Rinnai water heater and it uses its electric heating element to offset the heat losses from the hot water circulating system.
The second method to remove the cold water sandwich from circulating systems utilizes a small 2 to 6 gallon storage tank installed on the hot water outlet of the Rinnai water heater. This tank acts as a mixing tank to blend the cold water sandwich with hot water and eliminating its effect at fixtures.