Off peak heating solution required.

[Soulsurfer]

Hey all, I'm looking into a situation where a customer has been told they could no longer have oil delivered because of tank regs etc... so local DNO fitted them a new boiler (Electric) the old boiler was oil fired and 28kW new electric one is 14.4kW but running same amount of radiators. She uses the boiler only for the rads and immersion element in water cylinder for the dhw which as it's fed only off peak cheaper rate she says can't have a time clock to switch it on/off. Problem is her off peak supply is only on a 20 hrs in 24 cycle and DNO decides when it's off which is a.m. no problem but again 17:00-19:00 which is the problem as the whole house gets really cold apparently. She's been advised to have a booster switch on to override that 2 hour time when it's off she will need to use on peak electricity and it will cost many hundreds for them to fit.

I have only ever fitted booster switches into off peak hot water supplies etc.. is there such an item ? or would she need a new feed cable from main C/U to a big enough contractor which is triggered by a d.p. switch or something similar to manually turn on /off at 17:00-19:00 to run the boiler. ??

She also tells me that the smaller boiler as I thought runs constantly as it's much smaller rated. !! and to have a bigger one she needs to have a bigger supply to the property at £8,000 plus and a bigger boiler cost on top ! She also wants an alternative price for Farho's or similar to use for the 2 hr periods between.

Any advice would be very handy...

 

[Richard Burns]

I think you may need to reword your post.
What off peak rate provide 20 hours of off peak and four hours of on peak?
Are you saying that someone has connected the electric boiler to the off peak side of a DNO switched supply?

This is madness, the boiler should be planned to operate as far as possible on off peak rates but should not be unavailable at on peak rates.
It should have been wired to the permanent supply and the programmer used to control the operation times.

 

[Leesparkykent]

Economy 10 is normally the best tariff to be on with an electric boiler but not all suppliers offer it.

 

[Marvo]

You say it runs constantly and possibly the 14.4kW unit is too small, is she heating the entire house or is she using some common sense and just heating one or two rooms being used?

 

[Soulsurfer]

The tariff is Economy 20 in Jersey it's 20 hours of off peak at 10.2p per kWh and then 2 periods of 2 hours off altogether and she needs the on peak / general feed at 14.5p per kWh wired in through automatic changeover or contactor arrangement to fire back on using full price electricity for the period 17:00-19:00 as house gets cold too quickly apparently. She's using the much smaller rated boiler to heat all house rads 3 storeys up throughout and electricity only for immersion in cylinder not any heating coil etc..
She has thermostatic valves on all radiators but all wide open all the time so yep heating entire house at all times.

 

[Soulsurfer]

https://www.jec.co.uk/your-home/our-tariffs-and-rates/economy-20-(e20)/

 

[Richard Burns]

Still fairly much madness, what a rate!
Really if the house cools off that much in 2 hours then they need to think about insulating the house!
The whole intent of the tariff seems to be that the system does not consume high power at the times when the grid needs peak generation capability and so they can switch off the really high power systems.
If you bypass this then you are negating the effect of the tariff.
I assume the boiler is supplied from its own tails at the meter to its own board.
If you really wanted to bypass the rate for which the system is set up and the supply company do not mind you getting a discount whilst not complying with the rate plan, then you could install an automatic changeover switch in the CU location but the boiler would have to cope with a breif supply interruption and the switch would not be cheap.

 

[Soulsurfer]

That's just it, the automatic changeover switch is required at quite a cost apparently just like you say ;-) house is circa 30 yrs old and sea front very expensive but also huge heat loss potential, doesn't want further insulation just this auto switch onto general tariff or added Farho's in rooms to cover the 2 hour switch off at everybody finishing work peak time! Really old semi enclosed split cu feeding off peak to boiler through an enclosure with a hager dp main switch inside it and 16mm T&E's

 

[snowhead]

A new bunded oil tank would have been so much simpler.

 

[Richard Burns]

A manual changeover switch would be cheaper, however there are no particular problems electrically with supplying either / or supplies to the boiler so you could use a NO/NC contactor and timer relay.

 

[Soulsurfer]

All changeover switches I've found seem to be just very pricey and for generators.
Might have to pass on that job, seems too much of a nightmare situation.

 

[Soulsurfer]

A manual changeover switch would be cheaper, however there are no particular problems electrically with supplying either / or supplies to the boiler so you could use a NO/NC contactor and timer relay.

I'm not going to pretend that I am in anyway good with controls but I'm thinking if I say took a small feed to a time clock from general c.u. and then from time clock as switch line to the coil on a normally open contactor that could manage to switch the boiler back on when the off peak drops out would that be o.k. ? say 16mm t&e cable into contactor and out to boiler again on 16mm t&e. Would that be alright do you think ? I guess the contactor would need to switch in just after 17:00 hrs and off just before 19:00 too or the boiler would be getting it's off peak supply back on then and that might cause a problem too.