One boiler, two timeclocks

Buford T Justice

Hi Guys,

Here's an interesting one

A client of mine has two flats ,A and B. A had OFCH and B had storage rads. The tenants asked if they could install ofch in flat B, and offset the cost of this against the rent. Client said no problem and off they went.

Now, this was done with just the timeclock in flat B controlling the boiler, which heats both flats simultaneously. This can be sorted in plumbing terms with a couple of motorised valves but it gets interesting in electrical terms.

The client wants the boiler to be controlled by either timeclock simultaneously. as in, if A switches it on, its on, and if b switches on, it stays on until both timeclocks are switched off. Is it possible to have this done with contactors or a relay of sorts.

Now, if this was possible, the next thing is to avoid rows over oil, he wants to be able to meter the amount of time either timeclock is in the on position. Meters measuring in units are no good, as if both timeclocks are on at the same time, only one of them will be carrying the load to count up on the meter.

Can anyone think of a solution to this?

The alternative is a second boiler

M cebee

nothing much to the wiring- each flat is wired as a zone basically


timer/stat opens valve ,valve calls for heat


if the control circuit is LV you have to isolate at the DB if it's crossing into another apartment

else maybe SELV or wireless even



you won't be able to gauge oil usage via the timeclocks

Buford T Justice

M cebee wrote: »

you won't be able to gauge oil usage via the timeclocks

Can you meter time via each time clocks? use some math calculations to work out how much oil would be used for the time it's been on. Somewhere like 5L per hour?

M cebee

not accurately anyhow due to temperature variations and rads on/off etc.

only way would be 2 oil tanks and motorized valves

or 1 tank and flow metering via valves or something

hardly worth the bother

Antomus Prime

I agree with M cebee, it would be far too much work and not worth the hassle trying to devide usage between one tank, two tanks with motorised valves is really the only solution here, and would be much more cost effective

2011

I think that when you take everything into consideration the best solution is simply 2 boilers. When all is said and done it will not cost that much extra. Less chances of arguments too.

For a boiler to work efficiently it should be sized to match the load. A boiler that is either too large or too small will be far less efficient. How wold you decide what the boiler load for sizing purposes??

M cebee

yep another issue alright-boiler size


not a major issue wiring with correct size boiler -i did a job like this for a granny flat

hardly worthwhile if metering is needed

danjo

If you had two oil tanks and one burner would you not get airlocks in the oil feed?
What would happen if both tanks are open to feed at the same time? Maybe one tank would supply the lion's share.....probably the one with most oil in it.
I'm just guessing.

Antomus Prime

Couple of good points there, esp the boiler sizing! Ha ive been out of a plumbing job for that long now i'm loosing touch lol stupid recession lol

You'd pick up a second hand boiler out of the buy and sell handy enough, prob need a new burner though

2011

What would happen if both tanks are open to feed at the same time? Maybe one tank would supply the lion's share.....probably the one with most oil in it.
I'm just guessing.

You are correct. I was just about to say that.

Furthermore if both valves were open the tank with more oil would start to fill the one with less!!

M cebee

danjo wrote: »

If you had two oil tanks and one burner would you not get airlocks in the oil feed?
What would happen if both tanks are open to feed at the same time? Maybe one tank would supply the lion's share.....probably the one with most oil in it.
I'm just guessing.

oops:D my bad

i don't spend too long thinking up these things

can't really be done accurately except by clocking up hours with a counter for an estimate

separate boilers would be simpler if they need separate billing

Buford T Justice

I've done a price for a new boiler and tank, and with a second hand boiler its looking in the region that he won't have much change from €1000. I thought I'd explore the alternatives for the client before he goes with the second boiler, which I recommended to him

Thanks for the info guys

2011

Perhaps you could have 1 timeclock and one boiler only that heats both houses and simply split the bill? The domestic hot water could be plumbed so that it is heated by immersion only in each house. Then it does not matter if one house has more showers/baths than the other and both homes are warm.

Just a thought