storage heater performance

[Gill]

Bit of background - moved into a fixer-upper in June.  Electric only and heating provided by storage heaters all of which are between 20 and 30 years old and I think are functioning OK.  Was mentioned in another thread by @SteamyTea that there may be an issue with sizing or elements gone pop but i'm now curious about what performance is normal and if my SH have an issue or are just undersized for cold spells (in a poorly insulated property).   

 

Over the cold snap we needed to top up heat pretty early in the evening after running out of layers to put on as temps dropped down around 14 in the living room.  Today with temps between 5 and 9 the living room is floating around the 18 degree mark at 9pm which is quite nice really.

 

The two living room SHs are 3.4kw (24 brick models).  With the input maxed and the output set to min, they're tepid by 6 / 7pm so looking at around 12 ish hours heat release when the temps aren't below 0.   I have to say I assumed this was normal.  9am this morning (2 hours after the eco 7 clicked off), the top panel above the grill  of both SHs was piping hot - too hot to touch.  The outsides of the same top panel were hot but you could keep your hand on it.   Again I thought it would be normal to lose heat from the outside 1st?   

 

One is mounted on an external facing wall so I assume it's doing a rare job of heating the empty cavity wall.  The other is on a partition wall which warms the bedroom cupboard on the opposite side.  I don't have hourly usage but comparing our late summer electricity use with winter and assuming our water tank is using more to heat from lower temps, I've come up with a bit of a rough estimate of 32 KwH each night for the two living room SH (room size 6.2mx5.9mx2.9xm).

 

I'm thinking poor positioning and poor insulation is the reason they don't perform well in lower temps but I have nothing to back that up.  Any insight from other SH users would be helpful. 

 

 

 

 

 

[ProDave]

First thing, when you go to bed, make sure the output control is set to it's lowest setting, fully anti clockwise.  Then only turn the output control up later in the day when you sense they are starting to cool down.

 

If the heat output is constant across the whole with of the output grill then it is likely all elements are okay.  If it is cooler in the middle or at one end, one of the elements may have failed.  They are easy to replace but you need to let the core cool down before you can dismantle it and take the front row of bricks out to get at the elements.

 

I have had SH's in 2 previous houses, both poorly insulated and they were pretty rubbish because a poorly insulated house needs heat all the time you are using it, and if it runs out of heat the rooms quickly go cold.  If the house has enough insulation to stay work for a few hours when the heat runs out they would probably work a lot better.

 

All the sides of the heater are insulated.  Most of the heat output is by convection by allowing cold air into the bottom into the hollow middle of the core (where the elements are) and out of the top of the core exiting through the grill.  The output control opens a flap to allow easier convection as the core cools down.  Some have a crude thermostat in the form of a bi metalic strip that is supposed to automatically open the output flat as the core cools down.  One side effect of most of the heat exiting at the top of the heater, is my 1930's house with no floor insulation always had a pool of cold air at floor level that the SH just could not warm up.

[SteamyTea]

28 minutes ago, Gill said:

The two living room SHs are 3.4kw

They are a bit bigger than my living room one, but about the same input.

3.4 [kW] x  7 [h] = 23.8 kWh

If that stored energy is released evenly over the next 17 hours, that is a power output of 1.4 kW, which is not that high.

As you have two of them, you will get double that, so 2.8 kW, which is about the same as a 3 kW fan heater would churn out.

28 minutes ago, Gill said:

room size 6.2mx5.9mx2.9xm

36.5m², so almost as large as my house (which is 48m² over two floors).  As you say, one heater is attached to an outside wall, not the best place for them.  I moved mine to the party wall, but never actually bothered to measure the performance difference as I did it as soon as I moved in.  They are easy enough to move.

As your are in the frozen north, I suspect that they are undersized for a proper cold spell.  I had a house in Aylesbury and during one exceptionally cold spell, the gas CH could not get the house warm and I had to get some electric heaters, as did my neighbours.

 

One thing that can happen to SH is that they heat up to maximum before 7AM, then shit down and the output flap reopens (it closes when being charged up).  It then starts to heat the rooms up but does not loose enough energy to have to recharge before the E7 window closes.  This may mean you are loosing 2 hours of time shift.

This can be caused by either a faulty input thermostat, the automatic output flap not responding to the charge period (it is a bimetalic strip that gets separately heated when they SH is charging up), or a stuck open output flap.

You can sometimes hear the output flap slam shut (a good thing) but you don't hear them slam open.

 

What I suspect is happening is that they are a bit on the small side for really cold weather, it is what usually happens.

Do they work fine come April?

Edited January 5, 2023 by SteamyTea

[Gill]

Thanks @ProDave

 

Output we never increase. Even when they start to cool there's no noticeable difference when that changed. Could be too late in the day as if I'm not working at home, it's 8pm before I get home and they are already tepid. 

 

Across the grill the output seems OK and uniform until later in the day when the heat centralises. 

 

We have that floor level pool of cold air but thankfully the recent addition of underfloor insulation seems to have improved that from baltic air to cooler. Small steps... New windows (hopefully this month or early next) followed by CWI will hopefully improve further and I  can start to get a handle on heat loss /heat requirements before I consider any change to heating system. 

[SteamyTea]

2 minutes ago, Gill said:

uniform until later in the day when the heat centralises

My larger ones does that, 2 to 3°C difference between the centre and edges, when measured on the top of the front face.

 

[Gill]

8 minutes ago, SteamyTea said:

 

One thing that can happen to SH is that they heat up to maximum before 7AM, then shit down and the output flap reopens (it closes when being charged up).  It then starts to heat the rooms up but does not loose enough energy to have to recharge before the E7 window closes.  This may mean you are loosing 2 hours of time shift.

This can be caused by either a faulty input thermostat, the automatic output flap not responding to the charge period (it is a bimetalic strip that gets separately heated when they SH is charging up), or a stuck open output flap.

You can sometimes hear the output flap slam shut (a good thing) but you don't hear them slam open.

 

What I suspect is happening is that they are a bit on the small side for really cold weather, it is what usually happens.

Do they work fine come April?

 

If I find myself awake at 5am, I'll check they are not doing any dirty business. 😃

We moved in June so no idea how they perform in April. We held our till late November before turning one, then the other on. Taking today as a mild day - the living room is still quite pleasant so I'm inclined to say it will perform well outside of extremes. 

 

[SteamyTea]

Read your meter every time you get in, or when you leave, for a few days, see how much energy you are using.

There will be 3 readings on it, Total [t], Day [1] and Night [2].

We can probably estimate DHW usage quite well.

 

Does seem like your place is under insulated.

[Gill]

Just now, SteamyTea said:

 

Does seem like your place is under insulated.

 

It's a sieve. Attic has a good 50cm. Have now insulated the hatch. 

Windows are wood frame DG but most panels blown and haven't been cared for maybe in the last 5 years. Frost on the inside in the kitchen in the cold snap. 

Uninsulated wood panelling below windows is rotting away in a couple of windows - I suspect the unheated kitchen is suffering there. No Kitchen door to living room so a heavy curtain installed to try to reduce living room heat loss as the kitchen hit 7 degrees daytime in December . No CWI but that'll be next after the windows. 

The optimistic take is at least there is massive room for improvement. 

[Gill]

On 05/01/2023 at 22:16, SteamyTea said:

Read your meter every time you get in, or when you leave, for a few days, see how much energy you are using.

There will be 3 readings on it, Total [t], Day [1] and Night [2].

We can probably estimate DHW usage quite well.

 

Does seem like your place is under insulated.

 

 

A few days of meter reads has average of 50 units on the overnight and 8 day time. A few night units would be dishwasher which runs every other night and washing machine (once every 4 days ) . I'm estimating ~47 for heating and water ON. In the summer we'd be around 5 or 6 units on DHW. Not sure how much this would increase for colder water temps. My rough estimate of 32 for the two living room SH maybe a bit light.  One other SH which is a 1.7kw running in the bathroom. Maybe more like 38 units for both living room SHs. 

 

One question regarding BST to GMT - how does this work? I've read radio signal but not clear if the supplier shifts the window or the radio magic is supposed to do this. Noticed last night at 11.30pm the SH was on so must be coming on an hour earlier than bst. Tarrif doesn't start till midnight - at least that's what the supplier confirmed when I asked over summer. 

 

Edited January 7, 2023 by Gill

[ProDave]

On off times remain on GMT, so they DON'T got forward an hour in summer.

[SteamyTea]

58 minutes ago, Gill said:

Maybe more like 38 units for both living room SHs

Over how many day?

 

58 minutes ago, Gill said:

In the summer we'd be around 5 or 6 units on DHW

About right for two people, will go up a bit, maybe a kWh/day in the winter.

 

As @ProDave says, our radio switches are on GMT, but the billing window does change sometimes, but your energy provider will let you know.

They sometimes, for load balancing reasons, shift the time.  Sometimes I have had power in the afternoons for half an hour or so.  This is billed at the night rate.

[Gill]

22 hours ago, SteamyTea said:

Over how many day?

 

About right for two people, will go up a bit, maybe a kWh/day in the winter.

 

As @ProDave says, our radio switches are on GMT, but the billing window does change sometimes, but your energy provider will let you know.

They sometimes, for load balancing reasons, shift the time.  Sometimes I have had power in the afternoons for half an hour or so.  This is billed at the night rate.

 

Measured over 3 days.  Looking at last night, similar numbers of 52 units overnight, 11 day. So estimate 7 for DHW, 1 or 2 units unit for dishwasher, fridge... Probably 40 ish on the 3 SH each night. 

 

I'll check in with the supplier if I can ever reach them. I'm sure they quoted midnight to seven when I asked in the summer so if that is gmt the heating should be coming on at midnight at the moment unless it relates to the load balancing you mention. 

Edited January 8, 2023 by Gill

[SteamyTea]

48 minutes ago, Gill said:

52 units

So 52 kWh per night, or about 45 kWh for just heating.

While that seems high to me, I am in the warmest place in the land during winter (yesterday I used 8 kWh, 3 of which were DHW and 1 for everything else), I don't think it is excessive, except your place is a bit on the cold side.

Fixing drafts would help a lot with that.