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I don't think low return temperature is the problem, it's the temperature difference across the heat exchanger. I'm not 100% sure why it's undesirable to have a large differential, but maybe something will expand or contract??? Just guessing! About 20c - when it is up to temperature flow is...

I should clarify this - the boiler doesn't cut out entirely, but it goes into a "limp home" mode. This is in the D.99 menu as state S.53 which the manual describes as: "waiting time: temperature difference flow - return sensor too high". I appreciate this description makes it sound the wrong way...

I'm measuring the flow and return temperatures from these two menus in the boiler. I've confirmed the sensors are accurate with a temperature probe. What seems to happen is the temperature differential will start off at 20c and then climb up to 30c after a few minutes as the boiler gets...

I've checked in the manual about range rating, and I think I have been setting it correctly. I can only think it may need a complete power off or similar for the range rating to become effective. It does say in the manual that range rating isn't necessary as the boiler is auto-modulating...

I've just run through the online calculator and got a value of 35kw for required size. The house is about 3500sqft, and it's a mix of solid wall from the 1700s, filled cavity from the 1970s, and modern 2004 construction with Kingspan insulation boards. There's single glazing that's 100+ years...

It's a separate pump and boiler; the boiler is a Glowworm Ultracom 38hxi one, less than 6 months old.

I am assuming that I am right in saying that the hot water flow to a cylinder can't be balanced?

D_Hailsham, thanks very much for your detailed reply, certainly helps clarify a lot! I'm 99% sure that balancing isn't what is causing the issue. I have three zone valves; radiators, underfloor and hot water cylinder. I've tried heating the hot water cylinder up from 15c or so, and get the...

Yep, I've already been on the Grundfos website trying to get data, but it seems that you have to be an installer and they will post of spec data to you, I can't seem to download any public data.

I can't seem to find much information on the spec of the pump. I've checked the system pressure and it's about 1.2 bar, will increasing this help the pump flow more?

Hi everyone, I've got a problem with the return temperature dropping too much for my boiler, and the safety cut out comes on. I've been working out the flow rate and came to the conclusion the pump was flowing about 0.32 litres per second of hot water. This is for large four bed detatched...

Hi everyone, This is my first post on here so be gentle. :) I've had two heating engineers come in to try and resolve this problem. Both have changed small bits and pieces, but neither have seemed to resolve the problem. I have recently moved into a new house, it had a very old...